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941.
The multi-scale analysis of fracture toughness of ferroelectric ceramics under complicate mechanical–electrical coupling effect is carried out in this paper. The generalized stress intensity factor (SIF) arising from spontaneous strains and polarization transformation in switching domain zones is accurately obtained by using an extended Eshelby theory. Taking BaTiO3 ferroelectric ceramic for example, it is discovered that the crack propagation can be induced by domain switching arising from negative electrical field when the crack surface is parallel to the isotropic plane, and the obtained critical electric displacement intensity factor (EDIF) approximates closely to that obtained by the Green’s function method. Additionally, as pinning dislocations and slip dislocations can strongly influence properties of ferroelectric devices and induce the property degradation, it is necessary to investigate the dislocation toughening effects on fatigue and fracture mechanisms. The results show that the dislocation shielding and anti-shielding effects on mode II SIF, mode I SIF and EDIF are obviously different when a dislocation locates at a position near the crack tip. Through the calculation of the critical applied EDIF for crack propagation by using mechanical energy release rate (MERR) theory, it is discovered that the slip angles obviously influence fracture toughness, and the mode II SIF arising from dislocation has little influence on fracture toughness, however, the mode I SIF and EDIF arising from dislocation have great influences on fracture toughness. 相似文献
942.
S. K. Liaw S. Wang C. S. Shin Y. L. Yu N. K. Chen K. C. Hsu A. Manshina Y. Tver’yanovich 《Laser Physics》2010,20(8):1744-1746
By using a subring cavity incorporated with a saturable absorber, a stable single-frequency selection is realized in a linear-cavity
fiber laser, which is constructed using a broadband fiber mirror and a partial reflectance fiber Bragg grating as the cavity
ends. At 1550.33 nm, the laser has an optical signal-to-noise-ratio of >53.28 dB and with linewidth less than 1 MHz. The pumping
efficiency is 25% improved by recycling the residual pump power to gain medium. The power stability and wavelength stability
have also been studied. 相似文献
943.
We develop an anisotropic perfectly matched layer (PML) method for solving the time harmonic electromagnetic scattering problems in which the PML coordinate stretching is performed only in one direction outside a cuboid domain. The PML parameters such as the thickness of the layer and the absorbing medium property are determined through sharp a posteriori error estimates. Combined with the adaptive finite element method, the proposed adaptive anisotropic PML method provides a complete numerical strategy to solve the scattering problem in the framework of FEM which produces automatically a coarse mesh size away from the fixed domain and thus makes the total computational costs insensitive to the choice of the thickness of the PML layer. Numerical experiments are included to illustrate the competitive behavior of the proposed adaptive method. 相似文献
944.
扩展的Sinh—Gordon方程展开法与Kaup—Kupershmidt方程的Jacobi椭圆函数解 总被引:1,自引:0,他引:1
利用扩展的Sinh—Gordon方程展开法研究了Kaup—Kupershmidt方程的Jacobi椭圆函数解,此方法也适用于求解其他非线性演化方程,从而丰富了方程解的范围. 相似文献
945.
Guanrong Chen 《Applicable analysis》2013,92(1-4):257-279
A general linear quadratic (LQ) optimal control problem, with the dynamic system being governed by a higher-order vector-valued ordinary differential equation and with inequality-constraints on the state vector and/or the control input, is studied. Based on an explicit characterization result, optimal solutions are obtained in closed-form. A constructive method for finding the closed-form optimal solutions is proposed, and two illustrative examples are included 相似文献
946.
W. L. Lu B. Liu T. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(2):257-264
In this paper, we study cluster synchronization in general
bi-directed networks of nonidentical clusters, where all nodes in
the same cluster share an identical map. Based on the transverse
stability analysis, we present sufficient conditions for local
cluster synchronization of networks. The conditions are
composed of two factors: the common inter-cluster coupling, which
ensures the existence of an invariant cluster synchronization
manifold, and communication between each pair of nodes in the same
cluster, which is necessary for chaos synchronization. Consequently, we propose a
quantity to measure the cluster synchronizability for a network with
respect to the given clusters via a function of the eigenvalues
of the Laplacian corresponding to the generalized eigenspace
transverse to the cluster synchronization manifold. Then, we discuss
the clustering synchronous dynamics and cluster synchronizability
for four artificial network models: (i) p-nearest-neighborhood graph; (ii)
random clustering graph; (iii) bipartite random graph; (iv)
degree-preferred growing clustering network. From these network models, we are to
reveal how the intra-cluster and inter-cluster links affect the cluster
synchronizability. By numerical examples, we find that for the first
model, the cluster synchronizability regularly enhances with the
increase of p, yet for the other three models, when the ratio of
intra-cluster links and the inter-cluster links reaches certain
quantity, the clustering synchronizability reaches maximal. 相似文献
947.
Excited light and corresponding intrinsic fluorescence diffusion inside teeth tissue are an essential problem for light-based
carious lesion detection. Based on finite element numerical analysis of diffusion equation, the photon density distribution
of both excited light and autofluorescence of 2D premolar teeth model is obtained. The dependence of excited light and autofluorescence
density distribution inside the teeth model on the scattering coefficient of enamel (5–25 mm−1) and dentine (100–140 mm−1) is numerically simulated and analyzed. The fitted results reveal that fluorescence intensity decreases exponentially. Optical
penetration depth and fluorescence relative depth declined with the increment of scattering coefficient of enamel. And the
dentine had the opposite effect. Finally, the experiment of measurement of fluorescence intensity on the teeth surface is
conducted and the result is compared with the numerical computation. 相似文献
948.
949.
Naturally existing tritium in groundwater was applied as a tracer to evaluate the natural recharge of the Chingshui geothermal reservoir. The residence time (or, age) of Chingshui geothermal water was first determined with tritium data at 15.2 and 11.3 year using the plug flow and dispersive model, respectively. The annual natural recharge was then estimated by combining the use of the residence time and the fluid-in-place of the Chingshui geothermal reservoir. The natural recharge for Chingshui geothermal reservoir was estimated at 5.0 × 105 and 6.7 × 105 m3 year?1 using the plug flow and dispersive model, respectively. Chingshui geothermal water is largely from a fractured zone in the Jentse Member of the Miocene Lushan Formation. The dispersive model more adequately represents the fracture flow system than the simple plug flow model. 相似文献
950.
J E Boylan H Chen M Mohammadipour A Syntetos 《The Journal of the Operational Research Society》2014,65(2):227-241
Estimating seasonal variations in demand is a challenging task faced by many organisations. There may be many stock-keeping units (SKUs) to forecast, but often data histories are short, with very few complete seasonal cycles. It has been suggested in the literature that group seasonal indices (GSI) methods should be used to take advantage of information on similar SKUs. This paper addresses two research questions: (1) how should groups be formed in order to use the GSI methods? and (2) when should the GSI methods and the individual seasonal indices (ISI) method be used? Theoretical results are presented, showing that seasonal grouping and forecasting may be unified, based on a Mean Square Error criterion, and K-means clustering. A heuristic K-means method is presented, which is competitive with the Average Linkage method. It offers a viable alternative to a company's own grouping method or may be used with confidence if a company lacks a grouping method. The paper gives empirical findings that confirm earlier theoretical results that greater accuracy may be obtained by employing a rule that assigns the GSI method to some SKUs and the ISI method to the remainder. 相似文献