全文获取类型
收费全文 | 121篇 |
免费 | 9篇 |
专业分类
化学 | 78篇 |
力学 | 2篇 |
数学 | 10篇 |
物理学 | 40篇 |
出版年
2024年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1995年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有130条查询结果,搜索用时 15 毫秒
51.
InBr3 as a versatile and highly efficient catalyst for the synthesis of 3-allyl- and 3-benzylindoles
J.S. Yadav B.V. Subba Reddy S. Aravind G.G.K.S. Narayana Kumar A. Srinivas Reddy 《Tetrahedron letters》2007,48(35):6117-6120
Indoles undergo smooth alkylation with allylic and benzylic alcohols in the presence of 10 mol % of InBr3 under mild conditions to produce 3-allyl- and 3-benzyl indoles, respectively, in excellent yields and with high selectivity. This is the first example of the alkylation of indoles with benzylic alcohols using InBr3 as an acid catalyst. 相似文献
52.
P. Shajesh S. Smitha P. R. Aravind K. G. K. Warrier 《Journal of Sol-Gel Science and Technology》2009,50(3):353-358
The effect of an organically modified precursor, 3-glycidoxypropyltrimethoxysilane in an ambient pressure process involving
aging in silane solution for silica aerogels is presented. The effect of increasing trialkoxysilane/tetraalkoxysilane precursor
ratio and the influence of water to Si molar ratio on the gelation and adsorption properties were investigated. An optimum
water to Si molar ratio (8) gave the fastest gelation for all precursor ratios indicating a balance between the increase in
rate of hydrolysis and a decrease in concentration of the monomers. Surface area analysis proved that in the dried gel, the
organic groups are largely present on the pore walls and prevent the condensation of the silanol groups during drying. This
in turn prevents pore collapse and further increases the total pore volume. The inclusion of the organically functionalised
silane in the process further enhances the ambient pressure drying through this effect. 相似文献
53.
Conventional methods which extract dispersion parameters of an optical fiber using four wave mixing rely on the measurement of optical power in the generated wavelengths, and hence are prone to measurement errors. We propose and demonstrate a power-independent method to extract the dispersion curve of a fiber using four wave mixing (FWM). The analytical equations that have been traditionally used to estimate the phase mismatch in FWM are modified to cater to low-dispersion fibers, and are verified. Experiments to obtain the dispersion curve of a low-dispersion and highly nonlinear fiber are discussed and the results are analyzed. Limitations of any FWM-based method to extract the dispersion curve of a fiber are presented for the first time. 相似文献
54.
We study the entropy of an N-site Kac ring in a non-equilibrium state. As the system dynamically evolves towards equilibrium and eventually to the initial state exhibiting Poincaré recurrence, we see that the entropy saturates over a period of time which is large for large N. At about the time of order N, the system starts to return to its initial state. We show that there is indeed a perfect “recurrence of statistical fluctuations”, which we are able to explore, as Kac’s ring possesses a finite recurrence time. Entropy is shown here to be a periodic function of the Poincaré recurrence time. 相似文献
55.
Biswanath Das Rathod Aravind Kumar Ponnaboina Thirupathi 《Helvetica chimica acta》2007,90(6):1206-1210
A simple and efficient method has been developed for the synthesis of α‐amino nitriles from aldehydes, amines and trimethylsilyl cyanide (Me3SiCN) in the presence of a catalytic amount of cyanuric acid at room temperature. 相似文献
56.
57.
58.
MK Hossain-Ibrahim K Rezajooi JK MacNally MRJ Mason AR Lieberman PN Anderson 《BMC neuroscience》2006,7(1):8-21
Background
Inflammation around cell bodies of primary sensory neurons and retinal ganglion cells enhances expression of neuronal growth-associated genes and stimulates axonal regeneration. We have asked if inflammation would have similar effects on corticospinal neurons, which normally show little response to spinal cord injury. Lipopolysaccharide (LPS) was applied onto the pial surface of the motor cortex of adult rats with or without concomitant injury of the corticospinal tract at C4. Inflammation around corticospinal tract cell bodies in the motor cortex was assessed by immunohistochemistry for OX42 (a microglia and macrophage marker). Expression of growth-associated genes c-jun, ATF3, SCG10 and GAP-43 was investigated by immunohistochemistry or in situ hybridisation. 相似文献59.
Aravind Manerswammy Stuart H. Munson-McGee Robert Steiner Charles L. Johnson 《Journal of Thermal Analysis and Calorimetry》2009,97(3):895-902
D-optimal experimental designs are developed for differential scanning calorimetry experiments conducted under non-isothermal,
constant heating modes under the assumption that the kinetics can be described by an nth order model. Two separate cases are
considered: single-scan experiments in which the entire rate of reaction versus temperature curve is available, albeit only
at selected points, and multiple-scan experiments in which only the temperature at the maximum in the DSC curve is available
but it is known at several heating rates. For the single-scan experiment, the D-optimal heating rate and critical extents
of reaction where the data should be analyzed are determined. For the multiple-scan experiment the three D-optimal heating
rates are determined. For both cases, a hypothetical example is given which illustrates the success and limitations of this
approach. 相似文献
60.
Ahmed Sodiq Aravind V. Rayer Akinola A. Olanrewaju Mohammad R. M. Abu Zahra 《国际化学动力学杂志》2014,46(12):730-745
The pseudo–first‐order reaction rate constants (k0, s?1) for the reaction of carbon dioxide in aqueous solutions of sodium taurate (NaTau) and sodium prolinate (NaPr) were measured using a stopped‐flow technique at a temperature range of 298–313 K. The solutions concentration varied from 5 to 50 mol m?3 and from 4 to 12 mol m?3 for NaTau and NaPr, respectively. Comparing the k0 values, aqueous NaPr was found to react very fast with CO2 as compared with the industrial standard aqueous monoethanolamine (MEA) and aqueous sodium taurate (NaTau) was found to react slower than aqueous MEA at the concentration range considered in this work. For the studied amino acid salts, the order of the reactions was found to be unity with respect to the amino acid salt concentration. Proposed reaction mechanisms such as termolecular and zwitterion reaction mechanisms for the reaction of CO2 with aqueous solutions were used for calculating the second‐order reaction rate constants (k2, m3 mol?1 s?1). The formation of zwitterion during the reaction with CO2 was found to be the rate‐determining step, and the deprotonation of zwitterion was instantaneous compared to the reverse reaction of zwitterion to form an amino acid salt. The contribution of water was established to be significant for the deprotonation of zwitterion. Comparing the pseudo–first‐order reaction rate constants (k0, s?1) of various amino acid salts with CO2, NaPr was found to be the faster reacting amino acid salt. The activation energy for NaTau was found to be 48.1 kJ mol?1 and that of the NaPr was found to be 12 kJ mol?1. The Arrhenius expressions for the reaction between CO2 and the studied amino acid salts are 相似文献