wish后加宾语从句的话,一般表示的是不可能实现的愿望,所以要用虚拟语气.如果是和wishing同时的愿望,就要用动词的过去式.如：I wish I were a bird.
如果是希望的过去,则用had+过去分词的形式：I wish I had been there before