全文获取类型
收费全文 | 309篇 |
免费 | 32篇 |
国内免费 | 50篇 |
专业分类
化学 | 340篇 |
晶体学 | 2篇 |
综合类 | 2篇 |
数学 | 1篇 |
物理学 | 46篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 21篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有391条查询结果,搜索用时 15 毫秒
41.
Novel cationic palladacycles based on benzylidene-2,6-diisopropylphenylimines were prepared via C-H activation using Pd(CH3CN)2Cl2 as metal precursor. The complexes were fully characterized by IR and NMR spectroscopy, mass spectrometry and elemental analysis. The cationic palladacycles were found to be active catalysts for the polymerization of phenylacetylene producing largely trans-cisoidal PPA. 相似文献
42.
43.
Raymond Ziessel 《Journal of inclusion phenomena and macrocyclic chemistry》1999,35(1-2):369-379
Two unique systems are described where modification of the photophysical properties is observed in the presence of an adventitious cation. In the first system an enhancement of the emission properties of linear ruthenium(II) bis-terpyridine bearing a central chelating centre is found. In the second system restoration of the emissive properties of the chromophore is observed due to a conformation control of intramolecular electron transfer in a calix[4]quinone bearing an appended ruthenium(II) tris-bipyridine chromophore. 相似文献
44.
A mechanistic study on the Nieuwland catalysis for dimerization of acetylene is performed by detecting copper–acetylene and copper–monovinylacetylene π‐complexes and also by examining the kinetics under virtually the same reaction conditions employed in the industrial process. An efficient H/D exchange occurs between acetylene and protons in the Nieuwland catalytic system. Addition of a coordinating ligand to the conventional Nieuwland catalytic system results in improvement of the catalytic activity and selectivity for the acetylene dimerization. The kinetic analysis including the kinetic deuterium isotope effect provides valuable insight into the Nieuwland catalytic mechanism of the dimerization of acetylene. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
45.
A. B. Zaitsev E. Yu. Shmidt A. M. Vasil’tsov A. I. Mikhaleva A. V. Afonin I. A. Ushakov D.-S. D. Toryashinova 《Chemistry of Heterocyclic Compounds》2005,41(4):444-448
The oxime of 2-acetylcoumarone reacts with acetylene under pressure in the system KOH-DMSO unusually readily forming 2-(2-pyrrolyl)coumarone and the corresponding O-vinyl oxime. Under more rigid conditions 2-(1-vinyl-2-pyrrolyl)coumarone is formed. The possibility of a two-stage transformation of 2-acylcoumarones into 2-pyrrolylcoumarones has therefore been demonstrated for the first time.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 524–529, April, 2005. 相似文献
46.
47.
SHEN ChangSheng SUN YongZhi SUN DeKun & YANG HongSheng State Key Laboratory of Millimeter Waves School of Electronic Science Engineering Southeast University Nanjing China School of Chemistry Chemical Engineering Nanjing University Nanjing 《中国科学:化学》2010,(1)
By optimizing the microwave chemistry reactor made of the rectangular waveguide resonator,the methane conversion(the maximum 93.7%),the C2 hydrocarbon yield(the maximum 91.0%) and the acetylene yield(the maximum 88.6%) were all greatly increased under the microwave plasma.Furthermore,for the optimal reactor,the change of the methane conversion and the C2 hydrocarbon yield is little within the range of the pressures in the experiments.The C2 hydrocarbon is mainly made up of acetylene,and the selectivity for ... 相似文献
48.
Xiaofeng Luo Xiaoqing Liu Bo Chen Jianping Deng Wantai Yang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5611-5617
A facile methodology was developed to prepare a novel type of core/shell nanoparticles (NPs) with optical activity and with chemical bonds between the cores and shells. The cores were prepared via catalytic emulsion copolymerization of substituted acetylene comonomers in which one monomer contains azo groups in side chains. For preparing the core/shell NPs, the azo groups in the seed particles (i.e., cores) subsequently act as initiators for vinyl monomer to undergo free radical polymerizations, yielding the shells. This situation resulted in chemical bonds between cores and shells. Both the seed emulsion and core/shell nanoparticle emulsion exhibited optical activity, derived from the polyacetylenes adopting helical conformation of predominant handedness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
49.
Wilkinson's complex [RhCl(PPh3)3], anchored to phosphino-organosiloxane macromolecules grafted onto chrysotile asbestos, appeared to be an unusually effective and selective catalyst for the synthesis of vinylsilanes via gas-phase hydrosilylation of acetylene, particularly by methyldichlorosilane in a continuous-flow microreactor as well as in a laboratory reactor. Catalytic and kinetic parameters show an advantage for the catalyst based on the chrysotile-polyorganosiloxane support (catalyst CHR–Rh) over the phosphinated silica (catalyst A). 相似文献
50.