排序方式: 共有28条查询结果,搜索用时 15 毫秒
1.
2.
以人教版、苏教版、鲁科版高中化学教科书以及美版教科书中支撑"影响化学反应速率的因素"这一知识内容所涉及的实验内容为研究对象,从实验的设计和内容呈现等方面进行系统地比较,结果表明:国内的教科书中设计的实验探究性更强,对于学生能力的培养更加全面,美国教科书中设计的实验更注重吸引学生的注意力,激发学生的学习兴趣。最后综合分析了不同版本教科书的优缺点,并对实际教学提出一些建议。 相似文献
3.
Jorge A. Vila Yelena A. Arnautova Osvaldo A. Martin Harold A. Scheraga 《Journal of computational chemistry》2014,35(4):309-312
The goal of this study is twofold. First, to investigate the relative influence of the main structural factors affecting the computation of the 13C′ shielding, namely, the conformation of the residue itself and the next nearest‐neighbor effects. Second, to determine whether calculation of the 13C′ shielding at the density functional level of theory (DFT), with an accuracy similar to that of the 13Cα shielding, is feasible with the existing computational resources. The DFT calculations, carried out for a large number of possible conformations of the tripeptide Ac‐G XY ‐NMe, with different combinations of X and Y residues, enable us to conclude that the accurate computation of the 13C′ shielding for a given residue X depends on the: (i) (?,ψ) backbone torsional angles of X ; (ii) side‐chain conformation of X ; (iii) (?,ψ) torsional angles of Y ; and (iv) identity of residue Y . Consequently, DFT‐based quantum mechanical calculations of the 13C′ shielding, with all these factors taken into account, are two orders of magnitude more CPU demanding than the computation, with similar accuracy, of the 13Cα shielding. Despite not considering the effect of the possible hydrogen bond interaction of the carbonyl oxygen, this work contributes to our general understanding of the main structural factors affecting the accurate computation of the 13C′ shielding in proteins and may spur significant progress in effort to develop new validation methods for protein structures. © 2013 Wiley Periodicals, Inc. 相似文献
4.
5.
A.S. Skouras 《International Journal of Mathematical Education in Science & Technology》2013,44(1):12-34
This study presents a subset of factors and their association with students’ achievement in school algebra. The participants were students who had enrolled in 2007 at the ninth year of Greek public education (third year of middle school). A total of 735 students participated (aged 14–15 years) from 37 public secondary schools. The sample consisted of 378 girls (51.4%) and 357 boys (48.6%). A written algebra test and a questionnaire including demographic survey items were used to collect data. The results show that attitude towards mathematics (ATM) and the current teacher rating of mathematics performance were identified as the more significant predictors of algebra achievement, contributing by 18.1% and 24.7%, respectively, in total variance of mean at the end of ninth grade. 相似文献
6.
Jing-Jing Peng Shi-Yang Yue Yu-Hui Fang Xiao-Ling Liu Cheng-Hua Wang 《Molecules (Basel, Switzerland)》2021,26(23)
Selenocysteine (Sec) is the 21st non-standard proteinogenic amino acid. Due to the particularity of the codon encoding Sec, the selenoprotein synthesis needs to be completed by unique mechanisms in specific biological systems. In this paper, the underlying mechanisms for the biosynthesis and incorporation of Sec into selenoprotein were comprehensively reviewed on five aspects: (i) the specific biosynthesis mechanism of Sec and the role of its internal influencing factors (SelA, SelB, SelC, SelD, SPS2 and PSTK); (ii) the elements (SECIS, PSL, SPUR and RF) on mRNA and their functional mechanisms; (iii) the specificity (either translation termination or translation into Sec) of UGA; (iv) the structure–activity relationship and action mechanism of SelA, SelB, SelC and SelD; and (v) the operating mechanism of two key enzyme systems for inorganic selenium source flow before Sec synthesis. Lastly, the size of the translation initiation interval, other action modes of SECIS and effects of REPS (Repetitive Extragenic Palindromic Sequences) that affect the incorporation efficiency of Sec was also discussed to provide scientific basis for the large-scale industrial fermentation for the production of selenoprotein. 相似文献
7.
8.
9.
通过不同的工艺制备了稀土氧化物-钼(RE2O3-Mo)阴极材料的次级发射体,测定了材料的次级发射性能,采用SEM和能谱分析等手段研究了材料的微观结构。实验结果表明,影响材料次级发射性能的因素有:材料的化学成分、掺杂方式、烧结方法、热激活温度等。所有利于提高材料表面稀土氧化物含量的因素均可以提高材料的次级发射性能,这是因为稀土氧化物中的自由电子比较少,由一次电子激发出的二次电子在离开材料时,与材料体内自由电子碰撞的机会就小,而提高材料的次级发射性能。 相似文献
10.
本文运用双边市场理论,构建了平台型企业的定价模型及回归方程,并运用国内14家商业银行2001~2017年的实际运营数据,对构建的模型和方程进行了实证检验。研究结论表明,平台对买方价格决定的主要影响因素有:平台向消费者(买方)提供产品或服务的成本、买方边的需求价格弹性,产品(服务)差异化程度,以及相对方(商户)接入平台的数量;而平台对卖方价格决定的主要影响因素有:卖方给买方产生的网络外部性强度,卖方边的需求价格弹性,以及市场份额。 相似文献