backpa[机] 背板backn.后面；背脊；靠背；后背；后卫vt.支持；后退adv.向后地adj.向后的；后面的；偏远的；过时的；积欠的back mining复采back stopes向上回采工作面backeasting后向估计backed sand烘干砂back-dooradv.不正当地；adjbackfilling回填back motion倒转back piston后活塞backventingn.背通气管back player后排队员