An authoritative resource consisting of tables of data and current international recommendations on nomenclature, symbols, and units, this work continues to be the most accessed and respected scientific reference in the world.
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This handbook is designed to provide a selection of the most important and frequently used atomic spectroscopic data in an easily accessible format.

Critically evaluated data from the National Institute for Standards and Technology. Available data includes physical constants, atomic and molecular data, nuclear physics, condensed matter, and more.

The Digital Library for Physics, Astrophysics, and Instrumentation, the Astrophysics Data System (ADS) is a NASA-funded project which maintains searchable bibliographic databases for these fields and provides full-text scans of some scholarly astronomical literature.

Access to many images published in peer-reviewed AAS journals

The Planetary Data System (PDS) is a long-term archive of digital data products returned from NASA's planetary missions, and from other kinds of flight and ground-based data acquisitions, including laboratory experiments. But it is more than just a facility - the archive is actively managed by planetary scientists to help ensure its usefulness and usability by the world wide planetary science community.

NED is a comprehensive database of multiwavelength data for extragalactic objects, providing a systematic, ongoing fusion of information integrated from hundreds of large sky surveys and tens of thousands of research publications.