when necessary
必要时：在需要的时候
常用释义
英式发音
美式发音
基本释义
- 必要时：在需要的时候，表示某件事情只有在必要的时候才会发生或进行。
例句
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1·They are not afraid to tackle the issues or let the sparks fly when necessary.他们不怕应付这些问题, 必要时也不惜进行唇枪舌剑的激烈争论。来源: 《柯林斯英汉双解大词典》
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2·With any container that you choose, you need to ensure that it allows the water in it to drain when necessary.对于您选择的任何容器，您需要确保在需要的时候它能够排除里面的水。
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3·A new system allows a combine harvester, say, to send a call over to a tractor-trailer so the driver can unload the grain as and when necessary.例如，一种新的系统允许联合收割机向牵引拖车发送呼叫，以便司机可以在必要的时候卸载谷物。
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4·The government, when necessary, has recourse to the armed forces.政府在必要时可以动用军队。来源: 《牛津词典》
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5·When necessary, instinct is the most reliable resource you can fall back on.必要时，本能是你可使用的最可靠的资源。来源: 《柯林斯英汉双解大词典》
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6·Sometimes I watched the online classes again when necessary.有时候，我会在必要时再看一遍在线课程。
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7·Although they are big animals, elephants can move silently when necessary.虽然大象是大型动物，但在必要时它们可以悄悄地移动。
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8·Only flush the toilet when necessary: this means to not use the toilet as a garbage to avoid wasting water.只在必要时冲厕所：这意味着不要把厕所当作垃圾桶使用以避免浪费水。
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9·We create an opportunity for assessment and intervention, to help clients and communities cope effectively with their reality and change that reality when necessary.我们为评估和干预创造机会，帮助客户和各大团体有效地应对现实问题，并在必要时对现实做出改变。
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10·They generally tend to share very similar tastes in music and clothes, they spend their money in having a good time, and save for holidays or longer-term plans when necessary.他们通常倾向于在音乐和服装上有着非常相似的品味，他们把钱花在享乐上，并在必要时为假期或长期计划存钱。