"MEDLINE® is the National Library of Medicine® (NLM®) journal citation database. . .The MEDLINE database is directly searchable from NLM as a subset of the PubMed® database as well as through other numerous search services that obtain the data from NLM’s Data Distribution program. In addition to the comprehensive journal selection process, what sets MEDLINE apart from the rest of PubMed is the added value of using the NLM controlled vocabulary, Medical Subject Headings (MeSH®), to index citations.
PubMed has been available since 1996. Its more than 28 million references include the MEDLINE database plus . . . content not already in the MEDLINE database."