介绍一个学习用品作文说明文500字【一】
春姑娘踏着轻盈的脚步悄悄地来到了人间。春风吹过，万物复苏。小草宝宝好奇地从地下探出头来；竹子弟弟迫不及待地冲了出来；石榴树哥哥长出了嫩绿的新芽。不久，绵绵的细雨打破了春日的寂静，植物们欢快地喝下这“生命之水”。石榴树的新芽渐渐地长出了浅绿的叶子，竹子不知什么时候抽出了竹叶，一派生机勃勃的景色。
夏哥哥着急地奔向人间。太阳猛烈地照着，粉红的荷花和洁白的茉莉花相互媲美。荷花亭亭玉立，枝茎不停地往上伸，似乎要看美丽的景色，有的含苞欲放，有的还是花骨朵儿呢！茉莉也不甘示弱，它们散发着一阵阵浓郁的清香，吸引来了一群群可爱的小蝴蝶，它们翩翩起舞，像一位位舞者在展示自己的舞姿。
送走了烈日炎炎的夏天，便迎来了金灿灿的秋天。院子里的桂花树开出了一朵朵金黄的花朵，散发着一片诱人的`香味，就算十里远也能闻到。桂花如米粒般大小，要是远看，真不容易被发现呢！石榴树上，火红的果子在绿叶的衬托下，显得更美了，像一个个姑娘害羞了脸。有的神气地抬起头；有的双胞胎紧靠着，似乎在说悄悄话；还有的藏在绿叶里，似乎在跟我们玩捉迷藏呢！
冬天不知不觉地到了，树都落下了金黄的树叶，准备冬眠了。只有那腊梅勇敢地矗立着，开出了一朵朵鹅黄的花朵，幽幽的香气飘来，似有似无，闻起来却神清气爽。天空飘着白蝴蝶似的雪花，给大地铺上了银毯，给树木披上了银装，活像一位位雪人在指引方向。
我爱生机盎然的小院，更爱把它装饰如此美丽的大自然！
介绍一个学习用品作文说明文500字【二】
说明文是以说明为主要表达方式用来说明事物，阐明事理的`一种文体。它通过揭示概念来说明事物的特征、本质及其规律性，给人准确的科学知识或正确思想。一般可分为实体事物说明和抽象事物说明两大类，词典、教材、论文、实验报告、产品说明书、广告、解说词及科学小品等都属于说明文。
按写作方法,英语说明文主要分为下面六种类型
1.例证法 2.定义法 3.分类法 4.因果关系法 5.比较对照法 6.过程分析法
1.例证法
Our life today depends very much on energy. For example, machines have made our life easier than it used to be. The machines use energy, and energy is needed for heating, lighting, communications, carrying goods-everything. Factories use a great deal of energy to make the things that we use and buy and sell.
这段主要是讲能源问题。第一句为主题句,概括地说出"我们目前的生活很大程度上依赖能源"。接着用举例的方法从三方面说明能源的作用。
2.定义法
An ideal teacher must have the following characteristics. He should know his subject, but he can make mistakes if he is willing to learn. His personality is as important as his scholarship. An ideal teacher must be enthusiastic. He should be a bit of an actor and he shouldn't be afraid to show his feelings and express his likes and dislikes. An ideal teacher is one who grows, learns, and improves himself along with his students.
本段的展开是通过对"一个模范教师"下定义的方法,关键词"ideal teacher"在文中多次重复,能加深读者的印象。
3.分类法
As far as political views are concerned, people fall into three categories. First are the conservative people. Conservatives are opposed to sudden or great changes. Second are the liberal people. These people are in favour of progress and reform. But their opinions often seem too idealistic. Third are the moderate people. The moderates keep everything within reasonable limits. They are more practical in this hard world. In my opinion, most people seem to belong to this group.
本段把人按政治观点分为三类:保守派(conservative people、自由派(liberal people和温和派(moderate people,并对他们各自的特征进行了简要的分析。
4.因果关系法
Of the four seasons, I like spring best. I prefer spring because it is a season of much joy and gaiety. New life bursts out everywhere. Plants wear a green coat again and colourful flowers blossom in gardens and mountains. The old come outdoors for fresh air and the young plan for outdoor activities. Life becomes so energetic and happy.
第一句为本段主题句,末句是总结句。在主题句后, 作者用了四个句子阐述自己喜欢春天的理由。
5.比较对照法
I like having a twin sister. When she's happy, I'm happy. When she feels unhappy, I feel the same. Often, I know what she's going to say. Sometimes, I know what she's thinking. I like what she likes. I hate what she hates. We like the same music, the same food and the same books.
这段采用AB交错的比较方式,阐述孪生姐妹的相同特征。这种写法较流畅自然,给读者的印象也更鲜明突出。
6.过程分析法
There are several steps to plant a tree. First, dig a hole large enough for the tree, but the hole should not be too deep. Second, put the tree in the hole so that it is straight. Third, put the earth back into the hole again. Push it down hard with your foot several times. Finally, water the tree well, as often as possible.
这段分析了植树过程中的几个步骤。全段层次分明,连接词语(first, second, third, finally的使用加强了语句的连贯性。
Exercises
例１ 请根据Wang Hua 在学骑自行车时的几个步骤，写一篇短文，说明他是任何学会骑自行车的．
参考词汇： handle-bars 自行车把手 pedal 踏板 saddle 车座
Wang Hua is learning to ride a bicycle. Let’s watch him and see how he can get on his bicycle. He put his hands on the handle-bars. He puts his left foot on the left pedal, then he pushes himself hard forward with his right leg. Now he can move on together with the bicycle and his whole body is now on the bicycle. Then, he raises his right leg over the saddle and lower himself on the saddle. Now, he is on the bicycle and stepping the pedals hard with both legs. And the bicycle is going forward.
