全文获取类型
收费全文 | 217篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 157篇 |
晶体学 | 1篇 |
数学 | 6篇 |
物理学 | 60篇 |
出版年
2022年 | 3篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 2篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 25篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1973年 | 3篇 |
排序方式: 共有224条查询结果,搜索用时 148 毫秒
221.
Takahisa Miyata 《Topology and its Applications》2012,159(3):921-932
The extension problem is to determine the extendability of a mapping defined on a closed subset of a space into a nice space such as a CW complex over the whole space. In this paper, we consider the extension problem when the codomains are general spaces. We take a shape theoretic approach to generalize the extension theory so that the codomains are allowed to be general spaces. We extend the notion of extension type which has been defined for the class of CW complexes and introduce the notion of approximate extension type which is defined for general spaces. We define approximate extension dimension analogously to extension dimension, replacing the class of CW complexes by the class of finitistic separable metrizable spaces. For every metrizable space X, we show the existence of approximate extension dimension of X. 相似文献
222.
Sato Y Buban JP Mizoguchi T Shibata N Yodogawa M Yamamoto T Ikuhara Y 《Physical review letters》2006,97(10):106802
The role of Pr doping on double Schottky barrier formations at ZnO single grain boundaries was investigated by the combination of current-voltage measurements, atomic-resolution Z-contrast scanning transmission electron microscopy, and first-principles calculations. Although Pr segregated to the specific atomic site along the boundaries, it was found not to be the direct cause of nonlinear current-voltage properties. Instead, under appropriate annealing conditions, Pr enhances formations of acceptor-type native defects that are essential for the creation of double Schottky barriers in ZnO. 相似文献
223.
Effects of thermal treatments on the recovery of adsorbed water and photocatalytic activities of TiO2 photocatalytic systems 总被引:1,自引:0,他引:1
Nosaka AY Nishino J Fujiwara T Ikegami T Yagi H Akutsu H Nosaka Y 《The journal of physical chemistry. B》2006,110(16):8380-8385
The effects of thermal treatments on the rehydration process and photocatalytic activity were investigated by 1H NMR spectroscopy for six anatase abundant TiO2 photocatalysts with different properties. Acetic acid and benzoic acid were employed for photodecomposition in aqueous suspension. After the calcinations at 973 K, physisorbed water layers recovered relatively fast for P25, F4, and AMT-600 (shorter than 24 h) with no significant enhancement of the photocatalytic decomposition. On the other hand, for ST-01, UV-100, and AMT-100, the recovery was very slow (longer than 1 week) and only partially reversible, and the photocatalytic decomposition was considerably enhanced but retarded with rehydration. In the presence of adsorbed water, the binding of a carboxyl group of the molecules with adsorbed water is considered to compete with the direct adsorption on the surface, which reduces the amount of the direct adsorption and results in the reduction in the photocatalytic efficiency. In addition, the photocatalytic decomposition of benzoic acid with an aromatic ring was much faster in all of the TiO2 aqueous suspensions and more enhanced for the fully dehydroxylated TiO2 than that of acetic acid. These results suggest that the most efficient photocatalytic sites should be the hydrophobic sites on the TiO2 surface. The difference among the rehydration rates of different TiO2 is discussed in terms of thermally induced changes of surface morphology. 相似文献
224.
Machiguchi T Okamoto J Morita Y Hasegawa T Yamabe S Minato T 《Journal of the American Chemical Society》2006,128(1):44-45
The first example of direct spectroscopic detection of transient species, 1,4-zwitterions, generated in a ketene-alkene reaction is reported. Also, a striking result of the intervention of an unprecedented "1,4-zwitterion neutral dimer" is presented in a new mechanistic pathway; the ketene-alkene reaction gives the product cyclobutanone from the initial cycloadduct alpha-methyleneoxetane. 相似文献