四级作文抄范文会被看出来吗【一】
7月8号发表在《自然—医学》（Nature Medicine）的研究发现，当我们的皮肤细胞受到中波紫外线（UVB）的照射时，核糖核酸（RNA）的一种特殊形式“微小RNA”（micro RNA）即被损坏。被损坏的微小RNA随后会作为皮肤被晒伤的.信号释放出来，并激发邻近的健康细胞，引发炎症。整个过程的目的是为了移除被阳光损坏的细胞，因为这些细胞有可能会癌变。
美国加州大学圣地亚哥分校医学院的医学教授理查德.加洛（Richard Gallo）说道，我们的皮肤细胞可以检测到已的、受日光伤害的细胞，这些细胞会释放受损的RNA。其他因素也有可能在皮肤晒伤的过程中起到一定作用，不过研究结果认为，受损的RNA可以被看成是晒伤的分子标记。
研究结果对医疗情况有着一定的意义。比如，皮肤疾病牛皮癣的治疗方法之一就是接受紫外线照射。虽说紫外线能够减轻病症，但它也会提高皮肤癌的患病风险。而新发现显示，某些特定的RNA分子或许可以代替紫外线疗法，并且产生相同的益处。
此外，一些有特定类型自体免疫性问题的人即便只受到微量紫外线的照射，他们的皮肤也会在细胞开始损坏之前就产生灼烧感。对这些病人而言，阻塞微小RNA的通道可能会降低炎症。
然而，没有上述问题的健康人是不应该仅仅为了防止晒伤而去阻塞这个通道的，因为对身体来说，这是机体愈合和剥除受损细胞的一种重要的方式。加洛说道，炎症反应是人体自身对阳光酷晒的防护措施的一个正常部分。
四级作文抄范文会被看出来吗【二】
Dear Mary,
You said in your letter that many of your classmates wore fashionableclothes, but you couldn\'t afford them so you felt very depressed. There are dif-ferent views on people\'s clothes. The followings are my ideas:
Firstly, you shouldn\'t put too much emphasis on physical appearance.
Remember that the most important task for you today is to concentrate on yourstudies. No matter what you wear, you will really look your best when youcome out first in your examinations.
Secondly, you should understand that it is a fine virtue to live in fru-gality. Just as a famous saying goes, Frugality is the mother of virtue.
Since your family can\'t provide you with enough money to buy fashionableclothes, it is all the more necessary for you to try to lighten the financialburden of your family. And you will find the virtue of frugality benefit youa lot in your future life.
I hope you understand what I mean. Hope you will take a positive attitudetowards life and will be happy again when you read my letter.
Yours,
Anne
四级作文抄范文会被看出来吗【三】
张良所以能成为千古良辅，被后世谋臣推崇备至，不仅在于他能运筹帷幄，决胜千里，佐刘邦创立西汉王朝，还在于他能因时制宜，适可而止，最后，既完成了预期的事业，功成名就，又在那充满悲剧的封建专制时代里保存了自己。
在秦汉之际的谋臣中，他比陈平思虑深沉，比蒯彻积极务实，比范增气度宽宏。他与萧何、韩信并称为汉初三杰，却未像萧何那样蒙受锒铛入狱的侮辱，也未像韩信那样落得兔狗烹的下场。
自从汉高祖入都关中，天下初定，张良便托辞多病，杜门不出，屏居修练道家养生之术。
汉六年（公元前201年）正月，汉高祖剖符行封。因张良一直随从画策，待从优厚，让他自择齐地三万户。张良只选了个万户左右的留县，受封为“留侯”。
他曾说道：“今以三寸舌为帝者师，封万户，位列侯，此布衣之极，于良足矣。愿弃人间事，欲从赤松子（传说中的仙人）游。”他看到帝业建成后君臣之间的“难处”，欲从“虚诡”逃脱残酷的社会现实，欲以退让来避免重复历史的\'悲剧。
的确如此。随着刘邦皇位的渐次稳固，张良逐步从“帝者师”退居“帝者宾”的地位，遵循着可有可无、时进时止的处事准则。
在汉初消灭异姓王侯的残酷斗争中，张良极少参赞谋划。在西汉皇室的明争暗斗中，张良也恪守“疏不间亲”的遗训。张良堪称“功成身退”的典范。
心得：
《菜根谭》有云：“恩里由来生害，故快意时须早回头；败后或反成功，故拂心处切莫放手。”（恩：恩惠，蒙受好处。快意：得意，心情舒畅。拂心：不能随便依自己的心愿行事。）
这就是说：身处顺境被当政者恩宠征用，往往会招来祸患，所以一个人在名利、权位上志得意满时应该见好就收，要有急流勇退的明哲保身态度，尽早觉悟；不过遭受挫败后有时反而会使一个人走向成功之路，因此遭受打击不如意时，千万不可就此罢休，放弃追求。
四级作文抄范文会被看出来吗【四】
Dear my father and mother,
This letter is my inner feelings. I want to thank both of you for so many years’ care and help.
