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现在完成时的标志词(just，already，yet，for，since)用法讲义及练习
一、现在完成时概述
现在完成时表示 过去发生的动作与现在的联系，强调动作对当前的影响或状态持续至今。其标志词包括 for、since、just、already、yet 等，具体用法如下：
二、核心区别与用法
1. for 与 since
- for
- 接时间段（如 three hours、ten years），表示动作持续的时间长度。
- 例句：
- I have lived here for five years.（我在这里住了五年。）
- She has been awake for 10 hours.（她已醒了十小时。）
- since
- 接时间点（如 2008、last year）或 时间段+ago（如 three years ago），表示动作从某一时间点开始持续至今。
- 三种形式：
① since + 过去时间点：
- He has worked here since 2020.（自2020年起他就在这里工作。）
② since + 时间段 + ago：
- It has rained since three days ago.（自三天前开始下雨。）
③ since + 过去时从句：
- I haven't seen him since he moved to London.（自他搬到伦敦后，我再未见过他。）
总结：
- for + 时间段（强调时长） vs. since + 时间点（强调起点）
- 互换公式：
since + 时间点 = for + 时间段（例：since 2010 = for 15 years）
---
2. just、already 与 yet
- just
- 含义：表示“刚刚”，强调动作刚发生。
- 位置：紧接在 have/has 之后，过去分词之前。
- 例句：
- She has just left.（她刚离开。）
- already
- 含义：表示“已经”，用于肯定句，强调动作提前完成。
- 位置：
① 句中：have/has already done
② 句末：have/has done already
- 例句：
- I have already finished.（我已完成了。）
- The movie has started already.（电影已经开始了。）
- yet
- 含义：
① 疑问句中译为“已经”，否定句中译为“还（未）”。
- 位置：只能置于句末。
- 例句：
- Have you eaten yet （你吃了吗？）
- He hasn't arrived yet.（他还没到。）
总结：
- already（肯定句） vs. yet（疑问/否定句）
- just 仅用于肯定句，且位置固定。
三、易错点与注意事项
1. 时间点与时间段的区分：
- 时间段（如 three days）可用 for，时间点（如 Monday）用 since。
- 判断技巧：复数形式多为时间段（如 days），单数形式可能是时间点或时间段（如 a day 是时间段，Monday 是时间点）。
2. 终止性动词的否定用法：
- 终止性动词（如 leave）的否定形式可接时间段：
- I haven't left here since 2015.（自2015年起，我从未离开过。）。
3. 固定句型：
- It is/has been + 时间段 + since + 过去时从句：
- It is ten years since I met her.（自上次见她已过去十年。）。
四、综合对比表
标志词 含义 接续内容 句型位置 例句参考
for 持续时长 时间段 句末或句中 for 5 years
since 动作起点 时间点/从句 句首或句中 since 2010
just 刚刚 无 have与分词之间 has just left
already 已经（肯定） 无 句中或句末 already done
yet 还/已经 无 句末 not...yet
练习题
Fill with for, since, just, already, yet
My son went to the supermarket but he hasn't come back ______.
Leonard has ______ made his bed but he hasn't called his girlfriend ______.
Miriam has lived in Morocco ______ she was ten years old.
We have ______ met the new teacher at the high school.
The waiter has ______ brought me some coffee and biscuits.
Have they visited London ______ No, they haven't ______ been there.
That man has ______ come late again. His boss is very angry with him.
Has the girl lived in France ______ five years Yes, she arrived five years ago.
The plane has flown ______ twelve hours.
The businessman has worked in the same office ______ he was twenty-five years old.
There have been many accidents on this road ______ last year.
John has performed the same play ______ a long time.
The woman hasn't sold her car ______ but she wants to sell it.
I have known my boyfriend ______ we were at primary school.
My son went to the supermarket but he hasn't come back ______ .
Leonard has just made his bed but he hasn't called his girlfriend ______ .
Miriam has lived in Morocco ______ she was ten years old.
We have ______ met the new teacher at the high school.
The waiter has ______ brought me some coffee and biscuits.
Have they visited London yet No, they haven't ______ gone there.
That man has ______ come late again. His boss is very angry with him.
Has the girl lived in France ______ r five years Yes, she arrived five years ago.
The plane has flown ______ twelve hours.
The businessman has worked in the same office ______ he was twenty-five years old.
There have been many accidents on this road ______ last year.
John has performed the same play for a long time.
The woman hasn't sold her car ______ , but she wants to sell it.
I have known my boyfriend since we were at primary school.
Nick hasn't bought a ticket to the concert ______ .
I have ______ packed my clothes for the trip.
We have ______ returned from our summer vacation.
Dad hasn't arranged the flights ______ .
Michelle has ______ taken a lot of photos.
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