In general, the online database links to the full-text journal article if it is available. There may be a link or an icon that indicates the full-text is available.
If you are not able to determine if the library owns a journal, use the CitationLinker which is used to locate fulltext for a specific article using its PMID, author or citation information.
If you are unable to find articles online the Library can order them via InterLibrary Loan for you. This service is free to students, and available for a nominal fee for faculty, staff and the general public.