The 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.

The Astrophysics Data System (ADS) is a NASA-funded project which maintains three bibliographic databases containing more than 5.1 million records: Astronomy and Astrophysics, Physics, and ArXiv e-prints. The main body of data in the ADS consists of bibliographic records, which are searchable through our Abstract Service query forms, and full-text scans of much of the astronomical literature which can be browsed though our Browse interface. Integrated in its databases, the ADS provides access and pointers to a wealth of external resources, including electronic articles, data catalogs and archives. We currently have links to over 5.3 million records maintained by our collaborators.