例2
请写一篇短文介绍如何乘坐伦敦地铁．
内容提示如下：
1. 在售票处（booth购买辅币（token需30便士．
2. 在入口处将辅币投入狭孔（slot，你就可以走下地铁．
3. 在站台等车时，要站在白线以外．注意你要去的方向．不要站错站台．
4. 上下车应迅速，因为车门关闭很快．地铁内规定不准吸烟．
注意：短文的意思要连贯． 字数：100个左右．
If you want to travel by underground in London, you should first find the nearest underground entrance and buy a token for 30 pence in the booth. After you drop the token into the slot at the entrance, you can walk down the stairs. Stand back of the white line while waiting for the train on the platform. Make sure that you are on the right side of the platform for your train. When the train arrives, get on or get off quickly because the doors of the train close quickly. Smoking is not allowed in the underground.
例3
家用电脑体积下，价格低，造型优美，简单易用，使用方便，灵活；可用于计算，记事，打电话，打印信件；儿童可用它来学英语，做游戏． 你通过家用电脑能学会怎样使用微机；为将来寻找工作提供便利；电脑工作比人快数百倍；我们已经得到电脑的巨大帮助． 请根据以上内容写一篇介绍家用电脑的说明文． 字数120左右．
A Family Computer
A family computer is small. Its price is not high, and it has a good look. It can be used easily. You can calculate, make notes, call others and type letters, etc. Also, children can learn English or play games with it. Besides, you can use a family computer as a training computer. You can learn how to use an office computer, which can give you convenience to find a good job in a company. Computers can work hundreds of times faster than humans. We have been greatly helped by
computers.
例 4
请以The Importance of Trees 为题写一篇短文，说明保护森林的必要性．
1. 说明树木的主要用途：提供木材；吸水，防止水灾，旱灾；净化空气，美化生活．
2. 滥伐树木的危害；无计划砍伐造成水土流失，土壤沙化，造成水灾．
3. 每年都应植树造林，使其为人类更好服务等等．
字数：100左右．
As we all know, trees are very useful. They are of great benefit to man as follows. First, trees provide us with wood and other products. Second, their roots can allow the rain to sink in and keep the soil, so they help to prevent droughts and floods. Trees can help clean air and beautify life.
Unfortunately, nowadays in many parts of the world lots of people fail to realize the importance of trees. They have cut trees down in large numbers without a plan, which makes the soil washed away. They don’t know where there are no trees, the rain washes away the surface of the soil and this causes floods.
We ought to plant trees each year and carefully look after new trees in order not to make the forest slowly disappear. Only in this way can we make the forest serve man forever.
例 5
根据下表格提供的信息，请你推荐两本学中文的词典．
Dear Steve,
I’m pleased to learn that you and your classmates are learning Chinese. I’d like to recommend the following two dictionaries. The English- Chinese Chinese-English Dictionary is really a good one for beginners. It has 18,000 English words and 20,000 Chinese words. Besides plenty of examples, it has many notes telling you how to use a word. Xinhua Dictionary is the most popular Chinese dictionary, and it has a vocabulary of 10,000 words. It may also be useful to some advanced learners of Chinese. Of the two, ECCED is the more expensive, costing 52 yuan, and XD costs 11 yuan.
Please let me know if you want me to buy these dictionaries.
Yours, Li Yua
介绍一个学习用品作文说明文500字【三】
鲸类是一种生活在水中的哺乳动物，它具有和陆上哺乳动物相同的生理特徵，例如用肺呼吸、胎生等，更具备了一些为适应水生环境所演化出的特殊生理构造。鲸分为3类，分别是须鲸和齿鲸。这两大类的分群，再学术上主要是依据它们摄食方式之不同而定，须鲸主要的形态特徵是没有牙齿，但是有具大的鲸须，可用来筛选浮游生物。所以为滤食性。齿鲸亚目的主要特徵为有牙齿，掠食性，其牙齿的数目与排列方式受到食性的影向会有不同，全世界现存有13科约79种。
鲸鱼虽然有鱼字，其实它并不是鱼类，而是哺乳类动物，它有许多和鱼类极不相同的特性，例如一般鱼类是左右摆动尾鳍来使身体前进，而鲸鱼却是以上下摆动尾鳍的方式前进。它们利用前端的鳍状肢来保持身体平衡及控制力向，有些鲸鱼背部的上端还有能保持身体垂直的鳍呢！
鲸鱼是群集动物，它们通常成群结队的在海裏生活，可是当鲸鱼呼吸时，就需要游到水面上来，这时鲸鱼是利用头上的喷水孔来呼吸，呼气时，空气中的湿气会凝结而形成我们所熟悉的喷泉状。专家们甚至可以从喷水的高度、宽度及角度，来辨识鲸鱼的种类呢！鲸鱼的种类很多，大致分成齿鲸和须鲸两大类。
鲸鱼的表皮下有著极厚的脂肪层，那就是俗称的鲸油，它可以使鲸体保持温暖，而且也能贮存能量以供应不时之需。由於鲸鱼体内拥有许多特殊的构造，使它能够长时间的在水中屏庄呼吸、减慢心跳速度，因此当它沈到海底，总要经过一段长时间后，才会再浮出水面。除了具有贮存氧气的构造外，当身体某个部位需要大量的液供应时，体内还会有集中供应的特殊机能呢！
