Multidisciplinary database that provides some full text and some citations for thousands of journals. A good starting place for beginning research and quickly finding articles for a variety of topics.
Lots of articles covering range of topic areas, weighted towards sciences, but also includes social science titles. Easy basic search, flexibility with advanced search and linked citations makes it easier to find related articles.
Open-access archive for scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics.