全文获取类型
收费全文 | 409215篇 |
免费 | 3367篇 |
国内免费 | 1385篇 |
专业分类
化学 | 214628篇 |
晶体学 | 6545篇 |
力学 | 17885篇 |
综合类 | 7篇 |
数学 | 46774篇 |
物理学 | 128128篇 |
出版年
2020年 | 3422篇 |
2019年 | 3913篇 |
2018年 | 5282篇 |
2017年 | 5147篇 |
2016年 | 7344篇 |
2015年 | 4383篇 |
2014年 | 7123篇 |
2013年 | 17818篇 |
2012年 | 13165篇 |
2011年 | 16225篇 |
2010年 | 11574篇 |
2009年 | 11462篇 |
2008年 | 15251篇 |
2007年 | 15339篇 |
2006年 | 14401篇 |
2005年 | 13048篇 |
2004年 | 11848篇 |
2003年 | 10640篇 |
2002年 | 10542篇 |
2001年 | 11648篇 |
2000年 | 9066篇 |
1999年 | 6982篇 |
1998年 | 5982篇 |
1997年 | 5939篇 |
1996年 | 5598篇 |
1995年 | 4877篇 |
1994年 | 4932篇 |
1993年 | 4977篇 |
1992年 | 5268篇 |
1991年 | 5465篇 |
1990年 | 5156篇 |
1989年 | 5134篇 |
1988年 | 5081篇 |
1987年 | 4949篇 |
1986年 | 4691篇 |
1985年 | 6327篇 |
1984年 | 6615篇 |
1983年 | 5331篇 |
1982年 | 5757篇 |
1981年 | 5590篇 |
1980年 | 5295篇 |
1979年 | 5575篇 |
1978年 | 5762篇 |
1977年 | 5724篇 |
1976年 | 5780篇 |
1975年 | 5331篇 |
1974年 | 5382篇 |
1973年 | 5485篇 |
1972年 | 3819篇 |
1971年 | 3276篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
D. P. Zhelobenko 《Acta Appl Math》2004,81(1):355-383
An algebraic approach to harmonic analysis on reductive Lie groups is proposed. The case of complex semisimple Lie groups is considered in details. Some problems for real reductive Lie groups are discussed. 相似文献
272.
Using the result by D. Gessler, we show that any invariant variational bivector (resp., variational 2-form) on an evolution equation with nondegenerate right-hand side is Hamiltonian (resp., symplectic). 相似文献
273.
A model is developed for the flow of a slightly compressible fluid through a saturated inelastic porous medium. The initial‐boundary‐value problem is a system that consists of the diffusion equation for the fluid coupled to the momentum equation for the porous solid together with a constitutive law which includes a possibly hysteretic relation of elasto‐visco‐plastic type. The variational form of this problem in Hilbert space is a non‐linear evolution equation for which the existence and uniqueness of a global strong solution is proved by means of monotonicity methods. Various degenerate situations are permitted, such as incompressible fluid, negligible porosity, or a quasi‐static momentum equation. The essential sufficient conditions for the well‐posedness of the system consist of an ellipticity condition on the term for diffusion of fluid and either a viscous or a hardening assumption in the constitutive relation for the porous solid. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
274.
S. Aravinda N. Shamala Rituparna S. Roy P Balaram 《Journal of Chemical Sciences》2003,115(5-6):373-400
An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from
the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
275.
We obtain a lower bound on the number of prime divisors of integers whose g-ary expansion contains a fixed number of nonzero digits.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
276.
Received: 14 September 2001 / in final form: 28 April 2002 // Published online: 20 March 2003 相似文献
277.
278.
I. P. Kuranova K. M. Polyakov E. A. Smirnova W. E. Höhne V. S. Lamzin R. Meijer 《Crystallography Reports》2003,48(6):953-958
Crystals of Saccharomyces cerevisiae inorganic pyrophosphatase suitable for X-ray diffraction study were grown by cocrystallization of the enzyme with cobalt chloride and imidodiphosphate. Saccharomyces cerevisiae is a metal-dependent enzyme which catalyzes hydrolysis of inorganic pyrophosphate to orthophosphate. The three-dimensional structure of this enzyme was solved by the molecular-replacement method and refined at 1.8 Å resolution to an R factor of 19.5%. Cobalt and phosphate ions were revealed in the active centers of both identical subunits (A and B) of the pyrophosphatase molecule. In subunit B, a water molecule was found between two cobalt ions. It is believed that this water molecule acts as an attacking nucleophile in the enzymatic cleavage of the pyrophosphate bond. It was demonstrated that cobalt ions and a phosphate group occupy only part of the potential binding sites (two chemically identical and crystallographically independent subunits have different binding sites). The arrangement of ligands and the structure of the nucleophile-binding site are discussed in relation to the mechanism of action of the enzyme and the nature of the metal activator. 相似文献
279.
The operating principles, design, and characteristics of an ion source with a cold magnetron cathode and magnetic plasma compression are described. The source is intended for the injector of a linear proton accelerator. 相似文献
280.
L. M. Vasilyak M. N. Vasil’ev S. P. Vetchinin D. N. Polyakov V. E. Fortov 《Journal of Experimental and Theoretical Physics》2003,96(3):440-443
The action of an electron beam on ordered dust structures in glow and low-pressure RF discharges was studied experimentally. The electron beam produces destruction and dynamic displacement of the dust structure. In the center of a dust structure, an electron beam with a low electron energy (tens of eV) at currents up to 1 mA caused structural disordering and “melting” in the region of its action but did not excite external crystal regions. Local action of an electron beam with a high electron energy (25 keV) and a beam current above 10 mA caused deformation of the whole dust structure and shifted it in the horizontal direction so that it was carried away from the RF discharge zone. The effect of dust structure displacements can be used to locally remove particles from a plasma. 相似文献