Google Scholar - Google Scholar is a freely accessible web search engine that indexes the full text of scholarly...
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.
Scopus - Scopus is a bibliographic database containing abstracts and citations for academic journal articles.
ResearchGate - Access scientific knowledge, and make your research visible
ACI Scholarly Blog Index - ACI is revolutionizing the way people conduct research by enabling them to find the content they’ve...
Synthical - AI-powered collaborative research environment. You can use it to get recommendations of articles based on reading history, simplify papers, find out what articles are trending, search articles by meaning (not just keywords), and so on.