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   55篇
  免费   14篇
  国内免费   48篇
化学   102篇
晶体学   4篇
物理学   11篇
  2024年   1篇
  2023年   4篇
  2021年   4篇
  2020年   8篇
  2019年   4篇
  2018年   6篇
  2017年   4篇
  2016年   5篇
  2015年   5篇
  2014年   7篇
  2013年   8篇
  2012年   2篇
  2011年   6篇
  2010年   5篇
  2009年   6篇
  2008年   4篇
  2007年   4篇
  2005年   5篇
  2004年   5篇
  2003年   1篇
  2002年   2篇
  2001年   3篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1995年   2篇
  1993年   2篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1987年   1篇
  1981年   1篇
排序方式: 共有117条查询结果,搜索用时 9 毫秒
1.
The synthesis and characterization of metal poly-yne polymers containing disilane, disiloxane and phosphine groups in the main chain are described. The platinum and palladium poly-yne polymers were synthesized by polycondensation reactions between a metal chloride and an α, ω-bisethynyl complex in amines in the presence of cuprous iodide as a catalyst. The nickel poly-yne polymers were synthesized by an alkynyl ligand exchange reaction between a nickel acetylide and an α, ω-bisethynyl complex in diethylamine in the presence of cuprous iodide as a catalyst. The reaction of the platinum poly-yne polymer, containing disiloxane groups in the main chain, with copper (I) salts afforded adducts of η-2-bonded σ-acetylide polymer complexes. The reactions of the palladium poly-yne polymer, containing phosphine groups in the main chain, with transition-metal carbonyl complexes afforded polymer complexes which have phosphorus in the main chain-transition-metal bonds. A concentrated solution of the platinum poly-yne polymer containing disiloxane groups in the main chain forms a lyotropic liquid crystal in dichloromethane or 1, 2-dichloroethane.  相似文献   
2.
To extend the optical property characterization of metal–Cu2O polyhedra, 50 nm Au@Cu cubic cores are used to fabricate Au@Cu–Cu2O core–shell cubes, octahedra, and rhombic dodecahedra with tunable sizes. Despite the unusually large lattice mismatch of 15.1% between Cu and Cu2O, fine adjustment in the volumes of reagents introduced allows the formation of these heterostructures. To relieve the lattice strain, the metal cores are essentially never found to locate at the particle center, and slight lattice spacing shifts are recorded. Although efforts are made to reduce the heterostructure sizes, the Cu2O shells are generally too thick to reveal surface plasmon resonance (SPR) absorption band from the metal cores. Only the Au@Cu–Cu2O cubes with many cores located near the particle corners show observable SPR band red‐shift, but UV–vis spectra of all particle shapes are still dominated by Cu2O absorption and light scattering bands. Au@Cu–Cu2O cubes consistently show the most red‐shifted absorption bands than those of octahedra resulting from the optical facet effects.  相似文献   
3.
Four new heteroleptic [Cu(NN)P2]+-type cuprous complexes— 1 -TPP, 2 -POP, 3 -Xantphos, and 4 -DPPF—were designed and synthesized using a diimine ligand 2-(2′-pyridyl)benzoxazole (2-PBO) and different phosphine ligands (TPP, triphenylphosphine; POP, bis[2-(diphenylphosphino)phenyl]ether; Xantphos, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; DPPF, 1,1′-bis(diphenylphosphino)-ferrocene). All complexes were characterized using single-crystal X-ray diffraction, spectroscopic analysis (infrared, UV–Vis.), elemental analysis, and photoluminescence (PL). Single-crystal X-ray diffraction revealed complexes 1 – 4 as isolated cation complex structures with a tetrahedral CuN2P2 coordination geometry and diverse P–Cu–P angles. Their UV–Vis. absorption spectra exhibited a blue-shift sequence in wavelength with an enlarged P–Cu–P angle from 4 to 2 then to 3 and then to 1 . The PL emission peaks of 1 – 3 also exhibited a similar blue-shift sequence ( 2 → 3 → 1 ). Their PL lifetime in microseconds (~7.5, 5.1, and 4.7 μs for 1 , 2 , and 3 , respectively) indicated that their PL behavior represents phosphorescence. Time-dependent density functional theory (TD-DFT) calculation and wavefunction analysis revealed that S1 and T1 states of 1 – 3 should be assigned as metal–ligand and ligand–ligand charge-transfer (ML + L'L)CT states. Their UV–Vis. absorption and phosphorescence should be attributed to the charge transfer from the P–Cu–P segment to the 2-PBO ligand. Therefore, as the P–Cu–P angle increased (lower HOMO), the energy of S1 and T1 states also increased, following the change of PL color.  相似文献   
4.
