关于Runge－－Lenz矢量的方向和大小的讨论

描述行星规律的R-L矢量在笔者所见的文献中只指出了它的方向但末证明，本文对其加以了证明；并在此基础上比较简略地计算了它的大小；进而讨论了它的物理意义。     

Investigation of iodine concentration in salt,water and soil along the coast of Zhejiang,China

Objective: We aim to describe the environment iodine concentration in salt, water and soil along Zhejiang Province coast in the China foreland. It will be helpful for us to judge whether this area is insufficient in iodine and universal iodized salt is necessary or not. Methods: We collected iodized salt samples, drinking water samples (tap water in the towns, and well water or spring water in the villages), water samples from different sources (ditches, lakes, rivers) and soil samples through random sampling in June, 2005. Salt, water and soil iodine was detected by arsenic-cerium redox method. Statistical analysis was expressed as mean±SEMby Windows SPSS 13.0. Results: (1) The iodine concentration in salt was 27.9±4.33 mg/kg (n=108). (2) Seventy-five water samples were collected. The water iodine value was 0.6～84.8 μg/L (mean of 11.66 μg/L). The watershed along the Qiantang River has significantly higher iodine content than the water in Lin'an in mountain area (P＜0.01). The iodine content and mean iodine content of tap water, well or spring water and natural water sources were 4.30±2.43 μg/L (n=34), 23.59±27.74 μg/L (n=19)and 12.72±10.72 μg/L (n=22) respectively. This indicated that among environmental water sources, the ditch iodine content was the highest with river water iodine being the lowest (P＜0.01). (3) Soil iodine value was 0.11～2.93 mg/kg (mean of 1.32 mg/kg).Though there was no statistical difference of soil iodine in different districts (P=0.131), soil iodine content correlated positively with water iodine content. Conclusion: Iodine concentration in salt accords with national policy of adding iodine in salt. Foreland has more iodine in water than mountain area. The data reflected that water and soil iodine in foreland area was not high, which suggests universal iodized salt should be necessary. Environment iodine has relatively close association with pollution.     

解无数字计算题的几种方法

中学化学计算是学习化学的基础，学好化学计算有助于学生学好化学，提高科学探究的水平。考查化学计算能有效地考查学生的思维能力，无数据计算是培养学生创新能力，提高思维能力的较好题型。     

饲料防霉剂的性能和使用

着重介绍几种常见饲料防霉剂的霉抑制性、腐蚀性、挥发性、扩散性、离解性和相对功效，以及防霉剂的添加量及添加工艺．     

贺信

《职教论坛》编辑部:热烈祝贺贵刊在2019年度复印报刊资料转载指数排名中喜获佳绩!在“教育学学科期刊”全文转载排名中,贵刊转载量位列第4名,综合指数位列第13名。本排名是根据人大复印报刊资料近100种学术刊的全文转载数据,从转载量、转载率、综合指数三个维度统计形成。复印报刊资料系列刊是从国内公开出版的近4000种报刊上精选人文社科研究成果,并按人文社科二级学科进行分类、编辑、出版的二次文献。     

从阅读量谈高职外语教改的新思路

通过对当前我国的高职外语教学效果达不到用人单位满意的原因分析及对学生外语阅读量现状的反思,提出了充分挖掘阅读的内在魅力,扩大外语阅读量是提高外语学习效果的有效方法,为高职外语教学改革提供了新思路.     

浅谈初中语文教学中学生想象力的培养

学生创新思维能力的培养与提高是教育的最终目标,想象力是创新能力的翅膀。语文教师应有计划地让学生积累语文知识、训练语言表达能力、增加阅读量、进行写作训练,来培养、增强、提升学生的想象力。     

新目标初中英语词汇教学存在的问题及对策

一．初中英语词汇教学存在的主要问题 （一）,初中生英语词汇学习存在的主要问题 众所周知,要学好一种语言,词汇是关键。词汇就如同一个人的骨架,人要是没了骨头是无法站立的。学生要是没有英语词汇量,是不可能学好英语的。     

走进2010年格点中考题

近年来,中考经常出现格点类试题,题型新颖时尚,突出了数形结合的数学思想方法,主要考查同学的直觉推理和问题探究能力,还考查了学生的创新意识、决策意识和实践能力.格点问题操作性强,趣味性浓,现以2010年中考题为例加以说明.一、格点中的运动和对称例1(2010年宿迁市中考题)如图1,在平面直角坐标系中,O为原点,每个小方格的边长为1-个单位长度.在第一象限内有横、纵坐标均为整数的A、B两点,且OA=OB=10~(1/2).