全文获取类型
收费全文 | 26376篇 |
免费 | 992篇 |
国内免费 | 1316篇 |
专业分类
化学 | 9698篇 |
晶体学 | 204篇 |
力学 | 418篇 |
综合类 | 65篇 |
数学 | 14375篇 |
物理学 | 3924篇 |
出版年
2024年 | 36篇 |
2023年 | 375篇 |
2022年 | 280篇 |
2021年 | 296篇 |
2020年 | 452篇 |
2019年 | 680篇 |
2018年 | 610篇 |
2017年 | 438篇 |
2016年 | 513篇 |
2015年 | 593篇 |
2014年 | 898篇 |
2013年 | 1630篇 |
2012年 | 1002篇 |
2011年 | 1808篇 |
2010年 | 1423篇 |
2009年 | 1873篇 |
2008年 | 2042篇 |
2007年 | 1850篇 |
2006年 | 1419篇 |
2005年 | 1085篇 |
2004年 | 997篇 |
2003年 | 892篇 |
2002年 | 1139篇 |
2001年 | 589篇 |
2000年 | 555篇 |
1999年 | 581篇 |
1998年 | 476篇 |
1997年 | 370篇 |
1996年 | 463篇 |
1995年 | 430篇 |
1994年 | 388篇 |
1993年 | 313篇 |
1992年 | 280篇 |
1991年 | 208篇 |
1990年 | 182篇 |
1989年 | 202篇 |
1988年 | 126篇 |
1987年 | 133篇 |
1986年 | 116篇 |
1985年 | 152篇 |
1984年 | 128篇 |
1983年 | 77篇 |
1982年 | 116篇 |
1981年 | 112篇 |
1980年 | 68篇 |
1979年 | 46篇 |
1978年 | 48篇 |
1977年 | 61篇 |
1976年 | 48篇 |
1971年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In this paper, the detailed asymptotic behaviour of the solutions of a kinetic equation for quantum particles is studied. It is shown that this behaviour is sensitive not only to the total mass of the initial data but also to its precise behaviour near the origin. In some cases, solutions develop a Dirac mass at the origin for long times in a self-similar manner that is analysed in detail. 相似文献
22.
23.
Peter Clifford 《Annals of Combinatorics》2005,9(3):281-291
Motivated by recent results of Stanley, we generalize the rank of a partition λ to the rank of a shifted partition S(λ). We show that the number of bars required in a minimal bar tableau of S(λ) is max(o, e + (ℓ(λ) mod 2)), where o and e are the number of odd and even rows of λ. As a consequence we show that the irreducible projective characters of Sn vanish on certain conjugacy classes. Another corollary is a lower bound on the degree of the terms in the expansion of Schur’s
Qλ symmetric functions in terms of the power sum symmetric functions.
Received November 20, 2003 相似文献
24.
《Magnetic resonance in chemistry : MRC》2003,41(1):37-41
The oxidation of symmetrical disulfides [D ,L ‐cystine ( 1 ) and 3,3′‐dithiobis(propionic acid) ( 2 )] with hydrogen peroxide in D2O–NaOH solution (pH 10–11) was studied by NMR spectroscopy. Assignments of the proton and carbon NMR signals of starting materials ( 1 and 2 ) and products of oxidation are based on conventional 1D NMR methods (DEPT, selective spin decoupling). Formation of C—S bond cleavage products or, in case of 2 , partially oxidized intermediates was not detected. The accelerating effect of Cu2+ cations, but not Fe3+ cations, on the oxidation rate of 1 in basic medium was demonstrated. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
25.
Extending to r > 1 a formula of the authors, we compute the expected reflection distance of a product of t random reflections in the complex reflection group G(r, 1, n). The result relies on an explicit decomposition of the reflection distance function into irreducible G(r, 1, n)-characters and on the eigenvalues of certain adjacency matrices.Received December 8, 2003 相似文献
26.
A method for fabricating well-dispersed nanowire suspension has been demonstrated in the paper. Thin gold nanowires were prepared by template synthesis, and then functionalized with sulphonate group-terminated thiols before suspended in different solvents. The degree of aggregation of the obtained suspension was evaluated with transmission electron microscopy (TEM) and UV-vis spectroscopy. It was found that the degree of aggregation was predominated by the solvents, and the best degree of dispersion was obtained when isopropyl alcohol (IPA) was used as the solvent. The gold nanowires from the suspension can be selectively assembled onto chemically patterned substrates. This well-dispersed nanowire suspension is potentially useful for fabricating novel nanodevices. 相似文献
27.
B.V. Raghavaiah 《Journal of Physics and Chemistry of Solids》2004,65(6):1153-1164
PbO-Sb2O3 glasses added with different concentrations of As2O3 (10-55 mol%) were prepared to understand their IR spectra, elastic properties (Young's modulus E, Shear modulus G, microhardness H), optical absorption and dielectric properties (constant ε, loss tan δ, ac conductivity σac over a moderately wide range of frequency and temperature and breakdown strength in air medium at room temperature). Results have indicated that the structure of the PbO-Sb2O3-As2O3 glass is more rigid when the concentration of As2O3 is around 40 mol%. 相似文献
28.
Said Hadd 《Journal of Evolution Equations》2005,5(4):545-555
This paper studies the concept of controllability for infinite-dimensional linear control systems in Banach spaces. First,
we prove that the set of admissible control operators for the semigroup generator is unchanged if we perturb the generator
by the Desch–Schappacher perturbations. Second we show that exact controllability is not changed by such perturbations. 相似文献
29.
Fabio A. C. C. Chalub Peter A. Markowich Benoît Perthame Christian Schmeiser 《Monatshefte für Mathematik》2004,142(1-2):123-141
Kinetic models for chemotaxis, nonlinearly coupled to a Poisson equation for the chemo-attractant density, are considered. Under suitable assumptions on the turning kernel (including models introduced by Othmer, Dunbar and Alt), convergence in the macroscopic limit to a drift-diffusion model is proven. The drift-diffusion models derived in this way include the classical Keller-Segel model. Furthermore, sufficient conditions for kinetic models are given such that finite-time-blow-up does not occur. Examples are given satisfying these conditions, whereas the macroscopic limit problem is known to exhibit finite-time-blow-up. The main analytical tools are entropy techniques for the macroscopic limit as well as results from potential theory for the control of the chemo-attractant density.Present address: Centro de Matemática e Aplicações Fundamentais, Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003, Lisboa, Portugal 相似文献
30.
C. Sparber J. A. Carrillo J. Dolbeault P. A. Markowich 《Monatshefte für Mathematik》2004,141(3):237-257
We analyze the long-time behavior of transport equations for a class of dissipative quantum systems with Fokker-planck type diffusion operator, subject to confining potentials of harmonic oscillator type. We establish the existence and uniqueness of a non-equilibrium steady state for the corresponding dynamics. Further, using a (classical) convex Sobolev inequality, we prove an optimal exponential rate of decay towards this state and additionally give precise dispersion estimates in those cases, where no stationary state exists. 相似文献