threeleaf三叶threenum.三n.三；三个adj.三个的three - zone theory三区理论three dollars a dozen每打三美元three step controller三位调节器three-tube telecine三管式电视电影机three layers teaching三层次教学three-points method三点法three-phase machine三相电机three types of vortex三旋运动three-pin connector三针连接器three point smoothing三点平滑