ChemIDplus NLM NIH

U.S. National Library of Medicine
National Institutes of Health, Health & Human Services

ChemIDplus is a free, web search system that provides access to the structure and nomenclature authority files used for the identification of chemical substances cited in National Library of Medicine (NLM) databases. ChemIDplus also has structure searching and direct links to resources at NLM, federal agencies, U.S. states, and scientific sites. The database contains more than 400,000 chemical records, of which over 300,000 include chemical structures.