全文获取类型
收费全文 | 20985篇 |
免费 | 3175篇 |
国内免费 | 2519篇 |
专业分类
化学 | 7017篇 |
晶体学 | 156篇 |
力学 | 1528篇 |
综合类 | 496篇 |
数学 | 7307篇 |
物理学 | 10175篇 |
出版年
2024年 | 25篇 |
2023年 | 168篇 |
2022年 | 308篇 |
2021年 | 424篇 |
2020年 | 486篇 |
2019年 | 411篇 |
2018年 | 435篇 |
2017年 | 536篇 |
2016年 | 620篇 |
2015年 | 607篇 |
2014年 | 956篇 |
2013年 | 1417篇 |
2012年 | 1070篇 |
2011年 | 1407篇 |
2010年 | 1342篇 |
2009年 | 1612篇 |
2008年 | 1618篇 |
2007年 | 1623篇 |
2006年 | 1467篇 |
2005年 | 1233篇 |
2004年 | 988篇 |
2003年 | 1035篇 |
2002年 | 925篇 |
2001年 | 785篇 |
2000年 | 701篇 |
1999年 | 668篇 |
1998年 | 551篇 |
1997年 | 466篇 |
1996年 | 411篇 |
1995年 | 317篇 |
1994年 | 289篇 |
1993年 | 231篇 |
1992年 | 237篇 |
1991年 | 175篇 |
1990年 | 125篇 |
1989年 | 144篇 |
1988年 | 99篇 |
1987年 | 91篇 |
1986年 | 48篇 |
1985年 | 101篇 |
1984年 | 71篇 |
1983年 | 43篇 |
1982年 | 83篇 |
1981年 | 53篇 |
1980年 | 42篇 |
1979年 | 68篇 |
1978年 | 33篇 |
1977年 | 34篇 |
1976年 | 27篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
O. N. Lyubenko I. G. Ermolenko L. D. Patsenker Krasovitskii I. N. Tur 《Chemistry of Heterocyclic Compounds》2003,39(4):511-519
The behavior of dimethylamino-substituted 7H-benzo[de]pyrazolo[5,1-a]isoquinoline-7-ones, synthesized for the first time, under conditions of the Vilsmeier-Haack reaction. It has been shown that, on heating with POCl3 and DMF, they are converted by electrophilic substitution at the position ortho to the dimethylamino group, followed by cyclization of the iminium adduct to a quinazolinium salt. When an acetyl group is present, the Arnold reaction, leading to the formation of a chloroaryl, accompanies the heterocyclization. The rates and proportion of the reaction products depend on the position of the dimethyl groups relative to the pyrazole ring. 相似文献
132.
Employing positive-definiteness arguments we analyse Boson field states, which combine classical and quantum mechanical features (signal and noise), in a constructive manner. Mathematically, they constitute Bauer simplexes within the convex, weak-*-compact state space of the C*-Weyl algebra, defined by a presymplectic test function space (smooth one-Boson wave functions) and are affinely homeomorphic to a state space of a classical field. The regular elements are expressed in terms of weak distributions (probability premeasures) on the dual test function space. The Bauer simplex arising from the bare vacuum is shown to generalize the quantum optical photon field states with positive P-functions. 相似文献
133.
134.
Bogdan Nita 《General Relativity and Gravitation》2003,35(10):1865-1868
Algebraically special gravitational fields are described using algebraic and differential invariants of the Weyl tensor. A type III invariant is also given and calculated for Robinson-Trautman spaces. 相似文献
135.
136.
Based on the newly constructed two mutually conjugate 3-mode entangled states of continuum variablesin three-mode Fock space we introduce entangled fractional Fourier transform (EFFT) for the tripartite entangled staterepresentations, which are not a direct product of three 1-dimensional FFTs. The eigenmodes of EFFT are obtained,which is different from the usual Hermite polynomials. The EFFT of the three-mode squeezed state is derived. 相似文献
137.
M. B. Litvinova 《Journal of Applied Spectroscopy》2004,71(1):143-146
It has been established that undoped gallium crystals exhibit anti-Stokes radiation with energy corresponding to the interband recombination of these crystals. Its appearance is most probably determined by EL2 defects, and its intensity depends on the product of the cross sections for photoionization of electrons and the holes from these defects. 相似文献
138.
139.
Yanghyun Byun 《Foundations of Physics》2004,34(6):987-1003
We consider a representation of the state reduction which depends neither on its reality nor on the details of when and how it emerges. Then by means of the representation we find necessary conditions, even if not the sufficient ones, for a decomposition of the state vector space to be a solution to the basis problem. The conditions are that the decomposition should be Lorentz invariant and orthogonal and that the associated projections should be continuous. They are shown to be able to determine a decomposition in each of a few examples considered if the other circumstances are taken into account together. 相似文献
140.
Summary Our purpose is to extend results due to P. Chandra and L. Leindler concerning the order of approximation by means of Fourier series for functions belonging to generalized Lipschitz-classes. 相似文献