全文获取类型
收费全文 | 109篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
化学 | 96篇 |
力学 | 4篇 |
数学 | 11篇 |
物理学 | 13篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 18篇 |
2011年 | 13篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
121.
Using a one-pot synthesis, thiol-organosilica nanoparticles (NPs) made from (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, and (3-mercaptopropyl)methyldimethoxysilane have been successfully prepared. We compared the synthesis processes of thiol-organosilica NPs made of these three kinds of organosilicates, as well as particles made from tetraethoxysilicate (TEOS), at concentrations varying between 6.25 and 200 mM. We examined three types of synthetic conditions: the St?ber method, in which particles are prepared in 65% ethanol, and two entirely aqueous solvent syntheses, containing either 2% or 27% ammonium hydroxide. The synthetic mixtures were examined using transmission electron microscopy (TEM) to evaluate the as-prepared NPs. The formation trends and rates for these organosilica NPs vary with differing organosilicate precursors, concentrations, and synthetic conditions. The St?ber method is not suitable for formation of thiol-organosilica NPs as compared with the case of TEOS, but the conditions without ethanol and with 27% ammonium hydroxide are suitable for the formation of thiol-organosilica NPs. The size distributions of the formed NPs were evaluated using TEM and dynamic light scattering. The mean diameters of NPs increase with increasing concentrations of silicate, but the size distributions of NPs prepared under various conditions also differ between silicate sources. Thiol-organosilica NPs internally functionalized with fluorescent dye were also prepared using a one-pot synthesis and were characterized using fluorescence microscopy. The thiol-organosilica NPs retain fluorescent dye maleimide very well. In addition, rhodamine B-doped thiol-organosilica NPs show higher fluorescence than thiol-organosilica NPs prepared with rhodamine red maleimide. The surface of thiol-organosilica NPs contains exposed thiol residues, allowing the covalent attachment of fluorescent dye maleimide and protein maleimide. This is the first report describing the synthesis of thiol-organosilica NPs made of three kinds of thiol-organosilicates, differences in nanoparticle formation due to the kinds and concentrations of thiol-organosilicate and due to synthetic conditions, and the advantages of thiol-organosilica NPs due to the existence of both interior and exterior thiol residues. 相似文献
122.
A new algorithm of two-electron repulsion integral (ERI) calculations has been developed. In this algorithm, Cartesian axes
are rotated to make several coordinate components zero or constant using the Pople–Hehre algorithm, and ERIs are evaluated
at the rotated coordinate by the McMurchie–Davidson algorithm. The new algorithm applicable to (ss|ss) to (dd|dd) ERIs is implemented in the quantum chemistry program GAMESS. Test calculations show that the new algorithm reduces the computational
times by 10–40%, as compared with the Pople–Hehre and the Rys quadrature algorithms. 相似文献
123.
Suzuki Y Kanai M Matsunaga S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7654-7657
Access to chiral isoindolinones: The Mg-catalyzed enantioselective benzylic C-H bond functionalization of isoindolinones is described. A Bu(2) Mg/Schiff base catalyst (1:1) promoted the enantioselective addition of N-Boc-isoindolinones to aryl, heteroaryl, alkenyl, and alkyl imines, giving 3-substituted isoindolinones in 84-99?%?ee and 50:50-91:9?d.r. (see scheme). 相似文献
124.
Yudai Huang Rongrong Jiang Shu-Juan Bao Zhifang Dong Yali Cao Dianzeng Jia Zaiping Guo 《Journal of Solid State Electrochemistry》2009,13(5):799-805
Nanostructured LiAl
x
Mn2 − x
O4 − y
Br
y
particles were synthesized successfully by annealing the mixed precursors, which were prepared by room-temperature solid-state
coordination method using lithium acetate, manganese acetate, lithium bromide, aluminum nitrate, citric acid, and polyethylene
glycol 400 as starting materials. X-ray diffractometer patterns indicated that the particles of the as-synthesized samples
are well-crystallized pure spinel phase. Transmission electron microscopy images showed that the LiAl
x
Mn2 − x
O4 − y
Br
y
samples consist of small-sized nanoparticles. The results of galvanostatic cycling tests revealed that the initial discharge
capacity of LiAl0.05Mn1.95O3.95Br0.05 is 119 mAh g−1; after the 100th cycle, its discharge capacity still remains at 92 mAh g−1. The introduction of Al and Br in LiMn2O4 bring a synergetic effect and is quite effective in increasing the capacity and elevating cycling performance. 相似文献