【单选题】叶脉常在叶片背面隆起,是因为叶的背面()发达
【单选题】在高温使用条件下,为了防止爆燃,应根据()选用相应辛烷值的汽油。
【单选题】研究表明,教育机智随年龄增长而呈( )趋势。
【单选题】Everyone doesn’t agree to the plan. Some support it while I’m one of ______ opposed to it.
【单选题】In our eye, rod cells are responsible for ______, while cone cells are responsible for _______.
A.
night vision; moving object
B.
color vision; night vision
C.
night vision; color vision
D.
color vision; moving obsect
【多选题】Why is a rod photoreceptor cell from the retina exquisitely sensitive to light?
A.
The light-absorbing rhodopsin proteins are embedded in many pancake-shaped vesicles (discs) of membrane inside the outer segment of the photoreceptor cell.
B.
When the rod cell is stimulated by light, a signal is relayed from the rhodopsin molecules in the discs, through the cytosol, to ion channels that allow positive ions to flow through the plasma membrane of the outer segment.
C.
These cation channels close in response to the cytosolic signal, producing a change in the membrane potential of the rod cell.
D.
By mechanisms similar to those that control neurotransmitter release in ordinary nerve cells, the change in membrane potential alters the rate of neurotransmitter release from the synaptic region of the cell. Released neurotransmitters then act on retinal nerve cells that pass the signal on to the brain.
【单选题】患者,男性,57岁,刺激性呛咳,咳痰,有时带少量血丝。听诊右肺中部有局限性哮鸣音。X线摄片见右肺肺门附近有单侧不规则肿块状阴影,无邻近转移现象。应首先采取的治疗措施是
【单选题】( )是区别于马克思主义文学理论与非马克思主义文学理论的一个重要标志。
【判断题】( )低压电器分为控制电路和开关电路两大类。