arXiv is a curated research-sharing platform open to anyone. As a pioneer in digital open access, arXiv.org now hosts more than two million scholarly articles in eight subject areas, curated by our strong community of volunteer moderators.

arXiv offers researchers a broad range of services: article submission, compilation, production, retrieval, search and discovery, web distribution for human readers, and API access for machines, together with content curation and preservation. Our emphasis on openness, collaboration, and scholarship provide the strong foundation on which arXiv thrives.

Instrumentation Abstract Service is part of Astrophysics Data System (ADS), and is operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS is a digital library portal for researchers in astronomy and physics. The ADS maintains three bibliographic databases containing more than 10.1 million records including astronomy and astrophysics, physics, and arXiv e-prints. All abstracts and articles in the ADS are copyrighted by the publisher and their use is free for personal use only.

INIS (The International Nuclear Information System) hosts one of the world's largest collections of published information on the peaceful uses of nuclear science and technology. It offers online access to a unique collection of non-conventional literature. INIS is operated by the International Atomic Energy Agency (IAEA) in collaboration with over 150 members.

Scopus is a curated abstract and citation database of scholarly literature across 240 disciplines, covering documents dating back to 1788, cited references from 1970 onward, author profiles, books, publishers and institutional profiles.

A multidisciplinary database which provides access to 37 ProQuest databases, with a variety of content across more than 160 subjects including business, science and technology, health and medical, social science, arts and humanities, and international news. Contents include abstract, index, and full text articles.