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81.
人们在学习英语时,通常会自觉或不自觉地借助母语语言习惯来学习,这种现象就叫迁移。当迁移不当,在目的语中不能接受,影响学习时,就成了负迁移。本文对英语学习者在英语语音、词汇、语法和语用方面的负迁移情况进行一些分析和讨论。  相似文献   
82.
本提出金属表面附近层区的三维应力的新的测试方法,对于存在应力梯度的金属表面层研究有着特殊的意义。本在X射线宏观应力测试中采用非线性回归方法,较之常规应力测试的线性回归方法,可以得到更具合理性的应力参数,这些应力参数所表示的是金属表面厚度约(1.1~1.2)Ⅱo范围内的平均值。这里,Ⅱo=sinθψ·0/μ定义为能够产生X射线衍射的表面层的有效厚度,μ是X射线的线衰减系数。分析表明,自由表面附…  相似文献   
83.
提出了重调和方程的半解析解法,将Fourier方法和Morley元方法结合起来,克服了它们各自的缺点,最后给出此方法的误差估计。  相似文献   
84.
Recent progress made in research on negative refraction in two-dimensional photonic crystals is reviewed. Special attentions are paid to the research results of our group. We explore the underlying mechanism governing the occurrence of negative refraction in periodic and quasiperiodic photonic crystals. These results may be useful references for the application of photonic crystals. The perspectives of future research on negative refraction are briefly predicted.  相似文献   
85.
A new heuristic approach that resembles the evolution of interpersonal relationships in human society is put forward for the problem of scheduling multitasks represented by a directed acyclic graph. The algorithm includes dynamic-group, detachgraph and front-sink components. The priority rules used are new. Relationship number, potentiality, weight and merge degree are defined for cluster's priority, and task potentiality for tasks' priority. Experiments show the algorithm could get good result in short time. The algorithm produces another optimal solution for the classic MJD benchmark. Its average performance is better than five latter-day representative algorithms, especially six benchmarks of the nines.  相似文献   
86.
Silica nanoparticle is a possible safe carrier for gene therapy   总被引:2,自引:0,他引:2  
In order to develop a safe and effective gene therapy carrier, some toxicological and biodynamical experiments were carried out on silica nanoparticles (SiNPs). First we prepared SiNPs with appropriate portions of cyclohexane, deionized water and ethyl silicate, and then transfected the modified SiNPs and GFP plasmid DNA complex into the HT1080 cells to test the effectiveness of transfection for gene therapy. At the same time, we injected the SiNPs into a number of mice through tail vein. Then we made the mice crossed to evaluate the acute, long-term and reproductive toxicity. In vivo distribution analysis and pathological examination were made on both adult mice and their offspring. SiNPs were uniform and had an average diameter of 40 nm, and the modified SiNPs carried exogenous DNA molecules into target cells and the transferred GFP fusion gene was effectively expressed in the cells. The SiNPs injected via tail vein were widely distributed in almost all of tissues, and the injected mice had the ability to reproduce normally. The in vivo and in vitro results of this study clearly show that SiNPs can be used as a safe and effective carrier for gene transfection and gene therapy.  相似文献   
87.
88.
21世纪将是太平洋时代,未来的世界经济中心将由大西洋转到太平洋,东北亚位于太平洋的西北部,是指在日本海为中心,包括我国东北地区,俄罗斯远东地区,日本列岛,朝鲜半岛及蒙古人民共和国等地区,它是当今世界上国际经济联系密切,经济发展极富活力的地区,黑龙江省地处东北亚的中间位置,有着位置交通,自然资源,对外贸易,历史文化,人口劳动力,产业结构等诸方面地理环境的战略优势,本文试图通过对黑龙江地理环境的分析,来阐述黑龙江省在东北亚地区政治经济相互作用中的战略优势地位和作用。  相似文献   
89.
合成了目标配合物:碘化双 -[3,4 -二甲氧基苯甲醛缩氨基硫脲]合锌(II) ,其结构通过单晶X-射线衍射法确定.晶体属单斜晶系,C2/c空间群.配合物分子中,锌(II)与两个硫原子、两个碘原子配位形成轻微畸变的四面体结构,每一个3,4 -二甲氧基苯甲醛缩氨基硫脲配体与锌离子处于同一平面内,在晶体中分子之间以氢键连接形成网状结构.  相似文献   
90.
The optimizations geometries and interaction energy corrected by BSSE of the complexes between C4H4Y (Y=O, S) and CHiLi have been calculated at the B3LYP/6-311++G^** and MP2/6-311++G^** levels. Three complexes were obtained. Abnormally, the calculations showed that all the C10--Li14 bond lengths increased obviously but the blue-shift of C10-Li14 stretching frequency occurred after formed complexes. The calculated binding energy with basis set super-position error (BSSE) and zero-point vibrational energy corrections of complexes I-III is -45.757, -35.700 and -39.107 kJ·mol^-1, respectively. The analyses on the combining interaction with the atom-in-molecules theory (AIM) also showed that a relatively strong lithium bond interaction presented in furan homologues C4H4Y-LiCH3 systems. Natural bond orbital theory (NBO) analysis has been performed, and the results revealed that the complex I is formed with n-σ type lithium bond interaction between C4H40 and LiCH3, complex II is formed with TT-s type lithium bond interaction between C4H4O and LiCH3, and complex III is formed with TT-s and n-s type lithium bond interactions between C4H4S and LiCH3, respectively.  相似文献   
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