Here you will find links to Open Access search engines and tools to find research that is freely available to access.
BASE (Bielefield Academic Search Engine) - a multidisciplinary search engine to find scholarly resources. Links to citations and where available Open Access literature.
Core - one of the world's largest collection of Open Access research papers.
Directory of Open Access Books - contains Open Access books.
Directory of Open Access Journals (DOAJ) - contains open access, peer reviewed journals.
OAPEN - Open Access academic e-books.
Open Access Button - a service that helps you find free, full text articles legally.
UCL Press - Open Access - Open Access e-books published by UCL Press.
Unpaywall - similar to Open Access button but is a browser extension you add to your web browser.