Biomedical citations and abstracts (MEDLINE and OLDMEDLINE) from the U.S. National Library of Medicine. Additional citations, approximately 1% of the database, are from other sources.
PubMed provides access to bibliographic information that includes MEDLINE, OLDMEDLINE, as well as:
-The out-of-scope citations (e.g., articles on plate tectonics or astrophysics) from certain MEDLINE journals, primarily general science and chemistry journals, for which the life sciences articles are indexed for MEDLINE.
-Citations that precede the date that a journal was selected for MEDLINE indexing.
-Some additional life science journals that submit full text to PubMedCentral and receive a qualitative review by NLM
PubMed's in-process records provide basic citation information and abstracts before the citations are indexed with NLM's MeSH Terms and added to MEDLINE. New in-process records are available in PubMed daily (Tuesday through Saturday) and display with the tag [PubMed - in process]. New citations that have been indexed with MeSH terms, publication types, GenBank Accession numbers, and other indexing data are also available daily (Tuesday through Saturday) and display with the tag [PubMed - indexed for MEDLINE].
As of March, 2010 the MEDLINE/PubMed subset contains over 20 million citations produced during 63 years of indexing of the biomedical literature.