全文获取类型
收费全文 | 128篇 |
免费 | 8篇 |
专业分类
化学 | 98篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 11篇 |
物理学 | 22篇 |
出版年
2023年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 11篇 |
2011年 | 7篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 9篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
101.
The three-phase (vapor + ice + hydrate) (VIH) hydrate equilibrium was determined for cis- and trans-2-butene using a new and a simple experimental technique. The equilibrium measurements were done at temperatures between 248 to 272 K and pressures between 16.7 to 67.6 kPa for cis-2-butene, and for trans-2-butene between 245 to 272 K and 15.4 to 70.4 kPa. The accuracy of the experimental technique was verified by measuring hydrate dissociation pressures for pure propane below the ice temperature; the results obtained were in good agreement with those in the literature for pure propane. 相似文献
102.
The effect of partial charge parametrization on the fluid phase behavior of hydrogen sulfide is investigated with grand canonical histogram reweighting Monte Carlo simulations. Four potential models, based on a Lennard-Jones + point charge functional form, are developed. It is shown that Lennard-Jones parameters can be tuned such that partial charges for the sulfur atom in the range -0.40 < q(s) < -0.252 will lead to an accurate reproduction of experimental vapor-liquid equilibria. Each of the parameter sets developed in this work are used to predict the pressure composition behavior H2S-n-pentane at 377.6 K. While the mixture calculation provides a means of reducing the number of candidate parameter sets, multiple parameter sets were found to yield an excellent reproduction of both the pure component and mixture phase behavior. 相似文献
103.
104.
Force fields based on a Lennard-Jones (LJ) 12-6 plus point charge functional form are developed for acetone and chloroform specifically to reproduce the minimum pressure azeotropy found experimentally in this system. Point charges are determined from a CHELPG population analysis performed on an acetone-chloroform dimer. The required electrostatic surface for this dimer is determined from ab initio calculations performed with MP2 theory and the 6-31g++(3df,3pd) basis set. LJ parameters are then optimized such that the liquid-vapor coexistence curve, critical parameters, and vapor pressures are well reproduced by simulation. Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine the phase diagrams for the binary mixtures acetone-chloroform, acetone-methanol, and chloroform-methanol. The force fields developed in this work reproduce the minimum pressure azeotrope in the acetone-chloroform mixture found in experiment. The predicted azeotropic composition of x(CHCl3) = 0.77 is in fair agreement with the experimental value of x(CHCl3)expt = 0.64. The new force fields were also found to provide improved predictions of the pressure-composition behavior of acetone-methanol and chloroform-methanol when compared to other force fields commonly used for vapor-liquid equilibria calculations. NPT simulations were conducted at 300 K and 1 bar for equimolar mixtures of acetone-chloroform, acetone-methanol, and methanol-chloroform. Analysis of the microstructure reveals significant hydrogen bonding occurring between acetone and chloroform. Limited interspecies hydrogen bonding was found in the acetone-methanol or chloroform-methanol mixtures. 相似文献
105.
A series of (2E,6E)-2-(4-n-alkoxybenzylidene)-6-((benzo[d][1,3]dioxol-6-yl)methylene)cyclohexanones were synthesised by stepwise condensation reactions from cyclohexanone. The optical and thermal analysis of the series indicated the mesomorphic properties of some derivatives. The compounds with C7–C16 substituents showed the nematic phases in the range of 90–73°C. The single crystal X-ray analysis confirms the head to tail packing arrangement. 相似文献
106.
