3. Directory of Open Access Journals
A multidisciplinary, community-curated directory, the Directory of Open Access Journals (DOAJ) gives researchers access to high-quality, peer-reviewed journals. It has archived more than two million articles from 9,519 journals, allowing you to either browse by subject or search by keyword.
The site was launched in 2003 with the aim of increasing the visibility of open access scholarly journals. Content on the site covers subjects from science to law to fine arts and everything in between.
4. Education Resources Information Center
The Education Resources Information Center (ERIC), of the Institution of Education Sciences, allows you to search by topic for material related to the field of education. Links lead to other sites, where you may have to purchase the information, but you can search for full-text articles only.
The service primarily indexes journals, grey literature (such as technical reports, white papers, and government documents), and books. All sources of material on ERIC go through a formal review process prior to being indexed.
5. arXiv e-Print Archive
The arXiv e-Print Archive has been around since 1991 and is a well-known resource in the fields of mathematics and computer science. It is run by Cornell University Library and now offers open access to more than one million e-prints.