The SAO/NASA Astrophysics Data System (ADS) is a digital library portal for researchers in astronomy and physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 13 million records covering publications in Astronomy and Astrophysics, Physics, and the arXiv e-prints. Abstracts and full-text of major astronomy and physics publications are indexed and searchable through the new ADS modern search form as well as a classic search form.

SSOAR collects electronic full texts from the domain of the Social Sciences and makes these texts available according to the Berlin Declaration on Open Access to Scientific Knowledge.

The SSRN eLibrary consists of two parts: an Abstract Database containing abstracts on over 60,500 scholarly working papers and forthcoming papers and an Electronic Paper Collection currently containing over 38,400 downloadable fulltext documents in Adobe Acrobat pdf format. The eLibrary also includes the research papers of a number of Fee Based Partner Publications.