全文获取类型
收费全文 | 551篇 |
免费 | 54篇 |
国内免费 | 93篇 |
专业分类
化学 | 566篇 |
力学 | 9篇 |
综合类 | 26篇 |
数学 | 26篇 |
物理学 | 71篇 |
出版年
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 32篇 |
2013年 | 47篇 |
2012年 | 44篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 20篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 23篇 |
2004年 | 32篇 |
2003年 | 39篇 |
2002年 | 88篇 |
2001年 | 200篇 |
2000年 | 34篇 |
1999年 | 23篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有698条查询结果,搜索用时 15 毫秒
1.
胡敏 《武汉大学学报(理学版)》2003,(4)
●一水杨酸铜的流变相合成及表征 (RheologicalPhaseSynthesisandCharacterizationofCopperMonosalicyate) P .4 2 5~ 4 2 7杨毅涌 ,李良超 ,袁良杰 ,孙聚堂 ,张克立(武汉大学化学与分子科学学院 ,湖北武汉 4 30 0 72 )摘 要 :采用流变相反应法由水杨酸和氧化铜合成了一种具有新型结构的一水杨酸铜Cu(OC6H4CO2 )·H2 O .用粉末X射线衍射和红外光谱法表征了其晶体结构 ,研究了它的磁性和热分解反应 .Cu(OC6H4CO2 )·H2 O的晶体结构属单斜晶系 ,计算的晶胞参数为 :a =2 .136 2 8(6 7) ,b=0 .6 5 784 (2 2 ) ,c =1.5 94 0 9(5 0 )n… 相似文献
2.
Jing Lin CHEN Gang Qiang YIN Zhong Ning CHEN* State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Fuzhou 《中国化学快报》2003,(5)
Great attention is currently paid to the synthesis of polynuclear transition metal complexes as well as their photochemical, photophysical, and electrochemical properties. The design of multicomponent systems capable of performing useful light- and/or redox-induced function is of special interest1. The oxo-centered carboxylate-bridge trinuclear ruthenium clusters have been investigated extensively during recent decades because they have remarkable electron-transfer properties, intense visibl… 相似文献
3.
4.
Jing Ping WANG Qiang WU Jing Yang NIU* School of Chemistry Chemical Engineering Henan University Kaifeng 《中国化学快报》2002,13(9):915-918
It is becoming a focus to synthesize and assemble organic-inorganic materials, especially, to synthesize charge-transfer complexes formed by polyoxometalate and organic donors. They have attracted much attention because such complexes are active in their electric, magnetic and optic properties1-4, many investigations about them have been done and some crystal structures of them were reported5-6. But, the disadvantage of these crystals is instability at room temperature. According to the view… 相似文献
5.
Structural Features of a Polysaccharide from Centella asiatica 总被引:3,自引:0,他引:3
Xue Song WANG Jin You DUAN Ji Nian FANG* Shanghai Institute of Materia Medica Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 《中国化学快报》2004,15(2):187-190
Centella asiatica has been used as remedy for sodation, stabilization and against lepra, anabrosis1 in the oriental countries. The low-molecular-weight constituents in Centella asiatica have been investigated1. However, no polysaccharides have been reported. 1BI was the first polysaccharide isolated from C. asiatica, which had immunostimulating activity in vitro. In present study, we report the structural features of 1BI. Experimental Extraction, isolation and purification Dried C.… 相似文献
6.
Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process 总被引:3,自引:0,他引:3
YANG Donghui* HE Deping*& YANG Shangrun* . Department of Materials Science Engineering Southeast University Nanjing China . Department of Chemistry Nanjing University Nanjing China 《中国科学B辑(英文版)》2004,47(6):512-520
Metal foams, now one of research foci, are a newclass of materials with low densities and novel physi-cal, mechanical, thermal, electrical and acoustic prop-erties[1—8]. Demands from high-tech make Al alloyfoam, which has much higher specific strength than ofpure Al foam, the new development focus[9—11]. Melt foaming process is one of the approaches tofabricate Al foam and Al alloy foam and their porestructure (pore diameter and porosity) has close rela-tionship with the thermal decompo… 相似文献
7.
XU Long Ya * WANG Qing Xia LIN Li Wu XU Yi De Dalian Institute of Chemical Physics The Chinese Academy of Sciences Dalian Liaoning 《天然气化学杂志》1998,7(1):7-15
Ni/Si2催化剂具有较好的低碳烷烃与二氧化碳重整制合成气的反应性能,添加La2O3助剂和K2O助剂可提高催化剂活性和合成气收率,从而进一步改善催化剂的低碳烷烃与CO2重整制合成气的反应性能,研制的KLaNi/Si2催化剂,用于天然气与CO2重整反应制合成气可达97%的低碳烷烃转化率和95%以上的合成气收率。 相似文献
8.
Jun JIA Xing Wang WANG Yi Li ZHAO Yu ZHU Jing Chao TAO* Department of Chemistry Zhengzhou University Zhengzhou Chemical Engineering Institute of Henan Province Zhengzhou 《中国化学快报》2004,15(3):292-295
Proteins containing dinuclear Cu (II), Zn (II) centers play paramount roles in biology1. As mimetic of metal-dependent esterase, dinuclear Cu (II) and Zn (II) complexes have received a great deal of attentions2~6. They are of interest in the field of biomimetic chemistry to provide an improved understanding of the function of the biological sites and as potential catalysts for substrate oxidations. Schiff base type polydentate ligands which contain centeral hydroxyl group have been wid… 相似文献
9.
Yan Wu LI Liang HUANG* Institute of Materia Medica Chinese Academy of Medical Sciences & Peking Union Medical College Beijing 《中国化学快报》2002,13(10)
The natural product, hainanolide 1, also under the name harringtonolide2 demonstrated antitumor and antiviral activities in preliminary test. Its structure was determined by X-ray diffraction. The total synthesis of 1 was reported recently by Mander3. A different scheme of its synthesis has been studied in our laboratory4. Here the determination of the stereochemical structure of the key intermediate 2 in the synthesis was reported. HMBC and HMQC spectra identified the skeleton and H,… 相似文献
10.
Xiao Hong YAN Yue Wei GUO* State Key Laboratory of Drug Research Institute of Materia Medica Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 《中国化学快报》2005,16(3)
Marine organisms have been found to be a storehouse of steroids, particularly in term ofunique side-chain structures and unusual functionalization. Marine steroids are oftenfound in highly oxygenated forms and possessing various biological activities1.Previously, we reported the isolation and structural elucidation of three new marinesteroids, nanjiols A-C, which showed cytotoxicity against HL-60 and BEL 7402 celllines, from a soft coral Nephthea bayeri in East China Sea2. In continuation … 相似文献