scholarly-metadata
Semantic Scholar (Academic Graph)
An academic search engine and citation graph from the Allen Institute for AI, covering about 220 million papers with citation context. Search on the website, or use the free Graph API, which needs no key but runs on a shared, heavily throttled anonymous pool. Especially handy for following citation trails and seeing how papers relate. Under load the keyless API is frequently rate-limited, so the website is the more dependable route.
Why it’s useful & how it works
Keyless works but on a shared throttled pool (~5000 req/5min across ALL anon users) -> 429 under load, backoff mandatory. S2 no longer issues keys to gmail addresses, so this account stays on the shared pool.
What’s inside
~220M+ papers.
API access
https://api.semanticscholar.org/graph/v1/paper/DOI: <doi>?fields=...
Access
Programmatic API access (a key may be required — see the API tag).