焦耳一楞次定律的内容是什么?
参考答案:
电流通过导体所产生的热量(Q)与电流强度(I)的平方、导体的电阻(R)和通2电时间(t)成正比,其表达式为Q=I2Rt
_______ I paid a visit to this scenic spot, I was deeply attracted by its beauty.
A.Firstly
B.For the first time
C.The first time
D.At first
子宫颈内口松弛而致反复晚期流产的特点是()
A.在妊娠早期出现
B.流产前阵痛明显
C.破膜后胎儿立即娩出
D.娩出新鲜、无畸形发育的正常胎儿
E.发病前常无症状