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排序方式: 共有189条查询结果,搜索用时 15 毫秒
31.
Klein DJ Ivanciuc T Ryzhov A Ivanciuc O 《Combinatorial chemistry & high throughput screening》2008,11(9):723-733
Reaction networks are viewed as derived from ordinary molecular structures related in reactant-product pairs so as to manifest a chemical super-structure. Such super-structures then are candidates for applications in a general combinatoric chemistry. Notable additional characterization of a reaction super-structure occurs when such reaction graphs are directed, as for example when there is progressive substitution (or addition) on a fixed molecular skeleton. Such a set of partially ordered entities is in mathematics termed a poset, which further manifests a number of special properties, as then might be utilized in different applications. Focus on the overall "super-structural" poset goes beyond ordinary molecular structure in attending to how a structure fits into a (reaction) network, and thereby brings an extra "dimension" to conventional stereochemical theory. The possibility that different molecular properties vary smoothly along chains of interconnections in such a super-structure is a natural assumption for a novel approach to molecular property and bioactivity correlations. Different manners to interpolate/extrapolate on a poset network yield quantitative super-structure/activity relationships (QSSARs), with some numerical fits, e.g., for properties of polychlorinated biphenyls (PCBs) seemingly being quite reasonable. There seems to be promise for combinatoric posetic ideas. 相似文献
32.
Gordan OD Persson BN Cesa CM Mayer D Hoffmann B Dieluweit S Merkel R 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):6636-6639
Nano- and micromolding of elastic materials produces smoothed replicas of the mold structures. This limits the technique's resolution. Here we identified surface tension as the cause of smoothing and derived explicit equations for calculating molded feature shapes. The characteristic length scale for smoothing is given by the ratio of the interface tension to Young's modulus of the molded material. This approach offers the possibility to correct for the smoothing caused by surface tension during mold design. Moreover, it can be exploited to measure interface tension. 相似文献
33.
Dr. Artur Ciesielski Jürgen Weippert Dr. Artur Böttcher Yuyoung Shin Georgian Melinte Prof. Dr. Ovidiu Ersen Dr. Cinzia Casiraghi Prof. Dr. Xinliang Feng Prof. Dr. Klaus Müllen Prof. Dr. Manfred M. Kappes Prof. Dr. Paolo Samorì Dr. Marco Cecchini 《Chemphyschem》2016,17(3):352-357
Providing a quantitative understanding of the thermodynamics involved in molecular adsorption and self‐assembly at a nanostructured carbon material is of fundamental importance and finds outstanding applications in the graphene era. Here, we study the effect of edge perchlorination of coronene, which is a prototypical polyaromatic hydrocarbon, on the binding affinity for the basal planes of graphite. First, by comparing the desorption barrier of hydrogenated versus perchlorinated coronene measured by temperature‐programmed desorption, we quantify the enhancement of the strength of physisorption at the single‐molecule level though chlorine substitution. Then, by a thermodynamic analysis of the corresponding monolayers based on force‐field calculations and statistical mechanics, we show that perchlorination decreases the free energy of self‐assembly, not only enthalpically (by enhancing the strength of surface binding), but also entropically (by decreasing the surface concentration). The functional advantage of a chemically modulated 2D self‐assembly is demonstrated in the context of the molecule‐assisted liquid‐phase exfoliation of graphite into graphene. 相似文献
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35.
Dr. Zhengxing Qin Dr. Georgian Melinte Prof. Jean‐Pierre Gilson Prof. Maguy Jaber Prof. Krassimir Bozhilov Dr. Philippe Boullay Dr. Svetlana Mintova Prof. Ovidiu Ersen Dr. Valentin Valtchev 《Angewandte Chemie (International ed. in English)》2016,55(48):15049-15052
Zeolites are widely used in many commercial processes, mostly as catalysts or adsorbents. Understanding their intimate structure at the nanoscale is the key to control their properties and design the best materials for their ever increasing uses. Herein, we report a new and controllable fluoride treatment for the non‐discriminate extraction of zeolite framework cations. This sheds new light on the sub‐structure of commercially relevant zeolite crystals: they are segmented along defect zones exposing numerous nanometer‐sized crystalline domains, separated by low‐angle boundaries, in what were apparent single‐crystals. The concentration, morphology, and distribution of such domains analyzed by electron tomography indicate that this is a common phenomenon in zeolites, independent of their structure and chemical composition. This is a milestone to better understand their growth mechanism and rationally design superior catalysts and adsorbents. 相似文献
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Nicolae Aldea Rodica Turcu Alexandrina Nan Izabella Craciunescu Ovidiu Pana Xie Yaning Zhonghua Wu Doina Bica Ladislau Vekas Florica Matei 《Journal of nanoparticle research》2009,11(6):1429-1439
In this article, we focus on the structural peculiarities of nanosized Fe3O4 in the core-shell nanocomposites obtained by polymerization of conducting polypyrrole shell around Fe3O4 nanoparticles. The local structure of Fe atoms was determined from the Extended X-ray Absorption Fine Structure analysis
using our own package computer programs. An X-ray diffraction method that is capable to determine average particle size, microstrains,
as the particle size distribution of Fe3O4 nanoparticles is presented. The method is based on the Fourier analysis of a single X-ray diffraction profile using a new
fitting method based on the generalized Fermi function facilities. The crystallites size obtained by X-ray diffraction spectra
analysis was estimated between 3.2 and 10.3 nm. Significant changes in the first and the second Fe coordination shell in comparison
with standard bulk were observed. The global and local structure of the nanosized Fe3O4 are correlated with the synthesis conditions of the core-shell polypyrrole nanocomposites. 相似文献
38.
Fischer indole cyclization of phenylhydrazine and various ketones using carboxyl-functionalized ionic liquid, 1-carboxymethyl-3-methylimidazolium tetrafluoroborate (abbreviated as [cmmim][BF4]) as catalyst was successfully performed. The yields of thetarget compounds were 80-92%, the purities were 96-98%. The catalyst could be rocovered and reused for at least six times without significant loss in activity. 相似文献
39.
An initial model of the HBV epsilon RNA was built by the Biopolymer module of InsightⅡ.While its three-dimensional structure was obtained through structure optimization based on molecular dynamics simulation,the two active sites were found.A comparison with the experimental result indicated that the active sites may be the binding sites of the epsilon RNA in the RT-epsilon interaction.The result will be helpful to further discussion about the mechanism of RT-epsilon interaction and the study of HBV genom... 相似文献
40.
Sandu Ion Dumitrache Florian Fleaca Claudiu Cretu Ovidiu Morjan Ion 《Solid State Sciences》2009,11(10):1793-1796
In this work we report the synthesis of free-standing films of polymer/nanocarbon composites. The method consists in forming a thin film of carbon nanoparticles onto the water's surface. Through the free infiltration of the polymer between the nanoparticles which form the film, after the polymer is cured, we obtain free-standing films of polymer/nanocarbon composites. The composite films are homogeneous; they have 5 wt.% carbon nanoparticles within the polymer matrix and are a few micrometers in thickness. 相似文献