入乎“题”内 出乎“题”外

<正>华罗庚先生说过：“读书要从薄到厚，然后再从厚到薄．”解题就是这样，必须从薄到厚，入乎其内，想之又想，研解题策略；进而从厚到薄，跳出来看，出乎其外，删除枝蔓，留下根本，观题之不变．本文以苏科版数学教材八年级下册中的一道习题为素材，在原有背景下赋予新的问题，将中心对称图形与圆的知识结合，从而达到数学知识与方法的灵活运用．     

巧用废塑料瓶做实验几则

巧用废塑料瓶做实验几则贺承德（四川省阆中中学６３７４００）盛装液体饮料的大号塑料瓶壳具有透明、薄、易开孔、切割、加工等优点，虽软却有一定弹性，同时又有较大的体积（可见度大），利用它可以成功地做很多物理实验，特别是课堂演示实验，以下列举几则．一、演示...     

动脑筋 想一想(64)——间接度量

上期问题答案普通书籍用纸，一张纸的厚度通常不到０．１毫米。这么薄的纸，其厚度确实无法用尺子直接度量。不能直接度量的东西，我们可以想办法间接度量嘛。一张纸的厚度虽然不到０．１毫米，但是几百张纸的厚度加在一起就有几十毫米了，不就可以用尺子直接度量了吗？随便找一本厚一点的书，肯定会有好几百页，你就可以用尺子量一量这几百张纸有多厚了。当然，要知道一张纸有多厚，测量之后还要做一个小数的除法。例如，一本４８９页的书，厚度是２２毫米。按每两页一张纸计，也就是２４５（近似值）张纸共厚２２毫米，所以，每张纸的厚度…     

谈高考复习中的概括

“薄——厚——薄”，这是华罗庚学习数学的宝贵经验．他特别强调“由厚到薄”的消化、提炼过程，他说：“必须把学过的东西咀嚼、消化，组织整理，反复推敲，融会贯通，提炼出关键性的问题来”，“愈是懂得透彻，就愈有‘薄’的感觉”。     

“薄——厚——薄”读书法

名数学家华罗庚提倡读书要。“由薄到厚”，“由厚到薄”。薄→厚→薄，体现了读书的三个段及其转化特点。     

凸透镜成像规律及其应用

一、凸透镜及其作用 透镜可由玻璃制成的，表面是球面的一部分．按其厚薄的形状可分为凸透镜和凹透镜两类．中间厚，边缘薄的透镜叫凸透镜．[第一段]     

听取蛙声一片

药丸壳6个；药片壳6个；绿色、红色水彩各1管；蓝色、粉色、黄色不干胶各1张；长20厘米、宽10厘米的薄泡沫板1块；黑米6粒；双面胶若干。剪刀。材料：工具：步骤：1.将3个药丸壳外面涂上绿色，里面涂上红色。2.用双面胶将两片药丸壳粘成开口状，当作青蛙头部，如图（一），粘到泡沫板上。剪出和药片壳大小相等的黄色不干胶6片，将黑米分别放到6个药片壳内，然后在药片壳内垫上黄色不干胶粘到青蛙头部的上半部分（胶面朝外），当作青蛙眼睛，如图（二）。3.再取3个药丸壳一半，在外面涂上绿色，然后在它们的边缘涂上少许万能胶，压到青蛙头部…     

巧用教材培养学生的探究能力

教材是学生学习的根本，是学生各种知识来源的主渠道。许多高考试题就是教材所涉及知识的再现或知识点“包装”后的重新组合。古人云：书中有“黄金”。也就是说教材中有无穷无尽的知识宝藏，只要你愿意挖掘，善于挖掘，就会有丰厚的收获。所以，会学习的同学从不忽视课本，而是将课本认真阅读，反复钻研，达到“由薄到厚，再由厚到薄，再由薄到厚（拓宽、引申）”的境界，他们对课本中的所有内容都会字斟句酌，深思熟虑，从不忽视教材中任何细微的部分。最后达到深挖教材，广积知识，培养潜能，提高能力的目的。     

一题三解 各有其妙——第24届全国中学生物理竞赛预赛光学试题的讨论

如图1所示。L是一焦距为厂的薄凸透镜（F与F’为其焦点）．在透镜右侧焦点F’处放置一曲率半径大小为R的球面反射镜（其顶点位于F’处），透镜和球面镜组成一轴对称的光学系统．     

罂粟花

罂粟（yīng sù）花是种美丽的植物。它的色彩，任何画笔也描不出；它的花瓣薄得透明，像彩裙；它的种子和壳能入药。[第一段]     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.