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- Scope Expands for PubMed and Medline
TheNational Library of Medicine (NLM) produces 40 different biomedical databases with a total of more than 18 million records. As a branch of the National Institutes of Health (NIH) one of NLM's primary functions is to make the Medline and other NLM databases
easily accessible to health care professionals and consumers. Access to Medline has been relatively inexpensive (and now even free from NLM) compared to other comprehensive biomedical databases such as EMBASE because it is produced by a public agency.
When the first version of this page was written in 1995, there was no free Medline service that offered the entire file back to 1966 and fully exploited the MeSH subject structure. There were some commercial sources that provided stripped down versions of Medline on the Web and university students and faculty could search without direct payment on locally loaded files. Of course, the Library or other department at the University picked up the tab for all those searches.
As Web access proliferated, a common question was where could a user connect to a Free Medline service? Long-time users of Medline would not have thought to ask this question, because Medline had always been a fee-based service since it went online in 1971.
But on June 26, 1997 NLM took a "Megaleap" by offering free access to PubMed or Grateful Med to anyone with a Web connection. Since then, NLM has continually improved searching features and response time is outstanding due to an upgrade on August 3, 1998. Will Commercial vendors respond with value added products like full-text journal connections to keep their customers? Will University Libraries continue to pay considerable sums in subscription fees and network costs in order to load Medline files locally?
Database coverage, Currentness, full-text links, functionality of the search engine, and reliability are the major considerations in deciding which Medline system to use.
- Coverage
- refers to the number of years of data that a file contains. The complete Medline file currently starts in 1966 and includes articles that were written about two months ago. (There is an Oldmedline file for the 1960-65 publication years.) Many searchers consider 5 to 10 years of published data adequate for their research or patient care. However, when searching rare medical conditions, it is often necessary to go back much further in the medical literature in order to retrieve satisfactory information. Also, a complete file is essential for citation verification.
- Currentness
- is how soon after publication an article's citation appears in the database. NLM online databases are the most current because they are created there, but many vendors do a good job of adding current data as soon as they receive it from NLM. CD-Rom based databases usually are a month or two behind the online databases (Assuming that the local technicians load the discs promptly). The dates of update of a database refer to the date the last articles were indexed, not when the articles were published.
The real power of the Medline database is its subject indexing, which takes time to process. NLM offers a Pre-Medline (PreMed) data base of recent articles that have not been indexed by subject, but can be searched by author, title, or journal title. The PubMed Medline database includes PreMed as well as information provided by some journal publishers that links PubMed citations to online full-text articles. For some journals these links can be as current as the the day of publication of the articles. For example, check PubMed for an articles in the NewEngland Journal of Medicine on Thursdays and you will find a complete listing of all articles published that day or the week before. Most journals are not accessible so quickly, but they appear in PubMed two-three weeks before they are available in the printed index, Current Contents
- Links to Full-text
- Novice searchers often assume that Medline contains the actual text of the articles. Medline is only a bibliographic database, which means that it only provides pointers to the page,volume, and journal where one will find a particular article. Medline has abstracts for about 75% of its citations that were published in or after 1975. Some abstracts are quite long and many are informative but cannot substitute for the complete article.
A number of Medline Services including OVID and PubMed now provide links from their system to full-text articles at the journal publisher's site. NIH's PubMed Central has had a slow start with only two full-text journals as of February 2000 and thirteen in February of 2002.
Unfortunately, journal publishers charge (most would say unrealistic high prices) to access the full-text. There is a growing list of electronic journals on the Internet, as of March 15, 2000, fewer than 531 of the 4255 journals indexed in PubMed had Web links in PubMed to online full-text access.
However, over the last two years access to full-text has grown rapidly. By October 25,2001 more than 2,200 journals out of 4600 indexed in PubMed offered links to full-text articles.
Still many articles, especially those published before the mid 1990's, are only available in paper format from a medical library or commercial Document Delivery vendors.
The big issue is the continued high cost for online full-text articles.
