全文获取类型
收费全文 | 347篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学 | 258篇 |
晶体学 | 5篇 |
力学 | 18篇 |
数学 | 33篇 |
物理学 | 35篇 |
出版年
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 17篇 |
2013年 | 20篇 |
2012年 | 26篇 |
2011年 | 18篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 10篇 |
2005年 | 15篇 |
2004年 | 20篇 |
2003年 | 11篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
M. K. Bratenko Yu. V. Kadel’nik V. A. Chornous M. V. Vovk 《Russian Journal of Organic Chemistry》2008,44(2):247-250
Oximes of 4-(4-pyrazolyl)-3-buten-2-onees obtained by successive reaction of 3-aryl-4-formylpyrazoles with acetone and hydroxylamine at the treatment with iodine suffered an oxidative cyclization yielding 3-aryl-4-(5-isoxazolyl)pyrazoles. 相似文献
2.
3.
By reaction of 3-aryl(heteryl)-4-chloromethylpyrazoles with thiourea and sodium thiocyanate respectively 3-aryl(heteryl)-4-mercaptomethylpyrazoles and 3-aryl(heteryl)-thiocyanatomethylpyrazoles were obtained. The latter were subjected to thermal isomerization into 3-aryl(heteryl)-isothiocyanatomethylpyrazoles. 相似文献
4.
Ponomarenko S. P. Dul'nev P. G. Borovikov Yu. Ya. Sivachek T. E. Vovk D. N. 《Russian Journal of General Chemistry》2002,72(11):1743-1749
Complexes (1 : 2) of iron trichloride with N-oxides of pyridine, picolines, and 2,6-lutidine were studied by optical spectroscopy, dielectrometry, and conductometry. In solid complexes, three crystalline phases are in equilibrium; the nuclei of each of these phases can be detected in the oily state. The enthalpies of the coordination bonds are different in different phases. One of the phases of the 3-picoline N-oxide complex shows a strong orientation disorder; disappearance of the short-range order causes weakening of the coordination bonds by 1.6 kcal. The thermal motion of free base molecules in two phases of the 2,6-lutidine N-oxide complex is gaslike. In the solid phase of this complex, there is a strong distribution of the relaxation frequencies; the mean relaxation frequency is close to 220 Hz. Upon irradiation of the complexes with solar or UV light, specific coloration centers can form. Weak alternating electric fields initiate in some compounds reversible chemical reactions. The intermolecular and charge equilibria in the compounds are very labile; the energy of generation of the low-temperature electrical conductivity in them is close to 0.9 eV. 相似文献
5.
6.
1-Chlorobenzyl isocyanates react with 4-hydroxy-6-methylpyran-2-one and 4-hydroxycoumarin forming 4-aryl-3,4-dihydro-2H,5H-pyrano(chromeno)[3,4-e][1,3]oxazine-2,5-diones. The reaction of 1-aryl-2,2,2-trifluoro-1-chloroethyl isocyanates with the above substrates gives rise to structurally isomeric 2-aryl-2-trifluoromethyl-2,3-dihydro-2H,5H-pyrano(chromeno)[3,4-e][1,3]-oxazine-4,5-diones. 相似文献
7.
3-(3-Aryl-4-formyl-1-pyrazolyl)propionic acids are converted by Knoevenagel condensation under conditions of microwave activation
into 3-[3-aryl-1-(2-ethoxycarbonyl)-4-pyrazolyl]acrylic acids. Reduction of the latter with hydrazine hydrate in the presence
of Raney nickel gives 3-[3-aryl-1-(2-ethoxycarbonyl)-4-pyrazolyl]propionic acids.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 686–690, May, 2006. 相似文献
8.
3-Aryl(heteryl)-4-formylpyrazoles by condensation with malonic acid furnish 3-[3-aryl(heteryl)- pyrazol-4-yl]propenoic acids that in the presence of Raney nickel are reduced by hydrazine hydrate to 3-[3-aryl(heteryl)pyrazol-4-yl]propanoic acids. The successive conversion of both type acids into the corresponding acyl chlorides, esters, and amides was performed. 相似文献
9.
This paper presents the applicability of thin-layer chromatographic methods with a subsequent densitometric or video densitometric quantitation for determination of residues in controlling pharmaceutical equipment cleanliness. Analytical methods were developed for monitoring residues of pentoxifylline at 10 mg/M2 and mebendazol at 1 mg/M2 on stainless steel surfaces. Simulated samples were prepared by addition of a calculated amount of pharmaceutical (as a solution) on a 35 x 35 cm stainless steel surface. After evaporation of solvent, the residues were wiped with wetted cotton. The cotton was extracted with dichloromethan-methanol (1 + 1). Filtered extract was concentrated by vacuum evaporation and an aliquot applied to the plate, where standards were also applied. In the narrow concentration range near the acceptable residue limits, linear calibration curve could be obtained for both substances. The mean recovery (n = 4) obtained by densitometric quantitation was 93.4% for pentoxifylline and 85.6% for mebendazol, with coefficients of variation of 3.5 and 8.3%, respectively. Results of video densitometric quantitation did not differ significantly. However, data acquisition and evaluation is faster compared with densitometry and allows better archiving possibilities as required by the regulatory authorities. Both quantitation modes can be applied to routine control of pharmaceutical equipment cleanliness. 相似文献
10.
M. V. Vovk P. S. Lebed’ V. V. Pirozhenko I. F. Tsymbal 《Russian Journal of Organic Chemistry》2004,40(11):1669-1678
1-Chloroalkyl isocyanates and 1-chloroalkylcarbodiimides undergo regioselective cyclization with nitriles and esters of 2-benzimidazolylacetic acid to give derivatives of 1-oxo and 1-arylimino-1,2,3,5-tetrahydrobenzo[4,5]imidazo[1,2-c]pyrimidine respectively. The cyclocondensation of 1,1-dichloroalkyl isocyanates or N-(1-chloroalkylidene)carbamates with nitriles and esters of 2-benzimidazolylacetic acid afforded 1,5-dihydrobenzo[4,5]imidazo[1,2-c]pyrimidin-1-one derivatives.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 11, 2004, pp. 1715–1724.Original Russian Text Copyright © 2004 by Vovk, Lebed, Pirozhenko, Tsymbal.For communication III see [1]. 相似文献