yes, it is possible to research a technology and then demolish the academies in your town to get some space. you will get the effect of the researched technology even though you do not have any academy in your towns. (similar to workshop upgrades) however (unless you do not solely concentrate on academies) it takes VERY long time to research all of the technologies available in the library; (especially future researches 1,2,3) and some future reearches also may not pay off the gold you spent on scientists according to your gameplay.