全文获取类型
收费全文 | 35109篇 |
免费 | 1275篇 |
国内免费 | 265篇 |
专业分类
化学 | 24781篇 |
晶体学 | 281篇 |
力学 | 692篇 |
综合类 | 1篇 |
数学 | 6046篇 |
物理学 | 4848篇 |
出版年
2023年 | 167篇 |
2022年 | 324篇 |
2021年 | 433篇 |
2020年 | 612篇 |
2019年 | 600篇 |
2018年 | 417篇 |
2017年 | 389篇 |
2016年 | 946篇 |
2015年 | 839篇 |
2014年 | 1010篇 |
2013年 | 1719篇 |
2012年 | 2188篇 |
2011年 | 2471篇 |
2010年 | 1341篇 |
2009年 | 1184篇 |
2008年 | 2287篇 |
2007年 | 2105篇 |
2006年 | 2123篇 |
2005年 | 1974篇 |
2004年 | 1690篇 |
2003年 | 1387篇 |
2002年 | 1341篇 |
2001年 | 492篇 |
2000年 | 470篇 |
1999年 | 411篇 |
1998年 | 400篇 |
1997年 | 421篇 |
1996年 | 457篇 |
1995年 | 317篇 |
1994年 | 371篇 |
1993年 | 338篇 |
1992年 | 309篇 |
1991年 | 285篇 |
1990年 | 245篇 |
1989年 | 215篇 |
1988年 | 211篇 |
1987年 | 225篇 |
1986年 | 186篇 |
1985年 | 380篇 |
1984年 | 335篇 |
1983年 | 284篇 |
1982年 | 350篇 |
1981年 | 285篇 |
1980年 | 292篇 |
1979年 | 250篇 |
1978年 | 230篇 |
1977年 | 222篇 |
1976年 | 210篇 |
1975年 | 188篇 |
1974年 | 163篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The qualitative behavior of buckled states of two different models of elastic beams is studied. It is assumed that random imperfections affect the governing nonlinear equations. It is shown that near the first critical value of the buckling load the stochastic bifurcation is described asymptotically by an algebraic equation whose coeffficients are Gaussian random variables. The corresponding asymptotic expansion for the displacement is to lowest order a Gaussian stochastic process.Work supported by NSF Grant No. DCR81-14726.Work supported by NSF Grant No. DMS87-01895. 相似文献
102.
Michael Höft Jochen Weinzierl Rolf Judaschke 《International Journal of Infrared and Millimeter Waves》2002,23(7):1127-1146
Holography is a promising technique for power combining applications in the frequency range of short millimeter and submillimeter waves. In this paper, quasi-optical holographic power combining circuits are investigated. An equivalent network is utilized which rigorously models horn arrays and biperiodic dielectric structures in order to design computer-generated holograms. We apply the network model to a 5-element quasi-optical power combiner and demonstrate its capability. The hologram is designed for 150 GHz and has an efficiency of 92.5 % with a 90 % bandwidth of 5.3 %. With the aid of a broadband waveguide power divider and a vector field measurement system, the circuit is analyzed. 相似文献
103.
104.
105.
106.
107.
We study a small quantum system (e.g., a simplified model for an atom or molecule) interacting with two bosonic or fermionic
reservoirs (say, photon or phonon fields). We show that the combined system has a family of stationary states parametrized
by two numbers, T
1 and T
2 (‘reservoir temperatures’). If T
1 ≠ T
2, then these states are non-equilibrium stationary states (NESS). In the latter case we show that they have nonvanishing heat
fluxes and positive entropy production and are dynamically asymptotically stable. The latter means that the evolution with
an initial condition, normal with respect to any state where the reservoirs are in equilibria at temperatures T
1 and T
2, converges to the corresponding NESS. Our results are valid for the temperatures satisfying the bound min (T
1,T
2) > g
2 + α, where g is the coupling constant and 0 < α < 1 is a power related to the infra-red behaviour of the coupling functions.
Submitted: March 20, 2006. Revised: March 19, 2007. Accepted: May 11, 2007.
Marco Merkli: Partly supported by an NSERC PDF, the Institute of Theoretical Physics of ETH Zürich, Switzerland, the Departments
of Mathematics of McGill University and the University of Toronto, Canada.
Matthias Mück: Supported by DAAD under grant HSP III.
Israel Michael Sigal: Supported by NSERC under grant NA7901. 相似文献
108.
Michael J. Puls 《Archiv der Mathematik》2007,88(6):500-506
Let p be a real number greater than one. In this paper we study the vanishing and nonvanishing of the first L
p
-cohomology space of some groups that have one end. We also make a connection between the first L
p
-cohomolgy space and the Floyd boundary of the Cayley graph of a group. We apply the result about Floyd boundaries to show
that there exists a real number p such that the first L
p
-cohomology space of a nonelementary hyperbolic group does not vanish.
Received: 4 August 2006 Revised: 2 November 2006 相似文献
109.
110.
It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III–V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [35S]methionine. A protein with a molecular weight (Mr) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with Mr values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins. 相似文献