For example, if she is ovulating, she tends to be more attracted to men who have rugged, masculine features.
If she is menstruating, she is more likely to be attracted to a man who has a spear lodged in his chest, and duct tape over his mouth, going up in flames.
No further studies are expected.
[Thanks, S.R. I'm so surprised at you!]
Men should memorize this chart.
For more about women's behavior as it relates to menstrual cycles, check out The Straight Dope.