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 0 毫秒
21.
22.
A single layer of the Li‐Al layered double hydroxide (LDH) can be considered to be a structural synthon that can be stacked in a number of ways to give rise to the polytypes of the Li‐Al LDH family. The topotactic imbibition of lithium into gibbsite and bayerite precursors gives rise to crystalline 2H and 1M1 polytypes respectively. In contrast the sample formed through a gel to crystallite route is found to be a 1M1 polytype with stacking disorders whose local symmetry corresponds to the 1M2 polytype. On heating, a solid‐solid 1M1→1H polytype transformation is observed. 相似文献
23.
Phase-resolved information is necessary for many coastal wave problems, for example, for the wave conditions in the vicinity of harbor structures. Two-dimensional (2D) depth-averaging shallow water models are commonly used to obtain a phase-resolved solution near the coast. These models are in general more computationally effective compared with computational fluid dynamics software and will be even more capable if equipped with a parallelized code. In the current article, a 2D wave model solving the depth-averaged continuity equation and the Euler equations is implemented in the open-source hydrodynamic code REEF3D. The model is based on a nonhydrostatic extension and a quadratic vertical pressure profile assumption, which provides a better approximation of the frequency dispersion. It is the first model of its kind to employ high-order discretization schemes and to be fully parallelized following the domain decomposition strategy. Wave generation and absorption are achieved with a relaxation method. The simulations of nonlinear long wave propagations and transformations over nonconstant bathymetries are presented. The results are compared with benchmark wave propagation cases. A large-scale wave propagation simulation over realistic irregular topography is shown to demonstrate the model's capability of solving operational large-scale problems. 相似文献
24.
Anil Kamath Rajeev Motwani Krishna Palem Paul Spirakis 《Random Structures and Algorithms》1995,7(1):59-80
The classical occupancy problem is concerned with studying the number of empty bins resulting from a random allocation of m balls to n bins. We provide a series of tail bounds on the distribution of the number of empty bins. These tail bounds should find application in randomized algorithms and probabilistic analysis. Our motivating application is the following well-known conjecture on threshold phenomenon for the satisfiability problem. Consider random 3-SAT formulas with cn clauses over n variables, where each clause is chosen uniformly and independently from the space of all clauses of size 3. It has been conjectured that there is a sharp threshold for satisfiability at c* ≈? 4.2. We provide a strong upper bound on the value of c*, showing that for c > 4.758 a random 3-SAT formula is unsatisfiable with high probability. This result is based on a structural property, possibly of independent interest, whose proof needs several applications of the occupancy tail bounds. 相似文献
25.
S G Kamath 《Pramana》1988,30(4):299-304
The superconformal trace anomaly is worked out to one-loop order in perturbation theory for the 1+1 dimensional Wess-Zumino
model. 相似文献
26.
G. K. Kiran N. Munichandraiah P. Vishnu Kamath 《Journal of Solid State Electrochemistry》2018,22(12):3833-3843
Conversion anodes comprising non-stoichiometric black NiO suffer severe capacity fading in Li-ion batteries despite having a high Li+ ion diffusion coefficient. We attribute this capacity fading to (i) its small crystallite size (~?8 nm) and (ii) high charge transfer resistance (Rct ~?60–180 Ω cm2). Small crystallites enhance grain boundaries which promote Li+ ion diffusion without efficient material utilization. In contrast, the stoichiometric green NiO anodes deliver a stable capacity of 280 mAh g?1 over 50 charge-discharge cycles. The comparatively higher capacity of green NiO can be explained from its (i) large crystallite size (~?104 nm) and (ii) negligible Rct values. 相似文献
27.
Ethylenediamine bis(triphenylphosphine) monochlororhodium has been prepared by the interaction of Wilkinson's catalyst and ethylenediamine in benzene. The complex has been isolated and characterized by conventional and spectroscopic methods. The catalytic activity of the complex was investigated for the hydrogenation of 1-octene as a model reaction at a hydrogen pressure of 1 atmosphere (101 kPa) using methanol as a solvent. The influence of various factors such as catalyst, substrate concentrations and temperature have been studied. The hydrido complex has been identified as an intermediate product by IR and NMR studies. The experimental data are in accordance with a rate expression of the form: . 相似文献
28.
N. George B. V. Kamath A. G. Basrur K. R. Krishnamurthy 《Reaction Kinetics and Catalysis Letters》1997,60(2):379-386
The function of hydrogen used as carrier gas in catalytic dehydrogenation is to increase the selectivity and stability of
catalysts. It slows down catalyst deactivation by either inhibiting deposition of potential coke precursors or facilitating
their desorption by rehydrogenation. This function, in gas-solid catalytic dehydrogenation appears to be interphase mass transfer
controlled by increased hydrogen linear flow velocities decreasing the extent of deactivation. Besides, deactivation appears
to progress through two regimes, an initial short term followed by a long term deactivation. 相似文献
29.
βbc-Nickel hydroxide exhibit non-uniform broadening reflections in their PXRD pattern due to the presence of structural disorder.
βbc-Nickel hydroxide electrodes with smaller crystallite size and structural disorder reversibly exchanges 0.9e/Ni. Co/Zn/Ca/Cd-substituted
βbc-nickel hydroxide samples also display non-uniform broadening of reflections in their powder X-ray diffraction patterns with
smaller crystallite size and exchanges 0.7–0.8e/Ni. Hydrothermal treatment of βbc-nickel hydroxide slurry at 170 °C results in an ordering of reflections in their powder X-ray diffraction pattern with an
increased crystallite size. Crystalline β-nickel hydroxide electrode reversibly exchanges 0.3–0.4e/Ni. Hydrothermal-treated
Co/Zn/Ca/Cd-substituted βbc-nickel hydroxide slurries at 170 °C display sharp reflections with similar crystallite size and electrochemical activities
as that of crystalline β-nickel hydroxide. This clearly demonstrates that partial substitution of Co/Zn/Ca/Cd in the nickel
hydroxide matrix does not show any dramatic improvement in their electrochemical activity at 25–30 °C. Structural disordered
material with smaller crystallite size delivers electrochemical activity close to theoretical capacity. 相似文献
30.
Srikanth S. Kamath 《Journal of Dispersion Science and Technology》2013,34(9):1304-1310
A spray drying technique was applied to prepare composite microparticles of a water-insoluble herbicide, atrazine(AT) and a water-soluble herbicide 2,4-dichloro phenoxy acetic acid (2,4-D) for the purpose of improving the water solubility of AT. A homogenous mixture of an ethanol solution of AT and an aqueous 2,4-D solution at different ratios were spray dried using a laboratory scale spray drier. Quantitative elemental analysis suggested that the AT/2,4-D ratio in each composite microparticle was nearly the same as the desired formulation ratio. The resulting samples were characterized by powder x-ray diffractometry (XRD), differential scanning calorimetry (DSC), Fourier transform infra red (FT-IR) and scanning electron microscopy (SEM). It was found that the crystallinity of AT and 2,4-D were maintained in the composite particles. Moreover, the release of AT from dissolved composite microparticles was markedly improved because of an increase in the effective surface area following rapid dissolution of 2, 4 D. Hence, this study shows that it is possible to prepare AT-2,4-D composite microparticles using a laboratory scale spray drier and that this can improve the ability of AT to dissolve in water. 相似文献