Started in 1991, arXiv is a repository and distribution server for research articles in physics, mathematics, statistics, computer science, nonlinear sciences, and quantitative biology. arXiv is open access and operated by Cornell University Library.
The SPIE Digital Library contains an extensive research collection on optics and photonics from 11 peer-reviewed journals and over 8,000 conference proceedings. More than 18,000 conference papers and journals articles are added each year.
Covering Computer Science, Computer Engineering, Physics, and related subjects, IEL is an extensive collection containing almost 200 IEEE journals, magazines, and transactions as well as Institution of Engineering and Technology (IET) journals and magazines; 1,400+ IEEE conference titles; 20+ IET conference and seminar digests; and over 2,800 IEEE approved standards.
Compiled by the labs at CERN, DESY, Fermilab and SLAC, this database covers high-energy physics including journal articles, preprints, e-prints, technical reports, conference papers, and theses. It is based on SPIRES, and contains records from 1974 forward.