全文获取类型
收费全文 | 22916篇 |
免费 | 3328篇 |
国内免费 | 2443篇 |
专业分类
化学 | 16100篇 |
晶体学 | 276篇 |
力学 | 1353篇 |
综合类 | 187篇 |
数学 | 2296篇 |
物理学 | 8475篇 |
出版年
2024年 | 67篇 |
2023年 | 423篇 |
2022年 | 739篇 |
2021年 | 843篇 |
2020年 | 849篇 |
2019年 | 833篇 |
2018年 | 711篇 |
2017年 | 736篇 |
2016年 | 1015篇 |
2015年 | 1035篇 |
2014年 | 1170篇 |
2013年 | 1606篇 |
2012年 | 1866篇 |
2011年 | 1989篇 |
2010年 | 1297篇 |
2009年 | 1266篇 |
2008年 | 1463篇 |
2007年 | 1349篇 |
2006年 | 1217篇 |
2005年 | 970篇 |
2004年 | 774篇 |
2003年 | 658篇 |
2002年 | 632篇 |
2001年 | 461篇 |
2000年 | 454篇 |
1999年 | 481篇 |
1998年 | 422篇 |
1997年 | 423篇 |
1996年 | 463篇 |
1995年 | 365篇 |
1994年 | 381篇 |
1993年 | 272篇 |
1992年 | 254篇 |
1991年 | 233篇 |
1990年 | 165篇 |
1989年 | 129篇 |
1988年 | 117篇 |
1987年 | 97篇 |
1986年 | 95篇 |
1985年 | 85篇 |
1984年 | 58篇 |
1983年 | 49篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
113.
Lu Ban Liang Zhao Bang-Li Deng Yan-Ping Huang Zhao-Sheng Liu 《Analytical and bioanalytical chemistry》2013,405(7):2245-2253
A method based on reverse atom transfer radical polymerization (R-ATRP) and molecular crowding has been used for design and synthesis of monolithic molecularly imprinted polymers (MIPs) capable of recognizing ibuprofen (IBU). 4-Vinylpyridine (4-VP) was used as the functional monomer, and ethylene glycol dimethacrylate (EDMA) was the crosslinking monomer. Azobisisobutyronitrile (AIBN)–CuCl2–N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) was used as the initiating system. Compared with conventional radical polymerization-based IBU-MIPs, the imprinting effects of the obtained IBU-MIPs was enhanced, suggesting the merit of combination of reverse ATRP and molecular crowding. In addition, it was found that the polymerization time of the molecularly imprinted monolithic column, the amount of template, the degree of crosslinking, and the composition of mobile phase greatly affected retention of the template and the performance of molecular recognition . Figure
Schematic representation of molecular imprinting under molecular crowding conditions in the presence of R-ATRP 相似文献
114.
Polymer light-emitting electrochemical cells (PLECs) employ a thin layer of a luminescent conjugated polymer admixed with an ionic source and an ionic conductor for the in-situ formation of p-i-n junction and subsequent efficient injections of both electrons and holes.The junction formation enables the use of air-stable conductors as the cathode and a relatively thick emissive polymer layer that is more compatible with low-cost solution-based processes.This paper overviews the operation mechanism of the PLECs,the properties and drawbacks of the devices.The employment of crosslinkable ionic conductors to stabilize the p-i-n junction is reviewed.The resulting static junction electroluminesces light at high brightness,high efficiency,and prolonged lifetime.Silver paste and carbon nanotubes can be used as the cathode,thus,PLECs were fabricated by lamination.Using single wall carbon nanotubes coated elastic substrate as both anode and cathode,the PLECs can be made highly stretchable. 相似文献
115.
α,β-Unsaturated aldimines were specifically oxidized to amides with Oxone in the presence of AlCl3 as a Lewis acid in CH2Cl2. No migration of aryl group occurred in the rearrangement reaction. 相似文献
116.
