全文获取类型
收费全文 | 65729篇 |
免费 | 2287篇 |
国内免费 | 160篇 |
专业分类
化学 | 40910篇 |
晶体学 | 435篇 |
力学 | 1253篇 |
综合类 | 1篇 |
数学 | 12112篇 |
物理学 | 13465篇 |
出版年
2023年 | 472篇 |
2022年 | 455篇 |
2021年 | 830篇 |
2020年 | 1090篇 |
2019年 | 1048篇 |
2018年 | 1275篇 |
2017年 | 1146篇 |
2016年 | 2308篇 |
2015年 | 1935篇 |
2014年 | 2028篇 |
2013年 | 4113篇 |
2012年 | 4120篇 |
2011年 | 4196篇 |
2010年 | 2627篇 |
2009年 | 2239篇 |
2008年 | 3509篇 |
2007年 | 3214篇 |
2006年 | 2996篇 |
2005年 | 2893篇 |
2004年 | 2525篇 |
2003年 | 1985篇 |
2002年 | 1837篇 |
2001年 | 1197篇 |
2000年 | 1160篇 |
1999年 | 873篇 |
1998年 | 688篇 |
1997年 | 617篇 |
1996年 | 825篇 |
1995年 | 574篇 |
1994年 | 654篇 |
1993年 | 626篇 |
1992年 | 607篇 |
1991年 | 536篇 |
1990年 | 557篇 |
1989年 | 461篇 |
1988年 | 474篇 |
1987年 | 429篇 |
1986年 | 412篇 |
1985年 | 586篇 |
1984年 | 563篇 |
1983年 | 425篇 |
1982年 | 482篇 |
1981年 | 490篇 |
1980年 | 402篇 |
1979年 | 385篇 |
1978年 | 421篇 |
1977年 | 401篇 |
1976年 | 383篇 |
1975年 | 345篇 |
1973年 | 352篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
71.
Daniel B. Szyld 《Numerical Algorithms》2006,42(3-4):309-323
Given an oblique projector P on a Hilbert space, i.e., an operator satisfying P
2=P, which is neither null nor the identity, it holds that ||P|| = ||I –P||. This useful equality, while not widely-known, has been proven repeatedly in the literature. Many published proofs are reviewed, and simpler ones are presented. 相似文献
72.
73.
Possible Loss and Recovery of Gibbsianness¶During the Stochastic Evolution of Gibbs Measures 总被引:1,自引:1,他引:0
A.C.D. van Enter R. Fernández F. den Hollander F. Redig 《Communications in Mathematical Physics》2002,226(1):101-130
We consider Ising-spin systems starting from an initial Gibbs measure ν and evolving under a spin-flip dynamics towards a
reversible Gibbs measure μ≠ν. Both ν and μ are assumed to have a translation-invariant finite-range interaction. We study
the Gibbsian character of the measure νS(t) at time t and show the following:
(1) For all ν and μ, νS(t) is Gibbs for small t.
(2) If both ν and μ have a high or infinite temperature, then νS(t) is Gibbs for all t > 0.
(3) If ν has a low non-zero temperature and a zero magnetic field and μ has a high or infinite temperature, then νS(t) is Gibbs for small t and non-Gibbs for large t.
(4) If ν has a low non-zero temperature and a non-zero magnetic field and μ has a high or infinite temperature, then νS(t) is Gibbs for small t, non-Gibbs for intermediate t, and Gibbs for large t.
The regime where μ has a low or zero temperature and t is not small remains open. This regime presumably allows for many different scenarios.
Received: 26 April 2001 / Accepted: 10 October 2001 相似文献
74.
The presence of copper atoms as continuous networks at the grain boundaries of an aluminium-copper alloy has been considered not preventing the moving of dislocations during creep (or at least partially). The dislocations can bs absorbed by these boundaries and penetrate through them. That leads to changés of shape and structure of grains and also to the sliding of grains against each other. This was deduced from the accelerating increase in the sensitivity of the steady state creep rate to the applied stress of an aluminium 2·8 wt% copper alloy examined at wide range of temperatures (50–350 °C) and applied stresses (7–170 MPa). This rapid increase in the sensitivity parameter of the steady state creep rate occurs in Al-Cu alloys at quite higher ranges of applied stresses and may be attributed mainly to the contribution of the grain boundary movements to the creep strain. 相似文献
75.
