There are many services that provide access to openly available content:
Provides a simple way to broadly search for scholarly literature across many disciplines and sources: articles, theses, books, abstracts and court opinions, from academic publishers, professional societies, online repositories, universities and other web sites. | |
OAIster | A union catalogue of more than 25 million records representing open access resources harvested from open access collections worldwide |
CORE | COnnecting REpositories aggregates millions of scholarly articles from open access repositories. As of September 2018, it linked to over 134 million items |
BASE | Bielefeld Academic Search Engine (Bielefeld University, Germany) provides more than 50 million documents harvested from repositories |
Digital Commons Network | The Digital Commons Network brings together free, full-text scholarly articles from hundreds of universities and colleges worldwide |
JURN.org | JURN has a core collection of over 4,000 arts and humanities ejournals, all open access or otherwise free |
Dissem.in | A new service which offers researchers the ability to find the open access status of their publications |