NASA astrophysics data system

A NASA-funded project which maintains four bibliographic databases containing more than 4.0 million records: Astronomy and Astrophysics, Instrumentation, Physics and Geophysics, and preprints in Astronomy. The databases cover all the major journals, many minor journals, conference proceedings, several observatory reports and newsletters, many NASA reports, and PhD theses.

Harvard-Smithsonian Center for Astrophysics
Article indexes, Electronic journals
Freely accessible to the public via the Internet.