Provides access to collection of more than 80 databases of well-documented numeric data (including the NIST Chemistry WebBook and other sources of chemical and physical properties) from the National Institute of Standards & Technology (NIST). The data are from a variety of scientific disciplines including biotechnology, chemistry, materials science, mathematical modeling, physics, and more. Searchable by keywords, properties, and substances.

http://srdata.nist.gov/gateway/