at和in怎么用

at
介词 prep.

1.在...地点
They were already waiting at the gate when I got there.
当我到达那里时,他们已等候在门口了。
2.在...时刻
Jane will meet her boy friend at Christmas.
简将在圣诞节和她男友见面。
3.向,朝,对着
Don't shout at me.
别对我叫喊。
4.在...方面
He is an expert at troubleshooting.
他是位排解争端的能手。
5.因为,由于
I woke at the sound of the bell.
随着铃响,我醒了。
6.从事于,忙于
He is working hard at this thesis.
他正在努力地撰写论文。
7.以(某种价格、速度等)
They sold the cloth at a dollar a yard.
他们以每码一元的价格出售这种布。

in
介词 prep.

1.在...里,在...上
The two brothers study in the same class.
两兄弟在同一个班里上课。
The telephone is in the little study on the ground floor.
电话在一楼的小书房内。
2.在...之内;在...方面
He is lacking in courage.
他缺乏勇气。
3.从事于;参加着
She is in business.
她做生意。
4.穿着,戴着
He is dressed in black.
他穿黑衣服。
5.朝,向
She hurried away in the opposite direction.
她朝相反的方向匆匆离去。
6.(表示手段、方法、材料)用,以
They paid in cash.
他们用现金支付。
7.在...期间;在...以后
He'll come back in a week.
他将于一周之后回来。
I haven't met her in a long time.
我好长时间没有遇见她了。
8.处在...中
The room was in disorder.
房间里乱七八糟。
9.(表示数量、程度、比例)按,以;在...中
One child in twenty has this disease.
二十个小孩中有一个患有这种疾病。
10.在...身上,在...上
In him I see a future leader.
我在他身上看到了一个未来的领袖人物。
11.(表示过程)在...当儿;在...过程中
The work is in progress.
这工作正在进行中。
12.(表示动作的方向和结果)进入到...中;成,为
He pushed a button and set the machine in motion.
他按下按钮开动了机器。

副词 ad.

1.进;在里头
Please come in.
请进。
2.在屋里;在家
I called on him; but he wasn't in.
我去拜访他,但他不在家。
3.(车、船、季节等)已到达,已来临
Spring is in at last.
春天终于来了。
4.(庄稼)已收进;已成熟
The wheat crop is in.
小麦收进来了。
5.(服装等)时髦
Miniskirts are in again.
迷你裙又时髦起来了。
6.当政;当选
The Democratic Party is in.
民主党执政了。
7.【板】轮到击球,【网】(球)在界内
8.(加)入,(搀)入

at是指具体的某个事件段落、或某个小地点、
如在一点钟、at one o”clock. at the cinema.
IN是在某个大地点前或某个不太具体的时间、
如in China . in the afternoon.

at是指具体的某一点，例如：at9：00in是指某一段时间，例如：in the morning！

是啊 就是这样的
比如in London at home