Refer to one of Safavid's threads for my opinion on Islam's actual contribution to knowledge. In brief, all the highly advanced civilizations of that got conquered were already conserving/spreading technology and knowledge long before they got conquered by a religion that came from, let's face it, a bunch of relatively backward tribes who thought cities and their inhabitants were effiminate and useless, not unlike the mongols. This is clearly evident in the Islamic golden age, which was basically a cultural extension of the Persian and Egyptian empires in everything but religion. From academics, to healers, to art, to architecture, etc..The one massive advantage it conferred was a sort of "melting pot", but there needed to be something to mix in there in the first place.
Anyways, a lot of historians pinpoint the decline of "Islamic" knowledge to the utter destruction of Baghdad and it's Library. I'm lazy so straight from wiki:
"Iraq in 1258 was very different from present day Iraq. Its agriculture was supported by canal networks thousands of years old. Baghdad was one of the most brilliant intellectual centers in the world. The Mongol destruction of Baghdad was a psychological blow from which Islam never recovered. Already Islam was turning inward, becoming more suspicious of conflicts between faith and reason and more conservative. With the sack of Baghdad, the intellectual flowering of Islam was snuffed out. Imagining the Athens of Pericles and Aristotle obliterated by a nuclear weapon begins to suggest the enormity of the blow. The Mongols filled in the irrigation canals and left Iraq too depopulated to restore them." (Steven Dutch)