“Semantic Scholar is a free, nonprofit, academic search engine from AI2….See the Semantic Scholar FAQ

• “Semantic Scholar helps researchers find better academic publications faster. Our engine analyzes publications and extracts important features using machine learning techniques. The resulting influential citations, images and key phrases allow our engine to “cut through the clutter” and give you results that are more relevant and impactful to your work…
• Semantic Scholar is committed to supporting high-impact research and engineering by providing universities and organizations access to our data. Please visit http://labs.semanticscholar.org/corpus/ to find data to support your research. We request that any published research that makes use of this data cites the paper provided.
• We have millions of articles in our index and continually add more. We use a variety of carefully tuned mechanisms to make sure we only index high-quality publications. If a valuable publication appears to be missing from our index please send us a publicly accessible link where we can access the publication in PDF form. Please note, we are unable to add papers from social sites like ResearchGate and Google Scholar at this time…”