全文获取类型
收费全文 | 398篇 |
免费 | 35篇 |
国内免费 | 36篇 |
专业分类
化学 | 416篇 |
晶体学 | 6篇 |
力学 | 26篇 |
综合类 | 1篇 |
数学 | 5篇 |
物理学 | 15篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 26篇 |
2007年 | 39篇 |
2006年 | 27篇 |
2005年 | 39篇 |
2004年 | 33篇 |
2003年 | 24篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有469条查询结果,搜索用时 31 毫秒
71.
Kazem Barati William Clegg Mohammad Hossein Habibi Ross W. Harrington Arash Lalegani Morteza Montazerozohori 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):239-242
Transition metal complexes of Schiff base ligands have been shown to have particular application in catalysis and magnetism. The chemistry of copper complexes is of interest owing to their importance in biological and industrial processes. The reaction of copper(I) chloride with the bidentate Schiff base N,N′‐bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine {Nca2en, systematic name: (1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]} in a 1:1 molar ratio in dichloromethane without exclusion of air or moisture resulted in the formation of the title complex μ‐chlorido‐μ‐hydroxido‐bis(chlorido{(1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]‐κ2N,N′}copper(II)) dichloromethane sesquisolvate, [Cu2Cl3(OH)(C20H18N4O4)2]·1.5CH2Cl2. The dinuclear complex has a folded four‐membered ring in an unsymmetrical Cu2OCl3 core in which the approximate trigonal bipyramidal coordination displays different angular distortions in the equatorial planes of the two CuII atoms; the chloride bridge is asymmetric, but the hydroxide bridge is symmetric. The chelate rings of the two Nca2en ligands have different conformations, leading to a more marked bowing of one of the ligands compared with the other. This is the first reported dinuclear complex, and the first five‐coordinate complex, of the Nca2en Schiff base ligand. Molecules of the dimer are associated in pairs by ring‐stacking interactions supported by C—H…Cl interactions with solvent molecules; a further ring‐stacking interaction exists between the two Schiff base ligands of each molecule. 相似文献
72.
73.
74.
75.
Maurer J Sarkar B Kaim W Winter RF Zális S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(36):10257-10272
The tetranuclear complexes [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)Ru Cl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)- CH=CH-1,4)] (3 a) and [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (3b), which contain vinylpyridine ligands that connect peripheral Ru(PiPr(3))(2)(CO)Cl units to a central divinylphenylene-bridged diruthenium core, have been prepared and investigated. These complexes, in various oxidation states up to the tetracation level, have been characterized by standard electrochemical and spectroelectrochemical techniques, including IR, UV/Vis/NIR and ESR spectroscopy. A comparison with the results for the vinylpyridine-bridged dinuclear complex [PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)(CH=CHPh)] (6) and the divinylphenylene-bridged complexes [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,4)] (8a) and [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (8b), which represent the outer sections (6) or the inner core (8a,b) of complexes 3a,b, and with the mononuclear complex [(EtOOCpy)(CO)(PPh(3))(2)RuCl(CH=CHPh)] (7) indicate that every accessible oxidation process is primarily centred on one of the vinyl ligands, with smaller contributions from the metal centres. The experimental results and quantum chemical calculations indicate charge- and spin-delocalization across the central divinylphenylenediruthenium part of 3a,b or the styrylruthenium unit of 6, but not beyond. The energy gap between the higher lying styryl- or divinylphenylenediruthenium-based and the lower occupied vinylpyridineruthenium-based orbitals increases in the order 6<3 b<3 a and thus follows the conjugation within the non-heteroatom-substituted aromatic vinyl ligand. 相似文献
76.
