LitSuggest, developed by the NCBI/NLM, employs machine learning and information retrieval methodologies to generate document recommendations and categorized publication sets. Free
Scite is a citation tool using machine learning analyzing over 23 million full-text publications to power Smart Citations, which allows users to analyze citations. Fee
Semantic Scholar provides access to AI-driven search and discovery tools, along with open-access resources, and indexing of over 200 million academic papers from publisher partnerships, data providers, and web crawls. Free