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【多选题】
下列哪些操作是正确的A.
工作台使用前需要进行紫外杀菌30min
B.
进行接种操作时要保持带菌种的材料或者开口无菌容器在酒精灯火焰5cm的范围内
C.
工作台使用完毕后要开紫外灯进行灭菌
D.
工作台在使用过程中要通入无菌空气
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皮皮学刷刷变学霸
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【简答题】氟离子选择性电极是晶体膜电极吗?使用条件?
【单选题】对CH 3 Br进行亲核取代时,以下亲核试剂亲核性的比较,正确的是:
A.
HS - < H 2 S
B.
H 2 O < HF
C.
HO - < HS -
D.
RO - < RCOO -
【单选题】对 CH 3 Br 进行亲核取代时,以下离子亲核性最强的是( )
A.
CCl 3 CH 2 O -
B.
CH 3 CH 2 O -
C.
C 6 H 5 O -
D.
CH 3 COO -
【单选题】新斯的明治疗重症肌无力的机制是
A.
兴奋大脑皮质
B.
激动骨骼肌M胆碱受体
C.
促进乙酰胆碱合成
D.
抑制胆碱酯酶和激动骨骼肌N 2 胆碱受体
E.
促进骨骼肌细胞Ca 2+ 内流
【单选题】It can be inferred from the passage that in the early 1800’s children were generally regarded by their families as individuals who______
A.
needed enormous amounts of security and affection
B.
required constant supervision while working
C.
were important to the economic well-being of a family
D.
were unsuited to spending long hours in school
E.
were financial burdens assumed for the good of society
【简答题】In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communications.【46】H______, fiber optics was already a well-established commerci...
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