He was not at his office.他不在办公室。
He arrived at a little village last night.他昨天夜里到达一个小村庄。
He was standing at the door.他正站在门边。
There was a symphony concert at the music hall.音乐厅里有一个交响乐音乐会。
I sat at the back of the room.我坐在房间后面。
The meeting will open at 15:00.会议在下午三点钟开始。
Someone will knock on your door at midnight tonight.今晚午夜时分会有人敲你的门。
At the beginning of June an event occurred.六月初发生了一件事。
Staying up late will do you harm at your age.在你这样的年纪熬夜有害健康。
The children used to send me a card at Christmas.孩子们过去常常寄圣诞卡给我。
The soldiers are standing at attention.士兵们立正站着。
The roof is at a right angle to the walls.房顶和墙壁成直角。
I was there at a bound.我纵身一跃就到了那里。
He covered the distance to his house at a run.他一口气跑完了通往他家的路程。
We were frightened at the terrible sight.看到这可怕的景象,我们被吓呆了。
An extra book may be borrowed at the discretion of the librarian.图书管理员可以斟酌决定是否可以额外借阅一本书。
At the suggestion of our parents, we deferred the visit to the museum until the following day.根据我们父母的建议,我们将参观博物馆一事推迟到第二天。
I saw it at a distance.我从远处看见了它。
They opened fire at a range of 200 yards.他们在200码的射程处开火。
Somebody is knocking at the door.有人在敲门。
He threw the key at me.他把钥匙丢给了我。
I remember him at a banquet on that night.我记得那天晚上他参加了一个宴会。
She is good at describing things or expressing ideas.她善于描述事物或表达思想。
What do five books cost at two dollars a book?两美元一本的书,五本价钱是多少?
He is driving at (the rate of) seventy miles an hour.他正以每小时70英里的速度行驶。
The ship was going at full speed when it hit the rock.该船在全速行驶时触礁。
I must go and see what those children are at.我得去看看那些孩子们在干什么。
They were at their meal.他们正在吃饭。
At the sight of her appearance on the stage, the hall rang with thunderous applause.一看见她出现在舞台上,大厅里就掌声雷动。
They were gloomy at the thought of what they had to face.他们一想到不得不面对的事实就感到沮丧。

at, in, on
1.at,in和on都可表示时间。at通常指确切的某个时刻,如at six o'clock; in通常表示一天的某一部分,如in the morning(evening, afternoon); on则具体说明哪一天的上午或下午,如on Monday morning, on a summer's day。在谈论节日时,at通常指整个的节〔假〕日,不只指一天,如at Easter 在复活节,at Christmas在圣诞节; on可具体指节日的某一天,如on Easter Monday 在复活节后的星期一,on Christmas Day 在圣诞节(那天)。在谈论月份、季节、年份或世纪时,通常用介词in,如in the eighteenth century 在18世纪,in summer 在夏天,in March 在三月,in 1985 在1985。
2.at, in和on都可表示地方、位置。at多用于指空间某一点; in用来指有大小、体积和幅度的一个地方或位置。
3.at the weekend在周末(英国用法); on the weekend在周末(美国用法)。

at, after, by, for, from, over, through, with
这组词都可表示原因。其区别在于:
1.after是由其指时间的本意引申而来,含有明显的因果关系,可译为“经过…之后(所以)”; by是由其指方法、手段的本意引申而来,意思是“通过…手段〔途径〕(而产生某种结果)”; through是由其指媒介的本意引申而来,常指偶然或意外的原因,强调其不利或消极的因素; from是由其指起源、根源或由来的本意引申而来,可以是事物发生的原因,也可以是行为产生的动机; at一般指看到、听到或感觉到客观事物而产生某种感情、情绪、态度或行为的原因; for一般指由于客观原因(如举止、言语等)而导致某种结果; over常指造成某种情感的客观事物或原因; with是从其表示手段的含意引申而来的,指由于外界刺激而造成的精神上的或身体上的某种状况。
2.through后常接抽象名词; at常与angry, annoyed, astonished, mad, sad, shocked, marvel, wonder等形容词或动词搭配; for常与famous, well-known, admire, apologize, blame, punish, thank等形容词或动词搭配; over往往与cry, grieve, laugh等表示情绪的动词连用; with常常与表示感情的形容词(如affected, angry, excited, fatigued, pleased, tired等)、生理状况的形容词(如blind, ill, mad, numb等)和颜色的形容词(如blue, grey, green, livid, red等)或是表示身体运动的动词(如burst, shiver, shudder, tremble等)搭配。
3.在英式英语中,引起感情、心理刺激的如果是人或物,通常用with; 如果是言行或事件,则通常用at。

at, beside
这两个词都有“在…旁边”的意思。其区别在于:at表示有目的的接近; beside表示偶然的靠近。

at, by
这两个词都可表示“按照”“根据”“依照”“依从”。其区别在于:
1.at多接抽象名词; 而by多接具体名词。
2.这两个词都有“按…计算”的意思,不过by用于英式英语; at用于美式英语。

at, to
这两者均可表示方向, to一般是善意的; at含有寻衅的意味,往往是恶意的。例如:
The boy throws a bone to the dog.
那小孩扔了一块骨头给狗。(善意)
The boy throws a bone at the dog.
那小孩把一块骨头扔到狗身上。(恶意)