- A good search engine should have the following Functions:
-
- Limit searches to specific Fields
- Limit searches to MESH fields
- Search MESH Sub-Headings
- Explode MESH Headings, which means a hierarchy of sub-terms can be searched simply by entering a broader term. Novice searchers may not see the importance of this, but it is essential to effective searching. Some systems Explode terms automatically.
- Truncation of root words
- Boolean Logic - AND, OR
- Flexibility in output formats to printer or disk.
- Reliability
- depends how good one's Internet connection is, Web traffic, and bandwidth. All Web Medline services will be affected. The alternatives are dial-in and locally loaded databases, which are not dependent on fluctuations in Web traffic. Again cost is the major obstacle to their use.
- Conclusion
- If you have a lot of money, load Medline locally, pay a network technician to maintain the system, and use OVID for your search engine. The rest of us should try PubMed and the Web Version of Grateful Med(Discontinued in 2001). They are free, have access to complete files, are updated before any other service, have highly functional search engines, and are reliable with good response times.
Dr. Felix's Free Medline Page is a good place to get a quick description of the many other Medline services available on the Web.
If you do decide that you require a fee-based provider, remember that charges for Medline will be in addition to those that you pay to your Internet provider.
- is a "service of the National Center for Biotechnology Information (NCBI)
at the National Library of Medicine (NLM). PubMed has been developed in conjunction with
publishers of biomedical literature as a search tool for accessing literature citations and linking to
their full-text versions at publishers' Web sites. PubMed searches the 10 million citations in
MEDLINE supplemented by pre-Medline citations which do not yet have MeSH index terms and
by citations supplied electronically by publishers." PubMed also includes all the citations from the HealthStar Database, which specializes in Healthcare delivery. PubMed was released in mid November, 1996.
Use the following characters for Boolean operators.
'&' (AND, or intersection)
'|' (OR, or union)
'-' (NOT, or difference).
See the PubMed Tips page for detailed search procedures.
-
Grateful Med(GM) - was developed as a front-end to make searching NLM's direct command system accessible to healthcare professionals who wanted to search Medline without assistance from information specialists. GM helps users in formulating search strategies and using the MeSH vocabulary.
Originally GM was accessed via modem or Telnet, but in February of 1996, NLM released a Web Version. In the dial-in version searches can be formulated off-line, then Grateful Med logs in, performs the search and downloads the results. Interactive searching mode is also available. Telecommunications software is included for dial-in access. Grateful Med software was priced at $29.95. NLM discontinue further development for dial-in access.
The Web version interface is similar to the dial-in package, but with a Web form-search interface to guide searchers. No special software is needed for the Web version, just a Web browser.
Userids and passwords are not required to search databases on the Web version, but you still need a NLM User ID if you want to receive document delivery via Loansome Doc. See how to how to get a UserId and Password for NLM systems.
Loansome Doc was developed as a companion to Grateful Med to allow a user to tag citations and then send requests to a Medical Library for the delivery of the journal article. It was designed primarily for healthcare professionals who serve areas that are distant from a medical library. You must establish an account with a Library in the National Network of Libraries of Medicine in order to request document delivery. PubMed also offers ordering of articles via Loansome Doc.
GM currently has access to databases that PubMed doesn't have.
PubMed contains Medline files from 1966 to the most current, plus PreMed files. Currently Internet GM (IGM)
searches Medline HealthStar, PreMedline, and Aidsline files, Aidsdrugs, Aidstrials, Bioethicsline, ChemId, Dirline, Histline, Hsrproj, Oldmedline, Popline, Spaceline,
and Sdiline. Each file is searched separately. However, NLM is working on adding these files and many more to the PubMed system.
- is NOW Available on the Web (Sept 24, 1998) You can search both data and literature databases.
http://toxnet.nlm.nih.gov/
- Toxicology Data Search
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HSDB (Hazardous Substances Data Bank)
CCRIS (Chemical Carcinogenesis Research Information System) from the National Cancer Institute
GENE-TOX (Genetic Toxicology/Mutagenicity Data Bank) (EPA)
IRIS (Integrated Risk Information System) (EPA)
RTECS (Registry of Toxic Effects of Chemical Substances) from the National Institute for Occupational Safety and Health.
