Some sources will include full-text, but others will include the 
button which links to full-text when available and if not available, gives you the option to request articles for free through Interlibrary Loan's ILLiad service.
If you're looking specifically for books and ebooks, your best bet is to use the SLU Libraries' Catalog.
Look for books published by university presses and scholarly associations, written by authors with degrees and credentials in the field. Scholarly or academic books will also cite their sources and will have a lengthy list of references.
