There are many ways to find journal articles that have been posted online open access--often free of reuse restrictions.
If you're on campus, often the easiest thing to do is to Google or Google-Scholar search for the article, and follow the links. If you do this while on campus, you'll be able to connect to the full text of any articles that are either open access online or licensed by the Library (and accessible to you via CalNet).
If you're off campus and searching the open Web, you can still try Googling either the article title or the journal title, but you might not be able to read the full text of an article unless the article is posted open access. But there are MANY open access journal articles that are, indeed, online. Here are some other places you can check for full text articles online for free:
DOAJ indexes thousands of open access peer-reviewed research journals that span a wide variety of subjects from many publishers. DOAJ titles are included in the Library's catalog, with updates pushed out on a monthly basis.
Journal content in JSTOR published prior to 1923 in the United States and prior to 1870 elsewhere, freely available to anyone, anywhere in the world.
OMICS hosts over 700 open access journals in the sciences.
Excellent guide to historical U.S. newspapers that are freely available on the Internet.
Additionally, major publishers often provide a subset of their collections online under open access licenses as well:
Even if an article you're looking for isn't open access online, you can usually still find an electronic version via the Library catalog!! The library purchases and licenses thousands of journals and databases for use by students, faculty, and staff. Use the catalog to find the journal or article you're looking for, and paste a hyperlink to it in bCourses.
Here are tips on searching the Library catalog for electronic versions journal articles: