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   156篇
  免费   0篇
化学   137篇
力学   3篇
数学   14篇
物理学   2篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2014年   1篇
  2013年   2篇
  2008年   2篇
  2005年   1篇
  2002年   7篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1995年   7篇
  1994年   2篇
  1993年   1篇
  1992年   6篇
  1991年   7篇
  1990年   7篇
  1989年   7篇
  1988年   6篇
  1987年   4篇
  1986年   8篇
  1985年   8篇
  1984年   7篇
  1983年   7篇
  1981年   3篇
  1980年   2篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1976年   7篇
  1975年   5篇
  1974年   2篇
  1973年   5篇
  1972年   7篇
  1971年   2篇
  1970年   2篇
  1969年   1篇
  1968年   3篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1962年   2篇
排序方式: 共有156条查询结果,搜索用时 15 毫秒
1.
The electrochemical reduction of 1,1-dihalo-2-R-2-methylcyclopropanes was studied by polarography and preparative electrolysis. A mixture of stereoisomeric monoboro- and monochlorocyclopropanes was obtained with preparative yield of 60–70% in preparative electroreduction in methanol against a background of 0.1 M LiClO4. In the case of bromine derivatives of cyclopropanes (except when R = CN) an effect was found on the part of the current density on the ratio of cis and trans isomers, which was interpreted as a change, in dependence on current density, of the contributions of the reactions of reduction of the starting compounds (SN2 mechanism) and ionic pairs (SN1 mechanism). The effect of the solvent (CHCl3, DMF, DMSO, MeOH) and background salt (LiClO4, Et4NBr) on the ratio of stereoisomers is in agreement with this interpretation.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, Kazan. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2023–2032, September, 1992.  相似文献   
2.
The functions of action and energy are introduced on a manifold of ground states of the Euclidian scalar field functional of action. The differential identity connecting these two functions is proved.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 105, No. 3, pp. 438–449, December, 1995.  相似文献   
3.
4.
5.
We have established that direct phosphorus-selenium spin-spin coupling constants in cyclic compounds with P=Se exocyclic and P-C endocyclic bonds are found in the range1JPSe=–708 to –859 Hz; in this case, it is greater for the axial orientation of P=Se than for the equatorial orientation.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 776–780, April, 1990.  相似文献   
6.
It is established that the -chloroepoxide methyl 2-chloro-3-(3-nitrophenyl)-2, 3-epoxypropionate, in contrast to its a-chloroketone isomer methyl 3-(3-nitrophenyl-3-chloro-2-oxopropionate, forms 2-(3-nitrophenyl-3methoxycarbonylquinoxaline in reaction with 1,2-phenylene diamine, whereas the condensation of the achloroketone with 1,2 phenylene diamine gives 3-(-chloro-3-nitrophenyl)-2-oxo-1,2-dihydroquinoxaline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1105-1108, August, 1994.  相似文献   
7.
The interaction of synthetic analogs of active centers of iron-sulfur proteins with phosphates of different structures was studied. It was shown that the process involves ligand exchange and obeys the first-order reaction kinetic equation. The most rapid exchange occurred with the most acidic compound diphenyl phosphate.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2301–2305, October, 1992.  相似文献   
8.
9.
Mixed-ligand NiIII complexes with -nitroso--naphthol, -nitroso--naphthol,o-ethylxanthate, andN,N-diethyldithiocarbamate as ligands have been studied by ESR in liquid and frozen solutions. The degrees of symmetry distortion for the first coordination sphere of these complexes have been determined. It is shown that the transition from planar square NiIIL2 complexes to more stable octahedral NiIIIL2L and NiIIILL2 complexes occursvia the radical addition mechanism. A method for trapping short-lived radicals is suggested on the basis of the complex formation scheme.Translted fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1513–1515, August, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5050)  相似文献   
10.
Substituted anilides of 1,4-dithiene- and oxathienecarboxylic acids were synthesized. It was shown that the reaction of 3-phenyl-1,4-dithi-2-ene-2-carboxyl chloride with 2-aminopyridines, depending on the base used and the reaction conditions, leads to the formation of N-[3-phenyl-2-(1,4-dithi-2-en)ylcarbonyl]2-amino-pyridine and/or N,N-bis[3-phenyl-2-(1,4-dithi-2-en)-ylcarbonyl]pyridonimine. The data of IR, UV, and PME spectroscopy were used to confirm the structure of the synthesized compounds.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Science Center, Russian Academy of Sciences. Kazan 420083. Translated fro, Khimiya Geterotskiklicheskikh Soedinenii, No. 9, pp. 1191–1196, September, 1994. Original article submitted May 10, 1994.  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