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   214篇
  免费   2篇
化学   127篇
晶体学   1篇
力学   13篇
数学   24篇
物理学   51篇
  2022年   4篇
  2021年   11篇
  2020年   7篇
  2019年   8篇
  2018年   9篇
  2017年   7篇
  2016年   12篇
  2015年   3篇
  2014年   1篇
  2013年   9篇
  2012年   11篇
  2011年   15篇
  2010年   5篇
  2009年   3篇
  2008年   11篇
  2007年   16篇
  2006年   8篇
  2005年   8篇
  2004年   6篇
  2003年   6篇
  2002年   3篇
  2001年   1篇
  2000年   1篇
  1996年   3篇
  1995年   7篇
  1994年   3篇
  1993年   4篇
  1992年   2篇
  1990年   2篇
  1989年   4篇
  1988年   2篇
  1986年   2篇
  1985年   3篇
  1984年   4篇
  1983年   4篇
  1978年   1篇
  1975年   2篇
  1974年   4篇
  1972年   2篇
  1970年   1篇
  1969年   1篇
排序方式: 共有216条查询结果,搜索用时 62 毫秒
1.
The chelate oxides of bis(trimethylantimony) (Me3SbL1)2O (i = 1 or 2, L1-acetylacetonate, L2 - trifluoroacetylacetonate) and bis(triethylantimony) (Et3SbL1)2O have been obtained in 79–85% yields by a one-step oxidation of trialkylantimony withtertbutylhydroperoxide in the presence of -diketones in benzene at 20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 154–155, January, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 94-03-08846).  相似文献   
2.
Conclusions Iodonitromethane forms n complexes with organic ligands with low127I asymmetry parameters and positive charge on the iodine atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2790–2792, December, 1984.  相似文献   
3.
Black single crystals of Ta(4)Se(9)I(8) are obtained in a high yield by heating Ta, Se, and I(2) at 300 degrees C in 1:2.2:1.0 molar ratio. In the structure, the tantalum atoms form a square, with four Se(2) ligands bridging the Ta-Ta edges and one capping the square. Each Ta atom has two terminal iodine atoms. The compound is diamagnetic and has only two electrons for metal-metal bonding.  相似文献   
4.
The polarization observables Σ,P y ,T 1,P y ,P y are derived in proton polarization measurements of the \(\vec \gamma d \to \vec pn\) reaction, using a linearly polarized photon beam of energies between 300 and 600 MeV for c.m.s. proton emission angles of 90° and 120°. A multipole analysis is performed in the framework of the gauge-invariant pole model considering theγN→πN amplitudes and the deuteron structure without dibaryon resonances and with different sets of isovector and isoscalar dibaryon resonances. It is shown that the inclusion of dibaryon resonances substantially improves agreement with experimental data.  相似文献   
5.
The processes of degradation of 2,4-dichlorophenol (2,4-DCP) aqueous solutions under the action of atmospheric pressure of DBD in oxygen were studied. The degradation of 2,4-DCP proceeds efficiently, the degree of decomposition reaching 100%. The degradation kinetics of 2,4-DCP obeys a formal first-order kinetic law on concentration of 2,4-DCP. The effective rate constants depend weakly on the experimental conditions and are equal to ~ 2 s?1. Based on experimental data, the energy efficiency of 2,4-DCP decomposition was determined to be in the range of 0.039–0.173 molecules per 100 eV depending on the experimental conditions. The composition of the products was studied by gas chromatography, chromatography-mass spectrometry, UV/visible spectroscopy, fluorescent methods and some chemical methods. The main decomposition products present in the solution were found to be carboxylic acids, aldehydes and chloride ions, whereas carbon dioxide and molecular chlorine appear in the gas. The results obtained are compared with similar data from other advanced oxidation processes (AOP’s) methods.  相似文献   
6.
A method of resonant near-field microwave probing is developed for contactless diagnostics of a high-pressure plasma. The efficiency of this method in measuring the parameters of the plasma of an rf capacitive discharge in argon under atmospheric pressure is demonstrated. The experimental results are compared with the data obtained using the independent method, the microwave radiation “cutoff,” and with theoretical estimates.  相似文献   
7.
The known phosphonium chloride [HO(Me)CH]4PCl was prepared at ambient conditions from PH3 and acetaldehyde in aqueous HCl, and characterized by elemental analysis and 1H and 31{1H} NMR spectroscopy. Attempts to obtain the tertiary phosphine [HO(Me)CH]3P via reaction of [HO(Me)CH]4PCl with Na2SO3 or Et3N in aqueous media under Ar revealed that [HO(Me)CH]3P is unstable and equilibrates with the secondary phosphine [HO(Me)CH]2PH and acetaldehyde. A 1:4 reaction of [HO(Me)CH]4PCl with NaHSO3 at room temperature under Ar affords first the oxide [HO(Me)CH]2P(O)H and then the phosphinic acid [HO(Me)CH]2P(O)OH. A 1:1 reaction of [HO(Me)CH]4PCl with Na2S2O3 affords the sulfide [HO(Me)CH]3PS. 31{1H} and 1H NMR data for all the (α-hydroxyethyl)phosphorus species are reported for the first time.  相似文献   
8.
Russian Journal of General Chemistry - Tetraphenylantimony methacrylate Ph4SbO2CC(CH3)=CH2 and tetraphenylantimony crotonate Ph4SbO2CCH=CHCH3 were synthesized by the action of acids on Ph5Sb or on...  相似文献   
9.
Results of study of the $K^ - \to \pi ^0 e^ - \overline \nu \gamma $ decay at the ISTRA+ setup are presented. We observed 4476 events of this decay. The branching ratio is found to be $R = \frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (1.81±0.03(stat.)±0.07(syst.)) × 10?2 for E*γ > 10 MeV and θ* > 10°. For comparison with the previous experiment the branching ratio with cuts E*γ > 10 MeV, 0.6 < cos θ* < 0.9 is calculated: R = $\frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (0.47±0.02(stat.) ± 0.03(syst.)) × 10?2. For the cuts E*γ > 30 MeV and θ* > 20°, used in most theoretical papers, Br = (3.06 ± 0.09(stat.) ± 0.14(syst.)) × 10?4. For the asymmetry we get A ξ = ?0.015 ± 0.021. At present it is the best estimate of this asymmetry.  相似文献   
10.
Journal of Structural Chemistry - The structure of a binuclear niobium(IV) thiocyanate complex (Bu4N)4[Nb2(μ2-S2)2(NCS)8]·H2O (1·H2O) is studied by X-ray crystallography. Compound...  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