今天的主题是，不少小伙伴对写作时态感到很困惑，全文都用同一时态多半是不行，那么每一部分内容到底应该用什么时态来描述呢？下面为大家分享关于“时态”的写作技巧。
1
引言
现在时：适用于描述客观事实，过去的研究结果现在依然是真实的、有意义的，即使这个研究结果是很久以前发现的。
例句：
Many of the lakes and wetlands in the region are located in craters or valleys blocked by early Pliocene lava flows (Ollier & Joyce, 1964).
现在完成时：适用于描述的是相对近期的工作或者是直至目前仍然在进行的工作。
例句：
A great deal of research has been conducted on the basic techniques of nuclear transfer, but few experiments have been carried out to discover the most appropriate age of the cytoplasm to support nuclear transfer most effectively.
2
实验方法
通常用过去时（被动语态）来描述已经进行过的实验。
例句：
A 100 uL bolus of the nano-particles was injected subcutaneously and imaged 15 minutes after injection. For validation studies, animals were sacrificed with CO2, and the implanted nanoparticle bolus analyzed by dissection.
3
实验结果
用过去时：描述实验（你已经做过的实验，怎么做的实验）
用现在时：描述你的研究发现（实验表明了什么，通过实验你发现了什么）
例句：
Fig. 5(C) shows an obvious decrease in blood oxygenation during reduced blood flow due to elevated pressure. This pressure was measured with a Tonopen both at baseline and after the injection of 600 uL (ischemia). We then removed the needle from the eye and measured the IOP and R-SO2 15minutes later (reperfusion).
Fig. 5(D) demonstrates the B-mode R-SO2 map in the reperfusion condition. The reperfusion map is not in the exact same plane as the previous condition because we moved the PA/US transducer to measure the IOP and then repositioned it back onto the eye after the IOP measurement.
4
结果与讨论
常使用现在时和过去时两种时态。
现在时：通常用于解释研究结果，陈述不会随着时间而改变的事实
过去时：通常用于总结和描述实验的细节，实验观察到的现象。和第三部分描述你已经做过的实验一样，用过去时。
例句：
One limitation of this approach is spatial resolution. Rabbits’ retinal vessels are 20 mm deep. Therefore, using higher frequency ultrasound (>I5 MHz) increases the resolution while decreasing the penetration depth. 【任何情况都成立，不会随着时间而改变】
Because the main goal was imaging the retina, we selected the 15 MHz transducer with 580 um and 290 um as lateral and axial resolution, respectively. 【实验细节】
This poor resolution can be observed in en-face retina images. Previous investigators showed high resolution retina vessel in small animals but with photoacoustic microscopy [42] [36]. 【实验观察到的现象】
While an ideal technique would have good depth penetration and 50-micron resolution to determine if specific sections of the retina are hypoxic, this current PAOI approach cannot discriminate between the retina and the choroid, and it is possible that the area of study includes both features. 【这部分是对实验结果的解释，属于作者的客观感受，用现在时】
5
实验方法
通常结合了过去的研究和未来指导方向。
例句：
Future work will focus on applications of this technology to other patient cohorts.
好了，关于文章每个部分的常用时态总结如上，小编为大家简单总结一下：
过去时通常用于描述你已经做过的实验等工作，实验过程中观察到的现象；
现在时通常用于描述研究表明了什么东西，描述不会随着时间而改变的事实；
现在完成时通常用于描述相对近期的工作或者是直至目前仍然在进行的工作。
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