EST(四.形容词性从句定语从句).ppt

四形容词性从句-定语从句I定语从句的引导词：关系代词：在从句中作主语，宾语，表语，定语 We must take measures which can prevent corrosion.He is the engineer whom they knew very well.Light is the form of energy which enables us to see.关系副词：在从句中作状语 The days when we had to rely on“foreign oils”have gone forever.We know the reason why metals have little use in their pure state.,II.定语从句的种类：限制性定语从句：一般紧跟在先行词之后，两者间无逗号。The force that causes everything to fall toward ground is called gravity.非限制性定语从句：与主句用逗号相隔，其先行词可以是一个名词或代词，也可以是一个句子或句子的一部分。This type of meter is called a multimeter,which is used to measure electricity.从语法上讲，两者只有一点差别，但却能引起句意的巨大差别。如：The cells which have been used up must be changed.用完了的电池都得换掉。The cells,which have been used up,must be changed.这些电池，都用完了，都得换掉。前者受从句限制，特指“用完了的电池”；后者则不受从句约束，“这些电池”便可多可少。以下是一个更为极端的例子：I will wear no clothes which will distinguish me from my fellow-men.我不喜欢穿那种会使我显得与众不同的服装。I will wear no clothes,which will distinguish me from my fellow-men.我喜欢光着身子，这样就会使得我与众不同。前者的先行词为clothes,后者的先行词则为前面的句子，故两者的意义迥异.,II定语从句的形式:定语从句的种类只有两种，但结构形式却是多种多样，科技英语中常见的有下列形式：1.“介词+which+.”1).“介词+which+”构成介词短语，在句中作定语，主要介词是of,表示两种关系：所有关系，如：A force can be represented by a strait line,the length of which reprenets the magnitude of the force and the direction of which reprensents the direction in which the force acts.(一个力可用一条直线来表示，线的长度表示力的大小，线的方向表示力作用的方向。)两个of which 分别是length 和 direction的定语，表示所有关系，构成名词短语在从句中作主语。部分与全体的关系，如：There are 105 elements found in nature,most of which are metals.自然界中已发现有105元素，其中大多数是金属）类似结构主要有：a majorty of which 其中大多数 one oF which 其中只一 some of which 其中一些 each of which 其中每一个,2）“介词+which”构成介词短语，在从句中作状语，相当于一个关系副词，如：The reason for which(=why)he did that is quite obvious.(他那样作的原因是明显的)This the method in which(=how)the potiential difference is found(这是求电位差的方法)3）“介词+which”,其中介词是从句中动词短语的组成部分，介词一般位于动词之后，但科技英语中常常提前，如：We have to make clear the material of which this tool is made of.(to be made of)(我们必须搞清楚制造这个工具所用的材料)They study the machine of which we are making use.(他们研究我们正在使用的这台机器),2.分隔型：定语从句一般总是紧跟在先行词的后面，但有时由于结构上的原因，在从句和先行词之间夹入一个词、短语或句子，使两者分隔开来，这大体上有以下几种情况：1）被谓语分开：当先行词是主语，谓语又很短，而谓语从句却较长时，常把定语从句置于谓语之后，以保持句子平衡，如：Contact C is moved along the wire until a position is found at which the galvanometer shows no deflection.(将接触点C沿导线移动，直到电流计指针不偏转为止)Some elements are known the atoms of which usually do not combine with more than one of any other element.(众所周知，某些元素的原子通常不和其他任何元素的一个以上的原子相结合)2）被状语分隔：当主句状语较短时，为了避免被误认为是从句的状语而把它置于定语从句之前，这也形成定语从句与其先行词的分隔。如：There is no student in our class who does not study hard.(我们班没有不努力学习的学生。)The molecules exert forces upon each other which depend upon the distance between them.(分子相互间都存在着力的作用，该力的大小取决于它们间的距离),3）被定语分隔：当先行词后有多个后置定语（包括定语短语和定语从句）时，由于定语从句较长，往往就把它放在其他定语之后，这也造成定语从句与其先行词的分隔，如：The concept of energy leads to the principle of conservation of energy,which unifies a wide range of phenomena in the physical science.(能量的概念导致了能量守恒定律，该定律统一了物理科学中范围广泛的现象)There are a number of electric devices that will be discussed in more detail later on,which have the property of maintaining their terminals continuously at different potentials.(有许多将在后面更详细讨论的电气装置，它们都具有终端连续保持不同电位的特,3省略型：在限制性定语从句中，如关系连接词that,which,whom在从句中作宾语时，可以省略，如：The unit(that)we use to measure voltage is the volt.（我们用以测量电压的单位是伏特）The machine(which)we are designing is a new-type one.(我们正在设计的机器是一种新型的机器)另外，当定语从句的先行词是direction,way,distance 等名词时，引导从句的that 或“介词which”可以省略，如：The direction(in which)a force is acting can be changed.(一个力的作用方向是可以改变的)The way(in which)this matter can be used depends on its properties.(使用这种材料的方式取决于该材料的性质),III.定语从句实例：The earth contains a large number of metals which are useful to man.I have just repeated word-for-word the oath taken by George Washington 200 years ago,and the Bible on which I placed my hand is the Bible on which he placed his.我刚才逐字逐句复述了华盛顿在200年前宣读过的誓言；我用手按过的圣经，就是他按过的那本。Modulation is defined as the process by which some characteristic of one waveform is varied in accordance with another waveform.Materials that tightly hold their electrons in their atomic structure are called insulators.The sum of two complex numbers is defined as the complex number whose real part is the sum of the real parts of the two complex numbers and whose imaginary part is the sum of the imaginary parts of the two complex numbers.A new joint US-Israeli weapon system that uses laser beams to intercep and destroy short-range missiles was tested in the United States recently,Israeli officials said yesterday.Pressures on water supplies are already being seen in declining fresh-water fish populations.But more problems can be expected in food supplies,which in turn can create more international conflicts,immigration pressures and public health problems.,Reactors have recently been built which are capable of generating up to several hundred megawatts.No system is known from which it is possible to have useful work done without reducing the total energy of the system by the amount.众所周知，任何系统不可能使别的物体做了有用的功，而本身的总能量不减少与有用功相等的能量.From what is stated above,it is learned that the suns heat can pass through the empty space between the sun and the atmosphere that surrounds the earth,and that most of the heat is dispersed through the atmosphere and lost,which is really what happens in the practical case,but to what extent it is lost has not been found out.由上述可知，太阳的热量可以穿过太阳与地球周围的大气层之间的真空，而且这种热量在通过大气层时大都消失了。实际发生的情况正是如此。但这种热量的损失究竟达到什么程度，目前尚未弄清楚.The fundamental laws on which network theory is founded express relationships among voltages and currents at various places in a network.It is the authors intention that this text be one from which a student may teach himself.The happiest people are those who discover that what they should be doing and what they are doing are the same thing.,Exercises把下列句子译成汉语，注意定语从句的适当譯法：1.They eventually discovered the ore from which a new metal element can be extracted.2.The melting point of cast iron of which the carbon content is higher,is lower.3.Steel parts are usually covered with grease,which prevents them from getting rusted.4.All substances consist of a great many small particles which are called atoms.5.A bar of iron placed in a coil through which a current is flowing become magnetized.6.Ultrasonic sounds produce pulsed signals,by means of which various defects in metals can be detected.7.Day light comes from sun,which is a mass of hot,glowing gas.8.Temperature plays the same part in the flow of heat that pressure does in the flow of fluids.9.Now,there is more uniform temperature distribution,which has been achieved by an improved thermal design.10.This factory produced machine tools to which prescision instruments were attached.,