- Toxic Release Inventory(TRI)
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contains data on quantities of chemicals released into the environment
- Toxicology Literature Search
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DART (Developmental and Reproductive Toxicology) and its backfile ETICBACK
EMIC (Environmental Mutagenesis Information Center) and its backfile EMICBACK.
-
- collects all the Medline articles, relating to genetics or about 18% of the entire file. Genbank uses the same Entrez search engine as PubMed above. See the Molecular Biology Page for links to sequence databases
If you are serious about being a competent Medline searcher, you should use the Mesh subject headings. Now they are available online in a very convenient format that includes a permuted search, scope notes and tree information.
Printed MeSH Tools are also easy to use, but they are a bit expensive for those who search infrequently.
- MeSH - Annotated Alphabetic List $49.95 (U.S./Canada/Mexico) and $99.90 (other countries)
- Permuted MeSH, $40.95 (U.S./Canada/Mexico) and $81.90 (other countries)
- MeSH - Tree Structures Price: $44.95 (U.S./Canada/Mexico) and $89.50 (other countries).
The MESH contains many chemical names, but still more chemicals (80,000) or Names of Substances (NM) can be found in the Chemid, which can be searched either in Greatful Med or ChemId Plus. The latter offers structure searching. MeSH - Supplementary Chemical Records has been discontinued. All the chemical terms used in Medline are listed in MESH, but you may want to check for articles in Toxlit or Toxnet . Chemid has a Locator field that indicates which files have entries for a particular chemical. The reason for starting a chemical name search in Chemid is to find a Registry Number (RN), which can be used to search for a chemical in Toxlit or Toxnet files. It's very confusing to search by chemical names in these files due to the proliferation of synonyms and complexity of chemical compounds.
For more information see NLM Technical Bulletin Jan-Feb 1997, p.6-8.
"MeSH is also available on the NLM FTP server in 8-bit ASCII binary format
following the USMARC Authority Format. There is no charge for obtaining the file. Users are required to complete an online registration form before receiving the data."
The general rule has been that searching Medline at NLM via Medlars was much cheaper, but more difficult due to a less powerful search engine. Commercial vendors have charged much more until recently, but provided superior searching interfaces. NLM Introduced Grateful Med software to make its MEDLARS system easier to use, while commercial vendors significantly reduced their connect time charges, but still charge too much for printing and downloading citations retrieved from searching. And now there is PubMed from NLM whose searching power is almost as powerful as its commercial competitors .
Dialog offers the largest number of Databases to its searching customers and is strong in all fields including the biomedical ones. You can dial-in or Telnet to Dialog computers or buy complete databases on CD-Rom products. Over the years Dialog has led its competitors in the introduction of powerful searching features such as precise proximity searching that is very useful in full-text databases or those with no controlled vocabulary structure. But since Medline is a highly structured database, experienced MEDLARS users are at little disadvantage in achieving both precise and comprehensive retrieval. For complete technical information on just about any database see the Dialog Blue Pages
OVID Technologies started as CD-Plus and developed expertise in loading Medline on networked servers for medical libraries. CD-Plus grew quickly and its searching software was so successful that the company changed its name to OVID after the name of the software. In 1995 Ovid bought out a declining BRS, which had been bouncing around from one corporate owner to another. BRS was Dialog's strongest competitor in providing access to biomedical Databases. BRS targeted physicians with the service known as Colleague, which was essentially the regular BRS search interface with a few menus added to ease the pain of using a direct command language system. Now the OVID DOS (but not Windows) interface is available via dial-in or Telnet and not just on locally loaded systems. The old BRS interface is also still available.
Unlike many other Web sites that offer Medline, you will find that you can build search sets and printing and saving search results is convenient and available in many different formats.
