Not every database will provide the full text of every article you find. If you aren't instantly connected to the article's full text, keep an eye out for the Find This for Me link:
If you still can't get access, search Google Scholar or request it through Delivery/Interlibrary Loan:
​Make sure to set your Google Scholar library preferences so you can get the full text of articles through University of Nebraska-Lincoln Libraries subscriptions.
From the Scholar homepage: