#doi

Scholarly citations as open data — powered by OpenCitations (COCI), the open citation index. Unlike a metadata lookup, OpenCitations treats every citation as a first-class object: given a DOI you can list the papers that cite it (incoming citations) and the papers it references (outgoing), each annotated with its OpenCitations Identifier (OCI), the date the citation was created, the timespan between the two works, and whether it is a journal- or author-self-citation. Plus quick citation and reference counts for any DOI. It is built for citation-network and bibliometric work — research-impact analysis, self-citation detection, citation-timespan studies and science mapping — and is distinct from scholarly-metadata services (Crossref, OpenAlex). From a single paper to a whole reference graph, ideal for bibliometrics, research-analytics and reference-management tools. Open data from OpenCitations (CC0).

api.oanor.com/opencitations-api

DataCite as an API — the global registry of DOIs (Digital Object Identifiers) for research outputs. Where Crossref registers DOIs for journal articles, DataCite registers and describes DOIs for research data, software, samples, dissertations, preprints, models, images and other outputs, from repositories such as Zenodo, Dryad and thousands of institutions. /v1/search?query=climate full-text searches the registry and can be narrowed by resource type (type=dataset, software, text, image, audiovisual, collection, model and more), returning each DOI with its title, type, creators, publisher and publication year. /v1/doi?id=10.5281/zenodo.3509134 returns a single DOI's full metadata — title, resource type, creators, publisher, publication year, description, subjects, version, license and registration date. DOIs look like 10.5281/zenodo.3509134 (Zenodo) or 10.5061/dryad.xxxx (Dryad). Ideal for research-data discovery and citation, data-repository and reference-management tools, software-citation features and reproducibility workflows. Metadata is CC0 from DataCite. This is the registry of research data and software DOIs — distinct from the journal-article DOI index (Crossref) and from preprint and open-access services.

api.oanor.com/datacite-api

Search scholarly literature and look up rich publication metadata from Crossref, the DOI registry behind millions of journal articles, books, chapters, conference papers and datasets. Full-text search across 150+ million works with relevance or citation sorting and optional filters, retrieve any work by its DOI (plain, doi: or URL form accepted), and search journals and publishers. Every work comes back as a clean record with title, authors and ORCIDs, journal/container, publisher, publication date, volume/issue/page, ISSN/ISBN, abstract, subjects, license and citation count. Authoritative open scholarly metadata delivered through a fast, reliable API — ideal for reference managers, repositories, research analytics, discovery tools and academic apps.

api.oanor.com/crossref-api