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中国国花的问题至今悬而未决、分歧较大,然而牡丹和梅花分别在清代和民国时期被定为国花这一说法却得到了中国和国际社会的广泛认同.根据历代文献记载,结合牡丹和梅花的文化、社会和园艺发展情况,探讨和分析了牡丹和梅花分别在清代和民国时期成为国花的历史进程和文化价值,为进一步开展国花研究提供了理论和现实依据. 相似文献
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目睹和亲历美国洁净能源技术在政府和民间推动下的蓬勃发展及其对生产力发展和拓展就业机会产生的极大推动,联想到当前全球经济和能源危机对中国传统产业和高耗能低效率的产 相似文献
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4-羟甲基吡啶二聚体和三聚体氢键结构性质的理论研究 总被引:4,自引:2,他引:2
运用密度泛函理论B3LYP方法和6-311 G**基函数研究了4-羟甲基吡啶二聚体和三聚体氢键结构性质.构型优化和频率计算分别得到4个和2个稳定的二聚体和三聚体氢键异构体.经基组重叠误差和零点振动能校正后,最稳定的二聚体和三聚体的相互作用能分别为-29.017和-61.142 kJ/mol.振动分析表明二聚体和三聚体存在典型的红移型氢键.热力学分析显示,298.15 K和标准压力下,二聚体和三聚体的形成是一个熵减小的非自发放热过程. 相似文献
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对工程施工计划的编制意义和依据,编制条件和要求,工程施工计划的实施和协调、检查和修正作了一些叙述和探讨,以便使工程施工计划的编制和执行更具科学性、合理性、可行性,取得更好的效果. 相似文献
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市场营销简而言之,是一种发现、确定并满足需求的过程,具体说,就是通过市场交易,满足现实和潜在需求的综合性经营活动。这一定义包括了下列核心概念:需要和需求、产品、价值和成本、交换和交易、关系和网络、营销者和预期顾客、市场。 相似文献
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Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness. 相似文献
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Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly. 相似文献
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理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。 相似文献
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As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death. 相似文献
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Miao Maosheng 《华南师范大学学报(自然科学版)》2014,(6)
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula- 相似文献
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Yang Weitao 《华南师范大学学报(自然科学版)》2014,46(6):137-138
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re- 相似文献
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Bernard Kirtman 《华南师范大学学报(自然科学版)》2014,(6)
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that 相似文献
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Michael Springborg 《华南师范大学学报(自然科学版)》2014,(6):136
For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the 相似文献
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《上海师范大学学报(自然科学版)》2014,(5):550
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with 相似文献