... d t [ I ] [ I ] 0 e t d k - 公式 说明 43 3.2 自由基聚合机理 3.2 自由基聚合机理 高分子化学 （2）半衰期(half life period) 指引发剂分解至起始浓度一半所需时间，以t 1/2 表示，单位 通常为h -1 。对一级反应，常用半衰期来衡量反应速率大小。
2
?半周期
... half life半衰期 half life period半周期 half shadow apparatus半影装置 ...
Cefixime is characterized by broad spectrum, long halflifeperiod, less cross resistance to chemical reagent, small use dosage and wide scope of application.
头孢克肟抗菌谱广、半衰期长、交叉耐药性小、用药剂量小、适应症广泛。
2
I watch his face while he accounts for the past decade and a half of my life, a period during which he was probably spending his summers in Europe.
我望着他的脸，他讲述过去十来年，那十年是我人生的一半时间，在这段期间他可能在欧洲度过了每个夏天。
3
As with radioactivity, stories have a half-life-in other words a period by which half of newly promoted stories are relegated to a nether page.