BASE (Bielefeld Academic Search Engine)
BASE is one of the world's most voluminous search engines especially for academic web resources. BASE provides more than 100 million documents from more than 5,000 sources. You can access the full texts of about 60% of the indexed documents for free (Open Access). BASE is operated by Bielefeld University Library.
DOAJ is an online directory that indexes and provides access to high quality, open access, peer-reviewed journals.
All journals that were accepted into DOAJ before March 2014 are now required to reapply.