Not quite--the scientific evidence only points to the raising of numerous chemicals associated with pleasure and satiation (serotonin, prolactin, etc.), but women have many of the same chemical releases and there's no wives' tale about women falling asleep after sex. It's not even very statistically viable to talk about how quickly men fall asleep after sex, because most sex happens at night when people generally fall asleep anyways; and on the other hand, orgasms in both men and women have been shown to be somewhat effective at waking people up during the day, relieving certain types of headaches, etc; and the injection of testosterone-laden semen into the receptive mucosal tissue of the vaginal canal has been shown to be a low-grade anti-depressant for women. But at the very least, prolactin is an interesting part of the puzzle.