The URL in your address bar IS a persistent link.
There is also a "Permalink" link that appears in each result. It will take the user to that result list in Summon, and then they can link to full text from there.
If you click through to a full text article from Summon, the link in your browser bar is a persistent link IF the linking sidebar (open or collapsed) is on the right. Otherwise, follow the instructions for the individual provider.