Like Ovid, Silverplatter started as a provider of database systems to libraries, but now concentrates on databases and doesn't support networking technologies. It's strength has been a wide selection of databases in all fields. Its weakness has been the awkward Dos version of the SPIRS searching Interface. The WinSpires Windows version works much better.
AIDSLINE (AIDS Information onLINE)
- Subject: Acquired immunodeficiency syndrome (AIDS) and related topics
- Type: Bibliographic citations
- Coverage: All languages; publications from 1980 to present
- Updates: Weekly, with about 1,000 new citations added each month; the
file contains about 68,000 records
- Document Types: Journal articles, government reports, letters, technical reports, meeting abstracts/papers, monographs, special publications, theses, books and audiovisuals
CANCERLIT (CANCER LITerature)
- Subject: Major cancer topics
- Type: Bibliographic citations
- Coverage: Primarily English language items. Comprehensive and international scope since 1976; some citations were published as early
as 1963
- Updates: Monthly, with about 7,000 new citations added each month; the
file contains about 900,000 records
- Document Types: Journal articles, government reports, technical reports,
meeting abstracts and papers, monographs, letters, and theses
HealthSTAR (Health Services, Technology, Administration, and Research)
- Subject Clinical (emphasizes the evaluation of patient outcomes and the
effectiveness of procedures, programs, products, services, and
processes) and non-clinical (emphasizes health care administration and
planning) aspects of health care delivery; combines former HEALTH
(Health Planning and Administration) and HSTAR (Health
Service/Technology Assessment Research) databases
Type: Bibliographic citations
Coverage: Divided into two files based on year of publication: (1) a
current file covering 1990 to the present, and (2) a backfile covering
1975 through 1989; primarily English language, but international in
scope
- Updates Weekly, except for CATLINE records which are added monthly;
approximately 17,000 citations in each monthly update; current file and
backfile together contain about 2.5 million records
- Document Types Journal articles, technical and government reports,
meeting papers and abstracts, books and book chapters
- Special Features HealthSTAR contains relevant bibliographic records
from MEDLINE (1975 to present) and CATLINE (1985 to present), and unique
records from three sources: (1) records emphasizing health care
administration selected and indexed by the American Hospital Association
(AHA); (2) records emphasizing health planning from the National Health
Planning Information Center (only in the backfile); and (3) records
emphasizing health services research, clinical practice guidelines, and
health care technology assessment selected and indexed through NLM's
National Information Center on Health Services Research and Health Care
Technology (NICHSR). The file is produced by the AHA in cooperation with
the NLM. The Hospital and Health Administration Index, published by the
AHA, is produced from this file. Alternate source information is
provided for technical reports and related material selected by NICHSR
that may not be widely held by libraries.
MEDLINE (MEDlARS onLINE)
- Subject: Biomedicine
- Type: Bibliographic citations
- Coverage: All languages; publications from 1966 to the present. Recent
references are contained in the current file (MEDLINE); segmented
backfiles (currently BACK85, BACK80, BACK75, and BACK 66) contain older
material.
- Updates: Weekly, January through October and monthly,
November and December;
about 30,000 new citations are added each month.
The file contains about 7 million records.
The citations for each monthly update
are also searchable in a separate file called SDILINE
(Selective Dissemination of Information onLINE)
for those who need only the most recent literature.
- Document Types: Articles from more than 3,600 international biomedical
journals (some chapters and articles from selected monographs are found
in earlier years).
