全文获取类型
收费全文 | 414篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 262篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 72篇 |
物理学 | 82篇 |
出版年
2019年 | 4篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 7篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 16篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1996年 | 6篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 7篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1955年 | 2篇 |
1952年 | 2篇 |
排序方式: 共有423条查询结果,搜索用时 15 毫秒
101.
102.
M. R. Banks J. I. G. Cadogan I. M. Dawson I. Gosney K. J. Grant S. Gaur P. K. G. Hodgson D. E. Stevenson 《Chromatographia》1992,34(1-2):48-50
Summary Chromatographic separation of racemic amines, carboxylic acids and alcohols can be achieved with excellent resolution as measured in terms of the chromatographic separation factor by derivatization with a homochiral oxazolidin-2-one easily prepared in three steps fromendo-borneol. The resolved materials can be isolated in excellent yields by cleavage of the resultant diastereomers using conventional methods, which also allow recovery of the chiral resolving agent for re-use. 相似文献
103.
104.
105.
Banks T 《Physical review D: Particles and fields》1995,52(4):2462-2465
106.
The relative rates of reaction of thiirane and thiirane derivatives with NH3, a series of secondary amines including aziridine, and trimethylamine were determined in the gas phase by means of B3LYP/6-31+G(d)//HF/6-31+G(d) computations and transition state theory. Convergence of the results was selectively tested using the 6-311++G(d,p) basis set. Comparison with MP2/6-31 + G(d)//MP2/6-31G(d) computations was made in model cases. These results are significant in that they supplement the only reported gas-phase experimental study of this type of reaction. The reaction rates of thiirane with secondary amines can best be rationalized by means of an interplay of steric and polarizability effects. While beta-halo substituents retard S(N)2 reactions in solution, both 2-fluorothiirane and its acyclic model react more than l0(6) times faster with NH3 than the unsubstituted compounds in the gas phase. 2-Fluorothiirane was calculated to react with NH3 at C2 by a factor of 0.142 with respect to thiirane itself; attack at C3 was found to be 3.42 x 10(6) times faster than the parent compound. 2-Methylthirane reacts with NH3 at 0. 230 the rate of thiirane with a 12.8-fold regioselectivity for C3. In the reaction of 2,2-dimethylthirane and NH3, this preference for C3 increases to a factor of 124. Ground-state destabilization of cis-2,3-dimethylthiirane is sufficient to account for its calculated rate acceleration with respect to the trans isomer. 相似文献
107.
Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sites 总被引:3,自引:0,他引:3
Banks CE Davies TJ Wildgoose GG Compton RG 《Chemical communications (Cambridge, England)》2005,(7):829-841
Carbon, and particularly graphite in its various forms, is an attractive electrode material. Two areas of particular interest are modified carbon electrodes and carbon nanotube electrodes. In this article we focus on the relationship between surface structure and electrochemical and chemical reactivity of electrodes based on these materials. We overview recent work in this area which has led us to believe that much of the catalytic activity, electron transfer and chemical reactivity of graphitic carbon electrodes is at surface defect sites, and in particular edge-plane-like defect sites. We also question the claimed special "catalytic" properties of carbon nanotube modified electrodes. 相似文献
108.
1,2,3,4,7,7-Hexafluorobicyclo[2,2,1]hepta-2,5-diene gave 1,2,3,4-tetrafluorebenzene in at least 73% yield when heated to 450°C in a sealed tube; the CF2 bridge appeared, in part, as octafluorocyclobutane. Nucleophilic attack by sodium methoxide- methanol on the diene occurred exclusively at the CFCF bond, causing the formation of 1,2,4,7,7-pentafluoro-3-methoxybicyclo- [2,2,1]hepta-2,5-diene and a 1,4,5,6,7,7-hexafluoro-5-methoxybicyclo [2,2,1]hept-2-ene thought, on the basis of 19F nmr data, to be the 6--F,5--MeO isomer. Radical attack on 1,2,3,- 4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene by bistrifluoromethyl nitroxide took place at both olefinic sites, with a . 10:1 preference for the CFCF linkage; all three geometrical isomers of 5,6-bis(bistrifluoromethylamino-oxy)-1,4,5,6,7,7- hexafluorobicyclo[2,2,1]hept-2-ene were formed. 相似文献
109.
Alexander Goodwin Craig E. Banks Dario Omanovi? Richard G. Compton 《Analytica chimica acta》2005,533(2):141-145
Cathodic stripping voltammetry at a boron-doped diamond electrode utilising an insonated accumulation protocol is shown to be possible for the on-site trace detection of free manganese in seawater samples. No sample pre-treatment is required with the application of ultrasound providing a sensitive and selective protocol for the analysis of manganese. The protocol is used in the evaluation of manganese in seawater samples taken near the site of a former ferromanganese factory in the town Šibenik, Croatia. 相似文献
110.
A rapid polarographic method for determining low milligram quantities of indium in lead metal containing 2% of zinc and in zinc metal containing 2% of lead is described. In a supporting electrolyte of 10% D-tartaric acid adjusted to pH 2.0, a well-defined wave for indium is obtained after the precipitation of lead as the sulfate. 相似文献