属于常年发情的动物是?() ["A、牛","B、驴","C、狗","D、山羊"]
夏季高温季节,在中午是否能装运、领发易燃品() ["A、可以","B、不可以","C、严禁"]
属于季节性发情的动物是?() ["A、牛","B、猪","C、兔","D、山羊"]
“位于泄殖腔肛道背侧,有开口向下与肛道相通,其大小随年龄有显著变化,性成熟后逐渐消失。”根据以上描述可以判断出是?() ["A、胸腺","B、回肠淋巴集结","C、法氏囊","D、盲肠扁桃体"]
已知零件材料为钢要钻∮10mm的孔选择切削速度为31.4m/min,进给量为f=0.1mm/r。求2min后钻孔的深度为多少?
用一∮10mm钻头钻孔,选择进给量为f=0.2min/r,当钻了L=40mm时,用了T=0.5min。求钻孔时的切削速度是多少?