【简答题】求由摆线x=a(t-sint),y=a(1-cost)的一拱(0≤t≤2π)与横轴所围成的图形的面积.
【判断题】抗生素是某些微生物在其代谢过程中产生的能够抑制或杀灭其他病原微生物的化学物质。
【单选题】—Were there ___ sharks in the aquarium? —No, there weren't _____. [ ]
【判断题】灭菌是指杀灭或清除传播媒介物上的病原微生物,使其达到无害化的过程。
【判断题】RFID技术、传感器技术和嵌入式智能技术、纳米技术是物联网的基础性技术
【单选题】According to the statistics, among the homeless in New York there were ______.
A.
more people in families than single persons
B.
about six thousand families
D.
more families with two parents than one
【判断题】电源表面是铁壳,所以在防静电布过小的时候,允许放置在防静电区域外。 ( )
【单选题】我国10kV及以上电压等级的电力用户,供电电压正常允许的偏移范围是额定值的
【单选题】--- ___________ there any sharks in the aquarium? --- No, we didn’t see any.
【单选题】— Were there any dolphins in the aquarium? — ___________. We didn't see any in it. [ ]