全文获取类型
收费全文 | 162篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 97篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 8篇 |
物理学 | 55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 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 14篇 |
2008年 | 22篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有169条查询结果,搜索用时 15 毫秒
111.
S.K. Sharma P.K. Pujari K. Sudarshan D. Dutta M. Mahapatra S.V. Godbole O.D. Jayakumar A.K. Tyagi 《Solid State Communications》2009,149(13-14):550-554
We report results on positron annihilation spectroscopic (PAS) studies using lifetime and coincidence Doppler broadening techniques in zinc oxide (ZnO) nanoparticles (4 to 40 nm) synthesized by solid state pyrolytic reaction followed by annealing in the temperature range of 200 °C to 800 °C. Positron lifetime in the nanoparticles are observed to be higher than bulk lifetime in all the cases. Theoretical calculation of lifetime indicates the presence of either Zn or (Zn, O) vacancy clusters which migrate and anneal out at high temperature. Comparison of ratio spectra from coincidence Doppler broadening measurement and calculated electron momentum distribution indicates the presence of either Zn or (Zn, O) vacancies. In addition, photoluminescence (PL) measurements have been carried out to examine the role of defects on the intensity of emission in the visible region. 相似文献
112.
Jayakumar Beena Divya Kontham Kulangara Varsha Kesavan Madhavan Nampoothiri 《Applied biochemistry and biotechnology》2012,167(5):1314-1324
Five newly isolated lactic acid bacteria were identified as Weissella cibaria, Enterococcus faecium, and three different strains of Lactobacillus plantarum by 16S rRNA sequencing. Essential probiotic requirements of these isolates such as tolerance to phenol, low pH, high sodium chloride, and bile salt concentration were checked. Efficiency in adherence to mucin and hydrophobicity of the bacterial cell were also evaluated by in vitro studies. Antimicrobial activities against some pathogens were tried, and the sensitivity of these strains against 25 different antibiotics was also checked. Further studies revealed Weissella and Enterococcus as substantial producers of folic acid. Folate is involved as a cofactor in many metabolic reactions, and it has to be an essential component in the human diet. The folate level in the fermented samples was determined by microbiological assay using Lactobacillus casei NCIM 2364 as indicator strain. The three strains of L. plantarum showed significant inhibitory activity against various fungi that commonly contaminate food stuffs indicating their potential as a biopreservative of food material. 相似文献
113.
B.B. Lahiri S. Bagavathiappan P.R. Reshmi John Philip T. Jayakumar B. Raj 《Infrared Physics & Technology》2012,55(2-3):191-199
Active (lock-in and pulsed) thermography technique is used to quantify defect features in specimens of glass fiber reinforced polymer, high density rubber, low density rubber and aluminum bonded low density rubber with artificially produced defects. The relationship between phase contrast and thermal contrast with defect features are examined. Using lock-in approach, the optimal frequencies for different specimens are determined experimentally. It is observed that with increasing defect depth, the phase contrast increases while the thermal contrast decreases. Defects with radius to depth ratio greater than 1.0 are found to be discernible. The phase difference between sound and defective region as a function of square root of excitation frequency for glass fiber reinforced polymer specimen is found to be in good agreement with the predictions of Bennet and Patty model [1]. Further, using pulsed thermography, the defects depth could be measured accurately for glass fiber reinforced polymer specimen from the thermal contrast using the analytical approach of Balageas et al. [2]. 相似文献
114.
M. Jayakumar K. A. Venkatesan T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):79-85
The electrochemical behavior of ruthenium(III) and rhodium(III) in nitric acid medium has been studied at platinum and stainless
steel electrodes by cyclic voltammetry. The cyclic voltammograms consisted of surge in cathodic current occurring at potentials
of −0.13 V (Vs. Pd) and −0.15 V (Vs. Pd), which culminates into peaks at −0.47 V and −0.5 V due to the reductions of Ru(III)
and Rh(III) to their metallic forms, respectively. Electrodeposition was carried out at stainless steel electrode and unlike
palladium, the recovery of ruthenium and rhodium was limited to ~4% and ~14%, respectively. However, a different scenario
was observed in case of electrodeposition from a ternary solution containing all these platinum metals. Ruthenium and rhodium
deposited underpotentially in the presence of palladium and the recovery of ~20% and ~5% was observed for ruthenium and rhodium,
respectively. Evolution of RuO4 at the anode and deposition of RuO2 in the anodic side was observed in all cases during electrolysis of ruthenium(III) containing solutions. 相似文献
115.
Hamed Ashraf M. Shabana Ahmed A. Jayakumar Paramsothy Letherwood Michael D. 《Nonlinear dynamics》2011,66(4):809-824
Existing multibody system (MBS) algorithms treat articulated system components that are not rigidly connected as separate
bodies connected by joints that are governed by nonlinear algebraic equations. As a consequence, these MBS algorithms lead
to a highly nonlinear system of coupled differential and algebraic equations. Existing finite element (FE) algorithms, on
the other hand, do not lead to a constant mesh inertia matrix in the case of arbitrarily large relative rigid body rotations.
