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991.
Gupta LK Chandra S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(3-4):792-796
Complexes of Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) containing a tetradentate macrocyclic N-donor ligand have been prepared via template reaction of 2,3-pentanedione, ethylene-di-ammine and transition metal ions. The complexes have been characterized on the basis of the elemental analysis, molar conductance, magnetic moment susceptibility, IR, electronic and EPR spectral studies. The complexes are of high spin type and possess four coordinate tetrahedral five coordinate square pyramidal and six coordinated octahedral/tetragonal geometry. 相似文献
992.
We report gold nanoparticle based FRET assay to monitor the cleavage of DNA by nucleases. Fluorescence signal enhancement is observed by a factor of 120 after the cleavage reaction in the presence of S1 nuclease. The mechanism of distant dependent fluorescence quenching has been discussed. Our experimental results on distance dependent fluorescence quenching match quite well with theoretical findings obtained from the fluorescence quenching model by Gersten and Nitzan (Surf. Sci. 1985, 158, 165). Our experimental observation paradigm for the design of optical based molecular ruler strategies at distances more than double the distances achievable using traditional dipole-dipole Columbic energy transfer based methods. 相似文献
993.
We have carried out a series of molecular dynamics simulations to investigate the dynamics of X(-)-water (X = F, Cl, Br, and I) and water-water hydrogen bonds in aqueous alkali halide solutions at room temperature and also of Cl(-)-water and water-water hydrogen bonds at seven different temperatures ranging from 238 to 318 K. The hydrogen bonds are defined by using a set of configurational criteria with respect to the anion(oxygen)-oxygen and anion(oxygen)-hydrogen distances and the anion(oxygen)-oxygen-hydrogen angle for an anion(water)-water pair. The results of the hydrogen bond dynamics are obtained for two different cutoff values for the angular criterion. In both cases, similar dynamical behavior of the hydrogen bonds is found with respect to their dependence on ion size and temperature. The fluoride ion-water hydrogen bonds are found to break at a much slower rate than water-water hydrogen bonds, while the lifetimes of chloride and bromide ion-water hydrogen bonds are found to be shorter than those of fluoride ion-water ones but still longer than water-water hydrogen bonds. The short-time dynamics of iodide ion-water hydrogen bonds is found to be slightly faster, while its long-time dynamics is found to be slightly slower than the corresponding water-water hydrogen bond dynamics. Correlations of the observed dynamics of anion(water)-water hydrogen bonds with those of rotational and translational diffusion and residence times of water molecules in ion(water) hydration shells are also discussed. With variation of temperature, the lifetimes of both Cl(-)-water and water-water hydrogen bonds are found to show Arrhenius behavior with a slightly higher activation energy for the Cl(-)-water hydrogen bonds. 相似文献
994.
We describe the synthesis of novel 5-haloimidazole ribonucleosides as precursors of modified cobalamins. A regio- and stereoselective glycosylation of protected ribose with silylated 4(5)-haloimidazoles produces 5-haloimidazole ribonucleosides predominantly in the alpha-configuration (60-75%) without any 4-substituted imidazole ribonucleoside. The structure of the 5-fluoroimidazole ribonucleoside was confirmed by X-ray crystallography and 2D NMR spectroscopy. 相似文献
995.
[reaction: see text] Two simple TADDOL-derived monodentate ligands, the (1R,2S)-2-phenylcyclohexanol-derived phosphite and the N,N-(phenylbenzyl)phosphoramidite, give comparably high levels of enantioselectivity (90-96% ee) in the rhodium-catalyzed hydroborations of substituted styrenes bearing either electron-donating or electron-withdrawing substituents. Rhodium(I) chloride and tetrafluoroborate catalyst precursors give comparable results. Pinacolborane is superior to catecholborane in these reactions. 相似文献
996.
