全文获取类型
收费全文 | 1219篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 414篇 |
晶体学 | 19篇 |
力学 | 80篇 |
数学 | 194篇 |
物理学 | 518篇 |
出版年
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 37篇 |
2018年 | 31篇 |
2017年 | 42篇 |
2016年 | 40篇 |
2015年 | 17篇 |
2014年 | 30篇 |
2013年 | 65篇 |
2012年 | 42篇 |
2011年 | 42篇 |
2010年 | 39篇 |
2009年 | 34篇 |
2008年 | 29篇 |
2007年 | 46篇 |
2006年 | 34篇 |
2005年 | 34篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 48篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 20篇 |
1996年 | 13篇 |
1995年 | 19篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 20篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1973年 | 14篇 |
1972年 | 11篇 |
排序方式: 共有1225条查询结果,搜索用时 78 毫秒
111.
112.
Andrei V. Afonin Dmitry V. Pavlov Igor A. Ushakov Natalia A. Keiko 《Magnetic resonance in chemistry : MRC》2012,50(7):502-510
In the 13C NMR spectra of methylglyoxal bisdimethylhydrazone, the 13C‐5 signal is shifted to higher frequencies, while the 13C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the 1H‐6 chemical shift and 1J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(1H‐6) and 1J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the 1H shielding and one‐bond 13C–1H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The 1H, 13C and 15N chemical shifts of the 2‐ and 8‐(CH3)2N groups attached to the –C(CH3)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH3)2N group conjugate effectively with the π‐framework, and the 2‐(CH3)2N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the 1H, 13C and 15N shieldings. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
113.
114.
115.
116.
117.
118.
E. Šimečková P. Čižek M. Finger J. John P. Malinský V. N. Pavlov 《Hyperfine Interactions》1990,59(1-4):185-188
The angular distribution of γ-radiation from the decay of239Np oriented at low temperatures in gadolinium host was investigated. The orientation parameters B2 and B4 were determined.
The attenuation factors for two long-living states in239Pu at 391.5 keV and 285.4 keV were calculated. From the anisotropies measured the multipole mixing ratios for 11 gamma-transitions
in239Pu were deduced. The results obtained support the assignment of spins of the levels at 492.2 keV and 391.6 keV as 3/2− and 7/2−, respectively. 相似文献
119.
120.
The boundaries of phase equilibria involving calcium sulfate crystal hydrates in a citric acid solution were calculated. The influence exerted by an excess amount of sulfuric acid on the stability of calcium sulfate crystal hydrates in citric acid solutions was considered. The possibility of achieving a hemihydrate mode of citric acid extraction from calcium citrate was studied. 相似文献