全文获取类型
收费全文 | 3575篇 |
免费 | 834篇 |
国内免费 | 276篇 |
专业分类
化学 | 1607篇 |
晶体学 | 33篇 |
力学 | 30篇 |
综合类 | 16篇 |
数学 | 122篇 |
物理学 | 2877篇 |
出版年
2024年 | 11篇 |
2023年 | 43篇 |
2022年 | 82篇 |
2021年 | 110篇 |
2020年 | 141篇 |
2019年 | 120篇 |
2018年 | 111篇 |
2017年 | 99篇 |
2016年 | 132篇 |
2015年 | 139篇 |
2014年 | 183篇 |
2013年 | 267篇 |
2012年 | 225篇 |
2011年 | 257篇 |
2010年 | 206篇 |
2009年 | 259篇 |
2008年 | 202篇 |
2007年 | 230篇 |
2006年 | 217篇 |
2005年 | 173篇 |
2004年 | 157篇 |
2003年 | 163篇 |
2002年 | 183篇 |
2001年 | 147篇 |
2000年 | 158篇 |
1999年 | 111篇 |
1998年 | 122篇 |
1997年 | 44篇 |
1996年 | 39篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 34篇 |
1992年 | 32篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有4685条查询结果,搜索用时 46 毫秒
11.
《Surface and interface analysis : SIA》2003,35(2):146-150
We report the first application of pump–probe second harmonic generation (SHG) measurements to characterize optically induced magnetization in non‐magnetic multilayer semiconductors. In the experiment, spin‐polarized electrons are excited selectively by a pump beam in the GaAs layer of GaAs/GaSb/InAs structures. However, the resulting net magnetization manifests itself through the induced SHG probe signal from the GaSb/InAs interface, thus indicating a spin‐polarized electron transport across the heterostructure. We find that the magnetization dynamics are governed by an interplay between the spin density evolution at the interfaces and the spin relaxation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
12.
Density functional method (DFT) (B3p86) of Gaussian98 has been used to optimize the structure of the Tc_2 molecule. The result shows that the ground state for Tc_2 molecule is an 11-multiple state and its electronic configuration is {}^{11}Σ_g^-, which shows the spin polarization effect of Tc_2 molecule of a transition metal element for the first time. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions of higher energy states. So, that the ground state for Tc_2 molecule is an 11-multiple state is indicative of the spin polarization effect of Tc_2 molecule of a transition metal element: that is, there exist 10 parallel spin electrons. The non-conjugated electron is greatest in number. These electrons occupy different spacious tracks, so that the energy of Tc_2 molecule is minimized. It can be concluded that the effect of parallel spin of the Tc_2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell--Sorbie potential functions with the parameters for the ground state {}^{11}Σ_g^- and other states of Tc_2 molecule are derived. Dissociation energy D_e for the ground state of T_{c2} molecule is 2.266eV, equilibrium bond length R_e is 0.2841nm, vibration frequency ω_e is 178.52cm^{-1}. Its force constants f_2, f_3, and f_4 are 0.9200aJ·nm^{-2}, --3.5700aJ·nm^{-3}, 11.2748aJ·nm^{-4} respectively. The other spectroscopic data for the ground state of Tc_2 molecule ω_eχ_e, B_e, α_e are 0.5523cm^{-1}, 0.0426cm^{-1}, 1.6331×10^{-4}cm^{-1} respectively. 相似文献
13.
14.
Mattias Edn Jekabs Grins Zhijian Shen Zheng Weng 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,169(2):1
Using enhancement of the 27Al central-transition magnetization by applying RAPT prior to 27Al → 29Si cross-polarization, we demonstrate fast acquisition of 29Si one-dimensional MAS and two-dimensional 27Al–29Si HETCOR spectra on a new sialon phase Ba2Al3Si9N13O5. 相似文献
15.
16.
Ultrathin epitaxial Fe films on Cu(1 0 0) with perpendicular magnetization have been used as templates for the preparation of FCC Fe/Cu/Fe trilayers. The magnetic anisotropy and the coupling of these films have been studied by in-situ magneto optical Kerr effect measurements and Kerr microscopy. The magnetic coupling of both Fe layers is found to be dominated by magnetostatic interaction. Adsorbate-induced spin reorientation in the top layer also causes spin reorientation in the bottom layer. The governing role of the Fe-vacuum interface for the magnetism of the whole trilayer is demonstrated. 相似文献
17.
18.
R.S. Kraußhar 《Journal of Mathematical Analysis and Applications》2007,325(1):359-376
In this paper we study Clifford and harmonic analysis on some examples of conformal flat manifolds that have a spinor structure, or more generally, at least a pin structure. The examples treated here are manifolds that can be parametrized by U/Γ where U is a subdomain of either Sn or Rn and Γ is a Kleinian group acting discontinuously on U. The examples studied here include RPn and the Hopf manifolds S1×Sn−1. Also some hyperbolic manifolds will be treated. Special kinds of Clifford-analytic automorphic forms associated to the different choices of Γ are used to construct explicit Cauchy kernels, Cauchy integral formulas, Green's kernels and formulas together with Hardy spaces and Plemelj projection operators for Lp spaces of hypersurfaces lying in these manifolds. 相似文献
19.
研究了应用于锂二次电池正极的新型高能量密度存贮材料Li(AlxCo1-x)O2 (x=01—05)的磁性.发现Al3+的掺杂可导致Co3+中d电子自旋态发生变化,即有部分d电子进入高自旋态.伴随Co3+中电子状态的改变,材料结构演化也发生了相应变化,表现为c/a比增大明显减缓,较好地解释了材料结构对Vegard定律的正偏离.这对材料的微观结构与性能设计具有重要意义.
关键词:
锂电池材料
Li(AlxCo1-x)O2
磁性
自旋态
结构演化 相似文献
20.