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71.
Jacek Michalik Marek Danilczuk Janusz Turek Jaroslaw Sadlo 《Research on Chemical Intermediates》2007,33(8):793-806
This paper presents studies on paramagnetic intermediates, free atoms and radicals produced in γ-irradiated molecular sieves and their reactions with adsorbate molecules or exchangeable cations. Four different systems
have been investigated using EPR spectroscopy, Na-A/CH4, AgNa-A/CH3OH, Ag-SAPO-11/C2H4 and AgCs-rho/NH3. It was found that methyl radicals are formed in two different sites in Na-A/CH4 and in one of them they are stable at room temperature. The formation of Ag·CH2OH+ radical cation with one-electron bond between silver and carbon has been established in AgNa-A/CH3OH by EPR experiments with [13C]CH3OH and DFT calculations. In Ag-SAPO-11/C2H4 the stabilisation of biligand silver/ethylene complex, Ag0(C2H4)2 was postulated based on EPR and DFT results. Tetrameric silver clusters (Ag
4
3+
) produced radiolytically in AgCs-rho/NH3 strongly interact with two ammonia molecules as was deduced from the changes in superhyperfine structure of high-field EPR
line of Ag
4
3+
pentet for zeolite exposed to [14N]NH3 and [15N]NH3. The presented examples clearly show that the combination of radiation methods with EPR technique is very useful to study
the structure and reactivity of paramagnetic intermediates. 相似文献
72.
Jaroslaw Kwapisz 《Mathematische Zeitschrift》2000,234(2):255-290
Motivated by the computations in the theory of cohomological Conley index, cocyclic subshifts are the supports of locally constant matrix cocycles on the full shift over a finite alphabet. They properly generalize sofic
systems and topological Markov chains; and, via the Wedderburn-Artin theory of finite-dimensional algebras, admit a similar
structure theory with a spectral decomposition into mixing components. These components have specification, which implies
intrinsic ergodicity and entropy generation by sequences of horseshoes. Also, a zeta-like generating function for cocyclic
subshifts leads to simple criteria for existence of a factor map onto the full two-shift – which gives practical tools for
detecting chaos in general discrete dynamical systems.
Received June 30, 1997; in final form May 21, 1999 相似文献
73.
W. Wardencki Jaroslaw Orlita Jacek Namieśnik 《Analytical and bioanalytical chemistry》2001,369(7-8):661-665
Two extraction procedures, i.e. conventional liquid-liquid extraction (LLE) and liquid solid-phase microextraction (SPME)
for extraction of the oximes formed after derivatization of carbonyl compounds with o-(2,3, 4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) in alcoholic solutions have been compared. The limit of detection for
LLE followed by GC-ECD determination of C1–C6 was in the range of 0.23–3.3 μg/L, whereas for liquid SPME 0.005–0.33 μg/L. Both methods elaborated can be applied to the
determination of carbonyl compounds present in spirits and alcoholic beverages.
Received: 26 September 2000 / Revised: 14 January 2001 / Accepted: 16 January 2001 相似文献
74.
Jaroslaw Chojnacki Barbara Becker Antoni Konitz Wieslaw Wojnowski 《无机化学与普通化学杂志》2000,626(10):2173-2177
Compounds of general formula Au{SSi(OR)3}(PPh3), R = Pri ( 1 ), Bus ( 2 ) or But ( 3 ), have been obtained by reaction of AuCl(PPh3) with triethylammonium salts of respective silanethiols, (RO)3SiSH. Molecular and crystal structures of 1 , 2 , and 3 have been determined by the single crystal X‐ray structural analysis. Compounds 1 and 2 are the first structurally characterized metal derivatives of hydrolytically unstable trialkoxysilanethiols (PriO)3SiSH and (BusO)3SiSH. 相似文献
75.
The synthesis of new 1,4‐phenylene‐bis‐(N‐alkylaminomethane)‐bis‐phosphonates 3Aa–3Da by the addition of dialkyl or diaryl phosphites to the azomethine bond of 1,4‐phenylene Schiff bases is reported. Some NMR studies on the stereochemistry of dialkyl phosphite addition to terephthalic bis‐imines showing the exclusive formation of the meso‐form are presented. The mechanism and the origin of such a high stereoselectivity are discussed. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:144–151, 2000 相似文献
76.
77.
We introduce two axioms in Laguerre geometry and prove that they provide a characterization of miquelian planes over fields of the characteristic different from 2. They allow to describe an involutory automorphism that sheds some new light on a Laguerre inversion as well as on a symmetry with respect to a pair of generators. 相似文献
78.
Wojciech Zielenkiewicz Irina V. Terekhova Małgorzata Koźbiał Jaroslaw Poznanski Roman S. Kumeev 《Journal of Physical Organic Chemistry》2007,20(9):656-661
Complex formation of menadione with α‐, hydroxypropyl α‐, β‐, hydroxypropyl‐β‐, methyl‐β‐ and hydroxypropyl‐γ cyclodextrins in aqueous solution at 298.15 K was studied by using isothermal titration calorimetry, 1H NMR, and UV–vis spectrophotometry. The experimental data indicated the partial insertion of menadione into macrocyclic cavity upon formation of two alternative types of 1:1 inclusion complexes, whose thermodynamic parameters (K, ΔcG0, ΔcH0, and ΔcS0) were calculated. The influence of host size on the complex formation process was analyzed. β‐Cyclodextrin and its hydroxypropylated and methylated derivatives were found more effective binders towards menadione than α‐ and γ‐cyclodextrins. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
79.
We have used SOM and grid 3D and 4D QSAR schemes for modeling the activity of a series of dihydrofolate reductase inhibitors. Careful analysis of the performance and external predictivities proves that this method can provide an efficient inhibition model. 相似文献
80.
The paper contains a complete theory of factors for ray representations acting in a Hilbert bundle, which is a generalization of the known Bargmanns theory. With its help, we have reformulated the standard quantum theory so that the gauge freedom emerges naturally from the very nature of quantum laws. The theory is of primary importance in the investigations of covariance (in contradistinction to symmetry) of a quantum theory which possesses a nontrivial gauge freedom. In that case the group in question is not any symmetry group but a covariance group only – the case not yet investigated in depth. It is shown that the factor of a covariance group representation depends on space and time when the system in question possesses gauge freedom. In nonrelativistic theories, the factor depends on time only. In relativistic theory, the Hilbert bundle is built over spacetime while in the nonrelativistic case-over time. We explain two applications of this generalization: in the theory of a quantum particle in gravitational field in the nonrelativistic limit, and in quantum electrodynamics. 相似文献