问题 问答题 简答题

离子学说的实验证据是什么?

答案

参考答案:

1939年微电极发明以后,Curtis和Cole、Hodgkin和Huxley分别用毛细管微电极测量了枪乌贼大神经纤维兴奋时的电位变化,发现动作电位大于膜静息电位,出现了超射;1949年Hodgkin和Katz进一步做了“钠离子对枪乌贼大纤维中产生的动作电位的作用”的实验;根据一系列实验结果,1950-1952年Hodgkin和Huxley和Katz提出了著名的钠学说,即离子学说。钠学说随后得到各方面实验验证。1951年Keyns利用同位素24Na、42K标记实验,测量每次动作电位期间每平方厘米膜上Na+和K+的通量。

单项选择题 A1型题
阅读理解

第三部分 阅读理解(共15小题,每题2分,满分30分)

请认真阅读下列短文,从短文后各题所给的四个选项(A、B、C和D)中,选出最佳选项并在答题卡上将该项涂黑。

We find that bright children are seldom held back by mixed-ability teaching. On the contrary, both their knowledge and experience are enriched. We feel that there are many disadvantages in streaming(按能力分班) pupils. It does not consider the fact that children develop at different rates. It can have had effect on both the bright and the not-so-bright children. After all, it can be quite discouraging to be the bottom of the top grade.

Besides, it is rather unreal to grade people just according to their intellectual(智力) ability. This is only one aspect of their total personality. We care much about the development of all the pupils’ abilities to the full, not just their study ability. We also value personal qualities and social skills, and we find that mixed-ability teaching does good to these aspects of learning.

In our classrooms, we work in various ways. The pupils often work in groups; this gives them the chance to learn to work together, to share, and to develop leadership skills. They also learn how to deal with personal problems as well as learning how to think, to make decisions, to analyze(分析) an devaluate(评价) and to communicate effectively. The pupils learn from each other as well as from the teachers.

Sometimes the pupils work in pairs; sometimes they work on individual(个人) tasks, and they can do this at their own speed. They also have some formal class teaching when this is proper. We encourage our pupils to use the library, and we teach them the skills they need in order to do this well. An advanced pupil can do advanced work and it does not matter what age the child is. We expect our pupils to do their best, not their least, and we give them every encouragement to achieve this goal.

56. By “held back” in the first paragraph, the writer means “________”.

A. made to remain in the same class            B. forced to study in the lower class

C. drawn away form their studies         D. prevented from advancing

57. The writer’s purpose of writing this passage is to ________.

A. argue for teaching bright and not-so-bright pupils in the same class

B. advise pair work and group work for classroom activity

C. offer advice on the proper use of the library

D. tell us the importance of proper formal classroom teaching

58. What would be the best title for the text?

A. Pair work.      B. Group work.    C. Mixed-ability teaching    D. Individual tasks.