全文获取类型
收费全文 | 131篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 103篇 |
晶体学 | 1篇 |
数学 | 3篇 |
物理学 | 27篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 6篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 17篇 |
2007年 | 14篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1940年 | 3篇 |
排序方式: 共有134条查询结果,搜索用时 15 毫秒
81.
The regiospecific nucleophilic substitution during the ruthenium catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters was demonstrated. The nucleophile was selectively introduced at the position originally substituted with leaving group in the 2-DPPBA or ip-pybox ligated [RuCl(2)(p-cymene)](2) catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters. The chirality of the optically active allylic esters was also transferred to the alkylated products. 相似文献
82.
Optics and Spectroscopy - Intensity distribution and kinetics of the doublet components of the phosphorescence spectrum of triphenylene in a frozen solution of carbon tetrachloride are analyzed. It... 相似文献
83.
Hirokazu Miyoshi Tamaki Otani Namiko Irikura Motoi Nagata 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(3):1177-1183
The in situ 18F-γ-ray irradiation of SiO2 nanoparticles in an aqueous solution containing Ag+ led to the reduction of Ag+ to Ag0 aggregates or Ag0 nanoparticles in a small volume (0.1 ml) under air. 18F was used in the form of 18F-fluorodeoxyglucose, produced by a cyclotron at our University hospital. The in situ average absorbed dose at the distance of 1 µm in the solution volume (0.1 ml) was calculated to be 12.2 kGy equivalent to a point source of 20 MBq. The SiO2 nanoparticles had two effects; they enhanced the reduction of Ag+ to Ag0 aggregates and they acted as reaction sites to prevent aggregation. When Ag+ adsorbed on the surface of the SiO2 nanoparticles, Ag nanoparticles were formed by 18F γ-rays. The absorption spectra of Ag nanoparticles and Ag0 aggregates were markedly different. 相似文献
84.
Motoi Kawatsura 《Tetrahedron letters》2008,49(33):4873-4875
The ruthenium-catalyzed highly linear selective allylic amination of monosubstituted allylic acetates with secondary amines was developed. The regioselectivity was controlled by the Ru3(CO)12/2-DPPBA catalyst, and a linear-type aminated product was obtained as a single regioisomer. 相似文献
85.
The rate law ? d[O3]/ dt = k1[A][O3] + k3[A][O3]2/ (k4 + k5[O2]) has been found to obtain for the reaction of ozone with allene and with 1,2-butadiene. We now find that this rate law also applies to the reaction of ozone with ethylene and presumably with all lower alkenes. This generalizes the inhibiting effect of oxygen and accounts for the simplifed rate law found in the presence of excess oxygen. Oxygen itself is a product of the ozone–ethylene reaction, and we find that as [O3]0 increases, the (O2 formed)/(O3 used) ratio approaches 1.5. Values of k1, k3/k5 for ethylene are compared with those for allene, 1,3-butadiene, and propene. A generalized mechanism is postulated for the reaction of ozone with alkenes involving a chain sequence that produces oxygen and which accounts for the observed rate law. A specific mechanism is postulated for the reaction of O3 with ethylene, and the thermochemistry of the chain sequence is examined in detail. 相似文献
86.
O. V. Erina V. Yu. Khokhlov E. V. Butyrskaya L. S. Nechaeva 《Russian Journal of General Chemistry》2013,83(3):434-437
Computer simulation of molecular structures in the nicotinic acid-water and nicotinic acid-water-poly(N-vinylpyrrolidone) systems was performed, and the IR spectra of these systems were calculated. The theoretical and experimental IR spectra were compared. Parameters of hydrogen bonds in the studied systems were calculated. 相似文献
87.
88.
Motoi Tobita Yusuke Yasuda Eiichi Ide Jiro Ushio Toshiaki Morita 《Journal of nanoparticle research》2010,12(6):2135-2144
Metal nanoparticles need coating material so as to avoid aggregating to each other. On the contrary, there are occasions when the coating materials are required to be removed. Here, a theoretical model to relate removability of coating materials to their molecular structure is suggested. The model is used to find an optimum coating material, secondary amine, for use in low-temperature interconnection material. An interconnection made of methyloctylamine-coated silver nanoparticles was formed between a pair of copper electrodes by heating and pressurizing the nanoparticles and electrodes at 250 °C and 2.5 MPa, respectively, for 150 s. Shear strength and thermal conductivity of the formed interconnection were 17.8 MPa and 219 W/mK, respectively. This thermal conductivity value is greater than that obtained using Pb–Sn and silver solders. 相似文献
89.
Itoh T Matsushita Y Abe Y Han SH Wada S Hayase S Kawatsura M Takai S Morimoto M Hirose Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(36):9228-9237
Several types of imidazolium salt ionic liquids were prepared derived from poly(oxyethylene)alkyl sulfate and used as an additive or coating material for lipase-catalyzed transesterification in an organic solvent. A remarkably increased enantioselectivity was obtained when the salt was added at 3-10 mol % versus substrate in the Burkholderia cepacia lipase (lipase PS-C)-catalyzed transesterification of 1-phenylethanol by using vinyl acetate in diisopropyl ether or a hexane solvent system. In particular, a remarkable acceleration was accomplished by the ionic liquid coating with lipase PS in an iPr(2)O solvent system while maintaining excellent enantioselectivity; it reached approximately 500- to 1000-fold acceleration for some substrates with excellent enantioselectivity. A similar acceleration was also observed for IL 1-coated Candida rugosa lipase. MALDI-TOF mass spectrometry experiments of the ionic-liquid-coated lipase PS suggest that ionic liquid binds with lipase protein. 相似文献
90.
Toshiyuki Itoh Manabu Kanbara Shino Nakajima Yusuke Sakuta Shuichi Hayase Motoi Kawatsura Takashi Kato Kazutoshi Miyazawa Hidemitsu Uno 《Journal of fluorine chemistry》2009,130(12):1157-1163
The synthesis of a novel spiro type gem-difluorocyclopropane building block, 1,1,7,7-tetrafluoro-2,8-bis(hydroxymethyl)dispiro[2.2.2.2]decane (1), has been accomplished in optically pure form using chemo-enzymatic reaction protocol. Various types of diesters or dialkyl ether were prepared from diol (+)-1 or (−)-1 in optically active form and their helical twisting power (HTP) was evaluated by addition of 1.0 wt% to a non-chiral nematic liquid crystal host. Although their HTP values were not significant, all compounds showed liquid crystal property with SmC* phase when they were dissolved (20 wt%) in achiral nematic host liquid crystal. 相似文献