四阶行列式<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/74857a5d54b74d16bd80b2e49ec83d70.png" >下列乘积项中带负号的是（）. A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/18d660014dbd485ea7744917f949df9a.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/ea1835f05d1c4ea9a935ba24e1f16d13.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/5e03bd69e28f453ebcba9cc56318724e.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/a4fcb3ebeaa4403a83d7e73cd925e479.png" >

以下哪个家具是衣架。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/02285e456e2b4861a7f6319515f836c4.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/19a30f3b6d6846ceab656f4ea0e7eb9d.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/e14dbac89fea4066a9ae7bbd6d1dc080.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/612475075e2d434aac0d404ce94395ea.png" />

粒子在一维矩形无限深势阱中运动，其波函数为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/ccb78539e887462e803c7bea75cffe1e.png"/><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/57018789b142461e84fcd4b3d589400b.png"/>，那么粒子在<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/c4f51c5f7b9942b08c3978054538f220.png"/>处出现的概率密度为() A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/685ba90bd7f645e49a79f39c94d2396b.png"/> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/ae86558b318144dcb23e7b81b07b8f6b.png"/> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/b6ecdf9e50494fca951ec617d18aa93f.png"/> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/f3e3cd2b1a9749a28e8f2330e9f9adcf.png"/>

通电延时继电器线圈的图文符号是下列哪个：（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/41f542fb474746d391ea1d0da7523004.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/4e1b9dfd525b431cbfeb929283b0ba0d.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/e2923d894e59440792c132c579a6f36d.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/54bf824d584b4fdab6929f6a7f7c488f.png">

已知图(a)所示梁中点C的挠度为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/0d6b1c896e51418abc153835c4dd12ed.png"/>（a≥b），则图(b)所示梁中点C的挠度（）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/93731d611eba4bc7866c22a14d88acaa.png"/> A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/d68df831261a4f928840f7b55b186e91.png"/> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/cb1390433f4645f2859aed63118634ba.png"/> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/33e997fd31d24eff855f9776e960dd44.png"/> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/185621b86258475ca17377d734005d5e.png"/>

以Y表示实际观测值，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/7ff7fb91c85241d699c745709bde0b2c.png" />表示回归估计值，则普通最小二乘法估计参数的准则是使（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/0b69261eac7b49ea841e5eafaa8169eb.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/a427d3a4486e4abf94fab3a3e6b7031f.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/ba4f272af93c4f2cbb2daac516095ef7.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/3a4c73395bfd48caa9603f7b5fc45360.png" />

设二极管的端电压为U，则二极管的电流方程为（ ） 。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/8fc1bd7f467e423a9abedfbcf36b63bf.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/96c0065cd93f445abe2243c79b5a11f5.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/e7babcc7dd7c478bbabd8438754ba07b.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/dc06cb808c2a4d20b75fa70ba39feefe.png">

电子的自旋磁量子数ms只能取两个值：（） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/aad2605165ae49dca6d35f2442486d7d.png"/>，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/b26222bd1d104bc48e5b3e46fd0c96f3.png"/> B: 0，1 C: 1，-1 D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/53bfe01cafc4489694829394e57b81ab.png"/>，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/05ca8a938e7c4b13af4719339d2d12a9.png"/>

给定下述系统的差分方程，则__是非因果系统。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/df1ece1947ea4ec394f9801bb6a8623e.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/4963ffe14fd64ba983b60ad14bd498e2.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/3c6bc338aedb4d04baa637de5d7d9506.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202006/53dbdd529a5443188250b588e1de8d36.png">

利用替代法编程中常开触点对应的指令符号为：（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/b406fdddc2df4fa5a4101e1bb8cb9c59.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/1fdbc7cdabc04afab6cf08b2dd2cb791.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/9fc7f90d98ad49b8b3192379ace5d920.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202006/4ed446acaf5142c48011611260c96457.png">