全文获取类型
收费全文 | 153篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 94篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 7篇 |
物理学 | 50篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有160条查询结果,搜索用时 15 毫秒
31.
Renganathan Jayakumar Shanmugam Jayashree Balumuri Annapurna Sundaram Seshadri 《Applied biochemistry and biotechnology》2012,168(7):1849-1866
This study describes the characterization and optimization of medium components for an extracellular detergent, surfactant, organic solvent and thermostable serine alkaline protease produced by alkaliphilic Bacillus pumilus MCAS8 strain isolated from Pulicat lake sediments, Tamil Nadu, India. The strain yielded maximum protease (2,214?U/ml) under optimized conditions: carbon source, citric acid??1.5?% (w/w); inducer, soyabean meal??2?% (w/w); pH?11.0; shaking condition 37?°C for 48?h. The enzyme had pH and temperature optima of 9.0 and 60?°C, respectively. The enzyme displayed the molecular mass of 36?kDa in sodium dodecyl sulphate?Cpolyacrylamide gel electrophoresis study and exhibited activity at a wide range of pH (6.0?C11.0) and thermostability (20?C70?°C). More than 70?% residual activity was observed when the enzyme was incubated with dithiothreitol, ethylenediaminetetraacetic acid, ethylene glycol tetraacetic acid and H2O2 for 30?min. The protease activity was also enhanced by divalent cations such as Ba2+, Ca2+ and Mg2+ and was strongly inhibited by Fe2+, Zn2+, Sr2+, Hg2+ and urea. The enzyme retained more than 50?% of its initial activity after pre-incubation for 1?h in the presence of 5?% (v/v) organic solvents such as dimethyl sulphoxide and acetone. The protease could hydrolyse various native proteinaceous substrates (1?%?w/v) such as bovine serum albumin, casein, skim milk, gelatine, azocasein and haemoglobin. Wash performance analysis of enzyme revealed that it could effectively remove blood stains from the cotton fabric, thus making it suitable to use as an effective detergent additive. The protease enzyme also exhibited promising result in the dehairing of goat skin. The potency of the eco-friendly enzyme without using any chemicals against washing and dehairing showed that the enzyme could be used for various industrial applications. 相似文献
32.
S.K. Kulshreshtha O.D. Jayakumar V. Sudarsan 《Journal of Physics and Chemistry of Solids》2004,65(6):1141-1146
Mixed phosphates Al1−xGaxPO4 (0.0≤x≤1.0), with orthorhombic structure, have been prepared by co-precipitation method followed by annealing at high temperature (T≈1350 °C) and investigated by using powder X-ray diffraction and NMR spectroscopy. A systematic decrease observed for the unit cell parameters with increasing Ga3+ contents, suggests the formation of a solid solution between AlPO4 and GaPO4. 31P MAS NMR spectra of both AlPO4 and GaPO4 show a single peak at δ=−24.6 and −8.5 ppm, respectively. For mixed phosphates, multi-component 31P NMR spectra characterized by varying values of chemical shifts, have been observed due to the existence of different types of 31P structural configurations formed by varying number of Al3+ and Ga3+ as its next nearest neighbours. The intensity analysis of these component peaks suggested a perfectly random distribution of Al3+ and Ga3+ cations in these mixed phosphates. Chemical shift anisotropy parameters for the different structural configurations of 31P have been evaluated from the intensity analysis of the spinning side bands corresponding to different isotropic peaks. 27Al NMR spectra of mixed phosphate samples exhibited a slightly asymmetric broad peak at δ≈42.0 ppm, which is characteristic of the tetrahedral configuration of Al3+ ions with significant covalent bonding between the metal and oxygen ions. 相似文献
33.
P. Munshi P. Jayakumar P. Satyamurthy T. K. Thiyagarajan N. S. Dixit N. Venkatramani 《Experiments in fluids》1998,24(5-6):424-430
A steady-state vertical mercury-nitrogen flow system has been investigated using three tomographic algorithms. Void-fraction
profiles have been reconstructed by the data collected by a 60 mCi gamma-ray source and a single Na(Tl) detector. The results
indicate excellent agreement (within ±1%) between the least-squares-solution and the chord-segment-inversion algorithms. The
data-collection time for each data-ray was varied so that in each case 3000 counts could be collected to reduce the detrimental
effect of Poisson statistics in the reconstructed profiles. Eleven sets of data have been collected for nitrogen flow-rates
between 0.00123 and 0.00884 kg/s. The mercury flow-rates were between 17.6 and 34.1 kg/s. The resulting cross-sectional average
void varied between 0.10 and 0.38.
Received: 13 March 1997/Accepted: 12 September 1997 相似文献
34.
