具有抗衰老作用的是() A.维生素A B.维生素B C.维生素C D.维生素D E.

题型:单项选择题

问题:

具有抗衰老作用的是()

A.维生素A

B.维生素B

C.维生素C

D.维生素D

E.维生素E

考点:北京住院医师全科医学Ⅰ阶段临床药理学临床药理学题库
题型:单项选择题
将棱长为6厘米的正方体钢块锻压成一个长为8厘米,宽为3厘米的长方体,它的高是(  )厘米.
A.6B.9C.12D.4
题型:单项选择题

通过下列哪些性质可以鉴别以下各组物质,请将有关序号填在横线上.

①颜色;   ②气味;   ③味道;   ④状态;   ⑤硬度.

金和铜______;空气和水______;氨气和二氧化碳______;金刚石和玻璃______;糖水和盐水______.

题型:单项选择题

阅读下面文字,完成后面小题。(共5分)

①白居易在《荔枝图序》中这样描述荔枝,说荔枝“若离本枝,一日而色变,二日而香变,三日而味变,四日五日色香味尽去矣”。这样看来,“红颜易逝”似乎是荔枝的宿命了。

②为何荔枝的色香味会在很短的时间内变化呢?这还要从荔枝果实的结构说起。别看荔枝壳就像一身铠甲,其实那是不折不扣的“样子货”。这身“铠甲”不仅不能保护荔枝,还会带来不少麻烦。荔枝外果皮上那些“护心镜”模样的裂片突起,不仅很薄,内部组织之间还有很多空隙,很多宝贵的水分会从这些空隙跑出去,留下干巴巴的荔枝果实。

③不过,与干旱孤军奋战,还不是荔枝所要面对最糟糕的问题。荔枝壳还含有多酚氧化酶和过氧化物酶,这些酶会把很多无色的多酚类物质都加工成为黑色素,这就是会使荔枝颜色变深的褐变作用。这些酶的加工速度很快,“一日而色变”足以说明它们的工作效率。

④虽然荔枝在采摘一日之后,果肉还会保持相对良好的状态,但是用不了多久,它也会步果壳的后尘,而衰老的原因出在它自己身上。植物的果实(比如苹果、梨等)同我们人类一样,也需要喘气呼吸,在这个过程中,果实内的糖类物质会被逐渐消耗。只不过,这个过程进行得很缓慢,我们听不见它们的喘气声罢了。

⑤不过,荔枝的呼吸强度可以达到苹果或梨的4倍,不仅如此,从树上摘下来的那一刻起,荔枝的呼吸作用还会不断加强。其结果是果肉中的糖类物质被迅速消耗,维生素C也会迅速下降,同时还会产生一些气味不佳的醇醛类物质。荔枝在采摘二三日之后香味尽失,在很大程度上是他们“大喘气”的结果。

⑥除了本身“体质”的大缺陷,荔枝还有个不利于“美容养颜”的坏毛病,那就是释放乙烯。乙烯和我们常吃的香蕉有着不解之缘。为了便于运输,蕉农一般会在成熟前把青色的香蕉采收下来,等送到目的地之后,只要用乙烯一喷,在很短时间内青色的果实就会变成看起来黄澄澄的大香蕉了,这可能是北方吃到的香蕉总是淡而无味的一个原因。

⑦但乙烯不仅可以把青果催熟,而且可以把熟果催败。荔枝的危险之处正在于此,它们不但会释放乙烯,而且会越放越多。直到把自己催得“人老珠黄”,流水变味,释放量才会下降,可一切为时已晚。

⑧总之,种种自身缺陷注定荔枝在脱离大树之后,不用多久就会“香消玉殒”。

(有删改)

小题1:结合文章内容,说说作者为什么说荔枝壳是不折不扣的“样子货”。(3分)

小题2:阅读下面的文字,借助文章中相关知识,说说材料中的方法可以使荔枝保鲜的原因。(2分)

【材料】唐朝的杨贵妃爱吃荔枝,皇帝曾派人从四川派马疾驰到长安,只为把荔枝送给她吃。为了博得贵妃那难得的一笑,众多能工巧匠都得开动脑筋来使荔枝保鲜。据蔡襄的《荔枝谱》记载,在竹林里砍下一棵大竹子,凿开一个洞做成竹筒,把鲜红色的荔枝放在水分充足的竹筒里头,然后用泥或蜡密封。这样一来,荔枝能保藏到次年的冬天,依然保持着新鲜和美味。

题型:单项选择题

Over 70 percent of the "double single-child couples" in China need help from their parents in taking care of their own kids, according to a recent survey.

"Women of China" magazine and a consulting company carried out a survey recently on young couples of the "single-child" generation, the Morning Post reports. The couples surveyed were around 29 and have been married for three years on average, with university education and monthly income of 4.000 yuan ($531). Among them, 43.5 percent have kids.

Results show that 71.9 percent of the young couples have help from their parents in taking care of their kids.

Grown up as the "single-child", the only child in a family since the family planning policy was adopted in 1979, this generation depends much on their parents.

The parents of the "single-child" generation focused more on their children's physical well-being rather than their attitudes and values, according to some psychologists.

The research also found that the "double single-child couples" follow a rather traditional value system.

Survey shows that 27.5 percent of them got married after dating for one to two years, 25.2 percent two to five years, and 20 percent didn't tie the knot until dating for five years. Also, 30 percent of the couples were schoolmates, while 43.8 percent were introduced by someone.

Since their marriage are based on enduring relationships, 65.2 percent of the husbands and 62.9 percent of the wives think that compromise(妥协)and tolerance(宽容)are necessary in their marriage. Meanwhile, 21.7 percent of the husbands and 37.1 percent of the wives support the idea that happiness is the key standard for a marriage.

小题1:The best title for the passage should be_______.

A.Mom and Dad, Take Care of My Kid Please

B.Double Single-child Couples

C.The Problem of the Single Child

D.A Recent Survey By Woman of China"小题2:Which of the following is NOT supported by the passage?

A.The majority of the "double single-child couples" in China depend much on their parents.

B.The parents of the “single-child” generation more care about their study and education.

C.One-fifth of the couples surveyed didn't get married until dating for five years.

D.All the couples surveyed have university education and 30 percent of them were schoolmates小题3:Which of the following descriptions about “double single-child couples” is True ?

A.They are single child in either family and independent of their parents

B.They are single child in either family and they are dependent on their parents

C.They have at least two children and can afford to support themselves

D.They, who were introduced by someone, follow a rather traditional value system小题4:According to the passage, we can learn that ______ is necessary in marriage.

A.wealth

B.health

C.understanding

D.education

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开机过程中(发电机并网前)真空低常见原因有哪些?

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