Copyright laws protect authors, publishers, musicians, artists and others from having their work stolen or misused. Copying a song, a book or an image without permission is not legal. However, there are exceptions, which brings us to fair use.
Fair use exceptions were designed with education in mind. Fair use says that as a researcher you can copy sources for your own use when used for educational purposes--with limits.
This brief explanation of length of copyright & publications can help you determine if an author's work might be available for free, full text online.
Copyright protected life of the author + 70 years.
Copyright protected 95 years from date of publication.
All in the public domain.
You can copy full text articles from the library's databases for your own use. Copying them and distributing them to other people via email, blog or print probably would not be considered fair use. In EBSCO eBooks you can copy a limited number of pages from an eBook--the site automatically limits what you can do per publisher and title.
This is general information and does not constitute legal advice.