全文获取类型
收费全文 | 21874篇 |
免费 | 603篇 |
国内免费 | 521篇 |
专业分类
化学 | 3962篇 |
晶体学 | 934篇 |
力学 | 385篇 |
综合类 | 44篇 |
数学 | 11940篇 |
物理学 | 3680篇 |
无线电 | 2053篇 |
出版年
2023年 | 67篇 |
2022年 | 192篇 |
2021年 | 165篇 |
2020年 | 185篇 |
2019年 | 387篇 |
2018年 | 414篇 |
2017年 | 301篇 |
2016年 | 372篇 |
2015年 | 380篇 |
2014年 | 706篇 |
2013年 | 1447篇 |
2012年 | 647篇 |
2011年 | 1722篇 |
2010年 | 1525篇 |
2009年 | 1426篇 |
2008年 | 1516篇 |
2007年 | 1484篇 |
2006年 | 1185篇 |
2005年 | 997篇 |
2004年 | 898篇 |
2003年 | 736篇 |
2002年 | 679篇 |
2001年 | 456篇 |
2000年 | 434篇 |
1999年 | 422篇 |
1998年 | 401篇 |
1997年 | 312篇 |
1996年 | 355篇 |
1995年 | 352篇 |
1994年 | 326篇 |
1993年 | 249篇 |
1992年 | 255篇 |
1991年 | 179篇 |
1990年 | 184篇 |
1989年 | 172篇 |
1988年 | 108篇 |
1987年 | 125篇 |
1986年 | 91篇 |
1985年 | 160篇 |
1984年 | 115篇 |
1983年 | 68篇 |
1982年 | 91篇 |
1981年 | 122篇 |
1980年 | 106篇 |
1979年 | 61篇 |
1978年 | 108篇 |
1977年 | 91篇 |
1976年 | 90篇 |
1975年 | 39篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We show that there are close relations between extremal problems in dual Brunn-Minkowski theory and isotropic-type properties for some Borel measures on the sphere. The methods we use allow us to obtain similar results in the context of Firey-Brunn-Minkowski theory. We also study reverse inequalities for dual mixed volumes which are related with classical positions, such as ?-position or isotropic position. 相似文献
52.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
53.
An attempt is made to present a simple theoretical analysis of the energy-wave vector dispersion relation of the conduction electrons in heavily doped non-parabolic semiconductors forming band tails. We observe that the complex energy spectrum in doped small-gap materials whose unperturbed conduction band is described by the three band model of Kane is due to the interaction of the impurity atoms in the tail with the spin-orbit splitting constant of the valence band (Δ), For band-gap (Eg)<Δ the imaginary part predominates which tails in to the conduction band. For the opposite inequality the real part comes in to play which tails in to the split-off band. In the absence of the band tailing effect, the imaginary part of the complex energy spectrum vanishes and the same is also true for doped two-band Kane-type and parabolic energy bands respectively. The present formulation helps us in investigating the Boltzmann transport equation dependent transport properties of degenerate semiconductors and are expected to agree better with experiments. The well-known results of unperturbed three and two band models of Kane together with wide-gap parabolic energy bands have been obtained as special cases of our generalized analysis under certain limiting conditions. 相似文献
54.
LMB-018A是深圳拓微电子有限公司推出的内含控制器和驱动器的点阵式液晶显示模块。文中介绍了该模块的原理及功能.给出了其与DSP接口的硬件电路和软件设计方法。 相似文献
55.
56.
57.
Satyanad Kichenassamy 《Advances in Mathematics》2004,184(2):268-288
In 1985, Fefferman and Graham have constructed a local embedding of an arbitrary real-analytic manifold, of odd dimension n, into a Ricci-flat manifold of dimension n+2 admitting a homothety. They conjectured that their result remains valid in even dimensions, if logarithms are allowed in the expansion of the metric. In this paper, we (i) prove that such expansions exist and converge and (ii) establish the degree of non-uniqueness of the solution in terms of the coefficients in the expansion. 相似文献
58.
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
59.
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
60.
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