Use the *DMAT-command or *SMAT-command in a command snippet in the Solution branch. Make sure that you turn off distributed solution or you won't be able to do this since the full-file containing these matrices will be split into pieces.
[pre]!Stiffness
*SMAT,MK,D,IMPORT,FULL,file.full,STIFF
*PRINT,MK,Ksparse.matr
!Mass
*SMAT,MM,D,IMPORT,FULL,file.full,MASS
*PRINT,MM,Msparse.matr
!... and so on... use *DMAT for full matrix printout instead
[/pre]