Can I use a standard licensed image as a cover image of an academic journal?

Yes sure. the criteria however is that the print run stays under 500k (including e-books or similar). And a second criteria is, that the asset is not the main incentive to buy the item (like it would be with a mug). I cannot know how much your print run is, but for the second criteria, I'm pretty sure that you meet the requirement. 

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).