bottom on建立在bottomn.底部；底端adj.底部的v.触底；打(基础)bottom discharge opening底部卸料孔bottom sediment of fiver河流底泥bottom layer burial flux底层通量bottom articulated joint底部铰接缝bottom hole inclinometer井底测斜仪bottom two-layer frame底部两层框架Bottom- initiated Bomb孔底起爆弹bottom tribulation novel底层苦难小说bottom die of box-beam箱梁底模bottom pipe distribution下分式管分配