全文获取类型
收费全文 | 54篇 |
免费 | 3篇 |
国内免费 | 9篇 |
专业分类
化学 | 37篇 |
力学 | 3篇 |
数学 | 15篇 |
物理学 | 11篇 |
出版年
2022年 | 1篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1975年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有66条查询结果,搜索用时 0 毫秒
61.
The molecule of 4-tricyanovinyl-N,N-diethylaniline is disordered about an axis that is close to the axis passing through the 1,4-carbon atoms. The disorder is a 1:1 type of disorder that involves only part of the molecule as the diethylamino substitutent and the three nitrogen atoms of the tricyanovinyl substituent are ordered. The treatment of the nearly ‘whole-molecule disorder’ by employing a small number of restraints is described. Crystal data: C15H14N4, triclinic, P , a = 7.1996(5), b = 7.7232(5), c = 12.4171(8) , α = 99.350(1), β = 94.647(1), γ = 103.312(1)o and V = 657.90(8) 3 at –173 K. 相似文献
62.
Hydrazonyl bromides 2a,b reacted with active methylene compounds (dibenzoylmethane, acetylacetone, ethyl acetoacetate, phenacyl cyanide, acetoacetanilide, ethyl cyanoacetate, cyanoacetamide and malononitrile) to afford the corresponding 1,3,4,5- tetrasubstituted pyrazole derivatives 5-12a,b. Reaction of 12a,b with formamide, formic acid and triethyl orthoformate give the pyrazolo[3,4-d]pyrimidine, pyrazolo[3,4- d]pyrimidin-4(3H)one and 5-ethoxymethylene-aminopyrazole-4-carbo-nitrile derivatives 13-15a,b, respectively. Compounds 15 a,b reacted with benzhydrazide and hydrazine hydrate to afford pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine and [4-iminopyrazolo- [3,4-d]pyrimidin-5-yl]amine derivatives 16 a,b and 17 a,b. Reactions of compounds 17 a,b with triethyl orthoformate and carbon disulfide give the corresponding pyrazolo[4,3-e]- [1,2,4]triazolo[1,5-c]pyrimidine derivatives 18a,b and 19 a,b, respectively. 相似文献
63.
从含4,4'-二吡啶胺结构单元的双(二吡啶胺) 桥联配体出发,采用溶剂热法合成了两个结构新颖的配位聚合物:[CdL1Br2]n?7.5nH2O (L1 = N,N,N′,N′-四(4-吡啶)-1,4-苯二胺) (1)和[Cu2L2(μ1,1,3-SCN)2]n?nMeOH (L2 = N,N-二(2-吡啶)-N',N'-二(4-吡啶)-1,4-苯二胺) (2),对它们进行了元素分析、红外光谱等表征,并用X-射线单晶衍射测定了其晶体结构。单晶测试结果显示,配合物1中配体L1的四个吡啶N原子均参与配位,桥联了4个Cd原子,每个Cd原子与四个吡啶 N 原子和两个溴配位,形成六配位的八面体构型。通过这些配位作用,最终形成包含 Kagome 结构的三维超分子网络。配合物2 是由一维柱状 {Cu(SCN)}n 链通过 L2 桥联生成的二维结构。有趣的是,L2中具有螯合能力的2,2'-二吡啶胺单元并未参与配位,只有4,4'-二吡啶胺单元中的两个吡啶N原子分别与一个 Cu(I) 配位,连接了相邻两条平行的{Cu(SCN)}n 链,生成二维结构。 相似文献
64.
Rasha A. El-Ghazawy Ahmed M. Al-Sabagh Nadia G. Kandile Mahmoud R. Noor El-Din 《Journal of Dispersion Science and Technology》2013,34(10):1423-1431
Three raw fatty oils were used as precursors for demulsifiers. The hydrolyzed form of each oil was adducted with maleic anhydride then modified by esterification with polyethylene glycols or ethyleneoxide-propyleneoxide block copolymers. The demulsfication efficiency, coalescence rate, some surface active, thermodynamic properties, and partition coefficient of a selected demulsifier were investigated. The best demulsifier shows 100% demulsification after 19 minutes at 300 ppm. A correlation between demulsification efficiency and rheological properties of the investigated demulsifier was investigated. Also, emulsification kinetics were followed by microscopic photography. A mechanism following coalescence and flocculation of water droplets is proposed. 相似文献
65.
66.
N. G. Kandile H. T. Zaky M. I. Mohamed Abdel‐Sattar S. Hamad Elgazwy 《Heteroatom Chemistry》2003,14(4):334-341
4,6‐Disubstituted pyridazin‐3(2H) thiones 3a–f were prepared by thiation of 4,6‐disubstituted pyridazin‐3(2H)‐one 1a–f either with thiourea or phosphorus pentasulphide. The reactivity of 3a‐f towards nucleophilic and electrophilic species under different conditions was studied successively. The structure of the products was confirmed by NMR and mass spectral data. Mechanisms for their formation are also proposed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:334–341, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10157 相似文献