effective life短语¹⁸⁰⁰⁹⁸⁺¹ 基本例句 有效使用期,有效寿命 This report introduces the preparation and measurement of standard gas substances , along with a discussion of homogeneity, effective life and ways for further research. 介绍了标准气体的配制、测定方法，阐述了标准气体的均匀性、有效期以及今后研究的途径。 chemyq