Since 1879, the National Library of Medicine has published the
Index Medicus, a monthly guide to articles, in nearly five thousand selected journals. The last issue of Index Medicus was printed in December 2004, but this information is offered in the freely accessible
PubMed, among the more than fifteen million
MEDLINE journal article references and abstracts going back to the 1960s and 1.5 million references going back to the 1950s. In 1986 Director Lindberg's
Grateful Med project, named after the
Grateful Dead band, facilitated direct access to the NLM MEDLINE database by making it significantly more affordable for all health professionals. The National Library of Medicine runs the
National Center for Biotechnology Information, which houses
biological databases (PubMed among them) that are freely accessible on the Internet through the
Entrez search engine and
Lister Hill National Center For Biomedical Communications. As the United States National Release Center for
SNOMED CT, NLM provides SNOMED CT data and resources to licensees of the NLM
UMLS Metathesaurus. NLM maintains
ClinicalTrials.gov registry for human interventional and observational studies. Additionally NLM runs ChemIDplus, which is a
chemical database of over 400,000
chemicals complete with names, synonyms, and
structures. It includes links to NLM and other databases and resources, including links to federal, state and international agencies. ==Toxicology and environmental health==