原子、原子核常见错解分析

原子、原子核内容包括α粒子散射、能级、天然放射性现象、α射线、β射线、γ射线、核子、中子、质子、原子核、核能、质量亏损、裂变、链式反应、聚变等,以及原子核式结构、半衰期、核反应方程、爱因斯坦的质能方程等规律．所涉及的基本方法,由于知识点相对分散,要加强对物理现象本质的理解,运用逻辑推理的方法,根据已有的规律和事实、条件作出新的判断．在核能的计算时对有效数字的要求也很高。     

一道应用题的错解、正解、巧解和妙解

题 某厂要加工A、B两种不同型号的零件,其中A型1800个,B型640个．现有工人100名,每人每小时可加工A型零件5个,或加工B型零件4个．现将工人分成两组（每组至少有一人）,每组工人只加工一种零件．问：要使加工这两种零件所需的时间之和最短,应怎样分组？     

一道轨迹题的多种解法

题目 求与A（-1,0）、B（1,0）连线成60°角的动点P的轨迹方程．[第一段]     

几何概型中的一道易错题

无论是解古典概型题目,还是解几何概型题目,都必须事先弄清楚基本事件是什么,基本事件的发生是否是等可能的,这是我们解这两类概率题的前提,忽略了这两点,你就会在不知不觉中犯下错误,请看下面的例子。     

一道高考试题的别解

2006年全国卷Ⅱ22题：设数列{an}的前n项和为Sn,且方程x^2-anx-an=0有一根为Sn-1,n=1,2,3,…．[第一段]     

高三数学复习中的构造问题

数学解题的构造性思维和方法是解题研究的热点之一.就构造的具体方法,诸如构造函数、构造方程、构造图形等,方法颇多.本文通过例题,从思维的整体性角度探求构造思维形成的一些途径.1背景构造有些问题,当孤立地运用题设条件难以获得解题思路时,不妨把所考虑的问题置于特定的背景     

尝试“三种课型”着眼语文素养提高

全面提高学生的语文素养是贯穿《语文课程标准》的一个基本理念。语文素养是"以语文能力为核心,是语文能力和语文知识、语言积累、思想感情、思维品质、审美情趣、学习方法、学习习惯的融合",语文素养具有整合性和实践性,能够"促进学生德、智、体、美的和谐发展"。在新课程理念的指导下,可从改善课堂教学入手,尝试品析课、练习课、习作课,努力提高学生的语文素养。     

消参求曲线轨迹方程的三种典型类型

求曲线的轨迹方程在高考中出现的频率很高,我们在问题解决过程中应注意合理选择方法,常用的基本方法如待定系数法、直接法(定义法)、代入法、参数法,其中设元消参是学习中的一个难点.其实我们只要从设参变     

能量方程教学法初探

恒定流能量方程在水电工程中应用广泛,解决了很多工程实际问题。作为水电工程专业的学生应该理解和牢固掌握能量方程的应用。笔者在授课时强调了两方面内容的讲授,在帮助学生理解和应用上起到了较好效果。     

Genetic analysis of fruit shape traits at different maturation stages in sponge gourd

The fruit shape is important quantitative trait closely related to the fruit quality. However, the genetic model of fruit shapes has not been proposed. Therefore, in the present study, analysis of genetic effects for fruit shape traits （fruit length and fruit perimeter） in sponge gourd was conducted by employing a developmental genetic model including fruit direct effects and maternal effects. Analysis approaches of unconditional and conditional variances were applied to evaluate the genetic behavior of fruit shape traits at economical and physiological maturation times. The results of variance analysis indicated that fruit length and fruit perimeter were simultaneously affected by fruit direct genetic effects and maternal effects. Fruit direct genetic effects were relatively more important for fruit shape traits at whole developmental period. The gene expression was most active at the economical maturation stage （1-12 d after flowering） for two shape traits, and the activation of gene was mostly due to direct dominance effects at physiological maturation stage （13-60 datter flowering）. The coefficients due to different genetic effects, as well as the phenotypic correlation coefficients, varied significantly between fruit shape traits themselves at various maturation stages. The results showed that it was relatively easy to improve fruit shape traits for industrial purpose by carefully selecting the parents at economical maturation stage instead of that at physiological maturation stage.