1951 - present. Includes more than 22 million citations for biomedical literature from MEDLINE, life science journals, and online books. PubMed facilitates searching across several NLM literature resources including MEDLINE, PubMed Central, and Bookshelf. Citations may include links to full-text content from PubMed Central and Bookshelf. MEDLINE articles are indexed with MeSH (Medical Subject Headings). Use Get it at UC to locate the full text when not otherwise available.