工业上常用调节器的主要调节规律有哪些?
参考答案:
常调节的基本调节规律有:位式调节,比例调节,比例积分调节,比例积分微分调节这几种规律,分别简写为:PPIPID。
能对抗原进行特异性识别的细胞是
A.MΦ
B.浆细胞
C.K细胞
D.T细胞
E.NK细胞
(2013·厦门质检)Hardly ________ twelve when they realized that it was too late to catch the last train.
A.the clock had struck
B.the clock had been struck
C.had the clock been struck
D.had the clock struck