全文获取类型
收费全文 | 59903篇 |
免费 | 1989篇 |
国内免费 | 116篇 |
专业分类
化学 | 36988篇 |
晶体学 | 426篇 |
力学 | 1083篇 |
综合类 | 2篇 |
数学 | 11107篇 |
物理学 | 12402篇 |
出版年
2023年 | 418篇 |
2022年 | 444篇 |
2021年 | 691篇 |
2020年 | 904篇 |
2019年 | 914篇 |
2018年 | 1176篇 |
2017年 | 1066篇 |
2016年 | 2090篇 |
2015年 | 1747篇 |
2014年 | 1763篇 |
2013年 | 3804篇 |
2012年 | 3591篇 |
2011年 | 3506篇 |
2010年 | 2369篇 |
2009年 | 2042篇 |
2008年 | 3085篇 |
2007年 | 2886篇 |
2006年 | 2538篇 |
2005年 | 2588篇 |
2004年 | 2232篇 |
2003年 | 1835篇 |
2002年 | 1647篇 |
2001年 | 1177篇 |
2000年 | 1152篇 |
1999年 | 818篇 |
1998年 | 671篇 |
1997年 | 593篇 |
1996年 | 760篇 |
1995年 | 558篇 |
1994年 | 624篇 |
1993年 | 598篇 |
1992年 | 590篇 |
1991年 | 519篇 |
1990年 | 548篇 |
1989年 | 454篇 |
1988年 | 436篇 |
1987年 | 411篇 |
1986年 | 416篇 |
1985年 | 582篇 |
1984年 | 555篇 |
1983年 | 441篇 |
1982年 | 433篇 |
1981年 | 436篇 |
1980年 | 370篇 |
1979年 | 364篇 |
1978年 | 374篇 |
1977年 | 349篇 |
1976年 | 353篇 |
1975年 | 327篇 |
1974年 | 327篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
341.
Kateina Syslová Pavel imanec Josef Tichy 《Reaction Kinetics and Catalysis Letters》2005,87(1):165-169
Summary The oxidative dehydrogenation of crotonaldehyde to furan and maleic anhydride was carried out over K2HPMo12O40catalyst. A positive effect of water vapor on furan formation is explained by ability of the catalyst to isomerize 2E- to
2Z-crotonaldehyde.</o:p> 相似文献
342.
Modelling financial and insurance time series with Lévy processes or with exponential Lévy processes is a relevant actual practice and an active area of research. It allows qualitatively and quantitatively good adaptation to the empirical statistical properties of asset returns. Due to model incompleteness it is a problem of considerable interest to determine the dependence of option prices in these models on the choice of pricing measures and to establish nontrivial price bounds. In this paper we review and extend ordering results of stochastic and convex type for this class of models. We also extend the ordering results to processes with independent increments (PII) and present several examples and applications as to α-stable processes, NIG-processes, GH-distributions, and others. Criteria are given for the Lévy measures which imply corresponding comparison results for European type options in (exponential) Lévy models. 相似文献
343.
We present a way of introducing joint distibution function and its marginal distribution functions for non-compatible observables.
Each such marginal distribution function has the property of commutativity. Models based on this approach can be used to better
explain some classical phenomena in stochastic processes. 相似文献
344.
345.
346.
Zólomy A. Berceli T. Járó G. Hilt A. Marozsák T. 《Optical and Quantum Electronics》1998,30(11-12):969-983
Optical and Quantum Electronics - A new approach for the design and construction of low noise broadband optical receivers is presented utilizing distributed amplification based on hybrid integrated... 相似文献
347.
F. Máca 《Czechoslovak Journal of Physics》1993,43(9-10):941-945
We present the calculations of electronic structure and photoemission spectra for a lattice-matched Ag-Au(111) superlattice. The selfconsistent band structure exhibits a superlattice gap at about 1 eV below the Fermi level. A surface state is found in this gap and its dispersion properties are investigated. Its energy location is varied with location of surface terminating plane within the superlattice period. The calculated normal photoemission spectra explain well available experimental data. 相似文献
348.
José Natário 《General Relativity and Gravitation》2006,38(3):475-484
We find a class of warp drive spacetimes possessing Newtonian limits, which we then determine. The same method is used to
compute Newtonian limits of the Schwarzschild solution and spatially flat Friedmann-Robertson-Walker cosmological models.
This work was partially supported by FCT/POCTI/FEDER. 相似文献
349.
T. González-Lezana G. Delgado-Barrio P. Villarreal F.X. Gadéa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):227-232
The stabilization method is applied to the case of interacting resonances in the photo-dissociation of van der Waals clusters
composed by a rare gas atom bound to a dihalogen molecule. The study of an illustrative two-dimensional model consisting in
a T-shaped NeI2 molecule shows the adequacy of the method whenever the projection of the stabilization wave functions on the assumed prepared
initial state is accounted for. The agreement of the fragmentation cross-sections with some previous results using the effective
resolvent method and accurate close-coupling calculations is excellent. The method reveals its utility as a complementary
tool since allows, through the analysis of the stabilization wave function in terms of zero-order levels, a precise characterization
of the resonant states involved.
Received 5 April 2002 / Received in final form 24 May 2002 Published online 19 July 2002 相似文献
350.
A new and rather trivial model is suggested with mechanism that implies simultaneous violation of the zeroth and the second
laws of thermodynamics. Mathematically rigorous quantum theory reduces to a trivial application of the Golden rule formula.
It yields exciton on-energy-shell diffusion caused by bath-nonassisted excitation hopping between tails of different exciton
site levels ε1 < ε2 broadened by bath-assisted finite life-time effects. The elastic character of the hopping implies 1 ↔ 2-symmetric transfer
rate W. Thus the net diffusion exciton flow W(P
1 - P
2) and also, as argued, the net energy flow are possible due to different near-to-equilibrium exciton populations P
1 > P
2. As the sites are provided with two different baths, the population imbalance and the flows survive even for slightly different
local bath temperatures T
1 < T
2 < T
1ε2/ε1. Thus spontaneous exciton and also energy flows against temperature step become possible, in contradiction with the Clausius
form of the second law. Violations of both the laws disappear in the high-temperature, i.e. classical limit
Received 16 May 2001 and Received in final form 20 September 2001 相似文献