As of January 2013, the COnnecting REpositories (CORE) system, hosted at The Open University, provides access to millions of open access research articles aggregated from over 250+ repositories worldwide. The collection contains about 10 million metadata records and 1+ million full-text open access articles. The CORE system continuously updates the aggregated information, synchronising the metadata and content held in the provider repositories and including new repositories. The content of the collection can be accessed via the CORE API.
API access. The CORE API (http://core.kmi.open.ac.uk/api/doc) allows searching the collection, downloading full-text content (in plain text or pdf), finding related documents, accessing citation information or retrieving content statistics. The API is free to use and requires only an API key which is provided by the CORE team. There are two version of the API: a RESTful API (typically the choice for most applications), providing data in XML or JSON, and a Linked Open Data SPARQL endpoint (can be practical for systems that need to connect information from multiple sources).
Please check the CORE website, check information about the CORE family of projects (CORE, ServiceCORE and DiggiCORE) or contact the CORE team (Petr Knoth) for more information.