全文获取类型
收费全文 | 2751篇 |
免费 | 98篇 |
国内免费 | 9篇 |
专业分类
化学 | 1746篇 |
晶体学 | 15篇 |
力学 | 78篇 |
数学 | 549篇 |
物理学 | 470篇 |
出版年
2023年 | 30篇 |
2022年 | 49篇 |
2021年 | 78篇 |
2020年 | 64篇 |
2019年 | 77篇 |
2018年 | 44篇 |
2017年 | 39篇 |
2016年 | 127篇 |
2015年 | 84篇 |
2014年 | 99篇 |
2013年 | 165篇 |
2012年 | 227篇 |
2011年 | 211篇 |
2010年 | 111篇 |
2009年 | 131篇 |
2008年 | 171篇 |
2007年 | 163篇 |
2006年 | 143篇 |
2005年 | 111篇 |
2004年 | 124篇 |
2003年 | 97篇 |
2002年 | 101篇 |
2001年 | 34篇 |
2000年 | 26篇 |
1999年 | 25篇 |
1998年 | 26篇 |
1997年 | 16篇 |
1996年 | 29篇 |
1995年 | 18篇 |
1994年 | 28篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有2858条查询结果,搜索用时 46 毫秒
171.
Most K Köpke S Dall'Antonia F Mösch-Zanetti NC 《Chemical communications (Cambridge, England)》2002,(16):1676-1677
Molybdenum dioxo compounds [MoO2Cl(eta 2-pz)] and [MoO2(eta 2-pz)2] with pz = eta (2)-3,5-di-tert-butylpyrazolate have been synthesized; crystallographic data, catalytic activity, and oxo transfer properties are described. 相似文献
172.
173.
[reaction: see text] The synthesis of alpha-substituted alpha,beta-enones by a new metal iodide-promoted one-pot three-component reaction involving commercially available cyclopropyl ketones, aldehydes, and secondary amines followed by base treatment is described. 相似文献
174.
The Kohn-Sham exchange potential of finite systems is shown to approach different asymptotic limits on nodal surfaces of the energetically highest-occupied orbital than in other regions. This leads to barrier-well structures in the near asymptotic region, which have a strong influence on virtual orbitals and thus on excitation energies. Common approximations for the exchange potential do not exhibit these features. These asymptotic structures, however, can be correctly described by effective exact-exchange methods. Conditions for the presence of an asymptotic barrier well in the full exchange-correlation potential are discussed. 相似文献
175.
Diffraction-limited, 300-kW peak-power pulses from a coiled multimode fiber amplifier 总被引:1,自引:0,他引:1
We report a multimode, double-clad, Yb-doped fiber amplifier that produces diffraction-limited, 0.8-ns pulses with energies of 255 muJ and peak powers in excess of 300 kW at a repetition rate of ~8 kHz . Single-transverse-mode operation was obtained by bend-loss-induced mode filtering of the gain fiber. 相似文献
176.
Pioger P Couderc V Lefort L Barthelemy A Baronio F De Angelis C Min Y Quiring V Sohler W 《Optics letters》2002,27(24):2182-2184
We show numerically and experimentally that spatial trapping can be induced in quadratic media even if the pump pulse's duration is shorter than the group-delay mismatch between fundamental wave and second-harmonic components. The influence of phase mismatch and pulse power on the trapping effect is discussed. Spatial, temporal, and spectral behaviors that accompany self-trapped propagation are highlighted. 相似文献
177.
178.
A recent analysis of the experimental data on some physical phenomena ruled by the four fundamental interactions (electromagnetic, weak, strong and gravitational) seems to show the possibility of describing such interactions in terms of a deformation of the usual Minkowski spacetime, with a metric whose coefficients do depend on the energy of the process considered. In this paper, we show that such results can be accounted for in terms of a Kaluza-Klein-like scheme, based on a five-dimensional Riemannian space in which energy plays the role of the fifth dimension. The corresponding five-dimensional Einstein equations in vacuum are solved in some cases of physical relevance and it is shown that all the phenomenological metrics describing the four fundamental forces are recovered as special cases of the classes of solutions found. Possible developments of the formalism are also briefly outlined. 相似文献
179.
In this paper an infinite dimensional Morse theory for lightlike geodesics joining a point with a timelike curve on a class of Lorentzian manifolds is developed under intrinsic assumptions. It yields applications to the gravitational lens effect. In particular we show that the number of images in the gravitational lens effect is infinite or odd. 相似文献
180.
Fabio Podestà 《Monatshefte für Mathematik》1996,122(3):215-225
This work deals with positively curved compact Riemannian manifolds which are acted on by a closed Lie group of isometries whose principal orbits have codimension one and are isotropy irreducible homogeneous spaces. For such manifolds we can show that their universal covering manifold may be isometrically immersed as a hypersurface of revolution in an euclidean space. 相似文献