“that level drops once you reach actual achievement in the field. Those at the top of any scientific field are generally male.”
That is to be expected given that few women pursued advanced scientific training until recently. Re-analyze the data a few decades from now.
And there have indeed been some women at the top. Here is one:
http://en.wikipedia.org/wiki/Rosalyn_Sussman_Yalow
I belong to the (orthodox) synagogue in the Bronx where she was a long time member. The social hall has been named for her.