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891.
We propose an implementable BFGS method for solving a nonsmooth convex optimization problem by converting the original objective function into a once continuously differentiable function by way of the Moreau–Yosida regularization. The proposed method makes use of approximate function and gradient values of the Moreau-Yosida regularization instead of the corresponding exact values. We prove the global convergence of the proposed method under the assumption of strong convexity of the objective function. 相似文献
892.
On the truncated conjugate gradient method 总被引:7,自引:0,他引:7
Y. Yuan 《Mathematical Programming》2000,87(3):561-573
In this paper, we consider the truncated conjugate gradient method for minimizing a convex quadratic function subject to a
ball trust region constraint. It is shown that the reduction in the objective function by the solution obtained by the truncated
CG method is at least half of the reduction by the global minimizer in the trust region.
Received January 19, 1999 / Revised version received October 1, 1999?Published online November 30, 1999 相似文献
893.
The influence of polymer molecular-weight distributions on the outcome of pulsed field gradient (PFG) NMR self-diffusion
experiments has been considered. The self-diffusion coefficient, D, of monodisperse poly(ethylene oxide) (PEO) polymers has been determined in order to accurately determine the scaling behavior
of D both with molecular weight and concentration. In order to investigate the influence of polydispersity on the PFG NMR signal,
a model system consisting of ten reasonably monodisperse PEO polymers was made, and the PFG NMR signal intensities were recorded
at a low total concentration. The data were analyzed using both inverse Laplace transformation and nonlinear least-squares
fitting to a prescribed distribution function of D. Finally, the molecular-weight distribution was obtained by use of the values of the scaling parameters. We also present
some model calculations used to investigate the sensitivity of the degree of polydispersity on the NMR signal decays.
Received: 27 May 1999 Accepted in revised form: 19 October 1999 相似文献
894.
H. J. A. Philipsen H. A. Claessens P. Jandera M. Bosman B. Klumperman 《Chromatographia》2000,52(5-6):325-333
Summary The normal-phase chromatographic retention behaviour of polyesters on bare silica and on a polymer-based polyamine (PA) column
has been studied with a variely of binary mobile phases under isocratic conditions. The dependence of experimental retention
data on the degree of polymerization (p) and on mobile phase composition (φ) was characterized by to an approach developed by Jandera et al. The bulky repeating
unit and the relatively highly polar end groups of the polyesters both had a large influence on retention behaviour. The two
effects in combination explain the molar-mass-independent retention observed experimentally at a particular mobile phase composition
for all the mobile phase—stationary phase combinations investigated. These conditions were found to be independent of the
type of end group. End group separation on a silica column improves when the polarity of the less polar solvent is increased.
End group separation is better on the PA column because of a greater difference between the adsorption energy of the alcohol
and acid end groups. Better prediction of retention data on the PA column was achieved by use of an approach which assumes
two different types of adsorption site. Results enabled further understanding of retention behaviour in normalphase gradient
polymer-elution chromatography (NPGPEC) and explained both the dependence of the order of elution onp and differences between the end-group selectivity of different systems. 相似文献
895.
896.
Bing-sheng He 《计算数学(英文版)》2000,18(1):1-12
1.IntroductionLetHbeagivennxnsymmetricpositivesemidefinitematrixandcER".Inthispaperweconsiderthefollowingquadraticprogrammingwithasimplequadraticalconstraint1r--XTH. CTX=min2(1)s.tIlxlls5a,wheretheparameteraisprescribed.Thisproblemoccursfrequentlyintrustrationmethodforunconstrainedoptimization[11.Anumberofapproachesforsolving(1)havebeenproposedintheliterature[2,3,6,12--16].OnetechniqueistoapproximateaLagrangemultiplierAbyNewton'smethod.Theapproximationofthisparametermaybequitedelicate,ho… 相似文献
897.
Thomas F. Coleman Jianguo Liu Wei Yuan 《Computational Optimization and Applications》2000,15(2):103-123
We present a modified quadratic penalty function method for equality constrained optimization problems. The pivotal feature of our algorithm is that at every iterate we invoke a special change of variables to improve the ability of the algorithm to follow the constraint level sets. This change of variables gives rise to a suitable block diagonal approximation to the Hessian which is then used to construct a quasi-Newton method. We show that the complete algorithm is globally convergent. Preliminary computational results are reported. 相似文献
898.
We investigate the entanglement in a system of two coupling atoms
interacting with a single-mode field
by means of quantum information entropy theory.
The quantum entanglement between the two atoms and the coherent field is discussed by using
the quantum reduced entropy,
and the entanglement between the two coupling atoms is also investigated
by using the quantum relative entropy.
In addition, the influences of the atomic dipole--dipole interaction
intensity and
the average photon number of the coherent field on the degree of the entanglement is examined.
The results show that the evolution of the degree of entanglement between the two atoms
and the field is just opposite to that of the degree of entanglement between the two atoms.
And the properties of the quantum entanglement in the system rely on the
atomic dipole--dipole
interaction and the average photon number of the coherent field. 相似文献
899.
研究了在脉冲复合电铸过程中,当其它工艺参数一定时,镀液中纳米ZrO2颗粒含量、脉间、脉宽和阴极电流密度对复合电铸层中ZrO2复合量和沉积速率以及脉冲参数对复合电铸层表面形貌的影响,并对所制备复合电铸层的横截面进行了SEM观察和组成成分测定.结果表明,通过控制脉冲复合电铸过程中的工艺参数可以制备出由纳米颗粒复合量变化而导致其组织成分呈梯度分布的纳米功能梯度材料. 相似文献
900.
F. Fang C. C. Pain I. M. Navon M. D. Piggott G. J. Gorman P. A. Allison A. J. H. Goddard 《国际流体数值方法杂志》2009,59(8):827-851
A novel proper orthogonal decomposition (POD) model has been developed for use with an advanced unstructured mesh finite‐element ocean model, the Imperial College Ocean Model (ICOM, described in detail below), which includes many recent developments in ocean modelling and numerical analysis. The advantages of the POD model developed here over existing POD approaches are the ability:
- 1. To increase accuracy when representing geostrophic balance (the balance between the Coriolis terms and the pressure gradient). This is achieved through the use of two sets of geostrophic basis functions where each one is calculated by basis functions for velocities u and v.
- 2. To speed up the POD simulation. To achieve this a new numerical technique is introduced, whereby a time‐dependent matrix in the discretized equation is rapidly constructed from a series of time‐independent matrices. This development imparts considerable efficiency gains over the often‐used alternative of calculating each finite element over the computational domain at each time level.
- 3. To use dynamically adaptive meshes in the above POD model.