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.
There is not yet a specific option to search for only full-text articles, but because most of the papers on the site are free access, it is not often that you encounter a paywall.
You must become a member to use the services, but registration is free and enables you to interact with other scholars around the world.
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.
The ar Xiv 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.
Sixty percent of its content is open access, and you can filter your search accordingly.
Run by Indiana University, the Digital Library of the Commons (DLC) Repository is a multidisciplinary journal repository that allows users to check thousands of free and open access articles from around the world.