全文获取类型
收费全文 | 47篇 |
免费 | 0篇 |
国内免费 | 23篇 |
专业分类
化学 | 61篇 |
物理学 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2005年 | 1篇 |
2004年 | 6篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1985年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有70条查询结果,搜索用时 15 毫秒
21.
Metallocene-based homogeneous Ziegler–Natta catalysts produce mono-olefin-terminated oligopropenes with narrow molecular weight distributions, controlled stereoregularities, and molecular weights ranging from 100 to 30,000 g/mole in high yield slurry and solution processes. Steric and molecular weight control are influenced by metallocene structures, and by polymerization conditions such as temperature and propene concentration. Predominantly mono-vinylidene-terminated oligopropenes are attractive intermediates, and feedstock for the synthesis of a variety of polypropylene materials, including blends, block and graft copolymers. The key step is the chain end functionalization of the vinylideneterminated oligopropenes via double bond conversion reactions, followed by the controlled synthesis of polypropylene block and graft copolymers. In melt and solution processes the olefinic end groups have been converted into a variety of polar functional groups, e.g. hydroxy, carboxy, succinic anhydride, thiol and acrylic groups. The thiol-terminated oligopropenes are chain transfer agents in radical methylmethacrylate polymerization with chain transfer constant measured to be 0.2. Acrylic monomers and styrene are grown onto the thiol end group via a chain transfer reaction, thus producing a family of block copolymers, e.g. poly(propene-b-methylmethacrylate) and poly(propene-b-styrene). As demonstrated by SEM fracture surface analysis, the poly(propene-b-styrene) block copolymers are efficient dispersing agents for compatibilizing polystyrene/polypropene (70/30) blends. Homo- and copolymerization of acrylic oligopropene macromonomers yield novel classes of graft copolymers with pendant isotactic or atactic oligopropene chains. Hydroxy-terminated oligopropenes are useful initiators in caprolactone polymerization to form poly(propene-b-caprolactone) block copolymers. IR spectroscopic studies demonstrate that succinic anhydride-terminated oligopropenes, obtained by ene-type addition of maleic anhydride to the olefinic oligopropene end group, react with oligomeric diamine-terminated polyamide-6,6 in the melt to yield polypropene-b-polyamide-6,6-b-polypropene triblock copolymers. 相似文献
22.
CAI Yang LI Zhi hua YANG Yi quan YUAN You zhu ** State Key Laboratory for Physical Chemistry of Solid Surfaces Department of Chemistry Xiamen University Xiamen P. R. China 《高等学校化学研究》2002,18(3):311-315
IntroductionHeterogenization of HRh( CO) ( PPh3 ) 3 ( PPh3 :triphenylphosphine) for hydroformylation andselective hydrogenation has received considerableattention in the past several decades from bothacademic and industrial interests[1] . Besides themilestone preparation of water- soluble TPPTS andthe corresponding rhodium- phosphine complexessuch as HRh( CO) ( TPPTS) 3 ( 1 ) [2 ,3 ] ,supportedliquid- phase catalysts ( SLPC) [4— 6] and supportedaqueous- phase catalysts ( SAPC) [7]… 相似文献
23.
丙烯选择氧化制丙烯酸杂多酸催化剂的探索 总被引:2,自引:0,他引:2
丙烯选择氧化制丙烯酸是丙烯有效利用的途径之一 .目前工业上采用两步法生产 ,即丙烯先被氧化为丙烯醛 ,丙烯醛再被氧化为丙烯酸 .两步法中所使用的催化剂多为复合氧化物[1 ] .杂多酸催化剂由于富含晶格氧 ,有可能使丙烯一步被氧化为丙烯酸 [2 ] .其中具有 Keggin结构的杂多酸易于制备 ,化学稳定性及热稳定性好 ,被广泛用作多相选择氧化反应的催化剂 .我们选取 Keggin结构的杂多酸催化剂 ,调变其阴阳离子组成 ,用于丙烯一步氧化制丙烯酸 ,并对反应条件进行了考察 .1实验部分1 .1催化剂制备含铜、铬的杂多酸催化剂的制备方法见文献[3] .将三… 相似文献
24.
