首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   262篇
  免费   5篇
化学   214篇
晶体学   4篇
力学   2篇
数学   12篇
物理学   35篇
  2023年   2篇
  2022年   6篇
  2021年   6篇
  2020年   1篇
  2019年   9篇
  2018年   7篇
  2017年   6篇
  2016年   5篇
  2015年   6篇
  2014年   10篇
  2013年   22篇
  2012年   10篇
  2011年   16篇
  2010年   12篇
  2009年   9篇
  2008年   13篇
  2007年   20篇
  2006年   11篇
  2005年   14篇
  2004年   8篇
  2003年   7篇
  2002年   8篇
  2001年   7篇
  2000年   11篇
  1998年   3篇
  1996年   1篇
  1995年   3篇
  1993年   2篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1984年   2篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   6篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有267条查询结果,搜索用时 12 毫秒
51.
52.
In this study, affinity capillary electrophoresis (ACE) and quantum mechanical density functional theory (DFT) calculations were combined to investigate non-covalent binding interactions between the hexaarylbenzene-based receptor (R) and alkali metal ions, Rb(+) and Cs(+) , in methanol. The apparent binding (stability) constants (K(b) ) of the complexes of receptor R with alkali metal ions in the methanolic medium were determined by ACE from the dependence of effective electrophoretic mobility of the receptor R on the concentration of Rb(+) and Cs(+) ions in the BGE using a non-linear regression analysis. The receptor R formed relatively strong complexes both with rubidium (log K(b) =4.04±0.21) and cesium ions (log K(b) =3.72±0.22). The structural characteristics of the above alkali metal ion complexes with the receptor R were described by ab initio density functional theory calculations. These calculations have shown that the studied cations bind to the receptor R because they synergistically interact with the polar ethereal fence and with the central benzene ring via cation-π interaction.  相似文献   
53.
In the structure of the title salt [systematic name: 3‐(10,11‐dihydro‐5H‐dibenzo[a,d][7]annulen‐5‐ylidene)‐N,N‐dimethylpropan‐1‐aminium 2,4,6‐trinitrophenolate] of a tricyclic antidepressant, C20H24N+·C6H2N3O7, the dimethylaminopropyl subunit possesses a classical static conformational disorder. The central cycloheptadiene ring adopts a bent conformation that is intermediate between boat and chair forms, leading to a butterfly shape for the hetero‐tricyclic moiety. In a complementary fashion, donors from amitriptyline and acceptors from picrate form intermolecular C—H...O hydrogen bonds and N—H...O salt bridges. These hydrogen bonds cluster amitriptyline and picrate ions into a closed R44(36) hetero‐tetramer, whereas intermolecular C—H...π interactions between amitriptyline ions cluster them into homo‐dimers. Significant π–π stacking interactions are also observed between aromatic rings of amitriptyline and picrate, and these, combined with the C—H...π interactions, associate molecules into linear arrays along the [11] direction.  相似文献   
54.
55.
Copper diethyldithiocarbamate, cadmium diethyldithiocarbamate, lead diethyldithiocarbamate, nickel diethyldithiocarbamate and zinc diethyldithiocarbamate have been synthesized. They have been characterized using TG, DTA, IR spectroscopy, X-ray and atomic absorption spectrophotometry. The thermal conversion of the compounds is 54.36–88% at 1000°C. Their solubility in sodium hydroxide, mineral acids, organic solvents, distilled water and salts solution has been measured. Fungicidal activity of the dithiocarbamates has been tested by well or cup diffusion method using five fungi species. Their activity has also been tested by broth dilution method using six bacterial species. Minimum Inhibitory Concentration (bactericidal) is 6.25–25.00 μg mL−1.  相似文献   
56.
α,β-Unsaturated anilides bearing allylic leaving groups undergo photochemical electrocyclic ring closure to produce zwitterionic intermediates which eliminate carboxylate and phenolate leaving groups.  相似文献   
57.
58.
59.
60.
Partitioning of minor alpha-emitting actinides, especially U, Pu and Am from medium active alkaline waste is possible from intermediate level liquid wastes (ILLW) produced during spent fuel reprocessing following Purex process. This paper deals with the efficient removal of alpha-activity from ILLW by solvent extraction process. Counter current batch extraction with O/A ratio 2:1 as well as multistage mixer settler has demonstrated that most of the alpha-activity was removed from the alkaline effluents using 20% Versatic-10 (V-10) in dodecane after giving 3 to 4 contacts, thus converting alkaline waste as non-alpha waste. Under the optimum conditions (pH 9.0-9.5 and VA-10), both Pu(IV) and Am(III) are highly extractable whereas U(VI) is relatively poorly extracted. To assess the applicability of this process for regular treatment of the waste, a feasibility study on pilot plant scale using six stage mixer settler was operated to treat the ILLW. The results indicated that almost >99.90% alpha-emitting actinides are removed. Dilute nitric acid (0.5M HNO3) served as the most efficient strippant for all these actinides. This facilitate an easy regeneration of the extractant which can be recycled. This method is useful in obtaining alpha-free wastes and had positive impact on ease and safety aspects during subsequent waste treatment and long term storage.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号