There are a multitude of scientific articles, and thousands are published every year. There are also dozens of search and access platforms for these articles.
Web of Science is one of the “great” article searchers.Web of Science
Scopus One of the leading search engines, known for the quality of the articles.
Google Scholar Google’s search power, voted for scholarly articles. Less judicious than those mentioned above, but goes deeper.
Biblioteca Google Scholar
Microsoft Academic Research powerful search engine with very interesting visualizations
Microsoft Academic Research
Paperity multidisciplinary aggregator for searching Open Access articles
SciELO Platform that brings together the Brazilian scientific production
Science.gov Mechanism that aggregates much of US scientific production
EU Science Hub Search for publications from EU countries
EU Science Hub
My Science Work Collaborative Collection of articles
My Science Work
Paperscape Impressive visualization of the arXiv collection, an open repository of articles and papers