24 hours a day（一天24小时）前面要用介词吗

问题描述

要表示“一天24小时”“全天24小时”“每天24小时”等，英语可以用 24 hours a day 吗？请问前面要用介词吗？

老师答疑

谭老师：

▲你说的情况需要用表示持续的时间状语来表达，此类状语一般由介词短语或名词短语实现。

▲最常见的时间持续状语由 for 引导的介词短语充当：

1. These guys worked shifts around the clock for 24 hours a day for 6 straight days. 那些人可是三班倒替天天24小时不眠不断地整整干了6天。

2. Now that I run it for 24 hours a day, it is only $83 per hour. 既然我24小时营业，每小时的租金就只有83美元了。

3. In Paris many shops simply close down for August; in Washington, where the weather is sweltering, they remain open, some for 24 hours a day. 在巴黎，很多商店八月份直接关门；而在华盛顿，尽管天气酷热，商店还是要开门，有的甚至是24小时营业。

4. He often played for 24 hours a day and didn't even stop to have his meals. 他经常24小时不停歇地玩牌，甚至不能停下来吃顿饭。

5. It means that even if they work for 24 hours a day, they are laying over eight meters of track every minute. 这听起来是很疯狂，因为这意味着即使工人们一天工作24小时，也要每分钟铺8米铁道。

▲上述介词短语里在 for 之后的名词短语也能直接充当时间持续状语：

1. The order was so large that the factory had to keep running 24 hours a day for a whole year. 订单很大以致生产商一年内必须保持每天24小时生产。

2. Cold Jet provides worldwide customer phone support 24-hours a day, 7-days a week to assist with any product maintenance or repair issue. ColdJet为世界各地的客户提供全天候电话支持，帮助解决任何产品维护或维修问题。

3. In July 1927 a medical doctor and four Franciscan nurses kept a watch on her 24 hours a day for a two-week period. 1927年7月，一名医生和四名护士对她进行为期两周的一天24小时密切关注。

3. Open 24 hours a day seven days a week, and free to the public, the pool is owned by the Town of Saratoga. 本泳池属于萨拉托加镇，每周七天每天24小时免费向公众开放。

4. There are security guards on duty 24 hours a day and they patrol all over the neighborhood. 这儿一天24小时都有保安值班，他们会在社区里巡逻。

5. I would doubt whether the usage of glasses is falling because even people who wear contact lenses are not wearing them 24 hours a day. 我对眼镜的使用率正在下降的说法表示怀疑，因为即使佩戴了隐形眼镜，人们也不能一天24小时戴着。

▲此类名词短语的结构为：中心词是表示时间间隔的名词（如hour、day、week等），前面有表示数量的限定词，后置修饰语为：

1. 不定冠词 a/an 限定的名词短语，例子略。

2.each 限定的名词短语，如：A particular place is not receiving radiation for 24 hours each day. 某一特定的地点不会每天24小时接受日照。

3. 以介词 per 为中心的介词短语，如：This is the only bookstore in China which is open for 24 hours per day. 这是国内唯一一家营业时间达24小时的书店。

▲结论：表示“每天24小时”、“全天候”等意义时，既可以使用24 hours a day，也可以在其之前加上介词for，还可以把这两种结构中的 a 替换成 each 或 per。