真空中一点电荷q位于一立方体中心，则通过立方体每个表面的电场强度通量为（ ）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 铝合金拉伸实验的MOOC中，需要测试性能指标（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/418dff8a904f4789899ce32e4cd03b74.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/411578dcfdda41a3bc8821b9bfb1d916.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/806ea04e59cd436faec9f7992d126ee5.png" />与<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/61011c7d884349459d41d9f3670d7d0e.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/57ab5cc8b9dd4fb0961726058a6e9c52.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/806ea04e59cd436faec9f7992d126ee5.png" />与<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/61011c7d884349459d41d9f3670d7d0e.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/32ff0f454bde4334ae385089a853b9ac.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/ab0315aab0fa4918a53714026df50fa3.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/806ea04e59cd436faec9f7992d126ee5.png" />与<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/61011c7d884349459d41d9f3670d7d0e.png" />
- 铸铁拉伸实验的MOOC中，需要测试性能指标（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/53667f9a659c4652a1d73a3dd36986bf.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/875d968dec834cdfa4c3fe247d7aa2a8.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/5d8957af2d2a4f51819415939c6345f0.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/b636e1e0d6a94025871bb57705cf25bd.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/6219f1e929704d49b7379c136363c22b.png" />、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/b542e12f707949e0a011640e81330eea.png" />与<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/68fe4ce598db473387b30de3c218f70c.png" />
- 判定系数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/884048ab090f4001856b6b5be7ce702d.png" />可表示为( )。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/595552013f6f4712972e25f5205785e3.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/448d29a283a1437e972417c64c9186ba.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/0757164fbffa45a7afd4984db734d818.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/c804edbb8d30463a9074d63b355031d0.png" />
- 已知<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/e6d73bcaf9ea43ad8cc6d0448ce5cb54.png" />，其逆Z变换（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/334d49becc544757b952699488a42728.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/4ac8ed87292446f8852ade2dbcaaff0b.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/5f5aa1dfaebe47d788513626d79951af.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/0a7716a303934c79a9af73a051a1a98a.png" />
- 已知系统函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/e39da45535184440b4f478ab5106f452.png" />，系统微分方程为（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/ffc04b8a434a4c00b9143c405784376c.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/2f0eba48174d43b9b307acbb25fff331.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/c8b83cd3d24d48ac9619b499d191fd35.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202011/2d16a22cef6a4da2b8100854c0707ae8.png" />