Jayakumar Ramanathan 《manuscripta mathematica》1988,60(4):417-422
Isometric deformations of compact minimal surfaces in the standard three-sphere are studied. It is shown that a given surface admits only finitely many noncongruent minimal immersions intoS
3 with the same first fundamental form. 相似文献
35.
Jayakumar R. Taggart D.P. Parker M.R. Fleischmann H.H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(1):41-44
In the RECE-Christa device, hybrid-type compact toroid rings are generated by inducing large toroidal plasma currents I p in strong electron rings using a thin induction coil positioned along the ring axis. Starting from field-reversal values δp =50-120% of the original pure fast-electron ring, the induced plasma current I p raises δ to a maximum value of up to 240% with I p contributing more than 50% of the total ring current. The generated hybrid compact toroid configurations appear gross-stable during the full I p pulse length (half-amplitude width about 100 μs) 相似文献
36.
Bharali DJ Lucey DW Jayakumar H Pudavar HE Prasad PN 《Journal of the American Chemical Society》2005,127(32):11364-11371
A novel method for the synthesis of highly monodispersed hydrophillic InP-ZnS nanocrystals and their use as luminescence probes for live cell imaging is reported. Hydrophobic InP-ZnS nanocrystals are prepared by a new method that yields high-quality, luminescent core-shell nanocrystals within 6-8 h of total reaction time. Then by carefully manipulating the surface of these passivated nanocrystals, aqueous dispersions of folate-conjugated nanocrystals (folate-QDs) with high photostability are prepared. By use of confocal microscopy, we demonstrate the receptor-mediated delivery of folic acid conjugated quantum dots into folate-receptor-positive cell lines such as KB cells. These folate-QDs tend to accumulate in multi-vescicular bodies of KB cells after 6 h of incubation. Receptor-mediated delivery was confirmed by comparison with the uptake of these particles in folate-receptor-negative cell lines such as A549. Efficient two-photon excitation of these particles and two-photon imaging using these particles are also demonstrated. The use of these InP-ZnS nanoparticles and their efficient two-photon excitation can be potentially useful for deep tissue imaging for future in vivo studies. 相似文献
37.
[reaction: see text] The iminium ions generated in situ by the oxidation of N,N-diisopropyl-N-benzylamine using iodine react with diaryl ketones in the presence of TiCl4/R3N to give the corresponding 3,3-diarylcyclobutanones in moderate to good yields (49-86%). The 3,3-diarylcyclobutanone iminium ions formed in this transformation was reduced in situ with B2H6 to produce the corresponding 3,3-diarylcyclobutylamines (52-79% yields), a class of compounds with potential antidepressant activity. In addition, a series of N,N-dimethyl-3,3-diarylcyclobutylamines were synthesized by the reductive amination of the corresponding 3,3-diarylcyclobutanone derivatives. 相似文献
38.
[reaction: see text] Design and synthesis of a novel class of dendrons based on an AB(4) monomer are described. These dendrons have been evaluated by using dendritic encapsulation of a redox active core. The electrochemical properties of symmetric ferrocene-cored dendrimers show that significant alterations in redox potential and heterogeneous electron-transfer rate constants could be achieved even at lower generations. 相似文献
39.
S. N. Achary O. D. Jayakumar S. J. Patwe A. B. Shinde P. S. R. Krishna S. K. Kulshreshtha A. K. Tyagi 《Pramana》2008,71(5):941-946
Herein we report the results of detailed crystallographic studies of Ca1−x
Ba
x
Zr4P6O24 compositions from combined Rietveld refinements of powder X-ray and neutron diffraction data. All the studied compositions
crystallize in rhombohedral lattice (space group R-3 No. 148). A continuous solid solution is concluded from the systematic
variation of unit cell parameters. The variation of unit cell parameters with the composition indicates decreasing trend in
a parameter with increasing Ba2+ concentration contrast to an increasing trend in c parameter.
相似文献
40.
D. Santhosh Kumar K. P. Jayakumar S. Balachandran 《Journal of Physical Organic Chemistry》2010,23(8):783-788
1,2‐Diphenylethyl chloride undergoes solvolysis by SN1 mechanism in aqueous organic solvents. The α‐phenyl group of 1,2‐diphenylethyl chloride enters into conjugation with the developing carbocationic centre. The β‐phenyl group on the other hand was unable to extend its conjugation via neighbouring group participation due to steric inhibition of resonance in the formation of non‐classical carbocation. 1,2‐Diphenylethyl chloride thus behaves similar to 1‐phenylethyl chloride in its solvolysis pattern. The solvolytic rate studies of chloride and methanesulphonate of 1,2‐diphenylethyl alcohol in various aqueous organic solvents show that the dispersion observed in the Winstein–Grunwald plot is not due to a change in leaving group but due to the difference in solvation requirements of aromatic and aliphatic groups. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献