全文获取类型
收费全文 | 46417篇 |
免费 | 1287篇 |
国内免费 | 13篇 |
专业分类
化学 | 28131篇 |
晶体学 | 237篇 |
力学 | 758篇 |
综合类 | 1篇 |
数学 | 8747篇 |
物理学 | 9843篇 |
出版年
2023年 | 334篇 |
2022年 | 282篇 |
2021年 | 460篇 |
2020年 | 665篇 |
2019年 | 604篇 |
2018年 | 951篇 |
2017年 | 870篇 |
2016年 | 1683篇 |
2015年 | 1392篇 |
2014年 | 1341篇 |
2013年 | 3036篇 |
2012年 | 2866篇 |
2011年 | 2686篇 |
2010年 | 1790篇 |
2009年 | 1496篇 |
2008年 | 2364篇 |
2007年 | 2146篇 |
2006年 | 1912篇 |
2005年 | 1972篇 |
2004年 | 1702篇 |
2003年 | 1415篇 |
2002年 | 1229篇 |
2001年 | 950篇 |
2000年 | 951篇 |
1999年 | 663篇 |
1998年 | 513篇 |
1997年 | 431篇 |
1996年 | 574篇 |
1995年 | 409篇 |
1994年 | 483篇 |
1993年 | 439篇 |
1992年 | 468篇 |
1991年 | 395篇 |
1990年 | 443篇 |
1989年 | 360篇 |
1988年 | 368篇 |
1987年 | 329篇 |
1986年 | 320篇 |
1985年 | 447篇 |
1984年 | 410篇 |
1983年 | 324篇 |
1982年 | 325篇 |
1981年 | 341篇 |
1980年 | 278篇 |
1979年 | 272篇 |
1978年 | 270篇 |
1977年 | 260篇 |
1976年 | 277篇 |
1974年 | 251篇 |
1973年 | 263篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A new preconditioned conjugate gradient (PCG)-based domain decomposition method is given for the solution of linear equations
arising in the finite element method applied to the elliptic Neumann problem. The novelty of the proposed method is in the
recommended preconditioner which is constructed by using cyclic matrix. The resulting preconditioned algorithms are well suited
to parallel computation. 相似文献
42.
C. Adamuscin A.-Z. Dubnicková S. Dubnicka R. Pekárik P. Weisenpacher 《The European Physical Journal C - Particles and Fields》2003,28(1):115-118
A system of linear homogeneous algebraic equations for the coupling constant ratios of vector mesons to hadrons is derived
by imposing the assumed asymptotic behavior upon the VMD pole parameterization of an hadron electromagnetic form factor. A
similar system of equations with a simpler structure of the coefficients, taken as even powers of the vector-meson masses,
is derived by means of integral superconvergent sum rules for the imaginary part of the considered form factor using its
appropriate -function approximation. Although both systems have been derived starting from different properties of the electromagnetic
form factor and they each have their own appearances, it is shown explicitly that they are fully equivalent.
Received: 20 March 2002 / Revised version: 3 December 2002 / Published online: 7 March 2003 相似文献
43.
In this note we make a correction in the paper [1] by two of the authors. Specifically we modify an auxiliary localization
result and prove that the applications to the saturation theory of some outstanding conservative operators remain valid. Moreover,
we enrich a corollary dealing with the well-known Szász-Mirakjan operators.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
44.
Mátyás Bognár 《Acta Mathematica Hungarica》2004,102(1-2):37-84
The following generalization of the Hahn-Mazurkiewicz theorem is proved: Let (E,e) be a locally compact locally connected metric space. Let M be a continuum in this space and let d,e∈ M. Then there is a continuous mapping f: [0,1]→E such that f(0) = d, f(1)= e and M⊂f([0,1]). Also some corollaries of this theorem are proved. 相似文献
45.
Summary. We introduce linear semi-implicit complementary volume numerical scheme for solving level set like nonlinear degenerate diffusion
equations arising in image processing and curve evolution problems. We study discretization of image selective smoothing equation
of mean curvature flow type given by Alvarez, Lions and Morel ([3]). Solution of the level set equation of Osher and Sethian
([26], \[30]) is also included in the study. We prove and estimates for the proposed scheme and give existence of its (generalized) solution in every discrete time-scale step. Efficiency
of the scheme is given by its linearity and stability. Preconditioned iterative solvers are used for computing arising linear
systems. We present computational results related to image processing and plane curve evolution.
Received April 25, 2000 / Revised version received June 11, 2001 / Published online November 15, 2001 相似文献
46.
We derive the incompressible and compressible k–ε model for locally homogeneous turbulence. The model is rigorously derived on formal mathematical grounds using the MPP modelling technique. This lets us calculate by either analytical or numerical means the closure constants of the model. To cite this article: T. Chacón Rebollo, D. Franco Coronil, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
47.
We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields. 相似文献
48.
Lubomír Kubáček 《Mathematica Slovaca》2007,57(6):571-588
The multivariate model, where not only parameters of the mean value of the observation matrix, but also some other parameters
occur in constraints, is considered in the paper. Some basic inference is presented under the condition that the covariance
matrix is either unknown, or partially unknown, or known.
Supported by the grant of the Council of Czech Republic MSM 6 198 959 214. 相似文献
49.
We prove that directly reducible lattices and selfdual subdirectly irreducible lattices of locally finite length are determined by their sublattice-lattices. As a corollary we obtain that splitting varieties are closed under the isomorphism of sublattice-lattices iff they are selfdual. A class of selfdual non-closed varieties is given too. 相似文献
50.
V. D. Fedotov N. P. Obuchov R. A. Zadikhanov J. Spěváček J. Straka 《Applied magnetic resonance》1993,4(4):491-511
The combined analysis of1H and13C NMR relaxation data in solid lysozyme and some typical homopolypeptides was carried out by using “model-free” approach. Three types of relaxation transitions (γ’, γ and β) were revealed in the temperature range investigated. The microdynamical parameters of these motions were determined. From the comparison of these parameters with those of selected synthetic polymers it follows that the molecular motions in proteins and synthetic polymers are of the same nature. All these motions show pronounced anisotropic character. In the investigated temperature range no molecular motions corresponding to α-relaxation (liquid-like) transition were revealed. The hydration effects on parameters of the motions in proteins were considered. The most pronounced effect takes place for β-transition. The effect of Brownian rotation of protein molecule in solution on measured correlation function of local motions was also discussed. 相似文献