FOR FANS OF ABSTRACT EXPRESSIONISM, the journey to the small southwestern town of Kaiserslautern was worth the effort. There, the Pfalzgalerie played host to work little seen in Germany, by Helen Frankenthaler, Lee Krasner, Joan Mitchell, Elaine de Kooning, and Hedda Sterne. At first, the fact that the exhibition consisted entirely of women artists seems to have been downplayed by the curators, Britta E. Buhlmann and Annette Reich. The show's title made a gender-neutral impression; or was the curators' gambit simply to declare these artists central to the movement in order to draw more attention