Bibtex: how to get Book title in capital letters for german thesis?

[Dominik Cabrerizo]

Hi!

I am using Lyx to write my thesis and have a BibTex List in my document. 
The problem is that the Book titles are all wirtten in small letters 
except the first one, thats a capital.
I used JabRef to create the list.
Is there a way of changing this?

Thanks
Dominik