Report:MEDLINE/Common Ways to Access/Individual System Details/PubMed

PubMed

Additional Commentary

PubMed is the free-use search system developed by the National Library of Medicine (NLM), the same governmental organization that produces MEDLINE itself. PubMed is available via the National Center for Biotechnology Information Entrez retrieval system which hosts multiple other free-use search systems related to biology, chemistry, and health related topics.

The PubMed homepage.

Not only does PubMed offer the full range of MEDLINE (and OLDMEDLINE) coverage (from 1949-present), but users can also access some additional content, including: records (including off-topic records, usually general science or chemistry) from certain MEDLINE journals; records prior to the journal being selected for inclusion into MEDLINE; and some life science journals that submit full text to PubMedCentral and have also received a qualitative review by NLM.^[1] Additionally, "in-process records" (records prior to the completion of indexing) and "publisher supplied records" (records prior to the start of indexing) are available through PubMed.

While full text of cited articles are not available within PubMed itself, links to outside sources of full text articles are given on many of the individual record view pages. Users can limit the results to those that have links to full text articles, links to free full text articles, and/or abstracts available.

Testing shows that for a typical search, "blood thinner," results that have links to full text articles are around half of the total number of results, while results that have links to free full text articles are around 1/6th of the total number of results.

Users are given the option to enter a query directly in the search bar on the homepage or go to an advanced search page. The advanced search page offers searching within any of the fields available in MEDLINE in a graphical interface. Queries can also be further limited and modified after being run by using the Limits tab. A search history is displayed at the top of the advanced search page, complete with functionality allowing users to see previous queries, save individual queries, and combine queries. Queries are time-stamped; search histories will be cleared after eight hours of inactivity, and can also be accessed from the History tab within the interface.

The system offers additional limits and fields which are not pictured. The top part of this form can be expanded to display the search history, which allows users to combine previously-run queries..

PubMed "translates" basic user queries from these two search forms into more complex and thorough searches that include Medical Subject Headings (MeSH terms) and other supplementary concept records. This translation is called "Automatic Term Mapping." To view the query translation, users can select the Details tab within the interface. The Details interface can also be used as a command line-style interface.

The Details tab shows users exactly how the database was searched. The "Query Translation" seen at the top of this screenshot is the syntax used by PubMed to search the database. The original user input, "blood thinner," is seen at the bottom of the screenshot under "User query."

The Clipboard tab within the interface allows users to temporarily save records of interest. In order to save records, users must sign up for a free NCBI account and login prior to using PubMed. The hit list and "My NCBI" saved results both share a common layout, showing the title, authors, publication, and status of the record (e.g. indexed for MEDLINE or merely "in process").

The hit list and saved records have the same layout. An example of saved results is shown above.

Editor's Note:

PubMed is an excellent search system that puts the full utility of MEDLINE at the fingertips of users. The interface offers a range of different options, including the simplicity of single line keyword entry, the comprehensive limiting and field searching ability of the advanced search section, and the complexity of a command line interface in the Details tab.

The access to the publisher-provided and in-process data through PubMed is a big benefit to the system. Since PubMed is run by the same organization that provides and synthesizes MEDLINE, this additional data can be provided before the records are ever indexed by the system. Users who want the most cutting edge records ought to consult PubMed for this reason, if nothing else.

Allowing users to view detailed search histories as well as save individual records to multiple folders (available for registered users- sign up is free) are features typical of for-pay systems and cater to the needs of professional searchers.

The most interesting and useful aspects of PubMed, however, are the ability of the system to link to full text versions of the records and the ability of the system to automatically incorporate Medical Subject Headings and supplementary concept records into searches.

Additionally, in PubMed, the number of full text documents available merely one click away from viewing an individual record is greater than the number of full text documents available on-site for EBSCOhost, a for-pay search system that touts its enhanced full-text coverage. Even when solely comparing free full text documents available only a link away, PubMed comes out even or slightly ahead of EBSCOhost (although coverage is not congruent, and one may have full text the other does not and vice versa).

MEDLINE on PubMed offers many great, free features such as pulling subject headings into search queries, which makes searching easy and powerful for all users, regardless of experience as a searcher or with MEDLINE itself. The only downside to producing these extra hits is that there is no relevancy sorting within PubMed to prioritize the abundance of information.