As a retired college librarian, I know how academic libraries get their electronic materials: they buy a license. Almost always the license states firmly that the materials can be used remotely ONLY by current faculty, staff, and students. Most licenses allow on-site use by others, but many libraries, including the University of Pennsylvania, have a local policy against that. Temple and Penn State do let visitors access journals electronically on computers in their libraries.

If you have a library card, you can remotely access databases and fulltext journals through the Free Library of Philadelphia website. On the library's webpage, click on "databases" and you'll be taken to a list. "Expanded Academic ASAP" is a database that includes many journals. There aren't as many journals as the UPenn, but you may find something you want.