全文获取类型
收费全文 | 49647篇 |
免费 | 1659篇 |
国内免费 | 19篇 |
专业分类
化学 | 31759篇 |
晶体学 | 236篇 |
力学 | 1567篇 |
数学 | 7745篇 |
物理学 | 10018篇 |
出版年
2023年 | 377篇 |
2022年 | 298篇 |
2021年 | 499篇 |
2020年 | 676篇 |
2019年 | 639篇 |
2018年 | 1010篇 |
2017年 | 821篇 |
2016年 | 1533篇 |
2015年 | 1405篇 |
2014年 | 1413篇 |
2013年 | 2922篇 |
2012年 | 3408篇 |
2011年 | 3469篇 |
2010年 | 2090篇 |
2009年 | 1710篇 |
2008年 | 2975篇 |
2007年 | 3006篇 |
2006年 | 2654篇 |
2005年 | 2566篇 |
2004年 | 2205篇 |
2003年 | 1790篇 |
2002年 | 1562篇 |
2001年 | 912篇 |
2000年 | 778篇 |
1999年 | 551篇 |
1998年 | 417篇 |
1997年 | 372篇 |
1996年 | 478篇 |
1995年 | 302篇 |
1994年 | 355篇 |
1993年 | 355篇 |
1992年 | 393篇 |
1991年 | 336篇 |
1990年 | 317篇 |
1989年 | 320篇 |
1988年 | 257篇 |
1987年 | 262篇 |
1986年 | 229篇 |
1985年 | 396篇 |
1984年 | 355篇 |
1983年 | 248篇 |
1982年 | 335篇 |
1981年 | 318篇 |
1980年 | 278篇 |
1979年 | 272篇 |
1978年 | 254篇 |
1976年 | 272篇 |
1975年 | 249篇 |
1974年 | 258篇 |
1973年 | 250篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Coulomb systems in which the particles interact through thed-dimensional Coulomb potential but are confined in a flat manifold of dimensiond–1 are considered. The actual Coulomb potential acting is defined by particular boundary conditions involving a characteristic macroscopic distanceW in the direction perpendicular to the manifold: either it is periodic of periodW in that direction, or it vanishes on one ideal conductor wall parallel to the manifold at a distanceW from it, or it vanishes on two parallel walls at a distanceW from each other with the manifold equidistant from them. Under the assumptions that classical equilibrium statistical mechanics is applicable and that the system has the macroscopic properties of a conductor, it is shown that the suitably smoothed charge correlation function is universal, and that the free energy and the grand potential have universal dependences onW (universal means independent of the microscopic detail). The casesd=2 are discussed in detail, and the generic results are checked on an exactly solvable model. The cased=3 of a plane parallel to an ideal conductor is also explicitly worked out.Laboratoire associé au Centre National de la Recherche Scientifique-URA D0063. 相似文献
42.
Jean-Marc Hérard 《Comptes Rendus Mathematique》2006,342(10):779-784
We introduce a hyperbolic entropy-consistent model to describe three-phase flows, which ensures that void fractions, mass fractions and pressures remain positive through single waves occurring in the one dimensional solution of the Riemann problem. To cite this article: J.-M. Hérard, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
43.
This Note deals with optimal control problems with only one control variable and one state constraint, of arbitrary order. We consider the case of finitely many boundary arcs and touch times. We obtain a no-gap theory of second-order conditions, allowing us to characterize second-order quadratic growth. To cite this article: J.F. Bonnans, A. Hermant, C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献
44.
We consider the isothermal flow through a cylindrical flat chamber, a model of some particular heat exchanger, for which LDV measurements and a numerical simulation have been performed. Experimental results show the establishment of an important vortex zone, the secondary flow extending all along the chamber radius. This observation leads to an expected significant increase of the fluid mixing. Results issued from the numerical simulation appear to be in close agreement with experimental data. Nevertheless, the k–ε model used here must be improved to obtain a better approach near the vortex centre. To cite this article: S. Petitot et al., C. R. Mecanique 330 (2002) 593–599. 相似文献
45.
Pál Sohár Gábor Bernáth Géza Stájer Angela E. Szabo 《Magnetic resonance in chemistry : MRC》1989,27(9):872-876
Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments. 相似文献
46.
In this paper we propose a general integration scheme for a Multi-Criteria Decision Making model of the Multi-Attribute Utility
Theory in Constraint Programming. We introduce the Choquet integral as a general aggregation function for multi-criteria optimization
problems and define the Choquet global constraint that propagates this function during the Branch-and-Bound search. Finally the benefits of the propagation
of the Choquet constraint are evaluated on the examination timetabling problem. 相似文献
47.
48.
This paper is devoted to the proof of almost global existence results for Klein‐Gordon equations on Zoll manifolds (e.g., spheres of arbitrary dimension) with Hamiltonian nonlinearities, when the Cauchy data are smooth and small. The proof relies on Birkhoff normal form methods and on the specific distribution of eigenvalues of the Laplacian perturbed by a potential on Zoll manifolds. © 2007 Wiley Periodicals, Inc. 相似文献
49.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献
50.
Girard V Farrenq R Sorokin E Sorokina IT Guelachvili G Picqué N 《Chemical physics letters》2006,419(4-6):584-588
The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ν(1)+ν(4) (1) and ν(3)+ν(5) (1) transitions of (12)C(13)CH(2). The ν(1)+ν(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ν(2)+2ν(4) (2)+ν(5) (-1). 相似文献