bottom on建立在bottomn.底部；底端adj.底部的v.触底；打(基础)Bottom Water Oil Deposit底水油藏bottom half outer casing外下汽缸bottom stitching machine封底钉铆机bottom ring gas-supply底环补气bottom frame-shear wall底部框架抗震墙bottom of conduction band导带底bottom-cooled technique底部冷却技术bottom door winding shaft底门卷链轴bottom mounted breakwater混合式防波堤bottom out bottom upwards倒置, 反转