論文呢 應(yīng)該根據(jù)你寫的內(nèi)容來決定時(shí)態(tài).
如果是描述現(xiàn)在的狀態(tài)還是用一般現(xiàn)在時(shí),
但如果是講過去的事情,還是用過去時(shí).
具體你論文什么內(nèi)容不如跟我說說,幫你具體參謀一下.

用一般過去時(shí), 因?yàn)槭怯浭鲆惶煲呀?jīng)發(fā)生內(nèi)過的事容情

如: July 1st, sunny

It was Sunday and it was sunny today. I went to the park with my parents. There were thousands of people in the park. Some of them played chess under the big tree. Some of them rowed boat on the lake. We climbed the mountain and had a picnic on the top of the mountain. Then we picked up the rubbish and threw it into the dustbin because it was our duty to protect the environment. Although we felt tired, we were really happy.

日記記得是一天已經(jīng)發(fā)生的事，宜用一般過去式帶完成時(shí)（假如對(duì)現(xiàn)在產(chǎn)生影響）事實(shí)可以用一般現(xiàn)在時(shí)
I was very sleepy in the morning, so i didn't go running as usual. I had something for breakfast. My new day has begin. The results would come out today. My classmates all felt very nervous, so did I. Then one of my classmates called me, and invited me to play basketball in the afternoon. I like playing basketball, though I'm really poor at playing it. I and my parent visited redstart farm last Saturday,there're environment is so good.we're scavenge the hourse,The horse was leaded into the stable and each was put in a stall.Cows and sheep depends forage to feed.this so lifelikeness,we're got a lot of enjoyment from my job. in the end.owner preparative feasted on me.

日記記的是當(dāng)天已經(jīng)發(fā)生的事，用一般過去時(shí)。

大部分是用一般過去時(shí)，但是如果你寫的是你最近的近況，或者是習(xí)慣性動(dòng)作就用一般現(xiàn)在時(shí)，其實(shí)一篇日記里可以用上各種時(shí)態(tài)的。
January 13 2005
It was the first day of our winter holiday. All of us were very happy. Why? Because we have one months to do things we love to do. We are free. Although we have some homework. But we can finish them in several days. And the rest time we can make good use of. My god! We have been very tired after hard studying. In winter holidays, I want to have full sleep and eat good food in order to replenish myself. Last but not the least, I will have a good rest.

既然是摘要,那就是對(duì)已近發(fā)生的事做概括,所以主體最通常的時(shí)態(tài)是一般過去時(shí).一般現(xiàn)在時(shí) ，但如果是科技實(shí)驗(yàn)論文、產(chǎn)品說明摘要，一般只用一般現(xiàn)在時(shí)。