This tool is really fascinating. Basically, you pick a field, choose amongst a few timescales, and then you are presented with data on the proportion of women authors on published papers in that field. It offers a hierarchical view (so you can look at "aquatic ecology", or drill down specifically to "salt marshes"), and will give details about placement of authorship as well. Interesting to see how the different field vary; which ones have changed and which ones have not (as much); and where women and up in the list of authors (SPOILER ALERT! They are less often first or last).