全文获取类型
收费全文 | 149篇 |
免费 | 11篇 |
国内免费 | 40篇 |
专业分类
化学 | 195篇 |
物理学 | 5篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 17篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1990年 | 1篇 |
1978年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有200条查询结果,搜索用时 15 毫秒
101.
Şaban Uysal 《合成通讯》2013,43(1):84-92
2,4,6-Tris(4-hydroxybenzimino)-1,3,5-triazine (II) has been synthesized by the reaction of 1 equiv. melamine (I) and 3 equiv. 4-hydroxybenzaldehyde and characterized by means of elemental analysis, 1H NMR, Fourier transform–infrared spectroscopy, and liquid chromatography–mass spectrometry (LC-MS). 2,4,6-tris(4-(2-phenyl-2-keto-hydroxyiminoyloxy)benzimino)-1,3,5-triazine L (III) has been synthesized by the reaction of 1 equiv. II and 3 equiv. chloroisonitrozoacetophenone and characterized by means of the same methods. Four novel trinuclear Fe(III) and Cr(III) complexes involving tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH2) or bis(salicylidene)-o-phenylenediamine-(salophen H2) with L (III) have been synthesized and characterized by means of elemental analysis, Fourier transform–infrared spectroscopy, LC-MS (ESI+), and thermal analyses. The metal ratios of the prepared complexes have been determined using atomic absorption spectroscopy. The aim of the present study is to synthesize novel tridirectional-trinuclear systems and to present their effects on magnetic behavior of [salen or salophenFe(III)/Cr(III)] capped complexes. The complexes have also been characterized as low-spin distorted octahedral Fe(III) and as distorted octahedral Cr(III) bridged by keton-oxime group. 相似文献
102.
Nagendra B. Kondekar 《合成通讯》2013,43(9):1301-1308
A short and enantioselective formal synthesis of (R)-selegiline has been achieved using Jacobsen's hydrolytic kinetic resolution (HKR) of phenyl propylene oxide.
103.
Kiyoshi Endo Takahiro Kitagawa Kenji Nakatani 《Journal of polymer science. Part A, Polymer chemistry》2006,44(13):4088-4094
The effect of an alkyl substituted in the aromatic ring of the salen ligand on the polymerization of butadiene (Bd) with (salen)Co(II) complexes in combination with methylaluminoxane (MAO) was investigated. The activity for the polymerization of Bd was influenced significantly by the introduction of alkyl groups at the 3,3′,5,5′‐positions in the aromatic ring of the salen ligand, and both the polymerization rate and 1,4‐cis contents increased in the following order with respect to the alkyl group: H < CH3 < t‐C4H9. This is in good agreement with the bulkiness of the alkyl groups. The activity for the polymerization of the (salen)Co(II) complex possessing t‐C4H9 at the 3,3′‐positions was higher than that of the (salen)Co(II) bearing t‐C4H9 at the 5,5′‐positions. Thus, the introduction of bulky substituents at the 3,3′‐positions of the salen ligand was an important factor in achieving both high activity and high 1,4‐cis selectivity in the polymerization of Bd with (salen)Co(II) complexes in combination with MAO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4088–4094, 2006 相似文献
104.
Marzena Białek Krystyna Czaja 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6940-6949
Vanadium complexes with tetradentate salen‐type ligands were first time explored in ethylene polymerizations. The effects of the vanadium complex structure, the alkyl aluminum cocatalysts type (EtAlCl2, Et2AlCl, Et3Al, and MAO), and the polymerization conditions (Al/V molar ratio, temperature) on polyethylene yield were explored. It was found that EtAlCl2 in conjunction with investigated vanadium complexes produced the most efficient catalytic systems. It was shown, moreover, that the structural changes of the tetradentate salen ligand (type of bridge which bond donor nitrogen atoms and type of substituent on aryl rings) affected activity of the catalytic system. The complexes containing ligands with cyclohexylene bridges were more active than those with ethylene bridges. Furthermore, the presence of electron‐withdrawing groups at the para position and electron‐donating substituents at the ortho position on the aryl rings of the ligands resulted in improved activity in relation to the systems with no substituents (with the exception of bulky t‐Bu group). The results presented also revealed that all vanadium complexes activated by common organoaluminum compounds gave linear polyethylenes with high melting points (134.8–137.6 °C), high molecular weights, and broad molecular weight distribution. The polymer produced in the presence of MAO possesses clearly lower melting point (131.4 °C) and some side groups (around 9/1000 C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6940–6949, 2008 相似文献
105.
