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PubMed

PubMed is provided by the United States National Library of Medicine.

PubMed is a free search engine for accessing the MEDLINE database of citations and abstracts of biomedical research articles. The core subject is medicine, and PubMed covers fields related to medicine, such as nursing and other allied health disciplines. It also provides very full coverage of the related biomedical sciences, such as biochemistry and cell biology. It is offered by the United States National Library of Medicine at the National Institutes of Health as part of the Entrez information retrieval system. As with other indexes, the inclusion of an article or journal in PubMed is not endorsement. In 2007 MEDLINE contained over 17,000,000 records from more than 5,000 journals published in the United States and more than 80 other countries primarily from 1950 onwards. In addition to MEDLINE, PubMed also offers access to

OLDMEDLINE for pre-1966 citations. This has recently been enhanced, and records for 1951+, even those parts in the printed indexes, are now included within the main portion.
Citations to all articles, even those that are out-of-scope (e.g., covering plate tectonics or astrophysics) from certain MEDLINE journals, primarily the most important general science and chemistry journals, from which the life sciences articles are indexed for MEDLINE.
In-process citations which provide a record for an article before it is indexed with MeSH and added to MEDLINE or converted to out-of-scope status.
Citations that precede the date that a journal was selected for MEDLINE indexing (when supplied electronically by the publisher).
Some life science journals that submit full text to PubMed Central and may not have been recommended for inclusion in MEDLINE although they have undergone a review by NLM, and some physics journals that were part of a prototype PubMed in the early to mid-1990s.http://www.nlm.nih.gov/pubs/factsheets/pubmed.html

Many PubMed citations contain links to full text articles which are freely available, often in the PubMed Central digital library. In late 2007, the Consolidated Appropriations Act of 2007 (H.R. 2764) was signed into law and included a provision requiring the NIH to modify its policies and require inclusion into PubMed Central complete electronic copies of their peer-reviewed research and findings from its funded research. This is the first time the US government has required an Agency to provide open access to research and is an evolution from the 2005 policy, in which the NIH asked researchers to voluntarily add their research to PubMed Central.^[1] With an effective date of April 7, 2008, the Department of Health and Human Services has given notice: "The Director of the National Institutes of Health shall require that all investigators funded by the NIH submit or have submitted for them to the National Library of Medicine?s PubMed Central an electronic version of their final, peer-reviewed manuscripts upon acceptance for publication, to be made publicly available no later than 12 months after the official date of publication: Provided, That the NIH shall implement the public access policy in a manner consistent with copyright law."

PubMed is one of a number of search engines through which it is possible to search the MEDLINE database; the National Library of Medicine also leases the MEDLINE information to a number of private vendors such as Ovid and SilverPlatter--as well as many other vendors. PubMed has been available free on the Internet since the mid-1990s.

Information about the journals indexed in PubMed is found in its Journals Database, searchable by subject or journal title, Title Abbreviation, the NLM ID (NLM's unique journal identifier), the ISO abbreviation, and both the print and electronic International Standard Serial Numbers (pISSN and eISSN). The database includes all journals in all Entrez databases.

As of 20 October 2008, PubMed has 16,880,015 citations going back to the year 1865.^[2]

Searching PubMed

Telegram-style search
Clinical Queries / Systematic Reviews
Related Articles
Mapping to MeSH (headings) and Subheadings
Searching with tags and Boolean operators

Tags
Boolean operators

Alternative interfaces
See also
References
External links

Searching PubMed

For comprehensive, optimal searching in PubMed, it is necessary to have a thorough understanding of its core component, MEDLINE, and especially of the MeSH (Medical Subject Headings) controlled vocabulary used to index MEDLINE articles.

Telegram-style search

However, simple telegram-style search formulations can also be used, and they generally produce acceptable results^[3]. PubMed automatically links textwords to relevant MeSH terms. Aspects of the question can then be added successively, in a Google-like fashion, until a number of ?hits? judged manageable is achieved. No knowledge of actual MeSH terms, Boolean operators, English or American spelling, ?nesting?, or record-fields is required. PubMed?s intelligent search algorithm does (or implies) this in the background.

Clinical Queries / Systematic Reviews

A special feature of PubMed is the ?Clinical Queries? and ?Systematic Reviews? option which can be used to identify more relevant (robust) studies by automatically applying ?quality filters? to be applied to each search.

After a quick search, references which are judged particularly relevant can be marked and 'related articles' can be identified. If relevant, several studies can be selected and 'related articles' to all of them can be generated. The 'related articles' are then listed on order or 'relatedness' (not chronological order). To create the list of 'Related Articles' PubMed compares words from the Title and Abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm ^[4].

Mapping to MeSH (headings) and Subheadings

A strong feature of PubMed is its ability to automatically link to Medical Subject Headings (MeSH) and Subheadings. Examples would be: ?bad breath? links to (and includes in the search) ?Halitosis?, ?Writers cramp? to ?focal dystonia?, ?breast cancer? to ?breast neoplasms?. Where appropriate, these MeSH terms are automatically ?expanded?. Terms like ?nursing? are automatically linked to ?Nursing [Mesh]? or ?Nursing [Subheading]?. This important feature makes PubMed searches automatically more sensitive and avoids false-negative (missed) hits by compensating for the diversity of medical terminology.

Searching with tags and Boolean operators

Boolean operators

There are three Boolean operators: AND (intersection); OR (union); NOT (exclusion). NOT should be used with care as it may generate 'false-negative' results.

For example:

pnas drexler ke 1981

will yield a single reference, and is the equivalent of

pnas AND drexler ke AND 1981

whereas

pnas OR drexler ke OR 1981

will yield hundreds of thousands of articles, including all article published in 1981, all articles in PNAS (Proceedings of the National Academy of Sciences) and all articles by K.E. Drexler.

All Boolean operators are processed in a left-to-right sequence. The order in which PubMed processes a search statement can be changed by enclosing concepts in parentheses. The terms inside the parentheses are processed first as a unit and then incorporated into the overall strategy.

For example:

g1p3 AND (response element OR promoter)

is processed by ORing the search (response element OR promoter) first and then ANDing the resulting set of documents with g1p3.

Alternative interfaces

eTBLAST - a natural language text similarity engine for MEDLINE and other text databases.
GoPubMed - Explore PubMed/MEDLINE with Gene Ontology
HighWire Press - a medical search engine created by an online journal publishing house that searches within its collection of journals.
HubMed - An alternative interface to the PubMed medical literature database.
MeshPubMed - Explore PubMed/MEDLINE with Medical Subject Headings (MeSH)