全文获取类型
收费全文 | 1806篇 |
免费 | 23篇 |
国内免费 | 89篇 |
专业分类
化学 | 1817篇 |
力学 | 3篇 |
综合类 | 1篇 |
数学 | 7篇 |
物理学 | 90篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 34篇 |
2021年 | 28篇 |
2020年 | 36篇 |
2019年 | 59篇 |
2018年 | 30篇 |
2017年 | 52篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 41篇 |
2013年 | 66篇 |
2012年 | 155篇 |
2011年 | 67篇 |
2010年 | 69篇 |
2009年 | 110篇 |
2008年 | 108篇 |
2007年 | 109篇 |
2006年 | 97篇 |
2005年 | 108篇 |
2004年 | 96篇 |
2003年 | 65篇 |
2002年 | 49篇 |
2001年 | 19篇 |
2000年 | 33篇 |
1999年 | 37篇 |
1998年 | 48篇 |
1997年 | 21篇 |
1996年 | 31篇 |
1995年 | 29篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 31篇 |
1990年 | 46篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 9篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1918条查询结果,搜索用时 15 毫秒
71.
72.
73.
Asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through dynamic covalent kinetic resolution
The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures. 相似文献
74.
75.
76.
77.
Cláudia A. Kodaira Ana Valéria S. Lourenço Maria Cláudia F.C. Felinto Eduardo M.R. Sanchez Francisco J.O. Rios Luiz Antonio O. Nunes Magnus Gidlund Oscar L. Malta Hermi F. Brito 《Journal of luminescence》2011,131(4):727-731
Neodymium based fluorescence presents several advantages in comparison to conventional rare earth or enzyme-substrate based fluorescence emitting sources (e.g.Tb, HRP) . Based on this fact we have herein explored a Nd-based fluoroimmunoassay. We efficiently detected the presence of an oxidized low-density lipoprotein (oxLDL) in human plasma a well-known marker for cardiovascular diseases, which causes around 30% of deaths worldwide. Conventional fluoroimmunoassay uses time-resolved luminescence techniques, with detection in the visible range, to eliminate the fluorescence background from the biological specimens. By using an immunoassay based on functionalized Y2O3:Nd3+ nanoparticles, where the excitation and emission processes in the Nd3+ ion occur in the near-infrared (NIR) region, we have succeeded in eliminating the interferences from the biological fluorescence background, avoiding the use of time-resolved techniques. This yields higher emission intensity from the Nd3+-nanolabels and efficient detection of anti-oxidized low-density lipoproteins (anti-oxLDL) by Y2O3:Nd3+-antibody-antigen conjugation, leading to a novel biolabeling method. 相似文献
78.
Marcin Drag Jolanta Grembecka Paweł Kafarski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1591-1595
The design, stereo-, and enantioselective synthesis and activity prediction of aminophosphonic acids as new leucine aminopeptidase inhibitors will be discussed. 相似文献
79.
Akshay Kokil Sethumadhavan Ravichandran Jayant Kumar Ramaswamy Nagarajan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1004-1008
Polymers synthesized from naturally derived monomers are valuable since they decrease the reliance on petroleum based feed stocks. Cashew nut shell oil (CNSL) is a side-product from processing of edible Cashew nuts of Annacardium occidentale. One of the major components of CNSL is cardanol, which is a phenol derivative having an unsaturated pentadecyl substituent in the ‘meta’ position with varying amount of unsaturation (no double bonds to three double bonds). The substituent in the meta position can also be hydrogenated to yield completely saturated hydrogenated cardanol. Cardanol can be utilized to stabilize the dispersions of oil in water and vice versa since it displays amphiphilic behavior owing to the phenolic head and the C15 aliphatic tail. Here we report the horseradish peroxidase (HRP) catalyzed polymerization of cardanol at oil water interface to obtain polycardanol microcapsules. A synthetic analogue of hydrogenated cardanol, 3-pentadecylphenol (3PDP), was also oxidatively polymerized at the oil-water interface to obtain Poly(3-pentadecylphenol) microcapsules. 相似文献
80.
Monoamine oxidase (MAO) enzymes regulate the level of neurotransmitters by catalyzing the oxidation of various amine neurotransmitters, such as serotonin, dopamine and norepinephrine. Therefore, they are the important targets for drugs used in the treatment of depression, Parkinson, Alzeimer and other neurodegenerative disorders. Elucidation of MAO-catalyzed amine oxidation will provide new insights into the design of more effective drugs. Various amine oxidation mechanisms have been proposed for MAO so far, such as single electron transfer mechanism, polar nucleophilic mechanism and hydride mechanism. Since amine oxidation reaction of MAO takes place between cofactor flavin and the amine substrate, we focus on the small model structures mimicking flavin and amine substrates so that three model structures were employed. Reactants, transition states and products of the polar nucleophilic (proton transfer), the water-assisted proton transfer and the hydride transfer mechanisms were fully optimized employing various semi-empirical, ab initio and new generation density functional theory (DFT) methods. Activation energy barriers related to these mechanisms revealed that hydride transfer mechanism is more feasible. 相似文献