【单选题】如果某些病原体突破了第一道和第二道防线,即进人人体并生长繁殖,引起感染。有的有症状,就是患病;有的没有症状,称作隐性感染。不论是哪一种情况,机体都经历了一次与病原体斗争的过程,这种专门针对某一种病原体(抗原)的识别和杀灭作用为特异性免疫。譬如得过伤寒病的人对伤寒杆菌有持久的免疫力,那是因为伤寒杆菌刺激机体产生免疫应答,增加了巨噬细胞的吞噬功能,同时在体内还产生抗伤寒杆菌的抗体。人体的免疫系统又能把...
【简答题】()是指主要通过互联网营销替代传统营销手段,全面降低营销费用,改进营销效率,促进营销管理和提高企业竞争力。 A、销售型网络营销目标 B、服务型网络营销目标 C、品牌型网络营销目标 D、提升型网络营销目标
【单选题】三相半波可控整流电路,电阻性负载,当控制角( )时,整流输出电压与电流波形断续。
【多选题】In lesson 1.3a, Jonathon mentions that he learnt two valuable skills when he struggled to pass a first year university course. What were they?
【判断题】沉积岩的构造是指沉积物沉积时或沉积之后形成的各种构造。
【单选题】What does Count Dracula offer as a reason for Jonathon Harker to stay for a time at Castle Dracula?
A.
He wants Harker to remain in the castle as long as possible in order to perfect his English pronunciation.
B.
He wants to complete the transfer of land in England.
C.
Harker can accompany him to England.
D.
The weather is bad, so the Borgo Pass is treacherous.