全文获取类型
收费全文 | 58440篇 |
免费 | 1035篇 |
国内免费 | 158篇 |
专业分类
化学 | 32368篇 |
晶体学 | 834篇 |
力学 | 1976篇 |
综合类 | 2篇 |
数学 | 7340篇 |
物理学 | 17113篇 |
出版年
2022年 | 420篇 |
2021年 | 552篇 |
2020年 | 640篇 |
2019年 | 635篇 |
2018年 | 970篇 |
2017年 | 850篇 |
2016年 | 1514篇 |
2015年 | 1049篇 |
2014年 | 1381篇 |
2013年 | 3005篇 |
2012年 | 2876篇 |
2011年 | 3222篇 |
2010年 | 2159篇 |
2009年 | 2092篇 |
2008年 | 2729篇 |
2007年 | 2749篇 |
2006年 | 2491篇 |
2005年 | 2226篇 |
2004年 | 2069篇 |
2003年 | 1700篇 |
2002年 | 1561篇 |
2001年 | 1818篇 |
2000年 | 1403篇 |
1999年 | 1128篇 |
1998年 | 829篇 |
1997年 | 810篇 |
1996年 | 807篇 |
1995年 | 682篇 |
1994年 | 686篇 |
1993年 | 596篇 |
1992年 | 670篇 |
1991年 | 652篇 |
1990年 | 634篇 |
1989年 | 578篇 |
1988年 | 581篇 |
1987年 | 570篇 |
1986年 | 506篇 |
1985年 | 630篇 |
1984年 | 665篇 |
1983年 | 475篇 |
1982年 | 519篇 |
1981年 | 507篇 |
1980年 | 454篇 |
1979年 | 489篇 |
1978年 | 474篇 |
1977年 | 496篇 |
1976年 | 470篇 |
1975年 | 431篇 |
1974年 | 386篇 |
1973年 | 412篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
The aim of the paper is to investigate the limit behaviour of the least squares estimator of the shift parameter of nearly unstable, nearly stable, and nearly explosive AR(1) models. Both zero start and stationary cases are treated. Connection with the maximum likelihood estimator of the shift parameter of continuous time AR(1) processes is also discussed. 相似文献
142.
Bruzón M. S. Gandarias M. L. Muriel C. Ramírez J. Saez S. Romero F. R. 《Theoretical and Mathematical Physics》2003,137(1):1367-1377
We use the classical and nonclassical methods to obtain symmetry reductions and exact solutions of the (2+1)-dimensional integrable Calogero–Bogoyavlenskii–Schiff equation. Although this (2+1)-dimensional equation arises in a nonlocal form, it can be written as a system of differential equations and, in potential form, as a fourth-order partial differential equation. The classical and nonclassical methods yield some exact solutions of the (2+1)-dimensional equation that involve several arbitrary functions and hence exhibit a rich variety of qualitative behavior. 相似文献
143.
Periodica Mathematica Hungarica - 相似文献
144.
145.
Leibniz agebras are a generalization of Lie algebras, where no symmetry properties of the bracket are required. In this Letter we introduce a notion of R-matrices for this structure and the related Yang–Baxter equations, and discuss some of their basic properties. 相似文献
146.
A. V. Novikov D. N. Lobanov A. N. Yablonsky Yu. N. Drozdov N. V. Vostokov Z. F. Krasilnik 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):467
The dependence of photoluminescence spectra of structures with GeSi/Si(0 0 1) self-assembled nanoislands on growth temperature has been investigated. It was shown that the redshift of the island-related photoluminescence peak with a decrease of the growth temperature is associated with suppression of Si diffusion in the islands and an increase of Ge content in them. For the first time a photoluminescence signal from SiGe islands was observed at energies much lower than the Ge band gap. The energy position of the island-related photoluminescence peak is well described by the model of optical transition, which is indirect in real space. The photoluminescence signal at 1.55 μm from GeSi/Si(0 0 1) self-assembled islands was obtained up to room temperature. 相似文献
147.
Simulation of evaporation in operation area of an evaporator is considered. We obtained a formalized model of this process and optimum conditions of an engineering system on the basis on the analysis. 相似文献
148.
149.
150.
This study investigates the robust output tracking problem for a class of uncertain linear systems. The uncertainties are assumed to be time invariant and to satisfy the matching conditions. According to the selected nominal parameters, an optimal solution with a prescribed degree of stability is determined. Then, an auxiliary input via the use of an adapting factor, connected to the nominal optimal control, is introduced to guarantee the robustness and prescribed degree of stability for the output tracking control of the uncertain linear systems. This method is very simple and effective and can reject bounded uncertainties imposed on the states. A maglev vehicle model example is given to show its effectiveness. 相似文献