全文获取类型
收费全文 | 7209篇 |
免费 | 189篇 |
国内免费 | 264篇 |
专业分类
化学 | 849篇 |
晶体学 | 29篇 |
力学 | 34篇 |
综合类 | 9篇 |
数学 | 6166篇 |
物理学 | 575篇 |
出版年
2023年 | 12篇 |
2022年 | 20篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 211篇 |
2018年 | 235篇 |
2017年 | 96篇 |
2016年 | 50篇 |
2015年 | 72篇 |
2014年 | 240篇 |
2013年 | 592篇 |
2012年 | 277篇 |
2011年 | 490篇 |
2010年 | 386篇 |
2009年 | 472篇 |
2008年 | 508篇 |
2007年 | 460篇 |
2006年 | 392篇 |
2005年 | 255篇 |
2004年 | 203篇 |
2003年 | 202篇 |
2002年 | 150篇 |
2001年 | 162篇 |
2000年 | 159篇 |
1999年 | 197篇 |
1998年 | 185篇 |
1997年 | 154篇 |
1996年 | 199篇 |
1995年 | 192篇 |
1994年 | 184篇 |
1993年 | 169篇 |
1992年 | 98篇 |
1991年 | 32篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 16篇 |
1985年 | 51篇 |
1984年 | 64篇 |
1983年 | 47篇 |
1982年 | 51篇 |
1981年 | 54篇 |
1980年 | 38篇 |
1979年 | 37篇 |
1978年 | 38篇 |
1977年 | 29篇 |
1976年 | 20篇 |
1975年 | 17篇 |
1973年 | 12篇 |
排序方式: 共有7662条查询结果,搜索用时 15 毫秒
21.
The problem of nonparametric stationary distribution function estimation by the observations of an ergodic diffusion process is considered. The local asymptotic minimax lower bound on the risk of all the estimators is found and it is proved that the empirical distribution function is asymptotically efficient in the sense of this bound. 相似文献
22.
Hong-Nian Li Xiao-Xiong WangWang-Feng Ding 《Journal of Electron Spectroscopy and Related Phenomena》2006
Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C60 film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K3C60, K6C60, Ba4C60, Sm2.75C60 and Sm6C60 are calculated to help the quantitative analyses of the photoemission spectra for these compounds. 相似文献
23.
Lévy processes in matrix Lie groups are studied. Subordination (random time change) is used to show that quasi-invariance of the Brownian motion in a Lie group induces absolute continuity of the laws of the corresponding pure jump processes. These results are applied to several examples which are discussed in detail. 相似文献
24.
We construct cellular homotopy theories for categories of simplicial presheaves on small Grothendieck sites and discuss applications to the motivic homotopy category of Morel and Voevodsky. 相似文献
25.
We propose a new scheme for the long time approximation of a diffusion when the drift vector field is not globally Lipschitz. Under this assumption, a regular explicit Euler scheme–with constant or decreasing step–may explode and implicit Euler schemes are CPU-time expensive. The algorithm we introduce is explicit and we prove that any weak limit of the weighted empirical measures of this scheme is a stationary distribution of the stochastic differential equation. Several examples are presented including gradient dissipative systems and Hamiltonian dissipative systems. 相似文献
26.
In this paper, we present a numerical scheme for solving the coupled system of compressible miscible displacement problem in porous media. The flow equation is solved by the mixed finite element method, and the transport equation is approximated by a discontinuous Galerkin method. The scheme is continuous in time and a priori hp error estimates is presented. 相似文献
27.
28.
The additive renormalization% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiaabs7adaWgaaWcbaGaaeySdiaab6cacaqG0bqefeKCPfgBaGqb% diaa-bcaaeqaaOGaeyypa0Jaa8hiaiaacIcacaaIYaGaeqiWdaNaai% ykamaaCaaaleqabaGaeyOeI0IaaGymaiaac+cacaaIYaaaaGqadOGa% a4hiaiGacwgacaGG4bGaaiiCaiaacIcacqGHsislcaqGXoWaaWbaaS% qabeaacaqGYaaaaOGaai4laiaaikdacaGGPaGaa4hiaiaacQdaciGG% LbGaaiiEaiaacchacqGHXcqSdaWadiqaaiabgkHiTiaadkeacaGGNa% GaaiikaiaadshacaGGPaWaaWbaaSqabeaacaaIYaaaaOGaai4laiaa% ikdacaGFGaGaey4kaSIaa4hiaiaabg7acaWGcbGaai4jaiaacIcaca% WG0bGaaiykaaGaay5waiaaw2faaiaacQdaaaa!6C5C!\[{\rm{\delta }}_{{\rm{\alpha }}{\rm{.t}} } = (2\pi )^{ - 1/2} \exp ( - {\rm{\alpha }}^{\rm{2}} /2) :\exp \pm \left[ { - B'(t)^2 /2 + {\rm{\alpha }}B'(t)} \right]:\]is shown to be a generalized Brownian functional. Some of its properties are derived. is shown to be a generalized Brownian functional. Some of its properties are derived.On leave from Universidade do Minho, Area de Matematica, Largo Carlos Amarante, P-4700 Braga, Portugal. 相似文献
29.
Igor Chueshov 《Journal of Differential Equations》2007,233(1):42-86
We study von Karman evolution equations with non-linear dissipation and with partially clamped and partially free boundary conditions. Two distinctive mechanisms of dissipation are considered: (i) internal dissipation generated by non-linear operator, and (ii) boundary dissipation generated by shear forces friction acting on a free part of the boundary. The main emphasis is given to the effects of boundary dissipation. Under suitable hypotheses we prove existence of a compact global attractor and finiteness of its fractal dimension. We also show that any solution is stabilized to an equilibrium and estimate the rate of the convergence which, in turn, depends on the behaviour at the origin of the functions describing the dissipation. 相似文献
30.
We give a new and comparably short proof of Gittins’ index theorem for dynamic allocation problems of the multi-armed bandit type in continuous time under minimal assumptions. This proof gives a complete characterization of optimal allocation strategies as those policies which follow the current leader among the Gittins indices while ensuring that a Gittins index is at an all-time low whenever the associated project is not worked on exclusively. The main tool is a representation property of Gittins index processes which allows us to show that these processes can be chosen to be pathwise lower semi-continuous from the right and quasi-lower semi-continuous from the left. Both regularity properties turn out to be crucial for our characterization and the construction of optimal allocation policies. 相似文献