全文获取类型
收费全文 | 20365篇 |
免费 | 917篇 |
国内免费 | 64篇 |
专业分类
化学 | 14842篇 |
晶体学 | 104篇 |
力学 | 411篇 |
数学 | 3015篇 |
物理学 | 2974篇 |
出版年
2023年 | 152篇 |
2022年 | 161篇 |
2021年 | 313篇 |
2020年 | 338篇 |
2019年 | 362篇 |
2018年 | 329篇 |
2017年 | 320篇 |
2016年 | 729篇 |
2015年 | 667篇 |
2014年 | 714篇 |
2013年 | 1323篇 |
2012年 | 1515篇 |
2011年 | 1676篇 |
2010年 | 950篇 |
2009年 | 727篇 |
2008年 | 1470篇 |
2007年 | 1413篇 |
2006年 | 1334篇 |
2005年 | 1214篇 |
2004年 | 1007篇 |
2003年 | 814篇 |
2002年 | 707篇 |
2001年 | 252篇 |
2000年 | 246篇 |
1999年 | 156篇 |
1998年 | 150篇 |
1997年 | 138篇 |
1996年 | 189篇 |
1995年 | 115篇 |
1994年 | 96篇 |
1993年 | 122篇 |
1992年 | 110篇 |
1991年 | 86篇 |
1990年 | 70篇 |
1989年 | 56篇 |
1988年 | 56篇 |
1987年 | 53篇 |
1986年 | 79篇 |
1985年 | 114篇 |
1984年 | 105篇 |
1983年 | 60篇 |
1982年 | 88篇 |
1981年 | 93篇 |
1980年 | 86篇 |
1979年 | 66篇 |
1978年 | 72篇 |
1977年 | 56篇 |
1976年 | 53篇 |
1974年 | 37篇 |
1973年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This article explores the use of geometric algebra in linear and multilinear algebra, and in affine, projective and conformal geometries. Our principal objective is to show how the rich algebraic tools of geometric algebra are fully compatible with and augment the more traditional tools of matrix algebra. The novel concept of an h-twistor makes possible a simple new proof of the striking relationship between conformal transformations in a pseudo-Euclidean space to isometries in a pseudo-Euclidean space of two higher dimensions. The utility of the h-twistor concept, which is a generalization of the idea of a Penrose twistor to a pseudo-Euclidean space of arbitrary signature, is amply demonstrated in a new treatment of the Schwarzian derivative. 相似文献
92.
A paraxial ray-optics formalism proposed for designing radially symmetric variable-index lenses is extended to the case of lenses of elliptical symmetry of the index profile. 相似文献
93.
There is a general interest in ranking schemes applied to complex entities described by multiple attributes. Published rankings
for universities are in great demand but are also highly controversial. We compare two classification and ranking schemes
involving universities; one from a published report, ‘Top American Research Universities’ by the University of Florida's TheCenter and the other using DEA. Both approaches use the same data and model. We compare the two methods and discover important equivalences.
We conclude that the critical aspect in classification and ranking is the model. This suggests that DEA is a suitable tool
for these types of studies. 相似文献
94.
A series of molecular dynamics simulations have been performed to study the supramolecular structure of self‐assembled complexes formed by N‐dodecyltrimethylammonium cations and the synthetic polypeptide poly(α,L ‐glutamate). The influence of the type of solvent has been investigated, considering explicit environments of chloroform, water, and methanol on a stoichiometric complex containing 15 residues. In chloroform, the complex stabilizes in a regular structure: the polypeptide adopts an α‐helix conformation that is regularly surrounded by surfactant molecules to form electrostatic interactions through a multiple interaction pattern. However, this structure destabilizes in methanol and water: (a) the α‐helix unfolds in the two solvents and (b) the electrostatic links between the surfactant molecules and the polyanion are disrupted in aqueous solution, although these interactions are still preserved in methanol. The role of the solvent environment in stabilizing or destabilizing the polypeptide secondary structure, the organization of the surfactant molecules, and predominantly the surfactant–polypeptide supramolecular organization is discussed in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1122–1133, 2006 相似文献
95.
96.
We prove the vanishing of the Koszul homology group H
μ(Kos(M)μ), where μ is the minimal number of generators of M. We give a counterexample that the Koszul complex of a module is not always
acyclic and show its relationship with the homology of commutative rings. 相似文献
97.
Designing a majorization scheme for the recourse function in two-stage stochastic linear programming
José H. Dulá 《Computational Optimization and Applications》1993,1(4):399-414
We discuss issues pertaining to the domination from above of the second-stage recourse function of a stochastic linear program and we present a scheme to majorize this function using a simpler sublinear function. This majorization is constructed using special geometrical attributes of the recourse function. The result is a proper, simplicial function with a simple characterization which is well-suited for calculations of its expectation as required in the computation of stochastic programs. Experiments indicate that the majorizing function is well-behaved and stable. 相似文献
98.
José M. Figueroa-O'Farrill 《Communications in Mathematical Physics》1990,127(1):181-186
The recent identification of classical BRST cohomology with the vertical cohomology of a certain fibration is used to compute it in terms of the classical observables and the topology of the gauge orbits. When the gauge orbits are compact and orientable, a duality theorem is exhibited. 相似文献
99.
100.