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Research methodology - Course files - Internet and PubMed/Medline - Searching PubMed

GQuery - PubMed - MEDLINE


GQuery: Global Cross-database NCBI search (formerly Entrez) is the integrated, text-based search and retrieval system used at National Center for Biotechnology Information (NCBI) for the major databases, including PubMed, Nucleotide, Protein, Genome, Taxonomy, and others.


PubMed is a Web-based retrieval system developed by NCBI at the National Library of Medicine. It is part of NCBI's retrieval system. PubMed is a database of bibliographic information drawn primarily from the life sciences literature. The PubMed database includes more than 23 million citations: 23823088 items as of May 14, 2014, with 4324845 citations of free full text articles. As of May 14, 2014, 5648 journals are indexed in MEDLINE.

PubMed coverage

PubMed provides access to bibliographic information that includes MEDLINE, as well as:

  • 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 OLDMEDLINE citations that have not yet been updated with current vocabulary and converted to MEDLINE status.
  • Citations to articles that are out-of-scope (e.g., covering plate tectonics or astrophysics) from certain MEDLINE journals, primarily general science and general chemistry journals, for which the life sciences articles are indexed with MeSH for MEDLINE.
  • Some life science journals that submit full text to PubMed Central (PMC) and may not yet have been recommended for inclusion in MEDLINE although they have undergone a review by National Library of Medicine - National Institutes of Health (NLM), and some physics journals that were part of a prototype PubMed in the early to mid-1990's.
  • Citations to author manuscripts of articles published by National Institutes of Health (NIH)-funded researchers.


MEDLINE is the NLM bibliographic database that contains references to journal articles in the life sciences with a concentration on biomedicine. A distinctive feature of MEDLINE is that the records are indexed with NLM's controlled vocabulary, the Medical Subject Headings (MeSH).


MeSH is the acronym for "Medical Subject Headings." MeSH vocabulary is used for indexing journal articles for MEDLINE. The MeSH controlled vocabulary is a distinctive feature of MEDLINE. MeSH terms are arranged in a hierarchical categorized manner called MeSH Tree Structures.