Sonal Singhal Amit Kumar Chawla Sandeep Nagar Hari Om Gupta Ramesh Chandra 《Journal of nanoparticle research》2010,12(4):1415-1421
Thin films of Zn1−x
Cd
x
S (0.1 ≤ x ≤ 0.5) were prepared by using pulsed laser ablation technique on corning glass substrates. Phase transition from cubic to
hexagonal in Zn1−x
Cd
x
S films is determined by X-ray diffraction analysis. We observed a lowering in the phase transition temperature with increase
in the cadmium concentration. Transmission electron microscopy suggests the crystalline nature of thin films with average
particle size of 15 nm. The grown Zn1−x
Cd
x
S samples show the high peak intensity ratio of the near band edge emission to the defect center luminescence even at room
temperature, which indicates the small concentration of complex defects in the samples. Photoluminescence measurement show
stoichiometric dependence of the energy band gap and is found to have quadratic dependence on x. 相似文献
997.
Denis M Tsui J Thompson C Chandra K 《The Journal of the Acoustical Society of America》2010,128(5):EL274-EL278
In this work, a numerical method for modeling the scattered acoustic pressure from fluid occlusions is described. The method is based on the asymptotic series expansion of the pressure expressed in terms of sound speed contrast between the host medium and entrained fluid occlusions. Pade? approximants are used to extend the applicability of the result for larger values of sound speed contrast. For scattering from a circular cylinder, an improvement in convergence between the exact and numerical solutions is demonstrated. In the case of scattering from an inhomogeneous medium, a numerical solution with reduced order of Pade? approximants is presented. 相似文献
998.
We show how hot QCD equations of states can be adapted to make definite predictions for quarkgluon plasma at RHIC.We consider
equations of state up to O(g5) and O[g6(ln(1/g)+δ)]. Our method involves the extraction of equilibrium distribution functions for gluons and quarks from these equations of
state by capturing the interaction effects entirely in the effective chemical potentials. We further utilize these distribution
functions to study the screening length in hot QCD and dissociation phenomenon of heavy quarkonia states by combining this
understanding with the semi-classical transport theory. 相似文献
999.
The present paper reports the luminescence induced by plastic deformation of coloured alkali halide crystals using pressure steps. When pressure is applied onto a γ-irradiated alkali halide crystal, then initially the mechanoluminescence (ML) intensity increases with time, attains a peak value and later on it decreases with time. The ML of diminished intensity also appears during the release of applied pressure. The intensity Im corresponding to the peak of ML intensity versus time curve and the total ML intensity IT increase with increase in value of the applied pressure. The time tm corresponding to the ML peak slightly decreases with the applied pressure. After tm, initially the ML intensity decreases at a fast rate and later on it decreases at a slow rate. The decay time of the fast decrease in the ML intensity is equal to the pinning time of dislocations and the decay time for the slow decrease of ML intensity is equal to the diffusion time of holes towards the F-centres. The ML intensity increases with the density of F-centres and it is optimum for a particular temperature of the crystals. The ML spectra of coloured alkali halide crystals are similar to the thermoluminescence and afterglow spectra. The peak ML intensity and the total ML intensity increase drastically with the applied pressure following power law, whereby the pressure dependence of the ML intensity is related to the work-hardening exponent of the crystals. The ML also appears during the release of the applied pressure because of the movement of dislocation segments and movements of dislocation lines blocked under pressed condition. On the basis of the model based on the mechanical interaction between dislocation and F-centres, expressions are derived for the ML intensity, which are able to explain different characteristics of the ML. From the measurements of the plastico ML induced by the application of loads on γ-irradiated alkali halide crystals, the pinning time of dislocations, diffusion time of holes towards F-centres, the energy gap Ea between the bottom of acceptor dislocation band and the energy level of interacting F-centres, and work-hardening exponent of the crystals can be determined. As in the elastic region the strain increases linearly with stress, the ML intensity also increases linearly with stress, however, as in the plastic region, the strain increases drastically with stress and follows power law, the ML intensity also increases drastically with stress and follows power law. Thus, the ML is intimately related to the plastic flow of alkali halide crystals. 相似文献
1000.
The despatch bay is a critical interface within an organisation, linking the warehousing and transport operations. However, delays here have wider supply chain implications given that the flow of materials through the supply chain is disrupted. Despite this, there has been little research on improvement activities to this process. This paper uses a case study of a steel processor to develop a simulation model to test strategies for increasing despatch bay productivity. From the simulation results, it was found that a combination of improvements were needed, to both reduce process times and ensure the earlier receipt of orders. The research approach presented in this paper can be used in other business environments having similar operating conditions. 相似文献