全文获取类型
收费全文 | 50737篇 |
免费 | 1496篇 |
国内免费 | 34篇 |
专业分类
化学 | 28138篇 |
晶体学 | 234篇 |
力学 | 1029篇 |
数学 | 8163篇 |
物理学 | 14703篇 |
出版年
2023年 | 301篇 |
2021年 | 408篇 |
2020年 | 631篇 |
2019年 | 432篇 |
2018年 | 581篇 |
2017年 | 546篇 |
2016年 | 1276篇 |
2015年 | 1103篇 |
2014年 | 1208篇 |
2013年 | 2604篇 |
2012年 | 2137篇 |
2011年 | 2586篇 |
2010年 | 1271篇 |
2009年 | 1080篇 |
2008年 | 2417篇 |
2007年 | 2375篇 |
2006年 | 2164篇 |
2005年 | 1886篇 |
2004年 | 1509篇 |
2003年 | 1317篇 |
2002年 | 1212篇 |
2001年 | 1052篇 |
2000年 | 901篇 |
1999年 | 661篇 |
1998年 | 582篇 |
1997年 | 585篇 |
1996年 | 688篇 |
1995年 | 637篇 |
1994年 | 647篇 |
1993年 | 749篇 |
1992年 | 646篇 |
1991年 | 498篇 |
1990年 | 511篇 |
1989年 | 437篇 |
1988年 | 441篇 |
1987年 | 457篇 |
1986年 | 432篇 |
1985年 | 612篇 |
1984年 | 634篇 |
1983年 | 578篇 |
1982年 | 600篇 |
1981年 | 617篇 |
1980年 | 559篇 |
1979年 | 514篇 |
1978年 | 573篇 |
1977年 | 532篇 |
1976年 | 471篇 |
1975年 | 451篇 |
1974年 | 418篇 |
1973年 | 426篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Jürg Fröhlich Tai-Peng Tsai Horng-Tzer Yau 《Communications in Mathematical Physics》2002,225(2):223-274
We consider the nonlinear Hartree equation describing the dynamics of weakly interacting non-relativistic Bosons. We show
that a nonlinear M?ller wave operator describing the scattering of a soliton and a wave can be defined. We also consider the dynamics of a
soliton in a slowly varying background potential W(ɛx). We prove that the soliton decomposes into a soliton plus a scattering wave (radiation) up to times of order ɛ−1. To leading order, the center of the soliton follows the trajectory of a classical particle in the potential W(ɛx).
Received: 30 June 2000 / Accepted: 25 June 2001 相似文献
73.
Jörg Zintl 《Mathematische Zeitschrift》2002,242(3):415-426
74.
A cutting plane algorithm for a clustering problem 总被引:2,自引:0,他引:2
In this paper we consider a clustering problem that arises in qualitative data analysis. This problem can be transformed to a combinatorial optimization problem, the clique partitioning problem. We have studied the latter problem from a polyhedral point of view and determined large classes of facets of the associated polytope. These theoretical results are utilized in this paper. We describe a cutting plane algorithm that is based on the simplex method and uses exact and heuristic separation routines for some of the classes of facets mentioned before. We discuss some details of the implementation of our code and present our computational results. We mention applications from, e.g., zoology, economics, and the political sciences. 相似文献
75.
Joachim Käschel 《Proceedings Mathematical Sciences》1992,102(2):155-158
In Venkaiah [1] an algorithm for solving linear optimization problems based on the idea of the projective algorithm of Karmarkar,
is proposed. The essential simplification in the new algorithm is the use of a fixed projection operator. In this way the
algorithm requires onlyO(n
2
) operations to obtain a sufficient exact solution. In this note it is shown that in some special cases the algorithm of Venkaiah
yields a feasible solution that is far from the optimal one. 相似文献
76.
An acoustic pulse propagating on a two-mode fiber can act as a beam splitter in a scanning interferometer. When this device
is employed in white-light interferometry, the effects of distributed coupling and dispersive interferometer arms need to
be considered. A theory suitable for treating acousto-optic interaction of partially coherent light in a moving interaction
region was developed. It was found that differential optical dispersion should be negligible and the acoustic pulse length
short. Also the coherence time should be short but long compared to the intermodal group delay difference over a pulse length.
Experiments with long acoustic pulses were performed, and fairly good agreement with theory was obtained. 相似文献
77.
78.
79.
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
80.
Michael Grätzel 《Journal of Sol-Gel Science and Technology》1994,2(1-3):673-677
Transparent nanocrystalline films of oxide semiconductors such as TiO2 and Fe2O3 have been prepared on a conducting glass support employing a sol-gel procedure. The films are composed of nanometer-sized particles sintered together to allow for percolative charge carrier transport. The internal surface of these films is very high, roughness factors of the order of 1000 being readily obtained. Electric polarization was applied for forward and reverse biasing of the films and the resulting optical changes have been analyzed to derive their flat band potential. Band gap excitation of such nanocrystalline semiconductors produces electron-hole pairs which migrate through the film to be collected as electric current. Steady state photolysis and time resolved laser techniques have been applied to scrutinize the mechanism of light induced charge separation within the nanostructure. When derivatized with a suitable chromophore, TiO2 films give extraordinary efficiencies for the conversion of incident photons into electric current, exceeding 90% for certain transition metal complexes within the wavelength range of their absorption band. The underlying physical principles of these astonishing findings will be discussed. Exploiting this discovery, we have developed a new type of photovoltaic device whose overall light to electric energy conversion yield is 10% under simulated AM 1.5 solar radiation. 相似文献