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
- ALD
- ALDA
- Aldabra Islands
- aldan facies
- aldanite
- Aldan River
- Al-Daqahliyyah
- aldaric acid
- aldaric acid; saccharic acid
- Alday Gaiotto Tachikawa duality
- Alday-Gaiotto-Tachikawa duality
- Aldebaran
- aldehyde
- aldehyde-containing perfume
- aldehyde hydrate
- aldehydes
- aldehydes compound poisoning
- aldehyde-sulphoxylate
- aldehyde tanning
- aldehydrol
- Alden crater
- alder
- Alderamin
- Alder crater
- Alder ene reaction