全文获取类型
收费全文 | 797篇 |
免费 | 40篇 |
国内免费 | 11篇 |
专业分类
化学 | 481篇 |
晶体学 | 6篇 |
力学 | 48篇 |
数学 | 107篇 |
物理学 | 206篇 |
出版年
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 17篇 |
2019年 | 28篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 41篇 |
2015年 | 22篇 |
2014年 | 24篇 |
2013年 | 86篇 |
2012年 | 62篇 |
2011年 | 63篇 |
2010年 | 51篇 |
2009年 | 48篇 |
2008年 | 55篇 |
2007年 | 61篇 |
2006年 | 30篇 |
2005年 | 37篇 |
2004年 | 38篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有848条查询结果,搜索用时 125 毫秒
41.
Bünyemin OUT Burcu TOPALOLU AKSOY Süreyya Ouz TÜMAY Ahmet ENOCAK Serkan YELOT 《Turkish Journal of Chemistry》2020,44(1):48
Phenoxy- and naphthoxy-substituted bisphenol-bridged cyclic phosphazenes were synthesized in 2 steps and their thermal, photophysical, and electrochemical properties were investigated. The structures of the cyclic phosphazene compounds were determined by ESI-MS mass spectrometry and 1 H, 13 C, and 31 P NMR spectroscopies. The photophysical studies of phenoxy- and naphthoxy-substituted bridged cyclophosphazenes were investigated by means of absorption and fluorescence spectroscopies in different solvents. Thermal and electrochemical properties of the target compounds were also studied. Furthermore, the excimer emissions through intramolecular interactions in solution and in solid state were investigated by fluorescence spectroscopy and the theoretical calculations were performed in detail using DFT. 相似文献
42.
Armaan GÜNSEL Aye USLUOLU Ahmet Turgut BLGL TOSUN Büra Gülnur ARABACI Meryem Nilüfer YARAIR 《Turkish Journal of Chemistry》2020,44(4):923
This work reports on dyeing of nylon/elastane fabric with water-soluble phthalocyanines ( 1-4 ) bearing quinoline 5-sulfonic acid substituents on the peripheral or nonperipheral positions and determining the antibacterial efficiency of the phthalocyanine compounds and the dyed nylon/elastane fabrics. The light, washing, water, perspiration, and rubbing fastness properties of nylon/elastane fabrics dyed with phthalocyanines were also determined. The results showed that all dyed fabrics showed very good wet fastness values. The lightfastness value of the nylon/elastane fabric dyed with phthalocyanine dye ( 1 ) showed a much better value than the others. Also, the antibacterial efficiencies of the dyed nylon fabrics and the dye compounds were investigated against a gram-negative ( Escherichia coli ) and a grampositive ( Staphylococcus aureus ) bacteria by using disc diffusion method. The results showed that the dyed nylon/elastane fabrics and the compounds exhibited antibacterial activities against both bacteria. 相似文献
43.
Tong Wu Xiao Wang Ahmet Emrehan Emre Jinchen Fan Yulin Min Qunjie Xu Shigang Sun 《Journal of Energy Chemistry》2021,(4):48-54
Electrocatalysts for ethanol oxidation reaction(EOR)are generally limited by their poor durability because of the catalyst poisoning induced by the reaction intermediate carbon monoxide(CO).Therefore,the rapid oxidation removal of CO intermediates is crucial to the durability of EOR-based catalysts.Herein,in order to effectively avoiding the catalyst CO poisoning and improve the durability,the graphene-nickel nitride hybrids(AG-Ni3N)were designed for supporting palladium nanoparticles(Pd/AG-Ni3N)and then used for ethanol electrooxidation.The density functional theory(DFT)calculations demonstrated the introduction of AG-Ni3N depresses the CO absorption and simultaneously promotes the adsorption of OH species for CO oxidation removal.The fabricated Pd/AG-Ni3N catalyst distinctively exhibits excellent electroactivity with the mass catalytic activity of 3499.5 m A mg-1 on EOR in alkaline media,which is around 5.24 times higher than Pd/C(commercial catalyst).Notably,the Pd/AG-Ni3N hybrids display excellent stability and durability after chronoamperometric measurements with a total operation time of 150,000 s. 相似文献
44.
A new borophosphate compound with the composition (NH4) χ Mn((3?χ)/2)(H2O)2 [BP2O8]·(1?x)H2O was prepared under mild hydrothermal conditions and characterized by X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) methods. The title compound was synthesized from MnCl2·2H2O, H3BO3, and (NH4)2HPO4 with variable molar ratios by heating at 180 °C for 7 days in an autoclave. The X-ray diffraction data of the water insoluble polycrystalline powder was indexed using the TREOR program in hexagonal system with the unit cell parameters of a = 9.5104, c = 15.7108 Å, Z = 6 and the space group P65 (No.176). (NH4) χ Mn((3?χ)/2)(H2O)2 [BP2O8]·(1?x)H2O is isostructural with (NH4) χ M ((3?χ) 2)/II (H2O)2 [BP2O8]·(1?x)H2O (MII = Co, Cd, Mg; x = 0.5–1). Its unit cell parameters and hkl values were in good agreement with the other isostructural compounds. This is the first report presenting both the synthetic details and the indexed X-ray powder diffraction pattern of this compound along with the characterization by FTIR, thermal gravimetric analysis, scanning electron microscopy and EPR. 相似文献
45.
A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH2), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses,
IR, UVVIS and 1H and 13C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH2) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated
by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base,
as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN4 coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated
with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon
metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel
complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction
processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively. 相似文献
46.
47.
48.
49.
The behavior of proton transfer facilitated by a novel thiazole derivative, N-methyl-4-(4-phenoxyphenyl)thiazol-2-amine (MPPT),
across the water/1,2-dichloroethane (1,2-DCE) interface was investigated electrochemically. The ionic partition diagram for
MPPT was obtained from interpretation of the cyclic voltammograms. The apparent partition coefficient of MPPT was evaluated
by the shaking-flask method under experimental conditions, while that for the protonated form of MPPT was calculated from
its transfer potential obtained from the ionic partition diagram. It was suggested that the mechanism for transfer of MPPT
across the water/1,2-DCE) interface depends on the pH of the aqueous phase. The parameters of the facilitated proton transfer
across the water/1,2-DCE interface were evaluated as a quantitative measure of its lipophilicity. 相似文献
50.
S. R. Garaeva Ahmet Alper Aydin Adnan Aydin Bahattin Yalçin P. A. Fatullaeva A. A. Medzhidov 《Russian Journal of Applied Chemistry》2010,83(1):97-101
Structure of products formed in polyethylene oxidation by nitric acid was studied by NMR, IR, and electronic absorption spectroscopies
and derivatography. 相似文献