Lisbon universities are:
In your university you will find a library (biblioteca), and many others study rooms. But if you are a fond of studying out of your place, we suggest you the municipaly libraries:
http://blx.cm-lisboa.pt/
Specially at the periods before the examinations, the coffee places starts to be full of students. Many owners let you stay there studying. Some of them have even internet access. We can suggest you some! Just ask us.