全文获取类型
收费全文 | 298篇 |
免费 | 3篇 |
国内免费 | 6篇 |
专业分类
化学 | 124篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 40篇 |
物理学 | 133篇 |
出版年
2022年 | 3篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 6篇 |
2010年 | 13篇 |
2009年 | 8篇 |
2008年 | 5篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1969年 | 2篇 |
1942年 | 2篇 |
1933年 | 2篇 |
1931年 | 2篇 |
1923年 | 2篇 |
1893年 | 2篇 |
排序方式: 共有307条查询结果,搜索用时 484 毫秒
31.
We demonstrate a method of generating short pulses at 1350 nm by exciting Cerenkov radiation in a higher-order-mode fiber with a 1064 nm femtosecond fiber laser. We measure a 106 fs, 0.66 nJ output pulse. Cerenkov radiation in fibers allows for energy transfer between a soliton and a dispersive wave, providing an effective and engineerable platform to shift the wavelength of a femtosecond source. With appropriate design of the higher-order-mode fiber, this method of generating short pulses at 1350 nm can be extended to other wavelengths and to higher pulse energies. 相似文献
32.
Analyses are made of the interaction of the nonlinearly steepened, compression wavefront generated by a high-speed train in a tunnel with the tunnel portal ahead of the train. The ‘micro-pressure’ pulse emitted from the portal can rattle structures in nearby buildings, and the expansion wave reflected back towards the train can cause discomfort to passengers. It is concluded that the usual simplified approximation of one-dimensional propagation within the tunnel provides an adequate representation of interactions of the wave with the portal, and also with ‘windows’ in the tunnel wall near the portal. It is shown how a discrete distribution of windows can be used to produce a reflected expansion wave that varies linearly across the wavefront, and how the thickness of that wavefront can be made many times larger than the thickness of the incident compression wave profile. A detailed analysis of the wave radiated from the portal reveals that cumulative nonlinear effects of propagation over long distances make little or no contribution to the free-space radiation of the micro-pressure wave. 相似文献
33.
34.
The superconformal invariants in analytic superspace are found. Superconformal invariance is shown to imply that the Green's functions of analytic operators are invariant holomorphic sections of a line bundle on a product of certain harmonic superspaces. It is argued that the correlation functions for a class of sufficiently low dimension gauge invariant operators in N = 2 and N = 4 supersymmetric Yang-Mills theory can be evaluated up to constants. 相似文献
35.
36.
The static and dynamic tensile and compressive properties of Colorado Yule marble have been obtained from samples all secured from the same parent slab. Specimens were cored in the three principal directions of this transversely isotropic material, the axis of symmetry having been determined petrographically. Standard quasi-static and creep tests were performed, and both Hopkinson-bar and split-Hopkinson-bar tests were conducted for the collection of data at higher loading rates. Elastic constants evaluated for the material on the basis of the present investigation were compared with corresponding static and dynamic values from a previous series of tests conducted on a large block of Yule marble, and to dynamic constants for the same block determined in a separate investigation by means of wavespeed data secured from embedded crystal transducers. The behavior of Yule marble does not seem to conform to any well-known constitutive relation and is, thus, most easily characterized by suitable sets of experimental data. 相似文献
37.
We show that the supergeometry of the new minimal formulation of N = 1 supergravity is a limiting case of the non-minimal supergeometry for which the volume of superspace vanishes. The action for supergravity in this case is then no longer the superdeterminant of the vielbein but is analogous to a special form of the Fayet-Iliopoulos term allowed only for the new minimal supergeometry. We discuss the restrictions on matter couplings imposed by the new and non-minimal supergeometries. 相似文献
38.
Everett W. Howe 《Mathematische Annalen》1996,305(1):387-392
39.
Irreducible sigma models, i.e. those for which the partition function does not factorise, are defined on Riemannian spaces with irreducible holonomy groups. These special geometries are characterised by the existence of covariantly constant forms which in turn give rise to symmetries of the supersymmetric sigma model actions. The Poisson bracket algebra of the corresponding currents is aW-algebra. Extended supersymmetries arise as special cases. 相似文献
40.
Douglas Howe 《Journal of Pure and Applied Algebra》1981,21(2):161-165