全文获取类型
收费全文 | 24861篇 |
免费 | 750篇 |
国内免费 | 500篇 |
专业分类
化学 | 2788篇 |
晶体学 | 53篇 |
力学 | 377篇 |
综合类 | 50篇 |
数学 | 20962篇 |
物理学 | 1881篇 |
出版年
2023年 | 45篇 |
2022年 | 116篇 |
2021年 | 119篇 |
2020年 | 150篇 |
2019年 | 665篇 |
2018年 | 747篇 |
2017年 | 367篇 |
2016年 | 279篇 |
2015年 | 337篇 |
2014年 | 762篇 |
2013年 | 1524篇 |
2012年 | 873篇 |
2011年 | 1524篇 |
2010年 | 1392篇 |
2009年 | 1932篇 |
2008年 | 1930篇 |
2007年 | 1973篇 |
2006年 | 1472篇 |
2005年 | 935篇 |
2004年 | 833篇 |
2003年 | 737篇 |
2002年 | 511篇 |
2001年 | 470篇 |
2000年 | 469篇 |
1999年 | 550篇 |
1998年 | 501篇 |
1997年 | 381篇 |
1996年 | 505篇 |
1995年 | 525篇 |
1994年 | 516篇 |
1993年 | 393篇 |
1992年 | 310篇 |
1991年 | 201篇 |
1990年 | 192篇 |
1989年 | 216篇 |
1988年 | 143篇 |
1987年 | 139篇 |
1986年 | 149篇 |
1985年 | 199篇 |
1984年 | 173篇 |
1983年 | 91篇 |
1982年 | 158篇 |
1981年 | 120篇 |
1980年 | 104篇 |
1979年 | 83篇 |
1978年 | 85篇 |
1977年 | 63篇 |
1976年 | 53篇 |
1975年 | 34篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
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
52.
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
53.
Broadband dielectric spectroscopy was used to study the segmental (α) and secondary (β) relaxations in hydrogen‐bonded poly(4‐vinylphenol)/poly(methyl methacrylate) (PVPh/PMMA) blends with PVPh concentrations of 20–80% and at temperatures from ?30 to approximately glass‐transition temperature (Tg) + 80 °C. Miscible blends were obtained by solution casting from methyl ethyl ketone solution, as confirmed by single differential scanning calorimetry Tg and single segmental relaxation process for each blend. The β relaxation of PMMA maintains similar characteristics in blends with PVPh, compared with neat PMMA. Its relaxation time and activation energy are nearly the same in all blends. Furthermore, the dielectric relaxation strength of PMMA β process in the blends is proportional to the concentration of PMMA, suggesting that blending and intermolecular hydrogen bonding do not modify the local intramolecular motion. The α process, however, represents the segmental motions of both components and becomes slower with increasing PVPh concentration because of the higher Tg. This leads to well‐defined α and β relaxations in the blends above the corresponding Tg, which cannot be reliably resolved in neat PMMA without ambiguous curve deconvolution. The PMMA β process still follows an Arrhenius temperature dependence above Tg, but with an activation energy larger than that observed below Tg because of increased relaxation amplitude. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3405–3415, 2004 相似文献
54.
We give a criterion to decide if a given w-homogeneous derivation on A?k[X1,X2,X3] is locally nilpotent. We deduce an algorithm which decides if a k-subalgebra of A, which is finitely generated by w-homogeneous elements, is the kernel of some locally nilpotent derivation. 相似文献
55.
Zhaoyang Yin 《Monatshefte für Mathematik》2004,141(4):337-344
We prove under quite general assumptions the existence of a bounded positive solution to the semilinear Schrödinger equation in a two-dimensional exterior domain. 相似文献
56.
We prove the existence of solutions to nonlinear free boundary problem with singularities at given points. 相似文献
57.
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
58.
Walter Benz 《Monatshefte für Mathematik》2004,141(1):1-10
The lines of euclidean and hyperbolic geometries are characterized as metric lines in the sense of Blumenthal–Menger, and the lines of spherical and elliptic geometry as periodic ones. In euclidean geometries there do not exist periodic lines. 相似文献
59.
Victor Bondarenko 《Bulletin des Sciences Mathématiques》2003,127(3):191-206
In present paper the parabolic equation solution is built. The construction is reduced to iterative procedure. And convergence of the latter is proven. 相似文献
60.
In this paper, we consider Girsanov transforms of pure jump type for discontinuous Markov processes. We show that, under some quite natural conditions, the Green functions of the Girsanov transformed process are comparable to those of the original process. As an application of the general results, the drift transform of symmetric stable processes is studied in detail. In particular, we show that the relativistic α-stable process in a bounded C1,1-smooth open set D can be obtained from symmetric α-stable process in D through a combination of a pure jump Girsanov transform and a Feynman-Kac transform. From this, we deduce that the Green functions for these two processes in D are comparable. 相似文献