A. V. M. Chandramalar Y. Y. Lim Y. K. Leong 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,160(3):49-205
The effects of cis- and trans-1,2-, trans-1,4-cyclohexanedicarboxylic acid, 95% cis-1,3,5-cyclohexane tricarboxylic acid and cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid on the yield stress–pH behaviour of concentrated ZrO2 dispersions are reported. Adsorbed cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid imparts predominantly steric interactions. It forms a steric barrier keeping the interacting particles apart. Adsorbed cis- and trans-1,2 increase the maximum yield stress and this was attributed to a hydrophobic force resulting from the part of the cyclohexane ring sticking out into the solution which is devoid of charged or hydrophilic group. Adsorbed trans-1,4 increases the maximum yield stress by at least threefold and its configuration favours strong bridging interaction with an adjacent particle. Predominantly, cis-1,3,5 also increases the maximum yield stress but only by 60% at the same additive concentration. This was attributed to a smaller degree of bridging. 相似文献
77.
G. Y. S. K. Swamy K. Ravikumar K. Chandramohan N.V. Lakshmi 《Crystal Research and Technology》2001,36(11):1273-1279
The title compound [[Cu(shen)]2(tp)], {[Cu(C15H17O4N2)]2}, where tp = dianion of terephthalic acid and shen = (N‐salicylidene‐N'‐(2‐hydroxyethyl ethylene‐diamine)) has been prepared and its crystal structure determined by single crystal X‐ray diffraction at room temperature. The complex crystallizes in the orthorhombic space group Pbca with four formula units in a unit cell of dimensions a = 12.298(2), b = 14.214(2) and c = 16.436(2)Å. The structure consists of binuclear units with Cu(II) ion bridged by the tp ligand in a bis‐unidentate fashion. The five coordinate Cu(II) complex adopts a distorted square‐based pyramid. A crystallographic inversion center has been located at the center of the benzene ring of the tp bridging ligand. The Cu … Cu distance inside a same binuclear entity is 11.069Å. Intermolecular aromatic ring stacking interactions were observed with the shortest atom to atom contact being 3.423Å. 相似文献
78.
The crystal structure of [{Co(phen)2}2V4O12] · H2O consists of hexanuclear bimetallic clusters [{Co(phen)2}2V4O12]. The cyclic [V4O12]4‐ anion acts as a bidentate bridging ligand between the two [Co(phen)2]2+ cations. The π‐π stacking interactions between the parallel 1,10‐phenantroline (phen) groups play a significant role in stabilizing this structure. The title compound crystallizes in the P21/c space group. 相似文献
79.
Pure polycrystalline Li2C2 could be obtained by the reaction of lithium and graphite flakes in an arc-melting furnace. X-ray powder investigations on these samples confirm the crystal structure given by Juza, Wehle, and Schuster (Immm, No. 71, Z = 2) which is isotypic to Rb2O2 and Cs2O2. At about 500 °C a reversible phase transition (1st order) to a cubic modification (Fm 3 m, No. 225, Z = 4) has been observed. This high temperature modification can be described as an antifluorite-structure with disordered C22– dumbbells. 相似文献
80.
杯芳烃是由苯酚单元通过亚甲基连接而成的空腔型分子,具有衍生位点多,构象丰富等特点,被称为第三代主体分子。在分子层次,依手性因素的结构特点不同,可将手性杯芳烃分为具有手性亚单元的杯芳烃、固有手性杯芳烃和桥手性杯芳烃。在超分子层次,杯芳烃自身或杯芳烃与其他分子或离子在溶液中、晶态中或二维表面可通过非共价键力形成多种拓扑结构的纳米手性聚集体。研究手性杯芳烃和基于杯芳烃的超分子手性组装体的合成、结构和性能,不仅在理解手性起源、手性结构等方面具有理论意义,而且有望获得以分子识别为基础的手性传感器、手性催化剂、手性分离材料、手性载体和手性纳米材料。本文综述近十年来有代表性的分子手性杯芳烃和以杯芳烃为组分的超分子手性聚集体的设计、合成、结构和功能。着重展示杯芳烃骨架在形成新颖分子手性和超分子手性上的优势,以及杯芳烃单元在实现特定功能如手性识别时发挥的作用。相信随着杯芳烃合成技术和杯芳烃超分子设计的发展,必将进一步发挥杯芳烃的结构优势,涌现出更多性能优异的手性杯芳烃功能分子和超分子手性杯芳烃功能材料。 相似文献