Search Tools allow you to find articles by subject, author, keyword, or often other parameters. These are some of the best free tools. Please note that in most cases you will not be able to directly access the full text of articles you find, but will need to retrieve them from one of the open-access journal sites or from your library. The "Information by Subject" tab of this guide has a more comprehensive listing of search tools for different subject areas.
Many publishers of scientific and technical information allow you to search their content for free, even though they don't allow you to read their articles or papers for free. The following is a list of major scientific and technical publishers that allow free searching but not free access to the content.
These are some free search tools for finding books. Books are seldom available for free due to copyright, unless they were published more than 90 years ago.