1findr is a commercial platform for searching articles in peer-reviewed journals which also offers a free version. This version allows no advanced search option apart from narrowing results to include open access articles only.
Bielefeld Academic Search Engine and index for academic resources contains about 120 million documents. Around 60 % of its indexed content is open access.
CORE’s search engine and index for aggregated research publications from repositories and journals globally. Developed by JISC and the Open University it offers access to around 133 million articles.
Apart from searching for publications and the possibility to search for cited and citing articles, Dimensions also indexes grants, patents, and clinical trials. The free version offers limited possibilities.
DOAJ is a list of open access journals and a search service finding peer-reviewed and scholarly journals and articles.
Google Scholar is an index and search engine for academic content on the web.
OpenDOAR is a searchable global directory of open access repositories and their policies.
OSF Preprints is a platform with openly accessible preprints, or submitted manuscripts which are publically distributed before acceptance and peer-review in a traditional scientific journal. An advantage of publishing preprints is the speeding up of scientific communication and of sharing research results earlier, as it can take a long time between submission of an article till publication.
OSF Preprints is developed by Centre for Open Science (COS), a non-profit organisation with the goal of greater openness and reproducible research.
Zenodo is an open archive developed by CERN where researchers can deposit publications, preprints, software, and research data.
arXiv is a preprint archive mainly for physics, mathematics, computer sciences and related sciences. Run by Cornell University.
The Humanities Commons CORE repository is intended for open access articles, monographs and other publications and resources in the humanities. Humanities Commons is a nonprofit operation run by the MLA.
SocArXiv is an open archive of the social sciences for preprints, working papers and other outputs. It is operated by the University of Maryland and developed by the Center of Open Science (COS).