全文获取类型
收费全文 | 512篇 |
免费 | 44篇 |
国内免费 | 81篇 |
专业分类
化学 | 545篇 |
力学 | 8篇 |
综合类 | 5篇 |
数学 | 20篇 |
物理学 | 59篇 |
出版年
2019年 | 2篇 |
2018年 | 2篇 |
2015年 | 2篇 |
2014年 | 29篇 |
2013年 | 47篇 |
2012年 | 45篇 |
2011年 | 9篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 19篇 |
2005年 | 22篇 |
2004年 | 29篇 |
2003年 | 35篇 |
2002年 | 85篇 |
2001年 | 193篇 |
2000年 | 32篇 |
1999年 | 20篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
排序方式: 共有637条查询结果,搜索用时 0 毫秒
181.
Hai Ying HE Chen Lin Cheng Xue ZHAO* Xi Kui JIANG* Department of Chemistry Shanghai Jiaotong University Shanghai Shanghai Institute of Organic Chemistry Shanghai 《中国化学快报》2001,(12)
It has been suggested about forty years ago that the transition states of polarographic potential-determining steps possess free radical character1. However, the dual-parameter correlation analysis [eqn. (1)] have never been successfully applied to the redox potentials until our recent report on five series of aromatic compounds shows that polarographic processes are affected by the polar effect as well as the spin-delocalization effect2. The purpose of this paper is to study the correlation… 相似文献
182.
Wei Ping HUANG Xiu Cheng ZHENG Shou Min ZHANG Xiao Hang QIU Wei WEI Bao Qing LI Shi Hua WU* Department of Chemistry NanKai University Tianjin 《中国化学快报》2001,(12)
Introduction Carbon monoxide is ubiquitous air pollutants emitted by many sources. Total oxidation of carbon monoxide to carbon dioxide is employed to meet environmental regulations in an economic way. Precious metals (Pt, Pd) are well-known oxidation catalysts with high activity and stability, and are widely used for exhaust gas emission control. However, the high cost of precious metals and their sensitivity to sulfur poisoning have long motivated the search for substitute catalysts. … 相似文献
183.
A New 24, 30-Dinortriterpenoid from Paeonia delavayi 总被引:4,自引:0,他引:4
Shao Hua WU Xiao Dong LUO Yun Bao MA Xiao Jiang HAO Da Gang WU* Laboratory of Phytochemistry Kunming Institute of Botany Chinese Academy of Sciences Kunming 《中国化学快报》2001,(4)
We reported some constituents from the plant of Paeonia delavayi Franch1. Further investigation on the chemical constituents of the same plant resulted in the isolation and determination of a new triterpenoid, 3(, 4(, 23-trihydroxy-24, 30-dinorolean-12, 20(29)-dien-28-oic acid 1, in addition to five known compounds, 2(, 3(, 23-trihydroxy-12-oleanen-28-oic acid-(-D-glucopyranosyl ester2, palbinone3, 2-hydroxy-benzoic acid4, vanillic acid4, syringic acid5. In this paper we describe the structur… 相似文献
184.
Xiao Peng ZHAN Lu MENG* Faculty of Chemistry Northeast Normal University Changchun Department of Chemistry Yangzhou College of Education Yangzhou 《中国化学快报》2001,(8)
In recent years, the research of peroxy polyoxometalates (POMs) has attracted increasing attention because of the two reasons. First, peroxy POMs are more active as oxygenation catalysts in some oxygen transfer reactions1~5. Second, recent research from our group and others has established that peroxy POMs are more active antiviral agents and less toxic both in vitro and in vivo than the parent metal-free POMs6. In order to entirely understand the properties and activities of peroxy POMs… 相似文献
185.
The principle of alternate adsorption can be used to design and control specific molecular architectures1. Protein-polyion layer-by-layer assembly opens a possibility of organizing proteins with specific molecular architectural plan1 and studying redox proteins with electrochemical methods2. Recently, we reported electrochemistry of layer-by-layer {PSS/Mb}n films grown on PG electrodes1. In this work, layer-by-layer {PDDA/Hb}n films were fabricated on PG electrodes. Electrochemistry and … 相似文献
186.
Synthesis, Structure of a Symmetrically Substituted Stilbene with Strong Two-photon Absorption and Up-converted Blue Fluorescence 总被引:1,自引:0,他引:1
Xiao Mei WANG Guang Yong ZHOU Wen Tao YU Min Hua JIANG * State Key Laboratory of Crystal Materials Shandong University Jinan 《中国化学快报》2001,(11)
Symmetric substituted stilbenes have significantly potential application such as fluorescence microscopy, two-photon photodynamic therapy, optical power limiting, and three-dimensional storage1-2. These dyes have strong tendency of symmetric intra-molecular change transfer under the excited state. As a result, they usually exhibit large two-photon absorptivity (TPA), in the meanwhile emit strong up-converted fluorescence. On the other hand, their solutions generally display linear transmis… 相似文献
187.
Cai Qin QIN Ling XIAO Yu Min DU* Department of Environmental Science Wuhan University Wuhan 《中国化学快报》2001,(12)
Borohydride exchange resin (BER) a useful reducing reagent has been used in reduction of some carbonyl compounds and acyl halides1. When BER combines with a transition metal catalyst, it can reduce C=C double bonds2, halides2, nitro compounds3, cyano, diazo3 and azide compounds4. The support of BER is the synthetic macromolecule polystyrene. Here, we used chitosan as the support of borohydride. As known, chitosan is a renewable and abundant natural polysaccharide. Scheme 1 Preparat… 相似文献
188.
Yu Xin CUI Qiang XIAO Peng Fei TU* Department of Natural Medicines School of Pharmaceutical Sciences Peking University Beijing Department of Chemistry Lanzhou University Lanzhou 《中国化学快报》2001,(3)
AIDS has seriously affected human being's health and about 13.9 million people have been killed by AIDS in the world. So far, A. Paris et al1 found that Carnosic acid and its analogs posses inhibitory effect on HIV-1 protease and HIV virus replication activity. In order to clarify the structure-active relationship of this kind of compounds, a concise approach was designed, which is a convergent synthesis. Best to our knowledge, it is the first successful convergent route in total synthes… 相似文献
189.
Jian Li HUA Wei ZHANG Jing Dong LUO Jin Gui QIN* Department of Chemistry Wuhan University Wuhan 《中国化学快报》2001,(5)
Organic second-order nonlinear optical (NLO) materials have been extensively studied for their potential application involving telecommunications, optical information process and storage1. It has been found that the molecular hyperpolarizability of the NLO chromophores varys dramatically depending upon the donor-acceptor abilities as well as the nature of the conjugated bridge.Carbazole molecule has an isoelectronic structure of diphenylamine, and thus the introduction of electron acceptor (… 相似文献
190.
Wei CAO Wei LIAN Yu Bai BAI Chun Yan LIU Hui Bo SHAO* Center for Intelligent Materials United Research 《中国化学快报》2001,(3)
Metal complexes, which are composed of metal ions and amphiphile ligands, show some structural peculiarities in Langmuir-Blodgett (LB) films. In the past studies, the metal complexes were mainly composed of the transitional metal ions1,2. The metal ions in IA, IIA and IIIA were seldom mentioned. Further more, the aluminium element is at the position where the typical metal elements transit to the typical non-metal elements in the periodic table of elements and study on the properties of … 相似文献