Base: Bielefeld Academic Search Engine
BASE is one of the world's most voluminous search engines especially for academic web resources. BASE is operated by Bielefeld University Library.
BASE collects and indexes the metadata of web documents, provides more than 90 million documents from more than 4,000 sources. You can access the full texts of about 60% of the indexed documents for free (Open Access).
Academic search engine for students and researchers. Locates relevant academic search results from web pages, books, encyclopedias, and journals
The CORE collection contains millions of Open Access publications aggregated from institutional repositories, archives and journals. The collection is mainly composed of research articles from both humanities and sciences.
Search millions of free academic articles, chapters and theses.
Q-Sensei Scholary Search Engine searches and browses through their collection of the following sources: ArXiv, Ingeta Connect, LoC, PubMed, RePEc
Google Scholar provides a simple way to broadly search for scholarly literature across many disciplines and sources