首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   173篇
  免费   0篇
  国内免费   50篇
化学   204篇
晶体学   2篇
综合类   3篇
物理学   14篇
  2023年   2篇
  2022年   3篇
  2021年   1篇
  2019年   1篇
  2017年   12篇
  2016年   2篇
  2015年   5篇
  2014年   7篇
  2013年   17篇
  2012年   9篇
  2011年   5篇
  2010年   8篇
  2009年   10篇
  2008年   10篇
  2007年   24篇
  2006年   10篇
  2005年   8篇
  2004年   13篇
  2003年   4篇
  2002年   16篇
  2001年   9篇
  2000年   4篇
  1999年   5篇
  1998年   8篇
  1997年   5篇
  1996年   5篇
  1995年   3篇
  1994年   4篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1985年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有223条查询结果,搜索用时 0 毫秒
11.
本文研究了马来酸酐(MAn)在过氧化苯甲酰(BP)引发作用下与醋酸乙烯酯(VAc)的交替共聚反应。红外光谱证明了交替共聚物的结构,分析结果表明共聚物是由反应单体技1:1摩尔比例组成。当c(BPO)=6.8×10~(-3)moi/L,c(VAc)=3.4×10~(-3)mol/L,p(MAn)=32.7g/L,63~65℃反应18小时,转化率可达92%以上。  相似文献   
12.
正丁烷氧化制顺酐Ce基复合氧化物VPO催化剂研制   总被引:3,自引:0,他引:3  
张丰胜  杨廷录 《分子催化》2000,14(4):260-264
在用共沉淀方法制备的Ce-Fe复合氧化物中,加入VPO化剂制备复合VPO催化剂;井测试结构、氧化还原性能以及催化性能。实验结果表明,Ce-Fe复合氧化物的组成和数量均对复合VPO催化剂的结构产生较大的影响,Ce-Fe复合氧化物的加入,提高了复合VPO催化剂表面低温氧物种的活性,降低了品格氧物种的TPR出峰温度,无论在有无气相氧条件下,复合VPO催化剂的晶格氧均有良好的反应催化性能。  相似文献   
13.
采用稀土配位催化剂研究了马来酸酐、苯乙烯和N 苯基马来酰亚胺的三元共聚合反应 .考察了Al La物质的量的比、不同稀土元素、催化剂浓度、聚合反应时间、单体配比等因素对共聚合反应的影响 .利用核磁、红外、热分析等方法对共聚物进行了初步的表征  相似文献   
14.
间规聚苯乙烯的化学改性   总被引:4,自引:0,他引:4  
介绍了间规聚苯乙烯(sPS)的结构,特性和各种化学改性方法,包括在sPS侧链苯环上引入磺酸基,卤素等功能基因,在sPS分子链末端引入马来酸酐,丙烯酸酯等极性基因,与氢化丁二烯-苯乙烯热塑性弹性体(SEBS)形成接枝共聚物,及其与各类烯烃单体的共聚,对进一步拓宽sPs的应用领域具有重要意义。  相似文献   
15.
Polypropylene ionic thermoplastic elastomers have been prepared by melt radical grafting of maleic anhydride onto polypropylene in the presence of N-bromosuccinimide followed by neutralization of the resulting elastomeric grafted polypropylene using sodium salts. Sodium hydroxide and sodium acetate were compared in aqueous solution, as anhydrous or hydrated powders. The neutralization reaction was followed by Fourier transform infrared spectroscopy, allowing the development of a method to determine the effective neutralization degree. Important physical changes were recorded upon neutralization. Especially thermal stability, shear storage modulus and complex viscosity in the flow region were largely increased as a function of the neutralization degree.  相似文献   
16.
High-throughput experimentation was used for the functionalization of polybutadiene and polyisoprene with several kinds of nitroxide moieties at 135 °C, as well as for kinetic investigations of the controlled free radical grafting of styrene and maleic anhydride onto the functionalized polydienes at 125 °C. The functionalized polymers were analyzed by GPC, 1H NMR and FT-IR and the control of the grafting process was assessed by kinetic measurements and GPC analysis. The best control in the molecular weight of the grafts was observed for the polydienes functionalized with 4-oxo-TEMPO. TEMPO functionalization did not render sufficient nitroxide moieties to achieve controlled grafting, while polydienes functionalized with other 4-hydroxy TEMPO derivatives exhibited some level of grafting control at early reaction times, which was lost in later stages of the polymerization reaction. SG1 apparently decomposed at the tested reaction temperatures, as polydienes functionalized with SG1 did not show any level of control during the grafting process.  相似文献   
17.
In this study, the functionality of maleic anhydride was utilized in the maleic anhydride-styrene-methyl metacrylate (MAStMMA) terpolymer. First, the polyester of poly(ethylene adipate), PEA, polycondensation copolymer was synthesized from ethylene glycol and adipic acid monomers. PEA was then modified on its maleic anhydride units in the MAStMMA terpolymer which has been synthesized previously. This modified copolymer was characterized by FTIR (Fourier Transform Infrared spectroscopy). The viscosimetric and thermomechanical characterization of MAStMMA terpolymer and its modified copolymer were also performed and the results were compared. The modified copolymer obtained was found to be more elastic and more soluble, and had lower viscosity and density.  相似文献   
18.
A series of novel liquid crystalline epoxides with lateral substituents were cured with anhydrides and the cure kinetics was investigated by non-isothermal DSC technique. The results showed that the lengths of lateral substituents have great effect on the value of Ea. The curing reaction became less active, when the liquid crystalline epoxides have long lateral substituents and were controlled by diffusion at the late stage of cure. A nematic structure was observed by POM and XRD.  相似文献   
19.
Fe-Al络合催化苯乙烯-马来酸酐交替共聚   总被引:10,自引:1,他引:10  
应用Fe(acac)3 Al(i Bu)3(acac=乙酰丙酮)催化苯乙烯 马来酸酐共聚,制得富于交替的白色粉末共聚物.共聚反应动力学研究表明,共聚反应与单体浓度呈一级关系,表观活化能为486kJ/mol.  相似文献   
20.
本实验测定了二苄基马来酸酯甲醇溶液的荧光光谱,并发现马来酸酐对该荧光体系有猝灭作用,通过对不同马来酸酐浓度与各种浓度的二苄基马来酸酯甲醇溶液在400nm处荧光强度数据的分析,发现马来酸酐的浓度与荧光猝灭程度在一定范围内呈良好的线型关系。据此,提出了用荧光猝灭法对马来酸酐及二苄基马来酸酯的定量分析  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号