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71.
This paper addresses the problem of scheduling cascaded ‘blocked out’ continuous processing units separated by finite capacity
storage tanks. The raw materials for the product lines arrive simultaneously on the input side of the first unit. But every
unit can process only one product line at a time, thus giving rise to the possibility of spillage of raw material due to limited
storage capacity. The need to process multiple product lines and the added constraint of multiple intermediate upliftment
dates aggravate the problem. This problem is quite common in petrochemical industry. The paper provides a MINLP (Mixed Integer
Non-Linear Programming) formulation of the problem. However, for any realistic scheduling horizon, the size of the problem
is too large to be solved by standard packages. We have proposed a depth first branch and bound algorithm, guided by heuristics,
to help planners in tackling the problem. The suggested algorithm could output near optimal solutions for scheduling horizons
of 30 time periods when applied to real life situations involving 3 units and 3 product lines.
Preliminary version of the paper appeared in the proceedings of MISTA, 2005. 相似文献
72.
We introduce a single step memory dependence in the fully chaotic logistic map. This makes it a two dimensional system in general. However, we show that by using composite functions to define two one dimensional maps, it is possible to obtain some analytic results for the bifurcation structure. Numerical results support the calculated bifurcation scheme and, in addition, yield a further insight which allows the calculation of the convergence ratio for a new period adding scenario. 相似文献
73.
A ubiquinol side-chain hydrogenated version (PQS-2) of the recently introduced PQS is described. It forms catalytic nanomicellar reactors in water that provide the medium for highly reactive Ru carbene catalysts to effect both ring closing metathesis to trisubstituted olefins and cross-metathesis reactions at room temperature. The catalyst can be recycled without removal from the reaction vessel. 相似文献
74.
Estrogen induced proliferation of existing mutant cells is widely understood to be the major risk determining factor in the
development of breast cancer. Hence determination of the Estrogen Receptor[ER] status is of paramount importance. We have
carried out the synthesis and characterization of a novel NIR fluorescent dye conjugate aimed at measuring ER+ve status in-vivo.
The conjugate was synthesized by ester formation between 17-β estradiol and a cyanine dye namely: bis-1, 1-(4-sulfobutyl)
indotricarbocyanine-5-carboxylic acid, sodium salt. The replacement of the sodium ion in the ester by a larger glucosammonium
ion was found to enhance the hydrophilicity and reduce the toxic effect on cell lines. The excitation and emission peaks for
the dye were recorded as 750 and 788 nm respectively; ideal for non-invasive optical imaging owing to minimal tissue attenuation
and auto-fluorescence at these wavelengths. The dye (NIRDC1) has a significant drop in plasma-protein binding therefore leading to marked improvement in pharmacokinetic profile such
as dye evacuation in comparison to ICG. In addition the dye showed enhanced fluorescence quantum yield, molar extinction coefficient
and linearity in fluorescence relative to ICG. This dye can be potentially used as a target specific exogenous contrast agent
in molecular optical imaging for early detection of breast cancer. 相似文献
75.
Kurt Binder Benjamin Block Subir K. Das Peter Virnau David Winter 《Journal of statistical physics》2011,144(3):690-729
Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of
condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth,
etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations
of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple
Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces
for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls
(where “surface fields” may act). A generalization to off-lattice systems is described as well. The second method is based
on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model.
Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated,
including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial
free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method.
Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given. 相似文献
76.
Gamma-ray data from Fermi Large Area Telescope reveal a bilobular structure extending up to ~50° above and below the Galactic Center. It has been argued that the gamma rays arise from hadronic interactions of high-energy cosmic rays which are advected out by a strong wind, or from inverse-Compton scattering of relativistic electrons accelerated at plasma shocks present in the bubbles. We explore the alternative possibility that the relativistic electrons are undergoing stochastic 2nd-order Fermi acceleration by plasma wave turbulence through the entire volume of the bubbles. The observed gamma-ray spectral shape is then explained naturally by the resulting hard electron spectrum modulated by inverse-Compton energy losses. Rather than a constant volume emissivity as in other models, we predict a nearly constant surface brightness, and reproduce the observed sharp edges of the bubbles. 相似文献
77.
We consider the Sel’kov model of glycolytic oscillator for a quantitative study of the limit cycle oscillations in the system.
We identify a region of parameter space where perturbation theory holds and use both Linstedt Poincaré technique and harmonic
balance to obtain the shape and frequency of the limit cycle. The agreement with the numerically obtained result is excellent.
We also find a different extreme, where the limit cycle is of the relaxation oscillator variety, has a large time period and
it is seen that, as a particular parameter in the model is varied, the time period increases indefinitely. We characterize
this divergence numerically. A calculational method is devised to capture the divergence approximately. 相似文献
78.
Cooperative relaying is considered as an effective technique to enlarge the coverage area and enhance the system capacity for the future wireless systems. In this paper, an infrastructure based multi-antenna cooperative relay network has been investigated. Closed form expressions of outage probability and average error rate have been derived, when the relay and the destination perform selection combining of the signals. The relay is assumed to operate in the adaptive decode and forward mode. The effect of number of antennas installed on the relay and their placement has also been studied. 相似文献
79.
Subrata Bhattacharjee Shuhei Takahashi Kazunori Wakai Christopher P. Paolini 《Proceedings of the Combustion Institute》2011,33(2):2465-2472
Numerical analysis and scale analysis are combined in a novel manner in this work to develop closed-form expressions for flame geometry in opposed-flow flame spread over condensed fuels. A scale analysis is used to relate different geometric attributes to appropriate non-dimensional parameters. A comprehensive numerical model is then used to generate a large set of numerical data for flame height, flame length, and pyrolysis length as functions of different fuel and oxidizer parameters for flame spread in the thermal, kinetic, and radiative regimes. The numerical data is then correlated to scaled expressions and the unknown coefficients are numerically determined. It is shown that flame length, flame height, and pyrolysis length can be expressed in terms of the preheat length in different regimes of flame spread. An experimental approach is outlined to measure the preheat length necessary for accurately predicting the flame structure. Experimental images obtained from interferometry in two different regimes – downward spreading configuration and quiescent microgravity environment – are consistent with the proposed flame height correlation. 相似文献
80.
Biswajit GhoshRupanjali Bhattacharjee Pushan BanerjeeSubrata Das 《Applied Surface Science》2011,257(8):3670-3676
In this work, 650 nm polycrystalline SnS thin films were grown by thermal evaporation of high purity tin sulfide powder at 250 °C substrate temperature, followed by post deposition annealing at 200 °C and 300 °C for 2, 4 and 6 h, and at 400 °C for 2 and 4 h in argon ambient. The XRD pattern of the as-deposited and annealed SnS films led to the conclusion that the as-deposited films were polycrystalline in nature with preferentially oriented along (1 1 1) direction. The direct bandgap of all the films was found to be observed between 1.33 and 1.53 eV. Except for annealing at 400 °C all the films were nearly stoichiometric in nature, suggesting lower rate of desulfurization at that ambient. However, higher annealing temperature has resulted in the segregation of tin phase. All the films showed good absorption in the visible range. The as-deposited and annealed films showed p-type conductivity. Hall measurement revealed the carrier concentration and mobility ranging from 1015 to 1016 cm−3 and 0.8 to 31.6 cm2 V−1 s−1 respectively. The photoconductivity measurements of all the SnS films were carried out by recording the lowering of resistance of the respective films with time under illumination. 相似文献