Is it possible to use a direct link to the personal QRZ11-site,
eg. to use it in email-signature?

Ist es möglich einen Direktlink auf die eigene QRZ11-Seite zu nutzen,
zB. in einer Email-Signatur?

Yes it is:
hatetepe :// {wewewe} qrz11 dotcom slash show_prof.php?callsign=xxx

replace the xxx with your callsign
(i replaced the original uri to these "hatetepe" to hide it for search engines searching uri's )

Its quite easy:

http://www.qrz11.com/show_prof.php?callsign=your callsign

73s

Team