It depends - maybe three quarters of the abstracts took about a minute, sometimes less, since many are unreliable reports of drug tests that are closer to ads than info; there's also citation mongering resulting in three articles from exactly the same study, by the same authors saying the same result differently; plus many studies are confirmations from one population to another or are unique to tiny genetic lineages without broad implications; also many are review articles just in a new language or me-too studies. Others concern such topics as patient education improvements as opposed to changes in base medical knowledge. As for preliminary studies, these were a good source of gems, but unless they said something truly interesting they were easier to click past since not all that reliable. Finally there were some "we didn't find anything new" studies published; but not nearly enough get published (which has helped to cause the replication crisis.) Still some do.

In other words, there's a LOT of dross, but there are real gems lying there unread and uncited, too.

So only one in ten or a hundred articles might take an hour or more.

Average for all but the vital or good articles (after accumulating a good background and vocabularly), when I timed it back then: 100 an hour without losing any significant information. The vital remainder of 100 abstracts viewed took me (more of a guess, now) on average not more than double that amount of time, again; perhaps less time. That varied a lot because I was looking most keenly for overlooked knowledge(studies) and pairs of studies that were significant only once linked. Therefore I sometimes was willing to follow tangents to tangents just in case and could speed up at that point because it was nearly all dross.

Back when I was in university supposedly studying the history and philosphy of science and language, I had to visit medical libraries and use the CD disks from the then-private company Pubmed, and walk back and forth to a large, printed medical encycopedia chained to a pedestal and the desk-sized CD reader Pubmed provided. I don't include that reading as I took no surviving notes and wasn't counting abstracts way back then. Being able to research online when I returned to medical reading a couple of decades later was an immense relief. Switching tabs to get to a medical dictionary isn't nearly as much exercise, but it is a lot faster. Printed medical dictionaries for professionals have a LOT of pages to turn, in addition to the walking.