BASE

BASE (Bielefeld Academic Search Engine) is a specialized academic search engine developed and maintained by Bielefeld University Library in Germany. It indexes over 400 million scientific documents sourced from more than 12,000 content providers worldwide, including institutional repositories, digital libraries, preprint servers, and open-access journals. The platform is designed to help researchers, students, librarians, and other academic users discover scholarly materials across disciplines without the noise of general web search results. The search engine supports both basic and advanced search modes. In basic search, users can enter keywords, phrases, or document identifiers to retrieve relevant results. Advanced search allows filtering by author, title, subject, year, language, document type, and source. Users can also limit results to open-access materials or peer-reviewed publications. A browsing feature enables exploration by subject categories, content providers, or publication date. BASE provides a search history function that records past queries for easy retrieval. Registered users can log in to save searches, create alerts, and manage personal settings. The platform offers an ORCID iD integration, allowing researchers to link their publications directly to their ORCID profiles. For content providers and developers, BASE exposes an HTTP interface and an OAI-PMH interface for programmatic access to the index, enabling metadata harvesting and custom integrations. A set of tools supports quality control and metadata validation. The “Golden Rules” guide helps content providers ensure their metadata meets indexing standards. The “Validate Source” tool, called OVAL, checks the compatibility of OAI repositories with BASE requirements. These features help maintain