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81.
82.
RF SQUID behaviour due to grain boundary weak links in a bulk YBCO is observed at 77 K using modified commercial rf electronics.
Porous samples with lowI
c
are found to show this characteristic whereas dense samples with higherI
c
do not show SQUID behaviour.V-B modulation characteristic is found to be better when the rf pumping frequency is kept slightly higher than the resonance
frequency of the tank circuit. Designing of coil for tank circuit with appropriateQ has been found to be very crucial for seeing the SQUID behaviour. Estimation of parameters such as coupling constant, mutual
inductance, inductance and radius of the SQUID loop, have been made and their significance is discussed. Flux noise spectrum
of the bulk rf SQUID in flux locked mode is also reported. 相似文献
83.
M. Alcolea Palafox G. Tardajos A. Guerrero-Martínez V.K. Rastogi D. Mishra S.P. Ojha W. Kiefer 《Chemical physics》2007,340(1-3):17-31
FT-IR and FT-Raman spectra of the biomolecule 5-aminouracil were recorded in the regions 400–4000 cm−1 and 10–3500 cm−1, respectively. The observed vibrational wavenumbers were analyzed and assigned to different normal modes of vibration of the molecule. Density functional calculations were performed to support wavenumber assignments of the observed bands. A comparison with the molecule of uracil was made, and specific scale factors were employed in the predicted wavenumbers of 5-aminouracil. With the purpose of study the important molecule 5-aminouracil, its equilibrium geometry and harmonic wavenumbers were calculated for the first time by the B3LYP DFT method. The vibrational wavenumbers were compared with IR and Raman experimental data. Also good reproduction of the experimental wavenumbers is obtained and the % error is very small. All the tautomeric forms of 5-aminouracil were determined and optimized. The dimer forms were also simulated. The energy, atomic charges and dipole moments were discussed and several general conclusions were underlined. 相似文献
84.
P. Lakshmi Praveen K. Veera Bhadra Reddy N. Ajeetha D. P. Ojha 《Crystallography Reports》2009,54(7):1197-1201
A computational analysis of ordering in non-liquid crystalline p-n-alkyl benzoic acid, having 1 (1BAC), 2 (2BAC) and 3(3BAC) carbon atoms in the alkyl chain has been carried out with respect
to translatory and orientational motions, but detailed results are reported only for 3BAC. The evaluation of net atomic charges
and dipole moments at each atomic center has been carried out using complete neglect differential overlap (CNDO/2) method.
The modified Rayleigh-Schrodinger perturbation theory along with the multicentered-multipole expansion method has been employed
to evaluate long-range interactions, while a “6-exp” potential function has been assumed for short-range interactions. On
the basis of stacking, in-plane and terminal interaction energy calculations, all possible arrangements of a molecular pair
have been considered. A comparative picture of molecular parameters, such as total energy, binding energy, and total dipole
moment of 3BAC with higher homologous series liquid crystalline compounds having 4(4BAC), 5(5BAC), and 6(6BAC) alkyl chain
carbon atoms, has been given. It is found that, if a suitable functional group is attached to 3BAC, so that the length to
breadth ratio is increased, the molecule will show a change in the long-range order, the phase transition temperature and
other liquid crystalline properties. 相似文献
85.
The ground state geometries of [Alanine (Ala) + M2+] [M = Ca, Cu, and Zn) complexes were calculated in gas phase at B3LYP/6‐311++G(d,p) level of theory. Transition states (TSs) between different stable conformers of [Ala + M2+] complexes were also calculated. Among the different [Ala + M2+] complexes, the complex where metal cations coordinated to carboxylate group (? COO?) is found to be energetically most favorable. To calculate TSs, the ground state structures of any two conformers of [Ala + M2+] complexes were used. The ground state energies of two stable conformers and their TS structures were used to calculate the activation energy. The reactivity of different conformers of [Ala + M2+] complexes have been discussed in terms of energy difference between their highest occupied molecular orbital and lowest unoccupied molecular orbital. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 相似文献
86.
