搜题请搜索小程序“爱下问搜题”
问题 填空题

　　【4】　　 是数据库设计的核心。

答案

参考答案：【4】数据模型

解析：解析：数据模型是对客观事物及联系的数据描述，它反映了实体内部及实体与实体之间的联系。因此，数据模型是数据库设计的核心。

填空题

Rainmaking Scientific rainmaking was started by Vincent J. Schaefer after the year of (1) . A lucky (2) brought him to success. Schaefer was hired, during World War II, by Dr. Irving Langmuir to study how and why (3) forms on the wings of airplanes. The two went to New Hampshire because (4) were common and cold winds often blew. In New Hampshire, they were surprised to learn that the temperature of the clouds surrounding them was far below the (5) , and yet ice did not form there. After the war Schaefer went on the experiment. One morning a friend asked him to go for lunch. He went and left the (6) of the freezer up. When he returned from lunch, he found the temperature of the freezer was (7) than that required for ice crystals to remain solid. There were two choices now. He could wait for the freezer to lower the air temperature or he could add (8) ice. He chose the latter. Then when he did this, he happened to (9) a large amount of air. Suddenly he saw (10) were formed. He did the experiment again and succeeded in making a tiny snowstorm in the laboratory.
查看答案
问答题 简答题

简述检查胸膜摩擦音的方法。
查看答案