全文获取类型
收费全文 | 1392篇 |
免费 | 46篇 |
国内免费 | 8篇 |
专业分类
化学 | 992篇 |
晶体学 | 15篇 |
力学 | 17篇 |
数学 | 157篇 |
物理学 | 265篇 |
出版年
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 5篇 |
2017年 | 20篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 26篇 |
2013年 | 68篇 |
2012年 | 51篇 |
2011年 | 89篇 |
2010年 | 39篇 |
2009年 | 52篇 |
2008年 | 73篇 |
2007年 | 92篇 |
2006年 | 86篇 |
2005年 | 102篇 |
2004年 | 88篇 |
2003年 | 64篇 |
2002年 | 68篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 15篇 |
1974年 | 11篇 |
1973年 | 8篇 |
排序方式: 共有1446条查询结果,搜索用时 31 毫秒
101.
For a smooth projective irreducible algebraic curve C of odd gonality, the maximal possible dimension of the variety of special linear systems W
d
r
(C) is d-3r by a result of M. Coppens et al. Furthermore it is known that if the maximum dimension of W(C) for a curve C of odd gonality is attained then C is of very special type of curves by the recent progress made by G. Martens. The purpose of this paper is to chase an extension of the result of G. Martens; if dim W(C)=d-3r-1 for a curve C of odd gonality for some dg-4 and r1, then C must be either a smooth plane sextic, a pentagonal curve of bounded genus or a smooth plane octic. 相似文献
102.
Hegedus L Kirschner N Wittmann M Simon P Noszticzius Z Amemiya T Ohmori T Yamaguchi T 《Chaos (Woodbury, N.Y.)》1999,9(2):283-297
The polarization curve of an acid-base interface in a hydrogel medium has a diode characteristic. Two of each such electrolyte diodes can be combined to give an electrolyte transistor. When a salt is added to the alkaline or to the acidic part of a reverse biased electrolyte diode, the current response is highly nonlinear. If the salt is added to the acidic side, even bistability can be observed. This bistability can generate complex oscillations in a base-acid-base electrolyte transistor. These nonlinear effects are studied experimentally and theoretically. While the nonlinear salt effect can be explained with the Nernst-Planck equations, to understand the bistable behavior further investigations are necessary. (c) 1999 American Institute of Physics. 相似文献
103.
Hitoshi Suzuki Akira Ishiguro Takao Nishizeki 《Journal of Algorithms in Cognition, Informatics and Logic》1992,13(4)
This paper proposes a new data structure called a variable-priority queue. The queue supports, in addition to the ordinary queue operations, an operation MIN to find an item of minimum key and three operations to change keys of items. Any sequence of these m operations can be processed in O(m) time. Furthermore, as its application, this paper presents two efficient algorithms for network problems. The first finds multicommodity flows in cycles in linear time. The second, using the first, finds edge-disjoint paths connecting terminal pairs in a doughnut-shaped grid. The grid is bounded by two nested rectangles, and terminals are specified on the two rectangular boundaries outside the four corners. If there are k terminal pairs and all the terminals are ordered in clockwise order around rectangles, then the algorithm decides in O(k) time whether there are edge-disjoint paths connecting terminals in the grid, and actually finds edge-disjoint paths in O(k log k) time. 相似文献
104.
Takao Fukui 《General Relativity and Gravitation》1988,20(10):1037-1045
In order to study the origin of the fundamental constants and Dirac's large number, a cosmological solution in vacuum is presented in a seven-dimensional universe which is defined by adding extra three coordinates (e
2
G/c
4)1/2, (hG/c
3)1/2 and (Gm/c
2) to the four-dimensional spacetime coordinates. It has common features with Chodos-Detweiler's solution. The parameters appearing in this theory are estimated to meet the conditions required by the cosmological first-order phase transition and Dirac's large number hypothesis. 相似文献
105.
106.
The boundary between the spin-glass state and the ferromagnetic state (pF-G) of the bond-random (±J) Ising model in the face-centred cubic lattice at T = 0 is calculated by the method of tetrahedron approximation in the simple version. The obtained value is, pF-G = 0.682, which is a little larger than the triple point pt = 0.654, and the model shows the reentrant behavior. 相似文献
107.
Kunihiko Takabe Suguru Ohkawa Toshio Sato Gia Hien Tang Takao Katagiri 《Tetrahedron letters》1980,21(40):3883-3884
Dimerization of 3-methyl-3-butenenitrile (1) by lithium dialkylamide gave selectively 3,5,5-trimethyl-1-amino-4-cyanocyclohexa-1,3-diene (2), which was easily hydrolyzed by aqueous acid to afford 4-cyanoisophorone (3,5,5-trimethyl-4-cyano-cyclohex-2-enone) (3) quantitatively. 相似文献
108.
109.
An infrared, pulsed heterodyne laser radar using differential absorption technique with tunable lasers is proposed as a practical means of measuring dispersed air pollutants with range resolution. A system analysis shows that this scheme offers an adequate sensitivity for ranges up to several km. 相似文献
110.
Mizukoshi Y Seino S Okitsu K Kinoshita T Otome Y Nakagawa T Yamamoto TA 《Ultrasonics sonochemistry》2005,12(3):191-195
We prepared Au/gamma-Fe2O3 composite nanoparticles by sonochemically reducing Au(III) ions employing no stabilizer in the aqueous solution to form stable Au nanoparticles and allowing them to attach onto the surface of gamma-Fe2O3 particles with an average size of 21 nm. Size of the formed Au nanoparticle depended on the initial concentration of Au(III) ions. The number of the Au nanoparticles, supported on each gamma-Fe2O3 particle was controlled by changing the relative amounts of Au(III) ions and gamma-Fe2O3 particles. The composite nanoparticles exhibited a high affinity with glutathione, a tripeptide with mercapto group so that separation and manipulation of glutathione in aqueous solutions could be performed by application of external magnetic field. Because the surfaces of the Au nanoparticles were not shielded by any stabilizers, or naked, sonochemically prepared Au/gamma-Fe2O3 composite nanoparticles seemed to show stronger affinity to the glutathione than those by the radiochemical method. 相似文献