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71.
Kai Yu 《Tetrahedron》2009,65(1):305-55
Two chiral Mn(III) salen complexes were immobilized onto a series of mesoporous MCM-41 and MCM-48 materials with different pore sizes and the as-synthesized catalysts were active and enantioselective for the asymmetric epoxidation of styrene and indene. The results of XRD, FTIR, DR UV-vis, and N2 sorption showed that the chiral Mn(III) salen complexes were anchored in the channels of mesoporous materials. The influence of organic silicane dosage on the catalytic performance was studied and the optimum dosage of organic silicane for preparing heterogeneous catalysts was determined. Furthermore, the effect of the fine-tuning of pore size on the performance of heterogeneous catalysts was discussed. In general, larger pore size of the supports could lead to higher conversions and the compatible pore size with substrate may be responsible for the improved enantiomeric excess (ee) values. 相似文献
72.
以聚(苯乙烯-苯乙烯基膦酸)-磷酸氢锆(ZPS-PVPA)为催化剂载体, 通过3-氨丙基三甲氧基硅烷对其中无机磷酸氢锆的羟基进行修饰, 再与均相手性MnⅢ(salen)催化剂进行轴向配位固载, 实现了手性均相催化剂的非均相化. 催化剂的表征结果证实制得了非均相催化剂. 随后, 考察了该非均相催化剂对α-甲基苯乙烯、 苯乙烯以及茚不对称环氧化反应的催化性能. 结果表明, 以间氯过氧苯甲酸(m-CPBA)为氧化剂, 在 0 ℃反应 3 h, 催化剂用量为 0.03 mmol, 在轴向配体 N-甲基吗啉氮氧化物(NMO)的参与下, 催化剂能高效催化α-甲基苯乙烯的不对称环氧化, 反应的对映选择性(e. e.值)可达 91.5%, 转化率为 99%. 此外, 以茚为底物考察了催化剂的循环使用性能, 结果表明, 催化剂重复使用10次后, 反应的e. e.值(>90%)远高于在相同条件下均相MnⅢ(salen)催化剂催化茚反应的e. e.值(65%). 相似文献
73.
Kazuhiro Matsumoto 《Tetrahedron letters》2004,45(11):2385-2388
Pentagonal bipyramidal Hf(salen) complex 1 was found to serve as a catalyst for 1,4-addition reaction of thiol to N-(2-alkenoyl)-2-oxazolidinones. 相似文献
74.
The polymeric [N′,N′‐bis(salicylidene)ethane‐1,2‐diaminato(2?)]manganese(III) ([MnIII(salen)]) type complexes 1 and 2 were successfully applied to the oxidative kinetic resolution of secondary alcohols. The reaction proceeded readily at room temperature with excellent enantioselectivities of up to 99.9% ee. A variety of substrates, including aromatic and aliphatic alcohols, could be tolerated. The polymeric catalysts could easily be recovered and recycled. 相似文献
75.
76.
77.
Bredikhin A. A. Strunskaya E. I. Novikova V. G. Azancheev N. M. Sharafutdinova D. R. Bredikhina Z. A. 《Russian Chemical Bulletin》2004,53(1):213-218
The enantioselective partial hydrolysis of a number of racemic aryl glycidyl ethers in the presence of chiral Co(salen)-catalyst was studied. The enantiomeric composition of the isolated (R)-aryl glycidyl ethers was analyzed by 31P NMR using optically active substituted 2-chloro-1,3,2-dioxaphospholanes. A synthesis of -adrenoblocking agents (S)-toliprolol and (S)-moprolol based on the simultaneously obtained (S)-3-aryloxypropane-1,2-diols was proposed. 相似文献
78.
Asymmetric epoxidation of 6-cyano-2,2-dimethylchromene on Mn(salen) catalyst immobilized in mesoporous materials 总被引:1,自引:0,他引:1
Huidong Zhang 《Tetrahedron》2006,62(28):6640-6649
This article reports our recent work on the heterogeneous asymmetric epoxidation catalyzed by chiral Mn(salen) catalyst axially immobilized via phenoxyl groups and organic sulfonic groups. The asymmetric epoxidation of 6-cyano-2,2-dimethylchromene was especially presented in detail. The factors that affected the asymmetric induction, such as the nanopores and the external surface, the linkage length, and the modification of nanopores with methyl groups were discussed. It was found that the enantioselectivities increased with decreasing the nanopore sizes or increasing the linkage length in nanopore, and the Mn(salen) catalyst immobilized into nanopores generally gave higher ee values than those on the external surface. The heterogeneous Mn(salen) catalysts with modified nanopores gave a TOF of 14.8 h−1 and an ee value of 90.6% for the asymmetric epoxidation of 6-cyano-2,2-dimethylchromene, which were higher than the results (TOF 10.8 h−1, ee 80.1%) obtained for the homogeneous catalyst. 相似文献
79.
Enantioselective imidation of alkyl aryl sulfides with N-alkoxycarbonyl azide as a nitrene precursor was effected by using (OC)Ru(salen) complex 1 as catalyst. The steric and electronic nature of the N-alkoxycarbonyl group was found to strongly affect the enantioselectivity and the reaction rate, and high enantioselectivity (up to 99% ee) and good chemical yields were achieved by using 2,2,2-trichloro-1,1-dimethylethoxycarbonyl azide as the nitrene precursor at room temperature. 相似文献
80.
热力学稳定的带有大环配体的μ-氧桥联-双铁配合物,由于其两个铁中心之间的有趣的电子结构和磁相互作用而受到广泛关注。μ-氧桥联-双铁席夫碱配合物,[{Fe(tbusalphn)}2(μ-o)]
(1)和[{Fe(R,R-salchxn)}2(μ-o)] (2), 通过用咪唑或N-甲基咪唑的水溶液处理相应的单核铁氯化物,Fe(L)Cl,而获得。1和2的晶体结构通过x-射线结构分析而被确定。1属于三斜晶系,P-1空间群。2属于单斜晶系,P21/c空间群。由于1的配体带有庞大的叔丁基取代基,导致形成μ-氧桥联-双铁配合物时的空间拥挤,因此,其Fe-O-Fe夹角为176.5 o,几乎成平角。而2则由于配体上没有庞大的取代基,其Fe-O-Fe夹角为149.6o,明显小于1的Fe-O-Fe夹角。
本文还对两种μ-氧桥联-双铁席夫碱配合物及相应的单核铁氯化物的红外光谱、紫外-可见吸收光谱及圆二色光谱性质进行了研究。与相应的单体铁配合物相比较,生成μ-氧桥联-双铁席夫碱配合物后,出现一新的红外吸收带,归属于νFe-O-Fe振动。有趣的是,其数值与Fe-O-Fe夹角大小相对应。1和2除具有明显不同的Fe-O-Fe夹角外,它们的圆二色光谱却是相似的。
对1和2的磁性质研究表明,在这类化合物中两个铁(III)离子之间存在着强烈的分子内抗铁磁性偶合作用。另外,本文还采用循环伏安法对1和2的电化学性质进行了研究。 相似文献