null ①零，零的 ②无效的，无价值的 ③类光[的]†
null 零的；零
数据库 数据库管理系统及其实现技术 释文 null 空值
- drilling fluid mechanics
- drilling fluid phenolphthalein alkalinity
- drilling fluid pool
- drilling fluid preparation
- drilling fluid program
- drilling fluid purification
- drilling fluid rheology
- drilling fluid safety density window
- drilling fluid solid control system
- drilling fluid stability
- drilling fluid supervision
- drilling fluid tank level gauge
- drilling fluid technology
- drilling fluid treatment agent
- drilling for geological mapping
- drilling geological logging
- drilling hole electrochemical machining tool
- drilling hole structure
- drilling hydraulics
- drilling in coalbed methane
- drilling in pressure balance
- drilling instrumentation
- drilling in surface mining
- drilling intelligence
- drilling level