Guvench O Greene SN Kamath G Brady JW Venable RM Pastor RW Mackerell AD 《Journal of computational chemistry》2008,29(15):2543-2564
We present an all-atom additive empirical force field for the hexopyranose monosaccharide form of glucose and its diastereomers allose, altrose, galactose, gulose, idose, mannose, and talose. The model is developed to be consistent with the CHARMM all-atom biomolecular force fields, and the same parameters are used for all diastereomers, including both the alpha- and beta-anomers of each monosaccharide. The force field is developed in a hierarchical manner and reproduces the gas-phase and condensed-phase properties of small-molecule model compounds corresponding to fragments of pyranose monosaccharides. The resultant parameters are transferred to the full pyranose monosaccharides, and additional parameter development is done to achieve a complete hexopyranose monosaccharide force field. Parametrization target data include vibrational frequencies, crystal geometries, solute-water interaction energies, molecular volumes, heats of vaporization, and conformational energies, including those for over 1800 monosaccharide conformations at the MP2/cc-pVTZ//MP2/6-31G(d) level of theory. Although not targeted during parametrization, free energies of aqueous solvation for the model compounds compare favorably with experimental values. Also well-reproduced are monosaccharide crystal unit cell dimensions and ring pucker, densities of concentrated aqueous glucose systems, and the thermodynamic and dynamic properties of the exocyclic torsion in dilute aqueous systems. The new parameter set expands the CHARMM additive force field to allow for simulation of heterogeneous systems that include hexopyranose monosaccharides in addition to proteins, nucleic acids, and lipids. 相似文献
107.
Sudha D. Kamath Claretta S. D'souza Stanley Mathew Sajan D. George C Santhosh K. K. Mahato 《Journal of Chemometrics》2008,22(6):408-416
Pulsed laser‐induced autofluorescence spectra of pathologically certified normal and malignant colonic mucosal tissues were recorded at 325 nm excitation. The spectra were analysed using three different methods for discrimination purposes. First, all the spectra were subjected to the principal component analysis (PCA) and the discrimination between normal and malignant cases were achieved using parameters like, spectral residuals, Mahalanobis distance and scores of factors. Second, to understand the changes in tissue composition between the two classes (normal, and malignant), difference spectrum was constructed by subtracting mean spectrum of calibration set samples from simulated mean of all spectra of any one class (normal/malignant) and in third, artificial neural network (ANN) analysis was carried out on the same set of spectral data by training the network with spectral features like, mean, median, spectral residual, energy, standard deviation, number of peaks for different thresholds (100, 250 and 500) after carrying out 1st‐order differentiation of the training set samples and discrimination between normal and malignant conditions were achieved. The specificity and sensitivity were determined in PCA and ANN analyses and they were found to be 100 and 91.3% in PCA, and 100 and 93.47% in ANN, respectively. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
108.
A combined level set/ghost cell immersed boundary representation for floating body simulations
下载免费PDF全文
![点击此处可从《国际流体数值方法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A six degrees of freedom (6DOF) algorithm is implemented in the open‐source CFD code REEF3D. The model solves the incompressible Navier–Stokes equations. Complex free surface dynamics are modeled with the level set method based on a two‐phase flow approach. The convection terms of the velocities and the level set method are treated with a high‐order weighted essentially non‐oscillatory discretization scheme. Together with the level set method for the free surface capturing, this algorithm can model the movement of rigid floating bodies and their interaction with the fluid. The 6DOF algorithm is implemented on a fixed grid. The solid‐fluid interface is represented with a combination of the level set method and ghost cell immersed boundary method. As a result, re‐meshing or overset grids are not necessary. The capability, accuracy, and numerical stability of the new algorithm is shown through benchmark applications for the fluid‐body interaction problem. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
109.
S. G. Kamath 《Pramana》2006,66(2):325-344
The familiar trace identity associated with the scale transformationx
Μ
→ x′
Μ = e-λ
x
Μ
on the Lagrangian density for a noninteracting massive real scalar field in 2 + 1 dimensions is shown to be violated on a
single plate on which the Dirichlet boundary condition Φ(t, x1, x2 = -a) = 0 is imposed. It is however respected in: (i) 1 + 1 dimensions in both free space and on a single plate on which the Dirichlet
boundary condition Φ(t, x1 = -a) = 0 holds and (ii) in 2 + 1 dimensions in free space, i.e. the unconstrained configuration. On the plate where Φ(t, x1, x2
= -a) = 0, the modified trace identity is shown to be anomalous with a numerical coefficient for the anomalous term equal to the
canonical scale dimension, viz. 1/2. The technique of Bordaget al [Ann. Phys. (N.Y.),165, 162 (1985)] is used to incorporate the said boundary condition into the generating functional for the connected Green’s
functions. 相似文献