PDQ (Physician Data Query)
- Subject: Advances in cancer treatment, treatment protocols, information for patients, and criteria for patient acceptance in clinical trials. Doesn't use the typical MEDLARS interface, but a menu of cancer types and stages. The treatment protocols and patient information is also available via the Web on the CancerNet - NIH PDQ Gopher
- Type: Factual and referral
- Coverage: United States, Canada, and Western Europe; current
- Updates: Monthly
Return to Previous Page Position
-
- Subject: is NLM's newest database. It contains
in-process citations and abstracts to articles before they go into MEDLINE. The PREMEDLINE file is updated every weekday with basic citation data such as author, title, source, and abstract. These preliminary, unindexed citations have not gone through NLM's quality control process. (8/21/96)
TOXLINE (TOXicology Information onLINE)
- Subject: Toxicological, pharmacological,
biochemical and physiological effects of drugs and other chemicals
- Type: Bibliographic citations
- Coverage: Primarily English language items; international coverage
The database has been segmented: pre-1965 to 1980 material is found in
TOXLINE65, and 1981-forward citations are found in the TOXLINE file.
- Updates: Monthly, with about 10,000 new citations added each month; the
file contains about 1.8 million records
- Document Types: Journal articles, monographs, technical reports,
theses, letters, and meeting abstracts, papers and reports
TOXLIT (TOXicology LITerature from special sources)
- Subject: Toxicological, pharmacological, biochemical, and physiological effects of drugs and other chemicals
- Type: Bibliographic citations
- Coverage: Primarily English language items; international coverage. The
database has been segmented: pre-1965 to 1980 citations are found in
TOXLIT65, and 1981-forward citations are found in the TOXLIT file.
- Updates: Monthly, with about 10,000 new citations added each month; the
file contains about 1.65 million records
- Document Types: Journal articles, meeting papers, monographs, patents,
TOXNET (TOXicology data NETwork)
- TOXNET is a computerized collection of files on toxicology,
hazardous chemicals and related areas.
TOXNET files currently accessible include:
CCRIS (Chemical Carcinogenesis Research Information System)
- Subject: Chemical carcinogens, mutagens, tumor promoters, and tumor inhibitors
- Type: Factual
- Updates: Continuous; the file contains over 3,600 records
HSDB (Hazardous Substances Data Bank)
- Subject: Hazardous chemicals; toxic effects, environmental fate, safety and handling
- Type: Factual
- Coverage: Data is derived from a core set of standard texts and monographs, government documents, technical reports and the primary
journal literature.
- Updates: Continuous; the file contains about 4,400 records
RTECS (Registry of Toxic Effects of Chemical Substances)
- Subject: Potentially toxic chemicals
- Type: Factual
- Updates: Quarterly; the file contains about 115,000 records
- provides links to fact sheets from the NLM Specialized Information Service.
TRI (Toxic chemical Release Inventory) series
- Subject: Annual estimated releases of toxic chemicals to the environment and amounts transferred to waste sites
- Type: Factual
- Coverage: Currently, industrial submissions to EPA for the reporting
years 1987, 1988, 1989 and 1990
- Updates: New file added annually; TRI87 contains about 80,000 records;
TRI88 contains about 87,000 records; TRI89 contains about 86,000
records, TRI90 contains about 84,000 records.
(formerly Excerpta Medica) -- Files 72, 73
Coverage: June 1974 to the present
Updates: Weekly
Data Type: Bibliographic
Provider: Elsevier Science B.V., Amsterdam, Netherlands
The Excerpta Medica database, EMBASE, is one of the leading sources for searching the literature of biomedicine. It consists of abstracts and citations to over 3,500 biomedical and pharmacological journals published throughout the world. EMBASE is renowned for its coverage of the drug-related literature. Over 350,000 records are added each year to the database. The records are indexed by terms from EMTREE, a hierarchically ordered vocabulary of 35,000 medical and drug terms.
EMBASE on DIALOG is divided as follows:
File 72 1985 to the present EMBASNEW
File 73 June 1974 to the present EMBASALL
DIALINDEX Categories: BIOCHEM, BIOTECH, CASREGNO, ENVIRON, MEDENG, MEDICINE, NUTRIT, PHARM, PHARMR, POLLUT, RNMED, SAFETY, TOXICOL, TRADENMS
U.S. prices: $90/connect hour; $1.30/full format online type or offline print; $10.00/weekly DIALOG Alert; $20.00/biweekly DIALOG Alert (default)
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