在关系型数据库中,实现实体之间的联系是通过表与表之间的A.公共索引 B.公共存储 C

题型:单项选择题

问题:

在关系型数据库中,实现实体之间的联系是通过表与表之间的

A.公共索引

B.公共存储

C.公共元组

D.公共属性

考点:计算机等级考试数据库技术三级数据库技术笔试
题型:单项选择题

下列带传动中,传动比最准确的是()

A.同步齿形带传动

B.多楔带传动

C.V带传动

D.平带传动

题型:单项选择题

请你依据下列化学符号,填写相应空格:

①H ② C ③N ④O ⑤ Na+ ⑥Cl- ⑦OH-

(1)电子数相等的粒子是_________;(填写序号)

(2)在人体生理活动中不可缺少且由两种元素的离子构成的物质化学式是___________;

(3)写出一种由三种元素组成且在农业上作化肥的物质的化学式_________;

(4)由上述元素组成最简单的有机物的化学式是________。

题型:单项选择题

阅读理解。

     Scientists say they now have proof to support the old-fashioned advice that it's best to sleep on a problem.

They say sleep strengthens the memory and helps the brain organize the masses of information we receive

each day.

     The lead researcher Bob Stickgold at Harvard Medical School said, "Sleep helps us draw rules from our

experiences. It's like knowing the difference between dogs and cats even if it's hard to explain."

     The US research team studied how well students remembered connections between words and symbols,

reports New Scientist. They compared how the students performed if they had had a sleep between seeing

the words and having the test, and if they had not slept. They found that people were better able to remember

lists of related words after a night's sleep than after the same time spent awake during the day. They also

found it easier to remember themes that the words had in common. But they forgot around one in four more

themes if they had been awake.

     Prof. John Groeger, University of Surrey's Sleep Research Centre, said, "People have been trying for years

to find out what the purpose of sleep is, as we know that only certain parts of it have a restorative (促使康复

的) value."

     "We form and store huge numbers of experiences in the head every day, and sleep seems to be the way

the brain deals with them all."

1. The phrase "to sleep on a problem" in Paragraph l most likely means to "____".

A. pay full attention to a problem

B. wait until the next day for a decision

C. sleep to forget a problem

D. have difficulty in sleeping

2. In the study by the US research team, students were asked to ____.

A. put together words of similar meanings

B. remember words and their meanings

C. show their knowledge of words

D. make up lists of related words

3. Which of the following may be easier to remember?

A. Themes learned right before the test.

B. Rules from personal experiences.

C. Words learned before a good sleep.

D. Ideas stored together in the brain.

4. What may be the importance of the research?

A. It shows that sleep may help us manage information.

B. It helps find out the common themes of words.

C. It tells us that more sleep can improve health.

D. It proves the value of old-fashioned advice.

题型:单项选择题

一患者因胃部不适行上消化道造影,显示胃部充盈缺损,内镜检查可见胃黏膜局限性隆起,临床拟诊黏膜下肿瘤。

该患行影像学检查时,需和哪种疾病相鉴别()。

A.胃炎

B.胃下垂

C.胃外压性病变

D.胃扭转

E.贲门失弛缓症

题型:单项选择题

招股说明书或招股意向书刊登后至获准上市前,拟发行公司发生重大事项的,应于该事项发生后第1个工作日向中国证监会提交书面说明情况。( )

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