全文获取类型
收费全文 | 23780篇 |
免费 | 558篇 |
国内免费 | 460篇 |
专业分类
化学 | 4076篇 |
晶体学 | 936篇 |
力学 | 420篇 |
综合类 | 44篇 |
数学 | 15377篇 |
物理学 | 3945篇 |
出版年
2023年 | 64篇 |
2022年 | 206篇 |
2021年 | 167篇 |
2020年 | 175篇 |
2019年 | 452篇 |
2018年 | 506篇 |
2017年 | 339篇 |
2016年 | 368篇 |
2015年 | 377篇 |
2014年 | 702篇 |
2013年 | 1603篇 |
2012年 | 642篇 |
2011年 | 1753篇 |
2010年 | 1563篇 |
2009年 | 1530篇 |
2008年 | 1629篇 |
2007年 | 1621篇 |
2006年 | 1229篇 |
2005年 | 1063篇 |
2004年 | 913篇 |
2003年 | 717篇 |
2002年 | 684篇 |
2001年 | 480篇 |
2000年 | 458篇 |
1999年 | 467篇 |
1998年 | 467篇 |
1997年 | 359篇 |
1996年 | 415篇 |
1995年 | 417篇 |
1994年 | 406篇 |
1993年 | 323篇 |
1992年 | 310篇 |
1991年 | 218篇 |
1990年 | 206篇 |
1989年 | 202篇 |
1988年 | 130篇 |
1987年 | 147篇 |
1986年 | 112篇 |
1985年 | 192篇 |
1984年 | 145篇 |
1983年 | 91篇 |
1982年 | 120篇 |
1981年 | 141篇 |
1980年 | 122篇 |
1979年 | 73篇 |
1978年 | 123篇 |
1977年 | 106篇 |
1976年 | 110篇 |
1975年 | 45篇 |
1974年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
基于BDF的无约束优化方法的收敛性分析 总被引:3,自引:0,他引:3
1.介 绍 在上个世纪的七十年代末、八十年代初,基于常微分方程的优化方法或者说同伦方法是一类与拟牛顿法和共轭梯度法等我们所熟知的优化方法相竞争的重要方法[1-6,8,13,14,16].由于这类方法只是简单地利用现成的数值求解常微分方程的软件包,如CVODE[7]、LSODE[12],对同伦方程(一般是一个常微分方程的初值问题)进行计算,除了一些特殊的病态问题 相似文献
52.
Paulo D. Cordaro 《Advances in Mathematics》2004,184(1):89-118
Taking as a start point the recent article of Meziani [7], we present several results concerning the normalization of a class of complex vector fields in the plane which degenerate along a real curve. We mainly deal with operators with finite regularity and analyze both the local situation as well as the case of normalization near a circle. Some related questions (e.g., on semi-global solvability and on the normalization of a class of generalized Mizohata operators) are also discussed. 相似文献
53.
Reduced rank regression assumes that the coefficient matrix in a multivariate regression model is not of full rank. The unknown rank is traditionally estimated under the assumption of normal responses. We derive an asymptotic test for the rank that only requires the response vector have finite second moments. The test is extended to the nonconstant covariance case. Linear combinations of the components of the predictor vector that are estimated to be significant for modelling the responses are obtained. 相似文献
54.
In this paper we relate the operators in the operator representations of a generalized Nevanlinna function N(z) and of the function −N(z)−1 under the assumption that z=∞ is the only (generalized) pole of nonpositive type. The results are applied to the Q-function for S and H and the Q-function for S and H∞, where H is a self-adjoint operator in a Pontryagin space with a cyclic element w, H∞ is the self-adjoint relation obtained from H and w via a rank one perturbation at infinite coupling, and S is the symmetric operator given by S=H∩H∞. 相似文献
55.
Neutron irradiation of Cp2MoCl2 for 24 h afforded the radiotracer Cp299MoCl2 which was characterised by UV–Vis spectroscopy and thin layer chromatography. Binding experiments with the thiol containing protein human serum albumin (HSA) or calf thymus DNA, were monitored for 99Mo using a gamma counter. Under the conditions investigated, molar ratios of binding of 0.2:1 (Cp2MoCl2:DNA) and 9.4:1 (Cp2MoCl2:HSA) were calculated. The results are consistent with in vitro coordination studies that have shown strong preferential interaction of Cp2MoCl2 with thiols versus other donor sites in biomolecules including DNA. 相似文献
56.
Vinod Kumar Pragya Das R.P. Singh S. Muralithar R.K. Bhowmik 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):153-157
The fusion evaporation reaction 122Sn(14N, 4n)132La was used to populate the high-spin states of 132La at the beam energy of 60 MeV. A new band consisting of mostly E2 transitions has been discovered. This band has the interesting links to the ground state 2- and the isomeric state 6-. A new transition of energy 351 keV connecting the low-spin states of the positive-parity band based on the πh
11/2 ⊗ νh
11/2 particle configuration, has been found. This has played a very important role in resolving the existing ambiguities and inconsistencies
in the spin assignment of the band head.
Received: 12 August 2002 / Accepted: 18 March 2003 / Published online: 7 May 2003 相似文献
57.
M Gubinelli 《Journal of Functional Analysis》2004,216(1):86-140
We formulate indefinite integration with respect to an irregular function as an algebraic problem which has a unique solution under some analytic constraints. This allows us to define a good notion of integral with respect to irregular paths with Hölder exponent greater than 1/3 (e.g. samples of Brownian motion) and study the problem of the existence, uniqueness and continuity of solution of differential equations driven by such paths. We recover Young's theory of integration and the main results of Lyons’ theory of rough paths in Hölder topology. 相似文献
58.
D. Ruiz 《Journal of Differential Equations》2004,199(1):96-114
In this paper we study the existence of positive solutions for a nonlinear Dirichlet problem involving the m-Laplacian. The nonlinearity considered depends on the first derivatives; in such case, variational methods cannot be applied. So, we make use of topological methods to prove the existence of solutions. We combine a blow-up argument and a Liouville-type theorem to obtain a priori estimates. Some Harnack-type inequalities which are needed in our reasonings are also proved. 相似文献
59.
András Vasy 《Journal of Functional Analysis》2004,209(2):468-492
We show the exponential decay of eigenfunctions of second-order geometric many-body type Hamiltonians at non-threshold energies. Moreover, in the case of first-order and small second-order perturbations we show that there are no eigenfunctions with positive energy. 相似文献
60.
Multilinear interpolation is a powerful tool used in obtaining strong-type boundedness for a variety of operators assuming only a finite set of restricted weak-type estimates. A typical situation occurs when one knows that a multilinear operator satisfies a weak Lq estimate for a single index q (which may be less than one) and that all the adjoints of the multilinear operator are of similar nature, and thus they also satisfy the same weak Lq estimate. Under this assumption, in this note we give a general multilinear interpolation theorem which allows one to obtain strong-type boundedness for the operator (and all of its adjoints) for a large set of exponents. The key point in the applications we discuss is that the interpolation theorem can handle the case q?1. When q>1, weak Lq has a predual, and such strong-type boundedness can be easily obtained by duality and multilinear interpolation (cf. Interpolation Spaces, An Introduction, Springer, New York, 1976; Math. Ann. 319 (2001) 151; in: Function Spaces and Applications (Lund, 1986), Lecture Notes in Mathematics, Vol. 1302, Springer, Berlin, New York, 1988; J. Amer. Math. Soc. 15 (2002) 469; Proc. Amer. Math. Soc. 21 (1969) 441). 相似文献