first of all

英 [fɜːst ɒv ɔːl]

美 [fɜːrst əv ɔːl]

第一;首先

牛津词典

firstly在英国英语中比在北美英语中更通用。
Firstly is more common in BrE than in NAmE .
1. The brochure is divided into two sections, dealing firstly with basic courses and secondly with advanced ones.
  小册子分为两部分：第一部分涉及基础课程，第二部分涉及高级课程。
at first用以讲述最初阶段的情况，尤指与后来的不同情况相比较：
At first is used to talk about the situation at the beginning of a period of time, especially when you are comparing it with a different situation at a later period.
1. Maggie had seen him nearly every day at first. Now she saw him much less.
  起初玛吉几乎每天都见到他，现在见到他的次数少得多了。

adv

before anything else
1. first we must consider the garter snake
Synonym:firstfirstlyforemostfirst off

First of all, I want to thank my parents for bringing me into this world.
首先，我想感谢我的父母把我带到这个世界上。
First of all, let's set the scene.
首先让我们来叙述一下背景。
First of all, first of all, when I do business with him.
首先，首先，我和他做交易的时候。
First of all, I wanted to shake hands, all right?
首先我想和你握手言和好吗？
First of all, this paper described the definition and the security model of the identity-based encryption.
首先叙述了基于身份的加密定义和安全模型；
First of all, I've used the notion of modularity.
首先，我用到了模块的概念。
First of all, answer these questions
首先，回答这些问题。
My aim was first of all to determine what I should do next.
我的目标首先是要确定自己下一步该做什么。
First of all, this paper introduces a semantic component model and also makes extension to it.
首先，本文介绍了一种语义构件模型，并对其进行了扩展。
First of all, we need more research on biofuels.
首先，我们需要对生物燃料进行更多的研究。