全文获取类型
收费全文 | 174篇 |
免费 | 7篇 |
国内免费 | 41篇 |
专业分类
化学 | 213篇 |
综合类 | 1篇 |
物理学 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 11篇 |
2009年 | 15篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有222条查询结果,搜索用时 31 毫秒
71.
Shengbo Qing Wei Huang Deyue Yan 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4363-4372
A novel sulfonated aromatic diacid, 3,3′‐disulfonyl‐4,4′‐dicarboxyldiphenylsulfone (DSDCDPS), was successfully synthesized from 4,4′‐dimethyldiphenylsulfone by sulfonation and further oxidation. A series of sulfonated polybenzimidazoles (sPBI‐SS) with various sulfonation degrees was prepared from DSDCDPS, 4,4′‐sulfonyldibenzoic acid and 3,3′‐diaminobenzidine by solution copolycondensation in poly(phosphoric acid). The chemical structure of the resulting sPBI‐SS was confirmed by FTIR and 1H NMR. The DSDCDPS‐based sPBI‐SS with the number‐average molecular weights of 32,000–55,000 were easy to dissolve in polar aprotic solvents such as DMF, DMSO, and DMAc, and could be cast into transparent, tough, and flexible membranes. The membranes presented good thermal stabilities (5% weight loss temperatures higher than 430 °C), and the thermal degradation activation energies of the sulfonic group of sPBI‐SS40 evaluated under N2 by both Ozawa and Kissinger methods were 266.06 and 264.79 kJ/mol, respectively. The membranes also exhibited high storage moduli, glass transition temperatures (above 238 °C) and tensile strengths (~80 MPa), in addition to water uptakes (22.3–25.2%) and low swelling degrees (<14.0%). © 2005 Wiley Periodicals, Inc. J Polym Sci A: Polym Chem 43: 4363–4372, 2005 相似文献
72.
FU YuBin ZHAO ZhongKai LIU Jia LI KuiZhong XU Qian & ZHANG ShaoYun Institute of Materials Science Engineering Ocean University of China Qingdao China 《中国科学B辑(英文版)》2011,(5)
A unique sulfonated polyaniline/vanadate composite was synthesized and utilized as a composite anode in microbial fuel cells on ocean floor (BMFCs). X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed to characterize its chemical composition and morphology. Wettability of the composite anodes decreases due to the addition of polytetrafluoroethylene (PTFE). The electrochemical behavior of the composite anodes was investigated by means of linear sweep voltammetry and Tafel plot measurem... 相似文献
73.
74.
A series of sulfonated copolyimides containing pyrimidine groups (SPIs) were synthesized by random copolymerization of 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA), 2‐(4‐aminophenyl)‐5‐aminopyrimidine (PAPRM), and 4,4′‐diaminodiphenyl ether‐2,2′‐disulfonic acid (ODADS). Proton exchange treatment in 1.0 M sulfuric acid solution resulted in ionic cross‐linking of the sulfonated copolymers due to the acid (sulfonic acid)‐base (pyrimidine group) interactions and the membrane with more basic PAPRM moiety could absorb sulfuric acid to favor the proton transfer. The effects of the structure of the diamines on the properties of SPI membranes were evaluated by studying the membrane parameters including water uptake, proton conductivity, water stability, and methanol permeability. The basic pyrimidine groups introduced in the main chains could effectively resist membrane swelling due to the strong interchain interactions through basic pyrimidine groups and sulfonic acid groups. Compared with the corresponding uncross‐linked copolyimides (NTDA/ODADS/ODA), the acid–base copolyimides displayed excellent water stability. The SPI membranes also exhibited improved mechanical properties and decreased methanol permeability. However, the cross‐linked membranes showed lowered proton conductivities than the uncross‐linked ones because a small part of the sulfonic acid groups had been consumed during the cross‐linking process. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
75.
The Maron theory was used to deduce from mostly osmotic pressure and light-scattering data the interaction parameters as a function of concentration, temperature, and polymer molecular weight for solutions of polystyrene in seven different solvents. These interaction parameters were then utilized to calculate the activity coefficients of the solvent in more concentrated solutions for comparison with experimental values deduced from vapor pressure measurements. When order was absent in the polymers (all cases but two), the agreement between calculated and observed activity coefficients was found to be very good. In the two cases where order was present, the activity coefficients observed in the concentrated solutions were higher than those calculated. These deviations were employed to find the degree of polymer order both in solution and in the original polymers. 相似文献
76.
燃料电池用磺化聚酰亚胺质子交换膜材料的制备与性质 总被引:2,自引:0,他引:2
以联萘二酐、磺化二胺和含咪唑基团的非磺化二胺单体为原料,制备了一系列高相对分子质量的磺化聚酰亚胺,该类聚合物具有优异的溶解性和良好的成膜性.得到的质子交换膜具有优异的水解稳定性.苯并咪唑碱性基团的存在提高了磺化聚酰亚胺质子交换膜膜的溶胀稳定性和热稳定性、降低了膜的甲醇透过率.质子导电率测试结果表明,IEC值为2.55mequiv·g-1的膜室温条件下的质子导电率为0.121 S·cm-1,高于在相同测试条件下Nafion 117膜的质子导电率(0.09 S·cm-1). 相似文献
77.
聚偏氟乙烯-磺化聚醚砜相容性及其成膜性能 总被引:2,自引:1,他引:1
研究了聚偏氟乙烯(PVDF)-磺化聚醚砜(SPES)的相容性及其成膜性能.首先通过溶解度参数、粘度法和目测法研究共混溶液的相容性,接着采用浊度法测定了共混溶液的热力学性质,最后采用浸没沉淀法制备了共混膜并探讨了成膜性能.结果显示,PVDF和SPES为部分相容体系,随着SPES含量的增加,共混溶液相容性逐渐减小,当SPES含量增加到50wt%时,体系发生分相.共混溶液的成膜性能良好,SPES含量增加有利于体系发生液液分相,生成高孔隙率膜,并且极大的提高了PVDF膜的亲水性和水通量. 相似文献
78.
磺化酞菁金属主要用作液化气脱硫醇过程碱液氧化再生催化剂。为研究磺化酞菁金属易于失活的影响因素,对比探讨了5种磺化酞菁金属(Fe、Co、Ni、Cu、Zn )在相同溶剂以及不同溶剂中的聚集作用,并研究了聚集对催化氧化硫醇活性的影响。结果表明,磺化酞菁金属聚集受溶剂影响较大,溶剂极性越强,聚集越严重;磺化酞菁金属溶液放置时间越长,磺化酞菁金属聚集体粒径越大;金属种类不同,对磺化酞菁金属聚集也有影响。聚集导致CoSPc、CuSPc催化氧化硫醇活性显著降低20%左右。 相似文献
79.
80.
Hyoung‐Juhn Kim Seong Jin An Ju‐Yong Kim Jin Kyoung Moon Sung Yong Cho Yeong Chan Eun Hae‐Kwon Yoon Youngmi Park Ho‐Jin Kweon Eun‐Mi Shin 《Macromolecular rapid communications》2004,25(15):1410-1413
Summary: Fuel cells were designed for high temperature operations. Poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI) was synthesized in a solution of P2O5, CH3SO3H, and CF3SO3H. The PBI was dissolved in a mixture of CF3CO2H and H3PO4 and the solution was used for the preparation of Pt catalyst slurry for membrane electrode assembly. The single cell showed a current density of 280 mA · cm−2 at a cell voltage of 0.5 V with feeds of H2 and O2 at 160 °C and without external humidification.