Best thing we have is the German Frontbestand, the frontline inventory, compiled bi-monthly
Here you have it in a handy PDF file
http://www.theaerodrome.com/forum/ai...ntbestand.html
bottom post, as attachment.
I have found assorted numbers for effective battle strength associated mainly with the German offensives of 1918, and there are assorted production and delivery figures for some types. Compiling and piecing them together would give a more detailed month by month picture, but still fragmentary.
PS This is posted in the wrong place, it should be moved to Other WWI aviation.