全文获取类型
收费全文 | 75篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
化学 | 56篇 |
力学 | 1篇 |
数学 | 4篇 |
物理学 | 21篇 |
出版年
2022年 | 5篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2002年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有82条查询结果,搜索用时 0 毫秒
41.
Mechanistic insights into Heck and Suzuki‐Miyaura cross coupling reactions with C59M (M = Pd/Ni) catalysts were developed. Density functional theory was used for the analysis of all the intermediates and transition states possible during C‐C cross coupling reactions over the catalysts under study. Oxidative addition, a step common to both Heck and Suzuki‐Miyaura cross coupling reactions, was observed to proceed with smaller activation barriers over C59Pd. Heck coupling of iodobenzene with styrene was observed to proceed via oxidative addition, migratory insertion, and reductive elimination steps. The free energy barriers for oxidative addition, migratory insertion, and reductive elimination steps were 14.8, 11.6, and 4.8 kcal/mol, respectively, over C59Pd, and 17.4, 79.3, and 17.4 kcal/mol, respectively, over C59Ni, indicating oxidative addition and migratory insertion to be the rate‐determining steps over C59Pd and C59Ni, respectively. Similarly for Suzuki‐Miyaura coupling reaction, activation barriers for oxidative addition, transmetalation, and reductive elimination steps were 14.8, 52.4, and 7.9 kcal/mol, respectively, over C59Pd, and 17.4, 64.7, and 60.2 kcal/mol, respectively, over C59Ni, indicating transmetalation step to be the rate‐determining step over both the heterofullerenes. 相似文献
42.
Dr. Elena Vishnyakova Dr. Bruce E. Brinson Dr. Lawrence B. Alemany Dr. Manjusha Verma Prof. W. Edward Billups 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1452-1460
The hydrogenation of commercial graphite using lithium/ammonia as the reducing agent and tert‐butyl alcohol as a proton source was investigated. Characterization of the products after successive reductions of the same material by high‐resolution transmission electron microscopy revealed a new material that was replete with edge and circular dislocations. Analysis by solid‐state 13C NMR spectroscopy indicates that after three reductions, the remaining aromatic rings appear to be interior benzene rings. NMR spectroscopy also offers strong evidence for the presence of small amounts of tert‐butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely between the layers of the hydrographene. 相似文献
43.
A micro-LC method was developed for the fast and sensitive analysis of aromatic amines by electrochemical detection. The chromatographic separation of nine carcinogenic aromatic amines was performed on an ABZ + PLUS column with detection limits up to pM L(-1) levels. Mobile phase comprised of methanol-acetate buffer of pH 5 (45:55, v/v) used at a flow rate of 0.2 ml min(-1). The detection was performed with a 6 mm glassy carbon electrode at an applied potential of 0.8 V versus Ag/AgCl. An intraday RSD for retention time and peak area were between 0.22% and 0.73% and 1.86% and 4.03%, respectively. The interdays RSD for retention time and peak area were between 0.47% and 1.35% and 2.04% and 4.42%, respectively. The applicability of the assay has been demonstrated by analyzing these aromatic amines in lake water and synthetic food colour additives. A comparison is given between electrochemical and UV detection. 相似文献
44.
45.
46.
Direct transfer of micro-molded electrodes for enhanced mass transport and water management in PEMFC
Ashvini B. Deshmukh Vinayak S. Kale Vishal M. Dhavale K. Sreekumar K. Vijayamohanan Manjusha V. Shelke 《Electrochemistry communications》2010,12(11):1638-1641
Soft lithography technique is used to micropattern the electrodes on the electrolyte membrane of polymer electrolyte fuel cell (PEMFC) in order to alleviate the issues due to poor water management and inadequate reactant distribution in the fuel cell environment. Membrane electrode assembly with the micropatterned electrode has shown an increase in power density at a higher temperature as well as at a higher relative humidity when compared to a flat electrode. Consistency in cell performance is observed in the case of micropatterned electrodes. 相似文献
47.
Patil Shivaraj A. K.H. Nagachandra Mannekutla James R. Chavan Shrikrupa K. Inamdar Sanjeev R. 《Journal of fluorescence》2022,32(2):647-659
Journal of Fluorescence - With a view to understand the nature of solute solvent interactions, rotational reorientation times (τr) of three medium sized dipolar laser dyes viz.,... 相似文献
48.
A number of mercurated indoles were prepared. Their spectroscopic data (UV,ir,1H-NMR and13C-nmr) are reported. Our results contradict certain data appearing in previous reports on similar compounds. When heated in acetic
acid mercurated compounds decomposed, although the products formed were not identical with those obtained earlier from the
same substrates by the action of thallium(III) acetate in acetic acid. Reaction of l-methylindole-3-mercuriacetate with styrene
in the presence of lithium tetrachloropalladate furnished a product which was tentatively assigned the structure 9-methyl-1,3-diphenyl-1,
2, 3, 4-tetrahydrocarbazole. 相似文献
49.
Satish R. Inamdar 《Applied Physics A: Materials Science & Processing》2014,116(2):621-627
In this paper, we study the spatiotemporal dynamics of left-handed materials that contain nonlinear cavities. These materials, having a negative refractive index, exhibit a nonlinear electromagnetic behavior. The insertion of the left-handed material into an optical cavity results into a variety of branching behavior of optical oscillators that are degenerate. The optical Kerr cavity considered in this work contains a cubic nonlinearity. The objective of this work was to investigate how branching behavior can yield useful information about the relative amount of left-handed and right-handed material controlling the diffraction in cavity. We will apply the reductive perturbation method-based multi-equation bifurcation theory to a scalar nonlinear Schrodinger equation and show how period-doubling occurs during optical wave propagation. 相似文献
50.
The rotational dynamics of four structurally similar polar molecules viz., coumarin 440, coumarin 450, coumarin 466 and coumarin
151 has been studied in binary mixtures comprising of dimethyl sulphoxide and water at room temperature using the steady state
fluorescence depolarization method and time correlated single photon counting technique. The binary mixtures are characterized
by the fact that at a particular composition the viscosity (η) of the solution reaches a maximum value that is higher than the viscosities of either of the two co-solvents. The dielectric
properties of the solution change across the composition range and the qualitative features of the solvent relaxation dynamics
in complex systems are known to differ from those in simple solutions. A hook type profile of rotational reorientation time
(τ
r
) vs viscosity (η) is obtained for all the solutes in dipolar aprotic mixture of dimethyl sulphoxide-water, with the rotational reorientation
times being longer in organic solvent-rich zone, compared to the corresponding isoviscous point in water-rich zone due to
strong hydrogen bonding. Fluorescence lifetimes as well as rotational reorientation times are sensitive to the composition
of the binary solvent system under study than to the viscosity suggesting the importance of local structure. The results are
discussed in the light of hydrodynamic and dielectric friction models.
Dedicated to Professor M.I. Savadatti on his 77th Birthday. 相似文献