function keyWordsCut(parentObj,num){
  var wordsObjList = parentObj.find('a');
  var wordsNum = wordsObjList.size();
  if (num < wordsNum){
    var endIndex = wordsNum - 1;
    for (var i = num;i < endIndex; i = i + 1){
      wordsObjList.eq(i).hide();
    }
    parentObj.append('<span class="more-detail"> ...more</span>');
    parentObj.find('.more-detail').click(
      function(){
        parentObj.find('a:hidden').show();
        $(this).hide();
      }
    );
  }
}