数据库 数据库理论 释文 null value relational model 空值关系模型
- unit combination instrument
- unit commitment
- unit complex hyperball
- unit complex number
- unit construction area
- unit-coordinated control system
- unit crystal
- unit cube
- unit curriculum
- unit disc
- unit disk
- unit disk integral
- unit distance
- unit-distance graph
- unit distribution
- unit divisor
- unit doublet
- unit dyad
- united
- UnitedAfricanNational Congress
- United Aircraft Corporation Corporation
- United Arab Emirates' Drama
- United Arab Republic
- United Arab Shipping Company
- united archives room