全文获取类型
收费全文 | 4146篇 |
免费 | 252篇 |
国内免费 | 21篇 |
专业分类
化学 | 3198篇 |
晶体学 | 16篇 |
力学 | 80篇 |
数学 | 536篇 |
物理学 | 589篇 |
出版年
2023年 | 52篇 |
2022年 | 73篇 |
2021年 | 84篇 |
2020年 | 135篇 |
2019年 | 109篇 |
2018年 | 63篇 |
2017年 | 79篇 |
2016年 | 174篇 |
2015年 | 150篇 |
2014年 | 175篇 |
2013年 | 199篇 |
2012年 | 305篇 |
2011年 | 257篇 |
2010年 | 149篇 |
2009年 | 141篇 |
2008年 | 227篇 |
2007年 | 215篇 |
2006年 | 188篇 |
2005年 | 196篇 |
2004年 | 183篇 |
2003年 | 121篇 |
2002年 | 154篇 |
2001年 | 66篇 |
2000年 | 60篇 |
1999年 | 51篇 |
1998年 | 58篇 |
1997年 | 50篇 |
1996年 | 54篇 |
1995年 | 38篇 |
1994年 | 32篇 |
1993年 | 31篇 |
1992年 | 42篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 33篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 38篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 27篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1970年 | 13篇 |
排序方式: 共有4419条查询结果,搜索用时 15 毫秒
11.
Christoph Elschenbroich Jrn Plackmeyer Klaus Harms Olaf Burghaus Jürgen Pebler 《无机化学与普通化学杂志》2006,632(5):819-827
Trovacene Chemistry. 13 [1] On Being Lead and Mislead in the Synthesis of Di([5]trovacenyl)ketone Di([5]trovacenyl)ketone ( 3¨ ) has been prepared from lithio‐[5]trovacene and dimethylcarbamoyl chloride and studied by X‐ray diffraction, cyclic voltammetry, magnetic susceptometry and EPR spectroscopy. Slight variation of the synthetic protocol affords an unusual trinuclear complex 5 ? that is also fully characterized. Spin‐spin exchange interaction is smaller in 3¨ than in 1,1‐di([5]trovacenylethene ( 2¨ ), which differs from 3¨ by a replacement of O for CH2. The novel trinuclear complex 5 ? , however, displays exchange coupling very similar to that observed in 1‐methoxy‐2,5,6‐tri([5]trovacenyl)benzene ( 7 ? ). In both cases, an unsymmetrical triangular arrangement of S = 1/2 centers is encountered. These findings are discussed in terms of the nature of the respective spacers. 相似文献
12.
Tobias P. Kunzler Christoph M. Sprecher Nicholas D. Spencer 《Applied Surface Science》2006,253(4):2148-2153
Gradient surfaces allow rapid, high-throughput investigations and systematic studies in many disparate fields, including biology, tribology and adhesion. We describe a novel method for the fabrication of material-independent morphology gradients, involving a two-step process of particle erosion followed by a chemical polishing procedure that preferentially removes features with a small radius of curvature as a function of time. Gradients are fabricated on aluminium surfaces, but they may be readily transferred to other materials via a replication technique, which allows for the production of identical roughness gradient samples with any chosen surface chemistry. The gradients have been characterized by means of scanning electron microscopy and optical profilometry. Standard roughness parameters (Ra, Rq, Rz, Sm and Sk) were calculated from optical profilometry data. The roughness has also been assessed over different wavelength windows by means of a fast Fourier transformation approach. 相似文献
13.
14.
Gerd Herzog Christoph Schmoeger 《Proceedings of the American Mathematical Society》2003,131(11):3507-3509
We prove the converse of Raubenheimer and Rode's Banach algebra version of the Perron-Frobenius Theorem.
15.
Christoph Bohle 《Journal of Geometry and Physics》2003,45(3-4):285-308
The aim of this paper is to describe some results concerning the geometry of Lorentzian manifolds admitting Killing spinors. We prove that there are imaginary Killing spinors on simply connected Lorentzian Einstein–Sasaki manifolds. In the Riemannian case, an odd-dimensional complete simply connected manifold (of dimension n≠7) is Einstein–Sasaki if and only if it admits a non-trivial Killing spinor to
. The analogous result does not hold in the Lorentzian case. We give an example of a non-Einstein Lorentzian manifold admitting an imaginary Killing spinor. A Lorentzian manifold admitting a real Killing spinor is at least locally a codimension one warped product with a special warping function. The fiber of the warped product is either a Riemannian manifold with a real or imaginary Killing spinor or with a parallel spinor, or it again is a Lorentzian manifold with a real Killing spinor. Conversely, all warped products of that form admit real Killing spinors. 相似文献
16.
17.
The exciton-exciton interaction is investigated for spatially indirect excitons in coupled quantum wells. The Hartree-Fock and Heitler-London approaches are improved by a full two-exciton calculation including the van der Waals effect. Using these potentials for the singlet and triplet channel, the two-body scattering matrix is calculated and employed to derive a modified relation between exciton density and blue shift. Such a relation is of central importance for gauging exciton densities on the way toward Bose condensation. 相似文献
18.
Christoph Klingenberg 《Inventiones Mathematicae》1987,89(2):291-317
Ohne Zusammenfassung 相似文献
19.
20.