secondness第二性secondadj.第二的；次等的；再一个的num.第二n.片刻；秒adv.第二；其次v.支持；赞成；附和；调派second harmonic magnetic modulator二次谐波磁调制器second-order Hidden Markov ModelSecond school year second semester第二学年第二学期second-order differential system二阶微分方程组second period water supply project二期供水second-third trimester gestation中晚期妊娠second electron cyclotron harmonic二次电子回旋加速器谐波second-order multiplexed signals二次群复用信号second order sufficiency condition二阶充分条件second-order recurrent sequences二阶线性递归序列