In most cases journal articles will be immediately available online. However, a database may sometimes describe an article but not actually include a copy. You can search for the title of a journal in the eJournals directory to see if the journal is available in a different database. The library subscribes to over 200 databases, so it is usually worth checking.
You may also search the title of a journal in the library catalog to see if the library has a physical subscription in the Periodicals Collection. The catalog will provide a call number and note the volumes and years owned by the library.
If any particular article is just entirely unavailable, submit an Interlibrary Loan request to obtain a copy from another library.