RePEc (Research Papers in Economics) is a collaborative effort of hundreds of volunteers in 82 countries to enhance the dissemination of research in Economics and related sciences. The heart of the project is a decentralized bibliographic database of working papers, journal articles, books, books chapters and software components, all maintained by volunteers.
Google Scholar provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: peer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations.
JSTOR contains full-text articles from selected journals in a broad range of disciplines, including African-American studies, art, ecology, economics, education, history, law, literature, music, general science, sociology, and statistics.
Coverage of most journals starts from the beginning and excludes the most recent three to five years.