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101.
A classification of quantum systems into three categories, type I, II and III, is proposed. The classification is based on the degree of sensitivity upon initial conditions, and the appearance of chaos. The quantum dynamics of type I systems is quasi periodic displaying no exponential sensitivity. They arise, e.g., as the quantized versions of classical chaotic systems. Type II systems are obtained when classical and quantum degrees of freedom are coupled. Such systems arise naturally in a dynamic extension of the first step of the Born-Oppenheimer approximation, and are of particular importance to molecular and solid state physics. Type II systems can show exponential sensitivity in the quantum subsystem. Type III systems are fully quantized systems which show exponential sensitivity in the quantum dynamics. No example of a type III system is currently established. This paper presents a detailed discussion of a type II quantum chaotic system which models a coupled electronic-vibronic system. It is argued that type II systems are of importance for any field systems (not necessarily quantum) that couple to classical degrees of freedom. 相似文献
102.
The dynamical properties of exciton transfer coupled to polarization vibrations in a two site system are investigated in detail. A fixed point analysis of the full system of Bloch-oscillator equations representing the coupled excitonic-vibronic flow is performed. For overcritical polarization a bifurcation converting the stable bonding ground state to a hyperbolic unstable state which is basic to the dynamical properties of the model is obtained. The phase space of the system is generally of a mixed type: Above bifurcation chaos develops starting from the region of the hyperbolic state and spreading with increasing energy over the Bloch sphere leaving only islands of regular dynamics. The behaviour of the polarization oscillator accordingly changes from regular to chaotic. 相似文献
103.
104.
We propose a new perturbation approach to finitesize effects within the 4 field theory for a one-component order parameter with periodic boundary conditions. Our approach is applicable both above and belowT
c
. Renormalization-group calculations of finite-size scaling functions in three dimensions are compared with new Monte Carlo data for theL×L×L Ising model withL=8, 16, 32. The field-theoretic predictions are in good overall agreement with the Monte Carlo data.Dedicated to Professor Herbert Wagner on the occasion of his 60th birthday 相似文献
105.
Polarography of the copper(II)-complexes of chelating agents is shown to be a suitable basis for a summation parameter for the total concentration of these chemicals in water (expressed as the copper-complexation index). Using 12 chelating agents (ATMP, BAED, CDTA, DTPA, DTPMP, EDTA, EDTMP, EDTP, EGTA, HEDP, NTA, PBTC) all listed in DIN 38409-H26 and DIN 38413-P5 a satisfactory reproducibility of the method used was obtained. In addition several commercial tensides, detergents in washing and deliming products were investigated. 相似文献
106.
Reaction of the carbamoyl complex [C(NMe2)3][(CO)4FeC(O)NMe2] ( 1 ) with silver salts gives the dinuclear μ‐carbamoyl complex [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(HNMe2)] ( 2 ). Depending on the solvent, crystals of 2a with an asymmetrical or of 2b with a symmetrical internal NH···O bridge are formed. The dimethylamino group is originated from a further molecule of 1 from which an amino group is transferred to the “α‐CO” ligand of an intermediate oxidation product while the H+ ion probably comes from deprotonation of a guanidinium cation. The HNMe2 ligand cannot be replaced by CO but easily by PPh3 to give [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(PPh3)] ( 3 ). All complexes were studied by X‐ray diffraction analyses and the usual spectroscopic methods. 相似文献
107.
The carbamoyl complex [C(NMe2)3][(CO)4Fe{C(O)NMe2}] ( 1 ) reacts with InMe3 under loss of the methyl groups to produce a variety of compounds from which only the anionic cluster complexes [C(NMe2)3]3[Fe2(CO)6(μ‐CO){μ‐InFe(CO)4(μ‐O2CNMe2)InFe(CO)4}] ([C N 3]3[ 2 ]) and [C(NMe2)3]2[{(CO)4Fe}2In(O2CNMe2)]·THF ([C N 3]2[ 3 ]·THF) could be crystallized and characterized by X‐ray analyses. The anion [ 2 ]3? has a Fe2(CO)9‐like structure and both anions contain the carbaminato ligand either in a bridging or in a chelating function. 相似文献
108.
