First ald急救firstadj.第一的；最初的adv.首先；第一n.最初；(序数词)第一First Recorded Appearance Time第一次记录出现时间First-order electric circuit一阶电路first episode major depression首发重性抑郁症first order modal logic system一阶模式逻辑系统first-order mathematic model一阶数学模型first-order plus dead-time一阶惯性纯滞后First state to abolish slavery首个废除奴隶制的州First- episode schizophrenia首发精神分裂症first order logic axima system一阶逻辑公理系统first order floating frequency一阶纵飘频率