In this paper, new FE/MBS meshes that employ linear connectivity conditions and allow for arbitrarily large rigid body displacements
between the finite elements are introduced. The large displacement FE absolute nodal coordinate formulation (ANCF) is used to obtain linear element connectivity conditions in the case of large relative rotations between the finite
elements of a mesh. It is shown in this paper that a linear formulation of pin (revolute) joints that allow for finite relative
rotations between two elements connected by the joint can be systematically obtained using ANCF finite elements. The algebraic
joint constraint equations, which can be introduced at a preprocessing stage to efficiently eliminate redundant position coordinates,
allow for deformation modes at the pin joint definition point, and therefore, this new joint formulation can be considered
as a generalization of the pin joint formulation used in rigid MBS analysis. The new pin joint deformation modes that are
the result of C
0 continuity conditions, allow for the calculations of the pin joint strains which can be discontinuous as the result of the
finite relative rotation between the elements. This type of discontinuity is referred to in this paper as nonstructural discontinuity in order to distinguish it from the case of structural discontinuity in which the elements are rigidly connected. Because ANCF finite elements lead to a constant mass matrix, an identity generalized
mass matrix can be obtained for the FE mesh despite the fact that the finite elements of the mesh are not rigidly connected.
The relationship between the nonrational ANCF finite elements and the B-spline representation is used to shed light on the
potential of using ANCF as the basis for the integration of computer aided design and analysis (I-CAD-A). When cubic interpolation
is used in the FE/ANCF representation, C
0 continuity is equivalent to a knot multiplicity of three when computational geometry methods such as B-splines are used.
C
2 ANCF models which ensure the continuity of the curvature and correspond to B-spline knot multiplicity of one can also be
obtained. Nonetheless, B-spline and NURBS representations cannot be used to effectively model T-junctions that can be systematically
modeled using ANCF finite elements which employ gradient coordinates that can be conveniently used to define element orientations
in the reference configuration. Numerical results are presented in order to demonstrate the use of the new formulation in
developing new chain models. 相似文献
116.
Manickam Bakthadoss Anthonisamy Devaraj Jayakumar Srinivasan 《Journal of heterocyclic chemistry》2015,52(2):418-424
In this article, a simple method for the synthesis of bis(di(indolyl)aryl)methanes is described. The iodine‐catalyzed (5 mol %) reaction of indoles with various bis(salicylaldehyde) derivatives affords the bis(di(indolyl)aryl)methanes in excellent yields. The reaction works well under mild reaction condition with shorter reaction time. 相似文献
117.
Sayed FN Mandal BP Jayakumar OD Arya A Kadam RM Dixit A Naik R Tyagi AK 《Inorganic chemistry》2011,50(22):11765-11772
A series of Mn-substituted BaMgF(4) samples have been synthesized by a hydrothermal route. X-ray diffraction study reveals that the products are monophasic in nature. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) studies were carried out to investigate the morphology and stoichiometry for these compounds. X-ray photoelectron spectroscoy (XPS) and electron spin resonance (ESR) studies were done to confirm the oxidation state of dopant ion. Room temperature ferromagnetism was observed on Mn substitution at the Mg site in BaMgF(4) samples. The saturation magnetization increases initially, shows a peaking effect, and then decreases with further increase in Mn concentration in BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15). However, ferroelectricity was found to decrease with an increase in Mn concentration in the series of investigated BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15) samples. First-principle calculations, using the projector augmented wave potentials on Mn-substituted BaMgF(4), confirmed the decrease in magnetic moment with an increase in Mn content beyond certain concentration. These samples exhibit very weak magnetocapacitive coupling, which can be attributed to the very small magnetic signal observed in these samples. 相似文献
118.
Andrews Maneesha E. Murali Jayaraman Muralidharan Chellappa Madhulata Wuppalamarthy Jayakumar Rajadas 《Colloid and polymer science》2003,281(8):766-770
The molecular mechanism of the stabilization of collagen with hydrolyzable tannin, corilagin, has been investigated using techniques like centrifugation, shrinkage temperature, infrared spectroscopy, and differential scanning calorimetry. Thermodynamic measurements were also carried out for the collagen–corilagin interaction. Results of this study indicate the enthalpic nature of non-specific binding of collagen with corilagin. The shrinkage temperature increases linearly with corilagin, indicating that the helix–to–coil transition is hindered by corilagin interaction with collagen triple helix. This study suggests that ingested polyphenols (corilagin) alter the stability of the proline-rich protein in the gut. Thereby, the stability of collagen present in the serosa layer may be hindered. 相似文献
119.
The enhancement of hydrophilicity of DC air and oxygen plasma treated cotton fabric and its effect on the antimicrobial efficacy
when treated with neem leaf extract is reported in this paper. The axial and radial ion density distribution between the electrodes
was studied using Langmuir probe to place the fabric between the electrodes for effective plasma treatment. The effect of
system parameters viz., process gas pressure, DC power density and plasma exposure time on the hydrophilicity and hence the
antimicrobial efficacy after the neem leaf extract treatment was analysed and optimised. The functional group present in the
cellulose units of the cotton fabric before and after plasma treatment was identified and estimated using standard tests and
analysed using ATR–FTIR spectra. The surface morphology of untreated and plasma treated cotton fabric was analyzed with the
help of SEM micrograph. The mean pore diameter of the fabric matrix was calculated and air permeability was measured before
and after plasma treatment to account for the improved capillarity due to plasma treatment. The formation of functional groups
with increased polarity and improved capillary action of the plasma treated fabric enhances its hydrophilicity which in turn
improves the sorption of neem leaf extract and hence the antimicrobial activity. 相似文献
120.
D. Sajan N. B. Prathima C. Murali Krishna I. Hubert Joe V. S. Jayakumar 《Laser Physics》2007,17(10):1217-1221
The surface geometry of a methyl p-hydroxy benzoate (MPHB) molecule was studied by analysis of the SERS spectra adsorbed on silver colloid surfaces. For a reliable analysis of the SERS spectrum, we also performed density functional theoretical calculations. The large enhancement of the in-plane ring-stretching and ring-stretching modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a stand on orientation of MPHB on a silver surface. 相似文献