A series of nanosized cobalt oxide catalysts modified with phosphorus have been synthesized by the sol–gel method and investigated in the oxidative dehydrogenation of propane to propene.With the addition of phosphorus,the crystallite size of the catalyst was largely decreased,while the P species in the catalyst were highly dispersed.Compared to pure cobalt oxide,the P-modified samples showed higher propane conversion and enhanced propene selectivity.Over the PCoO catalyst with a P/Co atomic ratio of 0.05,the maximal propene yields of 15.7%with a propane conversion of 28.3%were obtained at 520℃. 相似文献
25.
SBA-15负载纳米CoMoO4催化剂催化丙烷氧化脱氢制丙烯 总被引:1,自引:0,他引:1
采用柠檬酸配位-浸渍法制备不同CoMoO4含量的系列CoMoO4/SBA-15催化剂, 通过X射线衍射、透射电镜和低温N2吸附法对样品进行了表征. 结果表明, 柠檬酸配位-浸渍法可在介孔分子筛孔道中形成高含量、均匀分散且有确定晶相的CoMoO4, 同时能够很好地保持载体的介孔结构. 与非负载的CoMoO4相比, 由柠檬酸配位-浸渍法制备的CoMoO4/SBA-15催化剂在丙烷氧化脱氢反应中具有更好的催化活性, 当CoMoO4的含量为13%(w)、反应温度为823 K时, 丙烯产率达到16.8%. 相似文献
26.
Qiyang Zhang Tianci Xiao Prof. Dr. Chengyuan Liu Dr. Tatiana Otroshchenko Prof. Dr. Evgenii V. Kondratenko 《Angewandte Chemie (International ed. in English)》2023,62(40):e202308872
The metathesis of ethylene with 2-butenes to propene is an established large-scale process. However, the fundamentals behind in situ transformation of supported WOx, MoOx, or ReOx species into catalytically active metal-carbenes and the intrinsic activity of the latter as well as the role of metathesis-inactive cocatalysts are still unsolved. This is detrimental for catalyst development and process optimization. In this study, we provide the required essentials derived from steady-state isotopic transient kinetic analysis. For the first time, the steady-state concentration, the lifetime, and the intrinsic reactivity of metal carbenes were determined. The obtained results can be directly used for the design and the preparation of metathesis-active catalysts and cocatalysts, thereby opening up possibilities for optimizing propene productivity. 相似文献
27.
28.
Copolymerization of propylene and nonconjugated dienes such as 1–9 decadiene (α–ω symmetric) and 7-methyl-1,6 octadiene (asymmetric) is carried out in the presence of highly active isospecific catalysts for propene polymerization. The incorporation of the diene is random and does not affect the isospecificity of the catalytic system. For a low amount of diene, whatever its structure, an activation effect is observed. For the symmetric diene, the reactivity of the second double bond gives rise to crosslinking. Derivatization through hydroboration or epoxydation is carried out in suspension, using a toluenetetrahydrofuran solvent mixture that is able to swell the polypropylene and dissolve the reactants. After hydroboration the copolymer is transformed into hydroxylated polymer through oxidation in a phase transfer condition. The epoxydized copolymer shows excellent adhesive properties on anodized stainless steel. 相似文献
29.
硅基介孔材料M41S因具有较大的孔径和比表面积而引起从事多相催化、吸附分离以及非金属材料等领域研究人员的极大关注,其中MCM-41是最具代表性的成员之一,但纯硅的MCM-41因无活性中心而不能用于催化领域,最近已有将SO4^2-/ZrO2超强酸及杂多酸负载到MCM-41上,使其成为 相似文献
30.
NiSO4/HY催化剂上丙烯齐聚反应研究 总被引:1,自引:0,他引:1
本文考察了NiSO_4/HY催化剂用于丙烯齐聚反应的催化性能,研究了镍含量、镍盐、焙烧温度以及反应条件对催化活性和选择性的影响,随镍含量增加,反应活性及二聚选择性都升高,镍含量为9一20wt%时活性达最好,液体收率达95wt%,随焙烧温度升高,二聚选择性不断升高。催化活性则在823K时有最大值。用吸附指示剂法测定了样品的酸分布,CO-TPD法测定了暴露的Ni中心量,XRD法测定了NiSO_4在HY上的分散阈值,讨论了它们与丙烯齐聚活性的关联。 相似文献