Lars Esser Roberto Macchieraldo Roman Elfgen Melanie Sieland Bernd Michael Smarsly Barbara Kirchner 《Molecules (Basel, Switzerland)》2021,26(1)
To gain a deeper understanding of the TiCl solvation effects in multi-component ionic liquids, we performed ab initio molecular dynamics simulations of 1-butyl-3-methylimidazolium [CCIm], tetrafluoroborate [BF], chloride [Cl] both with and without water and titanium tetrachloride TiCl. Complex interactions between cations and anions are observed in all investigated systems. By further addition of water and TiCl this complex interaction network is extended. Observations of the radial distribution functions and number integrals show that water and TiCl not only compete with each other to interact mainly with [Cl], which strongly influences the cation-[BF] interaction, but also interact with each other, which leads to the fact that in certain systems the cation-anion interaction is enhanced. Further investigations of the Voronoi polyhedra analysis have demonstrated that water has a greater impact on the nanosegregated system than TiCl which is also due to the fact of the shear amount of water relative to all other components and its higher mobility compared to TiCl. Overall, the polar network of the IL mixture collapses by including water and TiCl. In the case of [Cl] chloride enters the water continuum, while [BF] remains largely unaffected, which deeply affects the interaction of the ionic liquid (IL) network. 相似文献
109.
Harry F. Abts Kai Breuhahn Gunter Michel Karl Kohrer Peter Esser Thomas Ruzicka 《Photochemistry and photobiology》1997,66(3):363-367
Abstract— EUltraviolet (UV) light is the most important environmental insult to skin. Even a single exposure to UVB radiation can result in inflammation and may also lead to DNA damage and apoptosis in the acute response of the cutaneous tissue. To elucidate the complex alterations of gene expression in human keratinocytes underlying these UV responses we took advantage of differential display polymerase chain reaction (DD-PCR) technology's ability to detect qualitative and quantitative changes in gene expression in more than two cell populations simultaneously. We demonstrate that low-dose UVB (100 Jm-2 ) leads to both induction and down regulation of different genes during the 24 h after irradiation in a time-dependent manner. In addition to the identification of known genes as possible effectors or targets in the UV response of human keratinocytes, we here identify a new sequence that is negatively regulated by UVB irradiation and was termed HUR 7 (HaCaT UV repressed). In general our results showed that DD-PCR is a useful tool in the analysis of quantitative changes of mRNA levels in human keratinocytes after UV irradiation. The identification of new UVB-repressed genes offers the opportunity to identify unrecognized molecular mechanisms in the UV response of human cells. 相似文献
110.
Helmut Buschmann Hans-Dieter Scharf Norbert Hoffmann Peter Esser 《Angewandte Chemie (International ed. in English)》1991,30(5):477-515
A large number of successful methods for chirality transfer, using either stoichiometric or catalytic chiral auxiliaries, are in use today. However, there is a lack of practical and dynamic selectivity models, i.e. models which take into account the entire reaction sequence, and which allow simple and reliable assessment, optimization and prediction of selectivity in asymmetric syntheses. The models that are available are either too strongly biased to the steric requirement of the particular molecules reacting, but do not go beyond classical considerations of static facial differentiation, or they take a demanding, theoretical approach, which because of its inherent limitations and the great theoretical effort required has not yet found its way into the practical world of the synthetic chemist. The “Isoinversion Principle”, developed on the basis of Eyring's theory, closes this gap. With its aid, the synthetic chemist can determine the characteristic isoinversion temperature Ti for the reaction type of interest from a few temperature-dependent measurements of selectivity parameters. Ti then affords information on interesting questions such as optimization etc. The advantage of this method is that it is useful not only for stereoselectivity, but for any kind of process where selectivity in general (regio-,chemo-, etc) is generated at two or more stages of a reaction sequence, regardless of whether these reactions involve the ground state or a diabatic photoprocess. The present review will demonstrate that this generation of selectivity at two or more stages of a reaction sequence occurs more commonly than is generally thought. 相似文献