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1.
系列新型大孔径分子筛骨架结构设计   总被引:2,自引:0,他引:2       下载免费PDF全文
本文提出三种包含有五员环的新型(准)笼结构单元 ,并基于这些新型的二级结构单元 ,应用“二级结构 空间群组合法”辅以Σ变换设计了MIR系列属于正交晶系Ibam空间群含有16、20、24、28员环主孔道的大孔径新型沸石骨架拓扑结构。估设了这些新型分子筛结构的晶胞常数以及骨架T位原子及氧原子的坐标参数。然后通过能量最小化 ,确定它们稳定构象的全部晶体结构设计细节以及相应的生成热 ;进而讨论了这些结构的稳定性。通过对比、分析不同结构的生成热 ,得到分子筛骨架结构中插入六棱柱笼会使其生成热降低而使结构更趋稳定的推断。  相似文献
2.
Teo的C~2模型与其它稠合规则之间关系的研究   总被引:2,自引:0,他引:2  
提出了一个稠合型簇合物的稠合规则,讨论了唐氏拓扑结构规则和Mingos稠合规则的推广,扩大了两个稠合规则的应用范围.研究了在稠合型簇合物中Teo的C2模型与Mingos稠合规则、推广的唐氏拓扑结构规则和本文提出的稠合规则之间的关系.同时,利用提出的稠合型簇合物的稠合规则导出了超级簇合物"clusters of clusters"中原子和电子之间存在的魔数关系.  相似文献
3.
新型光离子化检测器的设计与应用   总被引:1,自引:0,他引:1  
将自行研制的PID光离子化检测器安装于气相色谱仪上,无需复杂的样品前处理,便可快速分析环境中的苯系物、醛类等物质。概述了此检测器的基本原理,详细介绍了其结构、电路系统的设计及性能测试结果。采用喷嘴与电极一体化的设计理念,使电离室的体积缩小到30"L,灵敏度提高,同时易于加工;微电流放大器的设计选用低噪声、低温漂的精密放大器AD549,获得了优良的信噪比与稳定的信号;选用氪灯为电离源,苯标准气体(0.9×10-6 mol/mol)为样品,仪器的检出限低于1×10-13 g/mL,定量的重复性良好;相对标准偏差(RSD)为1.24%。  相似文献
4.
AlPO_4-5分子筛是一种典型的具有十二元环主孔道的磷铝分子筛。它的骨架拓扑结构属六方晶系,我们发现这一结构可以演变成很多正交构型的骨架结构,本文采用计算机技术,在正交晶系中设计了与六方AlPO_4-5结构相关的64种分子筛骨架拓扑结构,并计算了它们的理论XRD谱图,讨论了它们存在的可能性,一个具有正交AlPO_4-5合成样品的XRD谱图与所设计的结构中一个XRD理论谱图吻合,证实了正交构型AlPO_4-5的存在。  相似文献
5.
交替烃拓扑结构计数的研究余荣泮,杨良准,刘训亭,胡启山,张自先,莫宇翔,陈琼,王成瑞(武汉大学化学系武汉430072)关键词拓扑结构计数,交替烃,分子轨道分子稳定性的研究是理论化学中一个重要课题,关于这方面的工作,共振论是富有成效的理论之一。在偶苯型...  相似文献
6.
The topology of the framework of a novel zeolite, named MCR-16, with cylindrical channels spanned by the 16-membered ring, is constructed, in which the sigma transformation is a conceptual device for inter-relating the known zeolite mordenite and the hypothetical MCR-16. The consistent molecular mechanics force field is used as the foundation for the discussion on the steric energy of the structure. The configuration energy is minimized by the simulated annealing method. The consequent Si–O, Si–Si and O–O distances and Si–O–Si and O–Si–O angles of the designed MCR-16 structure are all within the limits of the reasonable ranges.  相似文献
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8.
Summary Several characteristics of the topological regions determined by the more informative version of TMA for cured rubbers based on NR/CPE and NR/ENR blends as well as PA6/cured rubber blends correlate with static and dynamic mechanical properties. These rubbers differ substantially in the structure of their network and the related topological structure because CPE does not participate in cross-links when ENR can do it. The physical interactions caused by these additives also vary, due to the different polarity that influences the formation of physical networking junctions. In blends of PA6 and cured rubber the networking junctions are assumed as being physical nature only. From these facts and the above-mentioned results it could be preliminarily concluded that the correlation depends on the formulation and related structure of the composite, and on which of the characteristics have been compared. To understand the reasons for the existence, or lack of, correlation observed, further investigations are needed.  相似文献
9.
Using the novel version of thermomechanical analysis (TMA) method, a poly-ε-caprolactam (PA6) and its nanocomposite (PNC) containing 1.6 wt.% of montmorillonite (MMT) were examined. Several disc specimens of those as investigated in the first part of this article were then melted, annealed, and sheared at a rate of 0.5 s−1 engendering ca. 140% strain at 240 °C in a rotational rheometer, and next solidified in ambient air. In PNC as in PA6 specimens prepared in the same way, an amorphous isotropic structure in the surface layer up to 0.5 mm thick was identified, with topological regions differing in thermal expansion properties and related a state of order. This finding differs from other tests, which detect a high level of crystallinity. Probably, it is related with small thickness of the tested layer of material and kinetics of solidification in ambient air.An increase in the free volume fraction, VfTMA, evaluated as equal to 3ΔαTgα is the difference in linear thermal expansion coefficients below and above the glass transition temperature Tg) and resulted from melting, annealing, shearing, and next solidification in ambient air was observed. It suggests that these operations introduce into the specimen some amount of gases (e.g., evaporated water absorbed when cooling) what increases thermal expansion over high-temperature transition of the high-temperature topological region. It means that VfTMA is a sum of all voids within a specimen tested (not only a real free volume) independently on their origin. Because of this, it is better to term it as micro or nanoporosity.  相似文献
10.
A poly-ε-caprolactam (PA6) taken as a reference and its nanocomposite (PNC) containing 1.6 wt.% of montmorillonite were examined. The specimens as discs were prepared by compression moulding at 235 °C and 70 MPa. Using the novel version of TMA, in the PA6 and PNC specimens, within the temperature range from −100 to 250 °C, a semi-crystalline structure with anisotropy of distribution of the more ordered (crystalline?) portion was found in the surface layer up to 0.5 mm thick. The amorphous regions have differed in a state of order (different transition temperatures) and related compactness. The free volume fraction in amorphous regions determined in machine direction (normal to the surface) is increased when in transverse direction is reduced; simultaneously molecular weights of polymer chains between junctions were increased by incorporation of the nanofiller.  相似文献
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