I think what freddy is refering is those add on converter lenses on DCs, not Single Lens Reflex (digital/non-digital) lenses. SLR Lenses don't mount on the body with threads like your filters. And most major manufacturers have their own mounding which is different from one another. u Can't use a nikon SLR lens on a Canon without a converter and without loosing AF functionality.
yes there screw mounted cams.. afaik mainly for manual lens
but to answer freddy's question... nope slr lens are not ment to be mated with digicams... exceptions are for macro/close-up setups where normally a slr lens is REVERSED mounted.
technically, you can shoot through a (unreversed) slr lens...it's akin to shooting through something like a telescope less the ability to focus the slr lens independently and the magnification are dependent on the focal length and afaik, such adapters are non-existant.