全文获取类型
收费全文 | 117篇 |
免费 | 10篇 |
国内免费 | 49篇 |
专业分类
化学 | 127篇 |
力学 | 8篇 |
综合类 | 2篇 |
数学 | 17篇 |
物理学 | 22篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 10篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 13篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有176条查询结果,搜索用时 15 毫秒
71.
Controlling the crystallographic orientations of 2D perovskite is regarded as an effective way to improve the efficiency of PSCs based on 2D perovskite. In this paper, five different assistant solvents were selected to unveil the effect of solvents on crystallization and morphology of 2D perovskite in a solvent-assisted method. Results demonstrated that the effect of Lewis basicity on the crystallization process was the most important factor for preparing 2D perovskite. The stability of the intermediate, reacted between the solvent and the Pb2+, determined the quality of 2D film. The stronger the Lewis basicity was, the more obvious the accurate control effect on the top-down crystallization process of 2D perovskite would be. This could enhance the crystallographic orientation of 2D perovskite. The effect of Lewis basicity played a more important role than other properties of the solvent, such as boiling point and polarity. 相似文献
72.
An ab initio study of the possible interaction between several anions (F(-), Cl(-), N(3)(-), N(4)(-), and N(5)(-)) and tri-s-triazine molecule, an electron-deficient aromatic ring, has been carried out at the B3LYP and MP2 levels of theory. Minima are located corresponding to hydrogen bonding, pi-pi stacking, and reactive complexes. This novel mode of bonding suggests the development of new cyclophane-type receptors for the recognition of anions. 相似文献
73.
LC4—M材料复合型韧断主要影响因素的分析 总被引:5,自引:0,他引:5
通过分析LC4-M铝合金材料在不同复合比载荷下的断裂试验结果,参照常规断裂现象,修正了一般断裂试验中认定裂纹启裂方向的方法,结合不同复合比下裂尖附近应力三维、主应力方向的计算分析,得到:在裂端的钝化变形区域、应力三维度的极大值处,对应于裂纹的启裂位置,即使在高韧性材料中发生剪切断裂的情况下也是如此;裂纹的启裂方向在拉伸断裂时与启裂点最大拉应力方向有关,在剪切断裂时启裂点最大剪应力方向有关,引起两种形式断裂的主要因数和破坏机理有很大不同。 相似文献
74.
在RHF/6-31G^**,MP2/6-31G^**,B3LYP/6-31G^**水平下优化了5,6,9,10-四脱氢苯并环辛烯的平衡几何构型。用B3LYP/6-31G^**方法计算了该化合物的红外光谱、拉曼光谱、核磁共振谱。计算结果与实验结果吻合很好,从而在理论上证实了它的存在。用等键反应分析,自然键轨道方法对它的稳定性和共轭性分别进行了讨论。结果表明5,6,9,10-四脱氢苯并环辛烯分子平面刚性结构,可能稳定存在,但由于苯环共轭性的削弱和较高的张力,使得它易于分解。 相似文献
75.
Jin Guo Tingfeng Wang Dinan Wang Junfeng Shao Anmin Chen Mingxing Jin 《Applied Physics A: Materials Science & Processing》2014,117(3):1367-1374
The thermionic emission of the single-layer gold thin film and the two-layer film was assembled by gold padded with other metals (Ag, Cu, and Ni) and irradiated by the femtosecond laser pulse. Additionally, the emission was simulated by a two-temperature model combined with the Richardson–Dushman equation. It was found that the two-layer metal structure can change the electron temperature of the gold surface and control the thermionic emission compared with the single-layer gold film. With the same laser fluence, the two-layer film structure may shorten the duration of thermionic emission, and the duration of the thermionic emission can be further optimized by changing the proportion of thin film thickness with gold layer in the two-layer structure. The result can be especially beneficial in the context of ultrafast electron emission induced by femtosecond laser. 相似文献
76.
S~6中具有常数Kahler角的极小曲面 总被引:4,自引:0,他引:4
球面S6具有典型的近复结构,因而对于其中的曲面可引入Kahler角的概念.本文研究S6内具有常数Kahler角的极小曲面,得到了刚性定理.结合已有结果,易知Simon猜想对于这类曲面成立. 相似文献
77.
78.
The C-Hal (Hal = Cl, Br, or I) bond-length change and the corresponding vibrational frequency shift of the C-Hal stretch upon the C-Hal···Y (Y is the electron donor) halogen bond formation have been determined by using density functional theory computations. Plots of the C-Hal bond-length change versus the corresponding vibrational frequency shift of the C-Hal stretch all give straight lines. The coefficients of determination range from 0.94366 to 0.99219, showing that the correlation between the C-Hal bond-length change and the corresponding frequency shift is very good in the halogen-bonded complexes. The possible effects of vibrational coupling, computational method, and anharmonicity on the bond-length change-frequency shift correlation are discussed in detail. 相似文献
79.
Engineering thermal and mechanical properties of flexible fiber-reinforced aerogel composites 总被引:5,自引:0,他引:5
Yundan Liao Huijun Wu Yunfei Ding Shuai Yin Moran Wang Anmin Cao 《Journal of Sol-Gel Science and Technology》2012,63(3):445-456
Flexible aerogel was successfully supported onto 4-layer-aligned glass fibers through impregnation, followed by drying at atmospheric pressure. The prepared nanocomposites can achieve a low thermal conductivity of 0.026?W/(m·K), which holds great promising for their use in thermal insulation applications. By choosing different designs of the four fiber layers, in the terms of LLLL, LTLL, LLTT, LTLT, LTTL and LTTT, the laminated structures of aerogel composites can be accordingly controlled. Further microstructure characterization of the composites revealed the homogeneous dispersion of nanoporous structure through the aerogel matrix, as well as highly-aligned fibers to reinforce the structure. Detailed investigation on the thermal and mechanical properties of the prepared fiber-aerogel composites showed that their performances were highly related to the laminated design of fiber layers. The introduction of fibers as the backbone of the aerogel and the suitable design of their laminated structure can greatly improve the mechanical properties of the aerogel composites while maintaining a low thermal conductivity. 相似文献
80.
Competition between π···π interaction and halogen bond in solution has been investigated by using carbon nuclear magnetic resonance spectroscopy ((13)C NMR) combined with density functional theory calculation. Both experimental and theoretical results clearly show that there are no C-Cl···π or C-Br···π halogen bonds and only the π···π interactions exist in the binary liquid mixtures of C(6)D(6) with C(6)F(5)Cl and C(6)F(5)Br, respectively. The case is totally different for the binary liquid mixtures of C(6)D(6) with C(6)F(5)I in which the C-I···π halogen bonds not the π···π interactions are present. The important role of entropy in the competition between π···π interaction and halogen bond in solution was also discussed. 相似文献