3.3.1 概述 3.3.2 单表查询 3.3.3 连接查询 3.3.4 嵌套查询 3.3.5 集合查询 3.3.6 小结

2.4 关系代数 2.5 关系演算 2.6 小结

1.4 数据库系统的组成 1.5 数据库技术的研究领域 1.6 小结

1.2.1 数据模型的组成要素 1.2.2 概念模型 1.2.3 常用数据模型 1.2.4 层次模型 1.2.5 网状模型 1.2.6 关系模型

10.1 完整性约束条件 10.2 完整性控制 10.3 Oracle的完整性 10.4 小结

一、药物化学的定义 二、药物化学的研究内容 三、药物化学的任务 四、药物化学发展的动力 五、新药创制

How are molecular structures determined? One way is though the use of spectroscopic methods. Spectroscopy is the study of the interaction of energy with matter. When energy is applied to matter it can be absorbed, emitted, cause a chemical change, or be transmitted

Alkenes are hydrocarbons whose molecules contain the carbon-carbon double bond. Alkynes are hydrocarbons whose molecules contain the carbon-carbon triple bond

The primary source of alkanes is petroleum Natural gas consists chiefly of methane, but ethane, propane, butane, and isobutane are also present. Petroleum is a complex mixture of hydrocarbons that must be refined into different fraction before it can be used

An acid is a substance that can donate (or lose) a proton, A base is a substance that can accept (or remove) a proton