During my growth, you have made a lot of efforts and love for me. When I make a success, both of you are more excited than me, and support me to do better. Even though I have failed, you always share sorrow with me and encourage me not to give up. Especially, during my preparation for CET-4, the support from you is always everywhere. I have passed the exam successfully.
You love is so unselfish that I am deeply affected, so I will study hard to be a useful person and won’t make you disappointed. Anyway, I would like to express the deep gratitude to you.
With best wishes.
Sincerely yours,
Li Ming
四级作文抄范文会被看出来吗【五】
Dear all,
I am writing this letter to express my gratitude to my parents for teaching me to be positive and to be strong. “Educating the mind without educating the heart is no education at all.” is the opinion held by Aristotle. It is the experience of our forefathers, however, it is correct even today, including my parenting.
It is widely acknowledged that parenting, which can also be explained as family education, is of great significance in our character forming and manner acquiring. To be more detailed, setting good examples instead of just giving precepts is the greatest achievement of my parents. They not only taught me to think for the best and prepare for the worst; they taught me how. They not only told me the benefits of being strong in mind; they proved it. All those things require huge amount of time and work, but it’s worth it.
Without my parents’ contribution and education, I would never be who I am now. But most importantly, I would never be more gratitude to them than today.
Yours,
XXX
四级作文抄范文会被看出来吗【六】
这种奇怪的现象，令个个问题诞生在我脑海：为什么鼻涕虫怕盐？鼻涕虫为什么会融化？……我先问父母，妈妈说这是民谚，从老人那辈流传下来的，也不知道为什么。疑惑不解的我只好去请教“百科全书”——电脑。电脑很快解答了我的疑惑。鼻涕虫的表皮和别的动物不同，就相当于层细胞膜，而且它的水份含量很高,若鼻涕虫没有水的话但会亡，盐有脱水的\'作用,当洒在鼻涕虫身上时,外界盐浓度比内部盐浓度大，鼻涕虫身上的水就会进行脱水，相对的,鼻涕虫就会掉了。任何动物也样,只是有皮肤来防御.所以盐洒在有皮肤的动物上是不会有影响的，但洒在受伤(没有皮肤复盖的地方,就会有影响了。我恍然大悟，却还 有个疑问缠绕在我的心头：那人泡浓盐水会不会有事呢？我再仔细找了找，原来，人表皮有层角质层，由亡的细胞构成，不具有扩散的性质，说以人泡在浓盐水里是没事的，（例：海泡澡，海的盐浓度比人体内的高多了，但是人类去泡澡的话并不会像鼻涕虫样的缺水亡）。这下，我是真明白了。没想到条小小的鼻涕虫也有这么多科学道理呢！
从这个小小的生活现象中，我还 懂得了个道理：我们要善于观察生活中平凡的事物现象，遇到不会的事，要积极寻求答案，用科学去解决疑难，用真理来窥探世界。不要迷信，仔细发现，生活中还 有许多有趣的事等着我们呢！
