1) ScienceOpen is an incredible research and publishing network offering open access content from more than 37 million articles in all areas of science. Although you do need to register to view the full text of the articles, registration is free. The advanced search function is highly detailed, allowing you to find precisely the research you’re looking for.
2) The Social Science Research Network (SSRN) is a collection of papers from scholars in the social sciences community. The site offers more than 775227 research papers from 361117 researchers across 30 disciplines.
3) ERIC is an online library of education research and information, sponsored by the Institute of Education Sciences (IES) of the U.S. Department of Education. The service allows you to search by topics related to education. Links lead to other sites, where you may have to purchase information, but you can search for full-text articles only.
ERIC indexes journals, books and grey literature (such as white papers, technical reports and government documents). All sources of material on ERIC go through a formal review process prior to being indexed.