The activation of chiral Mn(salen) complexes with Ph3PO has been found to provide a good strategy for the asymmetric cyanosilylation of aldehydes. Aromatic aldehydes have been converted into the corresponding cyanohydrin trimethylsilylether in yields up to 95% and ee up to 67% using 0.25 mol% chiral Mn(salen) complex in combination with 10 mol% of achiral Ph3PO as additive. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
106.
Secondary alcohols were catalytically oxidized with diace-toxyiodobenzene as oxidant in the presence of salen-Mn(Ⅲ)complex to aiTord the eorrespoltding ketones, in up to 99% yield, using CH2Cl2 or water as reaction media. 相似文献
107.
Thomas Radoske Dr. Juliane März Dr. Michael Patzschke Dr. Peter Kaden Dr. Olaf Walter Dr. Moritz Schmidt Prof. Dr. Thorsten Stumpf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(70):16853-16859
The synthesis of three complex series of the form [AnCl2(salen)(Pyx)2] (H2salen=N,N′-bis(salicylidene)ethylenediamine; Pyx=pyridine, 4-methylpyridine, 3,5-dimethylpyridine) with tetravalent early actinides (An=Th, U, Np, Pu) is reported with the goal to elucidate the affinity of these heavy elements for small neutral N-donor molecules. Structure determination by single-crystal XRD and characterization of bulk powders with infrared spectroscopy reveals isostructurality within each respective series and the same complex conformation in all reported structures. Although the trend of interatomic distances for An−Cl and An−N (imine nitrogen of salen or pyridyl nitrogen of Pyx) was found to reflect an ionic behavior, the trend of the An−O distances can only be described with additional covalent interactions for all elements heavier than thorium. All experimental results are supported by quantum chemical calculations, which confirm the mostly ionic character in the An−N and An−Cl bonds, as well as the highest degree of covalency of the An−O bonds. Structurally, the calculations indicate just minor electronic or steric effects of the additional Pyx substituents on the complex properties. 相似文献
108.
Saili Wei Yuhai Tang Xiaoqian Xu Guojin Xu Yong Yu Yang Sun Yuansuo Zheng 《应用有机金属化学》2011,25(2):146-153
This communication describes the design and application of a novel catalytic epoxidation system derived from the initial immobilization of a homogeneous sulfonato (salen)Mn(III) complex on two solid carriers (silica gel and siliceous earth) and subsequent dispersion of the supported manganese complexes into ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMImPF6) and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF4) for recycling. The performance of chiral (salen)Mn(III) system in enantioselective epoxidation of olefins was investigated systematically. Even higher enantioselectivity than that of the homogeneous counterpart was obtained with similar catalytic activity. In particular, the best catalytic result is that the combination of the silica gel‐supported (salen)Mn(III) catalyst and BMImPF6 affords 97–100% ee for epoxidation of α‐methylstyrene, and high ee values were retained even after three cycles. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
109.
Kyu Young Hwang Hyoseok Kim Yoon Sup Lee Prof. Dr. Min Hyung Lee Prof. Dr. Youngkyu Do Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(26):6478-6487
Showing their true colors? Full emission color tuning in the visible region can be achieved with salen–aluminum complexes that are electronically modulated at C5 of the phenoxide ring in the salen moiety. Emission spectra for various substituents R5 are shown (EWG: electron‐withdrawing group, EDG: electron‐donating group).
110.
Two homochiral metallosalen complexes, Ni(salen) (salen = (1R,2R)-(-)-diaminocyclohexane-N,N'-bis(3-tert-butyl-5-(4'-benzoic acid)-salicylidene) 1 and Cu(salen) 2, have been synthesized and characterized by IR, microanalysis, TGA, powder and single-crystal X-ray crystallography. Both 1 and 2 crystallize in orthorhombic space group P21212 with Z = 4. For 1, a = 12.082(2), b = 15.447(3), c = 18.784(4) , V = 3505.7(12) 3, Mr = 731.50, Dc = 1.386 g/cm3, μ = 0.606 mm–1, F(000) = 1544, the final GOOF = 1.043, R = 0.0496 and wR = 0.1248 for 4791 observed reflections with I > 2σ(I). For 2, a = 12.181(2), b = 15.501(3), c = 18.877(4) , V = 3564.3(12) 3, Mr = 736.33, Dc = 1.372 g/cm3, μ = 0.665 mm–1, F(000) = 1548, the final GOOF = 1.062, R = 0.0575 and wR = 0.1508 for 4562 observed reflections with I > 2σ(I). The crystal structures of 1 and 2 are isostructural with very similar supramolecular structures. An infinite two-dimensional network is generated by hydrogen bonding interactions and intermolecular π···π interactions. 相似文献