科技论文中常用的两种时态是现在时和过去时。一般而言，在表述观察结果、已完成的行为及特定结论时应使用过去时。例如，描述实验结果时要使用过去时，因为实验已经结束，而你的结果尚未成为公认的“事实”。因此，那些主要涉及你自身工作的内容，如“摘要”、“材料和方法”以及“结论”部分都应使用过去时。
例1
a Higher temperatures resulted in less bud formation.
b The three images were taken about 90 minutes apart.
对于那些普遍认可的概念和观点用现在时表述。已经发表的结果通常被视为“事实”。 “前言”部分要使用现在时，因为其所介绍的是前人构建的知识。
例2
a The newly discovered planet is at least as big as Pluto.
b Most regions where this problem arises belong to category X.
如果用过去时描述已经发表的工作的结果，则表示你不认为该结果是“事实”，而仅仅是观察结果。
例3
Sultan observed that certain species of bacteria respond to light stimuli.
该句描述的是一个已经完成的实验。因此“observed”使用了过去时，然而“respond”却使用了现在时，这是因为这部分句子表述的是事实，是发表过的、已经存在的知识。
“讨论”部分是探讨你的工作与前人工作的关系，这部分最难写，因为同时涉及现在时和过去时。记住，通常情况下，展现数据图表时用现在时，描述假说和原理时也用现在时。
例4
The effect of TXY addition is shown in Figure 5.
当观察被重复进行或从过去持续到现在，则使用现在完成时。
例5
X has been of interest for the past three decades.
只有一种情况使用将来时，就是你的实验计划于将来实施。未来的实验一般不会出现在研究论文中，但会出现在基金申请中。
例6
We will examine if parallel universes exit.
练习：下列各句应使用过去时还是现在时(如果答案不只一个，请解释原因)。
1.In our study, tree size __________(increase) with reduction of pesticides.
2.The larva of the monarch butterfly__________(feed) on milkweed.
3.In our study, we__________(find) that there are significant flattenings of the PES along the reaction Pth with increasing cluster size, as Fig. 5__________(indicate).
4.In a study by Fermi, the vibrational levels__________(diverge) into the so-called Fermi dyad.
5.Females of this species__________(have)a unique projection from he dorsal part of the thorax.
6.Recent work by deValt (2001)__________(show) that nematodes__________(reproduce) readily in the laboratory.
7.A phagemid construct encoding 2 transgenes in tandem__________(can) be used to transform E. coli cells.
8.Table 3__________(show) that in our study, polychaetes__________(be) most abundant at depths of 10 to 16 m.
9.Baumann (1997)__________(find) that this bacterium__________(is) highly sensitive to pH.
10.We__________(observe) chemoattraction within 30 min of Shh addition.
11.Identification of restriction factors__________(give) us more knowledge of the host cell restriction system.
12.Our results__________(suggest) that the Asn5 glycosylation site __________(play) a critical role in the function of the KCEN 1 protein.
13.We__________(investigate) high-quality single crystals of vanadium oxide.
14.We__________(do) not observe rods in the diffraction patterns but instead well-defined Bragg spots, suggesting that at least 10 interatomic layers in the surface-normal direction__________(be)contributing to the interferences.
15.Coupled climate-carbon cycle models__________(suggest) that Amazon forests__________(be) vulnerable to droughts, but satellite observations__________(show) a green-up in intact evergreen forests of the Amazon in response to a short, intense drought in 2005.
16.The Ka value for β-cellobiosyl (approaching 103 M-1)______(be)comparable to that for many carbohydrate/protein interactions.
17. Hundreds of species of reef-building corals__________(spawn) synchronously over a few nights each year, and moonlight_________(regulate) this spawning event.
18.Arctic wind anomalies______(be) part of a global-scale pattern of highly unusual circulation in 2007, the causes of which______(be) as yet unclear.
19. To map pathways of motion, all observed Bragg diffractions of different planes and zone axes__________(be examine) on the femtosecond to nanosecond time scale.
20. ABSTRACT: The average translational energy_____(be) significantly lower than expected for the calculated surface temperature.
21. SUMMARY: In conclusion, we_____(find) significant deviations from the equilibrium behavior in fs-laser induced desorption of CO/Ru.
参考答案
1. increased
2. feed
3. found … indicates
4. diverged
5. have
6. showed… reproduce
7. can
8. shows … were
9. found … is/was
10. observed
11. gives
12. suggest … plays
13. investigated
14. did… are
15. suggest…are… showed
16. is
17. spawn …regulates
18. were… are
19. were examined
20. was
21. found