Moving text from Emacs to KDE

The KDE applications are nicely integrated with respect to text movement: you can copy text from one application and paste it into another one. The same holds true within Emacs. But is there a way to copy text from an Emacs buffer and paste it into a KDE application? If I do an ordinary copy in Emacs and a paste in KDE, the paste doesn't see the Emacs text at all. I know of one way but it's not very elegant: highlight the Emacs area with the mouse and then paste it with the middle mouse button. I'd much rather do it with an Emacs command if that's possible. I think I once found such a command, but I don't remember what it is. Paul