全文获取类型
收费全文 | 88341篇 |
免费 | 6970篇 |
国内免费 | 8560篇 |
专业分类
化学 | 29606篇 |
晶体学 | 455篇 |
力学 | 7860篇 |
综合类 | 1726篇 |
数学 | 38315篇 |
物理学 | 25909篇 |
出版年
2023年 | 704篇 |
2022年 | 1309篇 |
2021年 | 1557篇 |
2020年 | 1692篇 |
2019年 | 1994篇 |
2018年 | 1750篇 |
2017年 | 2086篇 |
2016年 | 2372篇 |
2015年 | 2010篇 |
2014年 | 3217篇 |
2013年 | 5814篇 |
2012年 | 3585篇 |
2011年 | 4312篇 |
2010年 | 3801篇 |
2009年 | 5276篇 |
2008年 | 5635篇 |
2007年 | 5887篇 |
2006年 | 5329篇 |
2005年 | 4629篇 |
2004年 | 4170篇 |
2003年 | 4127篇 |
2002年 | 3786篇 |
2001年 | 3132篇 |
2000年 | 3070篇 |
1999年 | 2768篇 |
1998年 | 2597篇 |
1997年 | 2111篇 |
1996年 | 1856篇 |
1995年 | 1619篇 |
1994年 | 1474篇 |
1993年 | 1255篇 |
1992年 | 1224篇 |
1991年 | 931篇 |
1990年 | 755篇 |
1989年 | 667篇 |
1988年 | 612篇 |
1987年 | 473篇 |
1986年 | 396篇 |
1985年 | 478篇 |
1984年 | 474篇 |
1983年 | 233篇 |
1982年 | 393篇 |
1981年 | 430篇 |
1980年 | 335篇 |
1979年 | 336篇 |
1978年 | 249篇 |
1977年 | 221篇 |
1976年 | 174篇 |
1974年 | 118篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
991.
Let A be a Weil algebra. The bijection between all natural operators lifting vector fields from m-manifolds to the bundle functor K
A
of Weil contact elements and the subalgebra of fixed elements SA of the Weil algebra A is determined and the bijection between all natural affinors on K
A
and SA is deduced. Furthermore, the rigidity of the functor K
A
is proved. Requisite results about the structure of SA are obtained by a purely algebraic approach, namely the existence of nontrivial SA is discussed. 相似文献
992.
Hubert Kalf 《Journal of Differential Equations》2004,205(2):408-423
We show that the point spectrum of the standard Coulomb-Dirac operator H0 is the limit of the point spectrum of the Dirac operator with anomalous magnetic moment Ha as the anomaly parameter tends to 0. For negative angular momentum quantum number κ, this holds for all Coulomb coupling constants c for which H0 has a distinguished self-adjoint realisation. For positive κ, however, there are some exceptional values for c, and in general an index shift between the eigenvalues of H0 and the limits of eigenvalues of Ha appears, accompanied with additional oscillations of the eigenfunctions of Ha very close to the origin. 相似文献
993.
In survival or reliability studies, the mean residual life or life expectancy is an important characteristic of the model. Whereas the failure rate can be expressed quite simply in terms of the mean residual life and its derivative, the inverse problem—namely that of expressing the mean residual life in terms of the failure rate—typically involves an integral of a complicated expression. In this paper, we obtain simple expressions for the mean residual life in terms of the failure rate for certain classes of distributions which subsume many of the standard cases. Several results in the literature can be obtained using our approach. Additionally, we develop an expansion for the mean residual life in terms of Gaussian probability functions for a broad class of ultimately increasing failure rate distributions. Some examples are provided to illustrate the procedure. 相似文献
994.
Simone Calogero 《Journal of Differential Equations》2004,204(2):323-338
The Nordström-Vlasov system is a Lorentz invariant model for a self-gravitating collisionless gas. We establish suitable a priori bounds on the solutions of this system, which together with energy estimates and the smoothing effect of “momentum averaging” yield the existence of global weak solutions to the corresponding initial value problem. In the process we improve the continuation criterion for classical solutions which was derived recently. The weak solutions are shown to preserve mass. 相似文献
995.
A program to compute many functions dependent on the electron density ρ(r) from the results of ab initio molecular calculations is presented. The program allows the generation of different one-, two-, and three-dimensional grids for further graphical representation or numerical analysis. Other options like extracting separate atom contributions to the function computed or locating maximum and minimum values are also implemented. A number of illustrative applications regarding different ρ(r)-dependent functions are presented and the performance and portability of the program is discussed. 相似文献
996.
采用基于相对论平均场的耦合常数解析延拓方法研究球形核的单粒子共振态.具体计算了Zr同位素链中巨晕核的核芯核122Zr阈值附近的中子共振态的能量、宽度和波函数,其结果同相应的散射相移法的结果一致. Using analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory, the energies, widths and wave functions for single-particle resonant states close to the continuum threshold are evaluated. Predictions are also compared with corresponding results obtained by the scattering phase shift method. 相似文献
997.
Yi Liu David D. Díaz Adrian A. Accurso K. Barry Sharpless Valery V. Fokin M. G. Finn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5182-5189
1,2,3‐Triazole‐based polymers generated from the Cu(I)‐catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182–5189, 2007 相似文献
998.
Testing goodness of fit for the distribution of errors in multivariate linear models 总被引:2,自引:0,他引:2
M.D. Jimnez Gamero J. Muoz García R. Pino Mejías 《Journal of multivariate analysis》2005,95(2):301-322
In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size. 相似文献
999.
Fabio Scardigli 《Foundations of Physics》2007,37(8):1278-1295
The Titius–Bode law for planetary distances is reviewed. A model describing the basic features of this rule in the “quantum-like”
language of a wave equation is proposed. Some considerations about the ’t Hooft idea on the quantum behavior of deterministic
systems with dissipation are discussed. 相似文献
1000.
得到局部G-凸一致空间上具有S-KKM性质的集值映射的新的几乎不动点定理和不动点定理.我们的结果对已有文献中的相应结论进行了改进和一般化. 相似文献