first 有多种词性，其中就有名词，剑桥词典对作名词的first的定义是：the first person or thing to do or be something, or the first person or thing mentioned，例句有： [ + to infinitive ] She was one of the first to arrive.和He is the first (= very willing) to admit that much of his success is due to his good looks ...
first和firstly作副词时完全同义，都可以表示“第一，首先”，都可用作句子副词，此时first也可写作first of all。 例如： First，I would like to thank everyone for coming. 首先，我要感谢各位光临。 Firstly，I would like to thank everyone who has contributed to this success.
1 贝塞尔方程 显然，这是一个二阶齐次线性常微分方程，其解为： 其中， 为阶数， 为第一类贝塞尔函数 (Bessel functions of the first kind)， 为第二类贝塞尔函数 (Bessel functions of the second kind)，有的也记为 。 第一类贝塞尔函数积分表达式 对于整数阶n， 该公式也叫： Hansen-Bessel formula. 对于非整数阶 ，且 ...