Guilin Xu Lingling Yang Min Zhong Chen Li Xiaojing Lu Xianwen Kan 《Mikrochimica acta》2013,180(15-16):1461-1469
We have combined the molecular imprinting and the layer-by-layer assembly techniques to obtain molecularly imprint polymers (MIPs) for the electrochemical determination of p-nitrophenol (p-NPh). Silica microspheres functionalized with thiol groups and gold nanoparticles (Au-NPs) were assembled on a gold electrode surface layer by layer. The electrode was then immersed into a solution of pyrrole and p-NPh (the template), and electropolymerization led to the creation of a polymer-modified surface. After the removal of the silica spheres and the template, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) were employed to characterize the surface. The results demonstrated the successful fabrication of macroporous MIPs embedded with Au-NPs on the gold electrode. The effects of monomer concentration and scan rate on the performance of the electrode were optimized. Excellent recognition capacity is found for p-NPh over chemically similar species. The DPV peak current is linearly related to concentration of p-NPh in the 0.1 μM to 1.4 mM range, with a 0.1 μM limit of detection (at S/N?=?3). Figure
Molecularly imprinted polymers (MIPs) and nanomaterials were combined to prepare a novel macroporous structured MIPs based electrochemical sensor for the investigation of an environmental pollutant, p-nitrophenol (p-NPh). The sensor exhibited a fast binding dynamics, good specific adsorption capacities, and high selective recognition to p-NPh. 相似文献
117.
Qian-Li Zhang Ai-Jun Wang Zi-Yan Meng Ya-Hui Lu Hong-Jun Lin Jiu-Ju Feng 《Mikrochimica acta》2013,180(7-8):581-587
We have prepared porous and network-like nanofilms of gold by galvanic replacement of a layer of copper particles acting as a template. The films were first characterized by scanning electron microscopy and X-ray diffraction, and then modified with cysteamine so to enable the covalent immobilization of the enzyme microperoxidase-11. The immobilized enzyme undergoes direct electron transfer to the underlying electrodes, and the electrode displays high electrocatalytic activity towards the reduction of oxygen and hydrogen peroxide, respectively, owing to the largely enhanced electroactive surface of the porous gold film. The detection limit of H2O2 is 0.4 μM (3 S/N). Figure
In this work, porous network-like Au films were prepared by galvanic replacement using Cu film as a sacrificial template. The cysteamine modified Au film was used to immobilize microperoxidase-11, which showed good stability and excellent electrochemical performance towards the reduction of O2 and H2O2, respectively 相似文献
118.
A simple and efficient protocol for preparing benzimidazoles via Fe(NO3)3 · 9H2O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields. 相似文献
119.
Abstract Cefpirome was synthesized in 37.7% overall yield from 3-chloromethyl-7-phenylacetylamino cephalosporanic acid p-methoxybenzyl ester (GCLE) by sequential substitution of C-3 chloride with iodide and 2,3-cyclopentenopyridine, followed by a one-pot procedure including deprotection of carboxyl group, hydrolysis of 7-phenylacetamido, and reaction with 2-mercaptobenzothiazolyl-(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetate (MAEM). The reaction conditions were as follows: obtained from GCLE at low temperature (?5 to 0 °C) and absence of light, 3-iodomethyl-7-phenylacetylamino cephalosporanic acid p-methoxybenzyl ester (GILE) without purification was reacted directly with 2,3-cyclopentenopyridine, in which the molar ratio of GCLE, NaI, and 2,3-cyclopentenopyridine was 1:2:4, and the molar ratio of the resulting compound p-methoxybenzyl 7-phenylacetylamido-3-(2,3-cyclopenteno-1-pyridinio)methyl-3-cephem-4-carboxylate iodide and MAEM was 1:1.1. The structure of the intermediate and the target compound obtained were determined by nuclear magnetic resonance spectra and mass spectroscopy. 相似文献
120.
New well-defined monodisperse oligocarbazoles-functionalized anthracenes An-OCZn (n = 1, 2, 3) have been synthesized through Suzuki cross-coupling reaction of the brominated oligocarbazoles and 9,10-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)anthracene. They show good solubility in organic solvents, including dichloromethane, chloroform, toluene, ethyl acetate, and tetrahydrofuran. It should be noted that, in the case of An-OCZn, the formation of the excimer based on anthracene unit is suppressed completely due to the introduction of oligocarbazoles in 9,10-position of anthracene so that an intense blue-emitting has been afforded. In addition, the obtained An-OCZn exhibit good electrochemical and thermal stabilities. Thus, the oligocarbazoles-functionalized anthracenes can be a class of promising candidates for novel blue-emitting materials employed in OLEDs or related devices. 相似文献