Provides a unit conversion calculator for energy, pressure, volume, temperature, mass, and power. Also has an interactive periodic table and Ideal Gas Unit calculator that uses both SI and English units.
A comprehensive physical reference data site from the National Institute of Standards and Technology (NIST). Contains databases, handbooks and links to molecular, atomic, spectroscopic data and much more. Also includes a calculator and searchable database of basic constants and conversion factors.
National Center for Biotechnology Information's databases provide information on the biological activities of small molecules. Locate bioassay and substance information records as well as compound structures.