“first day cover”的概念、定义、翻译、参考文献-科学参考

单词	first day cover
释义	first day cover Encyclopedia 工学集邮品释 first day cover首日封在新邮票发行首日，将该套邮票的全套或单枚贴在特制信封、普通信封或纪念信封的右上角，加盖当日邮政日戳或特制的首日纪念邮戳的信封。
随便看	partial sampling partial semigroup partial sequence partial set partial solar eclipse partial spread partial square partial stability partial subalgebra partial subgraph partial subset partial sum partial summation partial-summation formula partial summation of diagrams partial synthesis partial tide partial tone partial trace partial transformation partial transpose partial transversal partial truth assignment partial-variable stability partial variance

科学参考收录了854744条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。