Partially supported by the general research fund at the University of Kansas 相似文献
76.
Lithium (10–150 ng ml?1) in wine is determined by atomic absorption spectrometry by direct nebulization and after digestion with mixed acids. The results of methods are similar. Thirty-four wines from various Spanish provinces are analysed. 相似文献
77.
Gábor Dörnyei Marietta Bárczai-Beke Gábor Blaskó Péter Péchy Csaba Szántay 《Tetrahedron letters》1982,23(28):2913-2916
Regioselective demethylation of 3,4-dihydropapaveraldine (a) at 7 and 3' positions affords a properly substituted diphenolic key intermidiate (d) for the synthesis of reticuline and N-norreticuline. 相似文献
78.
V. Čápek 《Czechoslovak Journal of Physics》1991,41(10):975-989
A review of ideas leading to full rejection of any finite or partially-infinite order kinetic equation linearized in external field is given on grounds of the time-convolution Generalized Master Equations (GME). By two examples (two-level and band conduction problem), it is shown how standard kinetic equations result from GME in the lowest order approximations which obscure, however, a direct correspondence with the Kubo linear response theory. Without approximations, on the other hand, the rigorous approach is shown to be fully equivalent with the Kubo results. It is argued and illustrated that usual technical simplicity and seeming physical lucidity of standard theories (connected with the presence of field-independent transfer or scattering rates in the fielddependent linearized theory) are just owing to structural features which are solely due to the lowest order approximations involved. These features (i.e. also the possibility of standard physical interpretation of kinetic phenomena) are proved to disappear completely as far as the theory goes properly to higher orders. 相似文献
79.
Daniel Michelson 《Journal d'Analyse Mathématique》1989,53(1):1-138
The general problem studied has as a prototype the full non-linear Navier-Stokes equations for a slightly viscous compressible
fluid including the heat transfer. The boundaries are of inflow-outflow type, i.e. non-characteristic, and the boundary conditions
are the most general ones with any order of derivatives. It is assumed that the uniform Lopatinsky condition is satisfied.
The goal is to prove uniform existence and boundedness of solution as the viscosity tends to zero and to justify the boundary
layer asymptotics. The paper consists of two parts. In Part I the linear problem is studied. Here, uniform lower and higher
order tangential estimates are derived and the existence of a solution is proved. The higher order estimates depend on the
smoothness of coefficients; however this smoothness does not exceed the smoothness of the solution. In Part II the quasilinear
problem is studied. It is assumed that for zero viscosity the overall initial-boundary value problem has a smooth solutionu
0 in a time interval 0≦t≦T
0. As a result the boundary laye, is weak and is uniformlyC
1 bounded. This makes the linear theory applicable. an iteration scheme is set and proved to converge to the viscous solution.
The convergence takes place for small viscosity and over the original time interval 0≦t≦T
0. 相似文献
80.
Bajdik J. Pintye-Hódi K. Novák Cs. Kelemen A. Regdon G. Erős I. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):613-627
The extents of the protective effects of coating films on the surface of crystals were determined. Three different samples
were made with different quantities of coating fluid (Sepifilm LP 010 in 10% aqueous solution). Since the atomizing rate was
constant, the coating time increased in parallel with the volume of coating fluid applied. The direct measurement of film
thickness and smoothness is very difficult, and therefore indirect methods were used. Dimenhydrinate was chosen as model drug;
this is a heat-sensitive antihistamine with a low melting point. This temperature can be reached during the tableting process.
The behaviour of samples on exposure to heat was examined by differential scanning calorimetry. The water uptakes of the samples
were determined with an Enslin apparatus. Plasticity was studied with an instrumented tablet machine. These indirect methods
(thermal conductivity, water uptake and plasticity measurements) revealed connections between the results of the various experiments.
An overlong coating time decreased the protective effect of the coating film.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献