Ulrichsweb™ is the authoritative source of bibliographic and publisher information on more than 300,000 periodicals of all types–academic and scholarly journals, Open Access publications, peer-reviewed titles, popular magazines, newspapers, newsletters, and more from around the world.
In the JSTOR Database, Find a link next to the title of the journal, named "Publication Info." That will pop up the publication info where you will find the ISSN!
Once you select an article, notice the ISSN on the bottom on the detailed record page of the database.
To find the ISSN in the Science Direct database, you may need to go to the Journal itself.
Click Publications and select the journal you're seeking.