一般过去时需要表达出来时，常可加添“过去；曾经；过； 了；当时”等词。例如：

8. Some people thought that intelligent things from other planets might come to visit the earth.

某些人曾认为，其它行星的智慧生物可能会来访问地球。

9. Our crops often suffered heavy losses because of bad weather.

过去，我们的庄稼常因天气不好而严重减产。

10. The lunar eclipse was seen through a gap in the clouds.

人们透过云隙看到了月蚀。

11. Inflation was and still is the No. 1 problem for that country.

通货膨胀过去是、现在仍然是该国的首要问题。（“现在”系一般现在时表达加词）

12. In developing Eq. (8) the assumption was made that the projectile with canard in place is inherently stable.

在推导方程（8)时，本文曾假定装有鸭舵的弹丸本身是稳定的。

13. Thousands of years ago in Egypt, salt was used to embalm the dead.

在埃及，几千年前，盐就曾用于尸体防腐。

(三)现在完成时的表达加词。

现在完成时是科技英语中很常用的一种时态。需要表达出来时，常可加译“曾经；已经；一直；始终；过”等词。例如：

14. Since 1939，numerous scientific studies have been conducted to determine whether smoking is a health hazard.

自1939年以来，人们一直在进行大量的科学研究，以确定抽烟是否对健康有害

15. Recent research has shown a connection between smoking and cancer.

最近的研究已经证明了抽烟和癌症间的关系。

16. No one has ever found a way to create energy out of nothing.

从来就没有人发现过凭空创造能量的办法。

责任编辑：admin