下列函数表达中，（ ）是周期信号（ ）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 下列最稳定的自由基是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/7ff51d95af804e74bbffb2091d336668.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/a7bc08ef90914e13a5f795670eb1e67b.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/6f85cd60c27645c39d58990b87615ebf.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/f5d0c506ba09424a838f7aee98e94e43.png" />
- 下列关系正确的有（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/0c9a6360c85f4ff9bdb2b17b576df2e0.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/09c3ca64214040d89eaa8534fa21d895.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/3d88f37ec20c4604a8387c0e1088ad34.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/d48f61b369aa425384b1d565afb5d073.png" />
- 具有顺反异构体的物质是 ( ) 。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/9bf08e194cf24f80b9582238a48b2d98.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/6a33a313aebe4d5a8d8f6cd250361fec.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/f7a33598bdb74c3180f03e2517cac29c.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/d86d498d7c6b4594ad58fdbaad86028c.png" />
- 属于钙通道阻滞剂的药物是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/3112081992ed47f8bf358bd9942d5ebb.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/17c349ff9e8e450c971ceb98947611f8.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/4194526443744627b8a6fc1be47523d1.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/28cffdd18be74b33bc7d9efac912d8c3.png" />
- 阿糖胞苷的化学结构为（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/588c9b478695464b9617893b2e1c303a.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/86b60f7b512f43a29c8431f882722d1b.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/4546ccb30ea64350a626b0cd337e2c98.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202012/8f610edce6dd4a2e81ca814690e0b5ec.png" />