设L为正向圆周在第一象限中的部分，曲线积分 =（ ）https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/c1effc1e456543598ef67fc0e4a04d45.png
举一反三
- 下列微分方程中为常微分方程的是（） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/cbf228ed319846a786045d6f0d92c025.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/14d9810e378e4a9aa35b205b9bd1bfad.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/a9b59e4bfb9e4db6893102d624b7c7c1.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/8f273eb6feb642e2850f4654eae6b238.png" >
- 若产生主动土压力为Ea，被动上压力为Ep，所需的档土墙位移量分别为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/1e8f0b9e0cb8465593753c5f11598176.png" >、<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/9088e679a4184965804bc72eeb0a0d41.png" >，则下述()是正确的。 A: Ea＜Ep，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/7a1afdb198494646a3e13d5a5fc63803.png" >＞<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/9088e679a4184965804bc72eeb0a0d41.png" > B: Ea＞Ep，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/7a1afdb198494646a3e13d5a5fc63803.png" >＜<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/1e329449603e4588bd4943ce452bde27.png" > C: Ea＞Ep，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/1e8f0b9e0cb8465593753c5f11598176.png" >＞<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/9088e679a4184965804bc72eeb0a0d41.png" > D: Ea＜Ep，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/7a1afdb198494646a3e13d5a5fc63803.png" >＜<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/9088e679a4184965804bc72eeb0a0d41.png" >
- 草酸钙在pH=2的溶液中的溶解度（）。 A: 小于<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/f28fa10ebbe34a8389bda833d25ce26b.png"> B: 等于<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/6ffdcbe87c164ebbaa755a4fc6d40067.png"> C: 不确定 D: 大于<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/6ffdcbe87c164ebbaa755a4fc6d40067.png">
- 下列化合物在碱性条件下与水反应活性最大的是（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/406bdbdf0a5846b5999d5e6e856df268.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/5e91d438399146d8b423b2f88e676fe9.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/3c75eaa7ec1f4545b3bde86157628880.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/0d3304fae4274d339f5331f81c9b46ff.png" >
- 下列那个反应在反应过程中能生成碳正离子中间体？（） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/8b944ee7075041be92f60cc9d1c6dc0c.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/f406e4cb711c4b1cab88b2f238a3a886.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/41c9e4ca3e7942b086e173cf6c71a45d.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202004/ab040348ce1a4b0c8da1805df17c3906.png" >