设置采暖系统的地区进行围护结构主体部位传热系数的检测,冬季在()正常运行后进行。
参考答案:采暖系统
— Mr. Wang _____ be in the office. The light is still on.
— No, he _____ be. Because he phoned me from the farm just now. [ ]
A. may; mustn't
B. mustn't; mustn't
C. can't; can't
D. must; can't
质子数与中子数互换的核互为镜像核,例如是的镜像核,同样也是 的镜像核,利用镜像核可研究短寿命不稳定核。下列说法正确的是
A.和互为镜像核
B.和互为镜像核
C.核反应+→+是α衰变
D.一个质子和两个中子结合成氚核()时一定放出能量