Hello everyone,We know that K2 provides us to import all Joomla articles into K2 system... But is it possible to import K2 contents to Joomla core article compenent?Thanks...

No, such a feature is not available. And I have read so many threads related to this and from that I can easily make out that don't expect this features from Joomla works guys.
I am waiting for that day when "k2 to joomla" functionality" or whatever it called will be introduced. Once that facility is available I will switch to k2 instantly.