Example:
osgi> services (objectClass=com.github.tux2323*)
{com.github.tux2323.demo.chat.server.ChatServer}={service.id=26}
Registered by bundle: com.github.tux2323.demo.chat.server_1.0.0.qualifier [1]
No bundles using service.
A nice german article from Heiko Seeberger about OSGi filter can be found here.