Durga P. Ojha 《Molecular Crystals and Liquid Crystals》2014,593(1):104-113
The conformational behavior and influence of organic solvents on a nematogen, 4’-n-alkyl-4-cyanobiphenyl, with strong polar group propyl (3CB) that is of commercial and application interest has been studied with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the molecules show the interesting property in the organic solvents. The interaction energies of dimer complexes have been taken into consideration in order to investigate the most energetically stable configuration. An attempt has been made to develop an interesting computational model for nematogen at molecular level. 相似文献
87.
P. L. Praveen N. Ajeetha D. P. Ojha 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(2):229-234
A comparative computational analysis of molecular ordering in homologous series of monotropic nematic liquid crystal 4′-n-alkyl-4-cyanobiphenyl (nCB) molecules with alkyl groups, butyl (4CB), pentyl (5CB), hexyl (6CB), heptyl (7CB), has been carried out with respect to
translational and orientational motion. The atomic net charge and dipole moment at each atomic center were evaluated using
the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory and the multicenter-multipole
expansion method were employed to evaluate long-range intermolecular interactions, while a 6-exp potential function was assumed
for short-range interactions. Various possible geometrical arrangements of molecular pairs with regard to different energy
components were considered, and the most favorable configuration was found. A comparative picture of molecular parameters,
such as total energy, binding energy, and total dipole moment of 4CB, 5CB, 6CB, and 7CB, is given. The results are discussed
in the light of other theoretical observations. 相似文献
88.
Ojha AK Srivastava SK Singh RK Asthana BP 《The journal of physical chemistry. A》2006,110(32):9849-9853
We report on a new empirical relationship to explain the concentration-dependent isotropic Raman line width changes of a vibrational mode in uniform binary mixtures. The factors contributing to the intrinsic line width and several other broadening mechanisms are, in general, concentration-dependent. Concentration fluctuation in a microscopic volume and microviscosity are the two factors that are known to cause a concentration-dependent line width variation. These two factors combined in a specific manner successfully explain the variation of the line width with concentration strongly associated with binary systems. A readily usable empirical relationship for line width is suggested. It has been demonstrated that it can successfully explain the line width variation with concentration in a given class of hydrogen-bonded systems taking some representative binary mixtures. 相似文献
89.
S. Srividya S. Gautam P. Kumar U.S. Ojha S. Pal Harsh 《Applied Surface Science》2010,256(11):3563-3566
Carbon nanotube (CNT) based cold cathodes are considered to be the most promising material for fabrication of next generation high-performance flat panel displays and vacuum microelectronic devices. Adhesion of CNTs with the substrate and the contact resistance between them are two of the important issues to be addressed in CNT based field emission (FE) devices. Here in this work, a buffer layer of titanium (Ti) is deposited prior to the catalyst deposition and the growth was carried out using chemical vapor deposition (CVD) technique. There was significant increase in emission current density from 10 mA/cm2 to 30 mA/cm2 at the field of 4 V/μm by the use of titanium buffer layer due to much less dense growth of CNTs of smaller diameter. Field emission results suggest that the adhesion of the CNTs to the substrate has improved. The titanium buffer layer has also lowered the contact resistance between the CNTs and the substrate because of which a stable emission of 30 mA for a longer duration was obtained. 相似文献
90.
Shailesh Nagarkar Raj Ojha Jagrat Mankad Parag Patil Vivek Soni Ashish Lele 《Rheologica Acta》2006,45(3):260-267
The lyocell process involves dry jet—wet spinning of a solution of cellulose in N-methyl morpholine oxide monohydrate. Measurement of the elongation viscosity of lyocell is important for the design and optimization
of the lyocell process. We present a useful method for the determination of the elongation viscosity of lyocell by using a
combination of experimental measurements on a semi-hyperbolic die and viscoelastic simulations. 相似文献