首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   93篇
  免费   3篇
化学   40篇
力学   11篇
数学   10篇
物理学   35篇
  2023年   2篇
  2021年   4篇
  2020年   1篇
  2016年   5篇
  2015年   5篇
  2014年   4篇
  2013年   8篇
  2012年   7篇
  2011年   16篇
  2010年   5篇
  2009年   8篇
  2008年   5篇
  2007年   5篇
  2006年   3篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  2002年   1篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1996年   1篇
  1994年   1篇
  1987年   1篇
  1986年   1篇
  1984年   3篇
排序方式: 共有96条查询结果,搜索用时 0 毫秒
1.
Y2O3 nanoparticles and nanorods have been firstly synthesized in bulk Ti-Y films prepared by magnetron sputtering on Si (100) substrates at different temperatures. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) are used to characterize the structure, morphology, and composition of the as-synthesized nanoparticles and nanorods. The mechanical properties of the sputtered films are investigated using nanoindentation techniques. The results indicate that both the nanoparticles and nanorods have a pure cubic Y2O3 structure resulting from the reaction of Y atoms with the residual O2 in the vacuum chamber, and are free from defects and dislocations with uniform diameters of about 30 nm. The Y2O3 nanoparticles mainly distribute at the grain boundaries of the Ti matrix and the nanorods have lengths ranging from 250 nm to more than 1 μm with the growth direction parallel to the (002) plane. As the growth temperature elevates, the nanoparticles turn to be coarsening while more and longer nanorods are inclined to form. Compared with the Ti film, the TiY films have a remarkable increase in hardness, but do not exhibit expected increase in elastic modulus. Finally, the growth mechanism is also briefly discussed.  相似文献   
2.
Based on the theory of radiation transfer and a model that describes the structure and optical properties of biotissues, we have found spectral conditions of irradiation of the skin surface that ensure efficient generation of molecular oxygen O2 in the dermis due to the photodissociation of blood oxyhemoglobin. We show that, for maximal local O2 formation at depths z ≤ 0.2 mm, 0.2 mm < z ≤ 0.9 mm, 0.9 mm < z ≤ 2.5 mm, and z > 2.5 mm, it is more effective to use wavelengths in the intervals 418 ± 5, 575 ± 5, 585 ± 5, and 600 ± 5 nm, respectively. Physical reasons for the shift of optimal wavelengths toward the red range of the spectrum are described. We show that they are based on the selectivity of optical properties of the skin biotissue, which acts as of a kind of spectral filter the transmission curve of which depends on the depth. It is found that irradiation at a wavelength near 575 nm is optimal for the generation of a maximal amount of O2 in the intire bulk of the dermis.  相似文献   
3.
We present new characterizations of interval digraphs, interval graphs, and indifference digraphs, using linear orderings of edges and vertices. © 1996 John Wiley & Sons, Inc.  相似文献   
4.
The spectra of the absorption coefficients of external radiation by basic chromophores of human skin, such as melanin, basic tissue, and blood (including oxy- and deoxyhemoglobin), are studied in the wavelength range of 300–1000 nm. For estimates, analytical methods of the theory of light transfer are used, which take into account the multilayer structure of a biological tissue, multiple light scattering in a medium, and multiple rereflections of radiation between layers. The calculated spectra are compared with the wavelength dependences of the absorption indices of these components available from the literature. It is shown that the spectral behaviors of the coefficients and indices of absorption strongly differ, which is related to the selectivity of the optical properties of a biological tissue. The possibilities of predicting the absorption coefficients of the skin components from the absorption coefficient of the entire skin measured under conditions of variation of its biophysical parameters (the volume concentrations of melanin and blood vessels) over a wide range are evaluated.  相似文献   
5.
In this paper, analytic treatment of time fractional nonlinear operator equation has been presented by using Adomian’s decomposition method (ADM). To illustrate the procedure, the nonlinear Schrodinger (NLS) equation of fractional order has been solved. The solution is expressed in terms of Mittag-Leffler function. The present method performs extremely well in terms of accuracy, efficiency and simplicity.  相似文献   
6.
7.
8.
[reaction: see text] A new method for synthesizing phenanthridine and its related compounds was developed using the condensation of o-phenylaniline and its homologues with cyclic ketones under hydrothermal conditions.  相似文献   
9.
In this paper, we consider some transportation problems (TPs) with different types of fuzzy-stochastic unit transportation costs and budget constraints. These fuzzy stochastic costs are reduced to corresponding crisp ones in two different ways. For the first method, using the definition of αα-cut of the fuzzy numbers, expectation is taken separately on both lower and upper αα-cuts and then mean expectation is calculated with the help of signed distance. In the second procedure, we realize fuzzy random events (ξ?r)(ξ?r) and (ξ?r)(ξ?r) for the fuzzy random variable (ξ)(ξ). Using credibility measure of these events, mean chances for the above fuzzy random events are calculated and then expectation is taken to get the crisp expressions. The reduced deterministic problems of the fuzzy stochastic TP are solved using a real coded genetic algorithm with Roulette wheel selection, arithmetic crossover and random mutation. Few numerical examples are demonstrated to find the optimal solutions of the proposed models.  相似文献   
10.
Bhar  Suprio  Bhaskaran  Rajeev  Sarkar  Barun 《Potential Analysis》2020,53(1):203-221
Potential Analysis - We consider the following stochastic partial differential equation, $$begin{array}{@{}rcl@{}} &amp;&amp;dY_{t} = L^{ast} Y_{t} dt + A^{ast} Y_{t} cdot dB_{t}...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号