主要原因

Consequently it was the main measure to grasp the clinical characterlistic and combine multiple examinations to decrease misdiagnosis and mistreats for childhood nasopharyngeal cancer.

影像学检查是诊断儿童鼻咽癌的重要方法，认识不足和首发症状不典型是误诊的主要原因；掌握儿童鼻咽癌的临床特征并与多种检查相结合是减少误诊误治的主要措施。

But by relevant investigation in the near past, the author finds that some unreasonable education ideas of parents have already become main causes of overweighed homework assignments of student nowadays.

根据以往的教学经验，学生过重的课业负担主要来自于学校层面，然而通过近期相关调查发现，当今家长的一些不合理的教育理念已经成为学生过重课业负担的主要原因。

In order to understand the characteristics and rules of HIV diversity when passaged in vitro , the systematic study on the variation of env gene of HIV strain introduced from American in 1988 was carried out.

人免疫缺陷病毒的显著特征之一是其高度的变异性，这是HIV逃脱机体免疫监视的主要原因，也是HIV疫苗和治疗研究的主要障碍。

Rutting,whose main cause is shear failure of asphalt mixture,is one of the main damages of asphalt pavement.

车辙是沥青路面的主要破坏形式之一，沥青混合料的剪切破坏是其主要原因。

Scabbing on heavy rail steel is usually associated with the formation of crack.

重轨钢中结疤缺陷的形成主要与生产过程中裂纹的形成有关，裂纹形成后，在生产过程中发生氧化而形成氧化原点和脱碳是导致结疤形成的主要原因。

Apple tree canker also called rotten skin disease ,which is one of main diseases of fruit tree plant in north, and its harm is extremely serious. Moreover, the scope is widespread and it exists from the sapling to the senile tree in different degree. Apple tree canker is the main reason of the dead shoot, the dead tree and destroying the garden ,which also blocked the development of the north of fruit tree seriously.

果树腐烂病俗称烂皮病，是北方果树主要病害之一，危害十分严重，而且范围广泛，从幼树到衰老树均有不同程度的发生，是造成苹果树死枝、死树、毁园的主要原因，也严重地阻碍了北方果树的发展。

During the first part, investigate the numbers and location of the different nature reserve, and review about its development, discuss the cause about the rapid developmeng about the protection areas of nature around Beijing. During the second part, this paper use the Geographical Information System to analyze the different sight function, plot our distinct function about the protection area of nature around Beijing. In the third part of this paper, the ecology function was special analyzed. This paper picked up several factor about the ecology and establish mathematics model to detect the most rational ecology distribution, bring forward the new constructive, wilder constructive and combination project. In the last parts of the paper, this paper use the Geographical Information System to analyze the different brim about the protection area of nature around Beijing, calculating the p/a and figure coefficient, and bring forward the brim theory for the nature reserve and city system.

在数量布局方面，包括北京周边各个不同级别的保护区的数目、位置分配布局和发展趋势研究，探讨北京市周边自然保护区数目和面积在99年和2000年突然增长的主要原因，以及今后北京自然保护区的发展方向；在景观布局方面，主要根据不同自然保护区的空间和功能的不同，计算延庆县各个自然保护区的景观多样性指数和景观优势度指数，并结合地理信息系统和航片，划分出不同的景观功能区间，以及各个功能区间之间的相互关系；在生态布局方面，综合考察北京周边自然状况，提取多项因子，建立评价模型，计算出各项因子权重，从而对其自然保护区的生态功能布局的合理性进行评价和趋势分析，为本文提出北京市周边自然保护区新建、扩建与合并的方案提供依据；在边缘布局方面，利用边缘效应理论和研究方法，创新提出&边缘类型样块分析法&，提取多个样方并结合地理信息系统，计算p/a比和自然保护区边缘的形状系数，划出自然保护区边缘效应趋势变化图，考察北京周边自然保护区的边缘效应，以及对城市的生态边缘功能。

The fluctuation of terms of trade mainly result fwrm the crack-up of tea and silk and other agricultural product trade.

贸易条件的变动主要是由贸易结构的变化引起的，茶叶和生丝等农产品贸易的衰弱是造成贸易条件下降的主要原因。

The field investigation shows the landslide is rather stable without new activity phenomena such as fissures. further analysis finds that the slipmass ismainlycomposed of the huge block with the original beddings (para-bedrock) and with a long anti-slipping section with a low dip angle and nice permeability,that is why the landslide is still stable with high dip angle of slip surface in themiddle and upper parts.

但地表调查及钻探与洞探资料表明，滑坡表层无明显的新活动迹象，进一步分析表明，该滑坡滑体主要由保存原岩层序的假基岩组成，且假基岩走向与坡向达35°以上，解体程度低，前部存在较长的抗滑段、导水性好等特点是该滑坡总体稳定的主要原因。

Through screening and comprehensive analysis of childhood lead poisoning caused by automobile exhaust pollution is the main factor, as automobile exhaust lead dust accumulation in more than one meter above the ground, and that is exactly the children's activities with the breathing zone of pollution caused by it has become one of the major causes of childhood lead poisoning.

通过筛查和综合分析，造成儿童铅中毒的因素主要是汽车尾气污染，由于汽车尾气铅尘多积聚在地面以上1米的范围，这正好是儿童的活动与呼吸带，它所引起的污染已成为儿童铅中毒的主要原因之一。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。