研究了取代乙酸配体作为Nieulan催化剂对乙炔二聚反应性能的影响。结果表明,不同功能结构数目的影响,结果表明,不同功能结构数目的的氨羧配体均使催化剂的选择性提高。乙炔转化率略有下降,巯基乙酸配体的加入,则改变了乙炔二聚反应的机理,得到以乙醛为主的产物。  相似文献   
5.
利用简便易行的液相法,采用葡萄糖为还原剂,通过调整加料方式、反应温度、NaOH用量等条件,实现具有{110}截面八面体、八面体和短足形等形貌的Cu2O微/纳米结构的可控制备,运用透射电子显微镜、扫描电子显微镜、紫外可见分光光度计等对产物进行组成、结构、形貌和光响应的表征,对Cu2O的形貌结构和生长机理进行研究。对比和优化了具有不同形貌的Cu2O微/纳米结构对甲基橙染料的光催化性能。将不同形貌的微/纳米Cu2O作为防污剂复配的自抛光防污涂料,涂层磨蚀率、接触角与实海挂板实验证明该涂料具有良好的防污性能。  相似文献   
6.
采用聚丙烯酰胺(PAM)为软模板,在CuSO4、Na2SO3体系中调控合成了片状、海胆状、一维线、针状聚集体氧化亚铜晶体。研究了不同浓度Cu2+、不同PAM含量及不同温度对晶体生长的影响。结果表明,PAM促使氧化亚铜异相成核,氧化亚铜形貌随PAM质量分数的变化而变化:当c(Cu2+)=0.5mol.L-1时,PAM质量分数为3.0%(常温引入体系),产物主要为片状晶体;PAM质量分数为1.0%、3.0%时(高温引入体系),分别获得一维线状、海胆状晶体;当Cu2+浓度为0.1 mol.L-1时,体系中高温引入质量分数3.0%的PAM,得到片层状晶体;当Cu2+浓度为0.3、0.4 mol.L-1时,得到针状聚集体氧化亚铜晶体。分别用X射线粉末衍射、冷场发射扫描电子显微镜和激光粒度仪对所制备的产品进行了表征。  相似文献   
7.
The solubilities of cuprous bromide were measured at 24.8°C in aqueous KBr and in aqueous KBr-KNO3 mixtures. The results have been analyzed to give equilibrium constanns from formation of neutral and negatively charged complexes of CuBr, and sets of virial parameters suitable for calculation of activity coefficients for the complexes.  相似文献   
8.
吴朝辉 《化学教育》2017,38(1):70-72
通过实验探究和理论分析,发现Cu和FeCl3溶液反应颜色呈浅绿色的原因是:Cu和CuCl2反应生成CuCl白色沉淀,消耗了溶液中的Cu2+。根据这一结论,对一篇文章中的实验设计和观点进行修正,同时也对2道关于Cu与FeCl3反应的试题提出质疑并进行科学性改造,以服务于化学教学。  相似文献   
9.
介绍了基于科学核心观念建构下制备多彩氧化亚铜纳米粒子的学生实验。利用葡萄糖还原班氏试剂的方法制备了氧化亚铜纳米粒子,并观察和讨论了不同条件下制备的粒子的颜色和粒径。整个实验安全、简单、现象明显、试剂用量少。本研究通过让学生参与科研的全过程,培养了学生的创新能力,促进了科学核心观念的建构。  相似文献   
10.
合成气低温液相催化制甲醇和甲酸甲酯铜基催化剂体系研究 Ⅰ.氯化亚铜催化剂体系中各种因素的影响  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