全文获取类型
收费全文 | 303篇 |
免费 | 17篇 |
国内免费 | 10篇 |
专业分类
化学 | 26篇 |
晶体学 | 1篇 |
综合类 | 2篇 |
数学 | 66篇 |
物理学 | 47篇 |
综合类 | 188篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 32篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 12篇 |
2010年 | 7篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 20篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有330条查询结果,搜索用时 15 毫秒
81.
针对现有广告设计创意教学中存在的问题,从宏观的角度分析了其成因,从教与学两个方面提出了新的广告设计创意教学指导思想,总结和归纳了一些可行的实施方案。 相似文献
82.
This paper considers Markov chains on a locally compact separable metricspace, which have an invariant probability measure but with no otherassumption on the transition kernel. Within this context, the limit providedby several ergodic theorems is explicitly identified in terms of the limitof the expected occupation measures. We also extend Yosidasergodic decomposition for Feller-like kernels to arbitrarykernels, and present ergodic results for empirical occupation measures, aswell as for additive-noise systems. 相似文献
83.
Klaus W. Richter Hans FlandorferHugo F. Franzen 《Journal of solid state chemistry》2002,167(2):517-524
The title compounds MxTa11−xGe8 (M=Ti, Zr, Hf) were prepared from the pure elements by arc-melting and subsequent induction heating at temperatures between 1200°C and 1400°C. X-ray powder diffraction studies of the samples were performed using the Guinier technique and the respective powder patterns were refined with a structure model based on the orthorhombic Cr11Ge8-structure type (oP76, Pnma). The homogeneity ranges of the compounds were determined to be 0.9<x<1.3 (M=Ti), 0.7<x<1.3 (M=Zr) and 0.7<x<2.4> (M=Hf) by means of electron probe microanalysis. Chemical bonding, electronic structure and site preferences are discussed based on extended Hückel calculations performed on hypothetical binary Ta11Ge8. 相似文献
84.
The crystal and magnetic structures of Sr2(Fe1−xVx)MoO6 (0.03?x?0.1) compounds are refined by alternately using X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) data collected at room temperature. The refinement results reveal that the V atoms selectively occupy the Mo sites instead of the Fe sites for x?0.1. The 3d/4d cation ordering decreases with the increase of the V content. Slight distortions in the lattice and metal octahedra are shown at 300 K, and the distortions increase at 4 K. The magnetic structure at 4 K can be modeled equally well with the moments aligning along [001], [110] or [111] directions. The total moments derived from the NPD data for the [110] and [111] direction models agree well with the magnetic measurements, whereas the [001] model leads to a smaller total moment. Bond valence analysis indicates that Sr ions are properly located in the structure and Mo ions are compatible with both the Fe sites and the Mo sites. The electronic effects are suggested to be responsible for the selective occupation of the V on the Mo sites due to the different distortions of the FeO6 and MoO6 octahedra. 相似文献
85.
86.
87.
Abstract The apparent substitutional fraction, fs , of Rh and Ir implanted into Al single crystals at 293 K with peak concentrations of 0.17±0.01 at.% is 0.57 ± 0.02 and 0.47±0.02, respectively. Upon annealing to 593 K fs decreases and the critical angles of the impurities narrow due to partially coherent precipitate formation. Irradiation with 300 keV Ar ions at 77 K with deposited energy densities up to 20 dpa leads to precipitate dissolution accompanied by an increase of fs up to 0.70±0.02 for Al(Rh) and 0.82±0.02 for Al(Ir). The relatively high fs values do not decrease during annealing from 77 K to 293 K, indicating that vacancy trapping is not a dominant process. Precipitate formation seems therefore to limit the maximum obtainable fs values during implantation at 293 K for these systems. 相似文献
88.
从心理学角度分析了体育教育育人的特点,进而提出了高校体育教育中育人的条件,揭示了育人方法,即寓思想教育于知识性教育之中;热爱、理解学生,创设良好情感体验的教育情境;运用竞争机制,激发拼搏精神,培养进取意识;身体美和心灵美日臻完善、和谐统一;为人师表,潜移默化。 相似文献
89.
TANG Jiashan 《自然科学进展(英文版)》2006,16(8):803-807
Weighted occupation time processes associated with the super-Brownian motions on hyperbolic spaces are investigated. Longtime behavior and a central limit type theorem for the processes are obtained. For all dimension d≥2, the right normings for two fluctuations are t and t1/2, and the limit results are the Riemannian measure and some centered Gaussian random measure, respectively. 相似文献
90.
从电子设计制作竞赛活动与教学的关系、竞赛需求、竞赛训练的开放性、组织形式、心理培养等多个方面,分析了电子设计制作竞赛的特点,指出这项活动是开展集体主义教育的良好媒介,强调了集体主义教育中应着重把握的竞争与合作、个体与整体两个重要关系,以及教师在集体主义教育中的作用。 相似文献