Open Access (OA) scholarship is research that can be read online for free without copyright restrictions. Reaching the broadest readership without preventing those who cannot afford the high cost of journal publication, is the OA Goal.
Search thousands of OER Textbooks, Courses, Course Materials, Public domain books with over 155,000 open access records.
There are many places to begin your research. A good place to begin is Oaister which has over 30,000,000 open access records.
Google Scholar provides a mixture of OA and non-OA sources. Many will show links from database providers.