LD50 is the amount of a toxic agent (as a poison, virus, or radiation) that is sufficient to kill 50 percent of a population of animals usually within a certain time

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LD50（lethal dose 50%）之定義　　

半數致死量：是指在一定的時間內能夠引起試驗動物一半死亡的藥物劑量，通常用藥物致死劑量的對數值表示。