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   297篇
  免费   12篇
  国内免费   64篇
化学   342篇
晶体学   2篇
力学   1篇
综合类   6篇
物理学   22篇
  2022年   5篇
  2021年   2篇
  2020年   5篇
  2019年   3篇
  2018年   5篇
  2017年   11篇
  2016年   8篇
  2015年   9篇
  2014年   10篇
  2013年   34篇
  2012年   13篇
  2011年   7篇
  2010年   5篇
  2009年   6篇
  2008年   18篇
  2007年   15篇
  2006年   15篇
  2005年   24篇
  2004年   17篇
  2003年   20篇
  2002年   17篇
  2001年   8篇
  2000年   20篇
  1999年   17篇
  1998年   14篇
  1997年   7篇
  1996年   5篇
  1995年   14篇
  1994年   5篇
  1993年   11篇
  1992年   7篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1980年   3篇
排序方式: 共有373条查询结果,搜索用时 15 毫秒
131.
用3 氨丙基三乙氧基硅烷(APTES)作为偶联剂,通过溶胶 凝胶(Sol Gel)过程制得两相以共价键结合的透明苯乙烯 顺丁烯二酸酐共聚物/SiO2杂化材料.通过FTIR分析等证实了材料有机相与无机相间是以共价键结合的.分析了材料热处理温度和分别用盐酸或氨水作催化剂时对材料溶胶分数的影响、偶联剂及其用量对溶胶 凝胶体系凝胶时间的影响、并研究了杂化材料中无机含量对材料折射率和Tg的影响  相似文献   
132.
133.
刘蒲  刘晔 《应用化学》1999,16(1):58-61
开发了一种由顺酐直接加氢高选择性及高转化率制备琥珀酸酐的新方法,研究结果表明:钯三苯基膦催化体系对顺酐加氢具有较高的反应活性.在所考察的反应条件下,此催化剂体系对琥珀酸酐的选择性为100%,无其他副产物生成.并考察了三苯基膦/钯摩尔比,反应温度,氢气压力,催化剂和顺酐浓度对顺酐催化加氢生成琥珀酸酐的影响.在反应条件为PdCl2=125×10-3mol/L,n(顺酐)/n(Pd)≤2000,n(三苯基膦)/n(Pd)=4,T=373~393K,25MPa的氢压下于乙二醇二甲醚溶剂中反应1h以上,可使顺酐的转化率大于90%.  相似文献   
134.
This paper describes the nonisothermal crystallization of molten blends of two semicrystalline polymers, polypropylene (PP) and Nylon-6 (N6). A discussion details the effect of the concentration of the compatibilizing agent, maleic anhydride grafted polypropylene (MAH-g-PP), on the crystallization behavior. The crystallization thermograms showed one crystallization peak or two crystallization peaks, which were significantly affected by the presence of MAH-g-PP. The crystallization temperature of N6 levels off down as the concentration of MAH-g-PP increases, whereas that of PP stays at a roughly constant temperature. These blends containing the compatibilizing agent exhibited concurrent crystallization at the crystallization temperature of PP. The crystallization behavior are also studied by optical microscopy under crossed polarizers. © 1994 John Wiley & Sons, Inc.  相似文献   
135.
萧聪明  叶俊 《应用化学》2005,22(6):643-0
顺丁烯二酸酐羧化淀粉的制备;淀粉;顺丁烯二酸酐;羧化  相似文献   
136.
137.
138.
Reactivity and swelling of nanometer films of alternating maleic anhydride copolymers were investigated in dependence on the kind of comonomer and molar mass of copolymer in aqueous solution at pH 7.4 and pH 3.0 in order to reveal their characteristics under physiological conditions. Fully hydrolyzed (maleic acid) chains of the copolymers with styrene, propene, and ethylene comonomers covalently bound to SiO2 substrates showed a "mushroom" swelling behavior at pH 7.4 with a layer thickness scaling of N3/5. Decreasing the environmental pH was found to induce a comonomer-dependent shrinking or collapse of the immobilized polymers due to the change in ionization. From the swelling kinetics of non-hydrolyzed chains, the time constants and characteristics of swelling and anhydride hydrolysis were determined and found to depend on the type of comonomer. The short- and long-term swelling kinetics [l approximately t and approximately ln(t)1/2] were found to be in agreement with theoretical models of polymer swelling, while at intermediate time scales enhanced swelling was observed due to hydrolysis reaction of maleic anhydride groups. The findings elucidate the variety of properties of maleic anhydride copolymer films under physiological conditions, which can advantageously be applied for biofunctionalization of different templates.  相似文献   
139.
采用非水滴定法中的无机碱直接滴定方法测定了马来酸酐在聚丙烯上的接枝率,并对该方法作了可行性验证,讨论了非水滴定中的两个难点:化学计量比的确定和滴定终点的判断。通过傅立叶红外光谱法(FTIR)对聚丙烯马来酸酐接枝物的纯化效果、自由基引发反应对非水滴定的影响及聚丙烯接枝马来酸酐的反应机理作了定性分析,并结合非水滴定的数据绘制了红外定量校准曲线。  相似文献   
140.
Maleated glycidyl 3‐pentadecenyl phenyl ether with styrene (MGS) was synthesized from glycidyl 3‐pentadecenyl phenyl ether (GPPE), maleic anhydride (MAH) and styrene (St) in the presence of AIBN initiator at 80°C, and then the resultant MGS was applied as a compatibilizer to prepare SBR/silica composites. Meanwhile, the commercial compatibilizer bis‐(triethoxysilylpropyl) tetrasulfide (named Si69) added into composite was also prepared for comparison purpose. The synthetic MGS structure was characterized by GPC and FTIR, and SBR/silica compounds with different compatibilizer were analyzed using RPA, DMA and so on. The results showed that M?n and M?w of MGS were 19,538 g/mol and 23,790 g/mol, respectively. The curing time of compounds with MGS increased, whereas the maximum and minimum torques decreased. The addition of MGS decreased Payne effect of SBR/silica compounds, which implied an improvement of silica dispersion in the compounds. Bound rubber content of compound with MGS was about 1.7 times higher than the absence and 1.5 times higher than that with Si69. The tensile strength of the composites was improved by increasing compatibilizer loading, and the optimum value was observed at 6 phr of MGS. Meanwhile the use of MGS can improve the anti‐aging property of composite. According to DMA, the tanδ value at 0°C of composite with MGS was higher than composite without compatibilizer suggesting that MGS can improve the wet skid resistance of composite. The SEM analysis revealed that introduction of MGS enhanced the compatibility between SBR and silica. Copyright © 2015 John Wiley & Sons, Ltd.  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