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排序方式: 共有197条查询结果,搜索用时 46 毫秒
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22.
Raimund J. Ober Viswanath Ramakrishna E. Sally Ward 《Journal of mathematical chemistry》1999,26(1-3):15-26
It is shown that the system theoretic concepts of reachability and observability are relevant to the analysis of NMR experiments.
Moreover, the sets of reachable states are examined and Lie theoretic criteria are given for the reachability of the system.
The question is investigated how the set of reachable states depends on the class of input functions that are allowed. Both
one‐dimensional and multi‐dimensional NMR experiments are considered.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
Direct numerical simulations with a C3-chemistry model have been performed to investigate the transient behavior and internal structure of flames propagating in an axisymmetric fuel jet of methane, ethane, ethylene, acetylene, or propane in normal earth gravity (1g) and zero gravity (0g). The fuel issued from a 3-mm-i.d. tube into quasi-quiescent air for a fixed mixing time of 0.3 s before it was ignited along the centerline where the fuel–air mixture was at stoichiometry. The edge of the flame formed a vigorously burning peak reactivity spot, i.e., reaction kernel, and propagated through a flammable mixture layer, leaving behind a trailing diffusion flame. The reaction kernel broadened laterally across the flammable mixture layer and possessed characteristics of premixed flames in the direction of propagation and unique flame structure in the transverse direction. The reaction kernel grew wings on both fuel and air sides to form a triple-flame-like structure, particularly for ethylene and acetylene, whereas for alkanes, the fuel-rich wing tended to merge with the main diffusion flame zone, particularly methane. The topology of edge diffusion flames depend on the properties of fuels, particularly the rich flammability limit, and the mechanistic oxidation pathways. The transit velocity of edge diffusion flames, determined from a time series of calculated temperature field, equaled to the measured laminar flame speed of the stoichiometric fuel–air mixtures, available in the literature, independent of the gravity level. 相似文献
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25.
Weissmüller J Viswanath RN Kibler LA Kolb DM 《Physical chemistry chemical physics : PCCP》2011,13(6):2114-2117
Theory links the reactivity of metal surfaces to the interatomic spacing and, hence, to the tangential strain. We point out that this proposition can be experimentally verified by exploiting a seemingly unrelated phenomenon, the mechanical deformation of solid bodies when charged in an electrolyte. Such experiments allow the strength of coupling between adsorption enthalpy and strain to be quantified. For hydrogen adsorption on Pd, the result agrees with ab initio computation and with trends that can be inferred from experiment on pseudomorphic layers strained by epitaxy with misfitting substrates. The data suggest that experimentally accessible strain values afford a variation of the adatom concentration by several orders of magnitude and a significant shift of the reaction along the 'volcano curve' of reactivity versus adsorption strength. 相似文献
26.
Tae Young Kim Tae Hee Lee Jong Eun Kim Rajeswari M. Kasi Chong S. P. Sung Kwang S. Suh 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6872-6879
A nonaqueous dispersion of poly(3,4‐ethylenedioxythiophene) (PEDOT) was prepared with the use of polymeric ionic liquid (PIL) as a polymerization template and phase transfer medium. A detailed investigation was performed to understand the role of PIL in the course of polymerization and phase transfer reaction. On the basis of our findings from X‐ray photoelectric spectroscopy (XPS), we propose a mechanism by which the PIL leads to the nanostructured PEDOT colloids in various organic solvents and thus facilitating smoother surface morphologies of the PEDOT‐PIL films. In addition, the enhancement of charge transport was observed for PEDOT‐PIL complex when compared with PEDOT without PIL. Raman spectroscopy indicates that there is a reduced interaction between the charge carriers on the PEDOT and the counter ions bound to PIL, thus promoting charge carrier hopping rates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6872–6879, 2008 相似文献
27.
We prove the existence of a Lie bracket on the space of 1-formson a Poisson manifold. This gives rise to a calculus of skewsymmetriccontravariant tensors dual to Cartan's calculus of forms. 相似文献
28.
This paper presents three newly developed Markov models for Identical unit parallel, k-out-of-n and standby arrangements with common-cause failures. Generalized expressions for system reliability and mean time to failure are developed. The plots of system reliability and system mean time to failure are shown 相似文献
29.
Gregory T. Linteris Valeri I. Babushok Peter B. Sunderland Fumi Takahashi Viswanath R. Katta Oliver Meier 《Proceedings of the Combustion Institute》2013,34(2):2683-2690
Several agents are under consideration to replace CF3Br for use in suppressing fires in aircraft cargo bays. In a Federal Aviation Administration (FAA) performance test simulating the explosion of an aerosol can, however, the replacements, when added at sub-inerting concentrations, have all been found to create higher pressure rise than with no agent, hence failing the test. Thermodynamic equilibrium calculations as well as perfectly-stirred reactor (PSR) simulations with detailed reaction kinetics, are performed for one of these agents, C6F12O (Novec 1230), to understand the reasons for the unexpected enhanced combustion rather than suppression. The high pressure rise with added agent is shown to depend on the amount of agent, and can only occur if a large fraction of the available oxidizer in the chamber is consumed, corresponding to stoichiometric proportions of fuel, oxygen, and agent. A kinetic model for the reaction of C6F12O in hydrocarbon–air flames has been developed. Stirred-reactor simulations predict that at higher agent loadings, the inhibition effectiveness of C6F12O is relatively insensitive to the overall stoichiometry, and the marginal inhibitory effect of the agent is greatly reduced, so that the mixture remains flammable over a wide range of conditions corresponding to those of the FAA test. The present findings are consistent with and support the earlier analyses for C2HF5 and CF3Br, which were also evaluated in the FAA test. 相似文献
30.
Sankaran Viswanath 《代数通讯》2013,41(11):3903-3933
We continue the study of stabilization phenomena for Dynkin diagram sequences initiated in the earlier work of Kleber and the present author. We consider a more general class of sequences than that of this earlier work, and isolate a condition on the weights that gives stabilization of tensor product and branching multiplicities. We show that all the results of the previous article can be naturally generalized to this setting. We also prove some properties of the partially ordered set of dominant weights of indefinite Kac–Moody algebras, and use this to give a more concrete definition of a stable representation ring. Finally, we consider the classical sequences B n , C n , D n that fall outside the purview of the earlier work, and work out some easy-to-describe conditions on the weights which imply stabilization. 相似文献