Use Google Scholar to search for scholarly books and articles.
1) http://americanliterature.com/100-great-short-stories
2) http://www.englishlibrary.org/stories.html
3) http://www.classicshorts.com
4) http://americanliterature.com/twenty-great-american-short-stories
5) http://www.openculture.com/2013/10/read-14-short-stories-from-nobel-prize-winning-writer-alice-munro-free-online.html
The library has more than 500 databases where you can search for articles, images, audio files videos and more. The list of databases below is just a sampling of what's available. More library databases are available at http://ucmercedlibrary.info/doing-research/databases.
Search by subject or browse full text of more than 500 scholarly journals in social sciences, humanities, and sciences, to their earliest issues. Many titles extend as far back as late 19th or early 20th centuries; most recent 3-5 years not included.