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   37篇
  免费   0篇
能源动力   1篇
无线电   18篇
一般工业技术   4篇
冶金工业   11篇
自动化技术   3篇
  2022年   2篇
  2021年   1篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2014年   1篇
  2012年   3篇
  2011年   1篇
  2009年   3篇
  2008年   4篇
  2007年   1篇
  2006年   2篇
  1999年   1篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1993年   2篇
  1991年   1篇
  1987年   1篇
  1985年   1篇
  1977年   1篇
排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
Eigenmodes propagating in cylindrical dielectric gratings (CDGs) are studied. Solution of the boundary value problem on propagation of electromagnetic waves in CDGs is reduced to solution of a system of two integrodifferential equations (IDEs) of the second kind. The singular components of the kernels of the IDEs entering the system are separated and analytically transformed. The collocation and Galerkin methods are applied to solve the first and second IDEs, respectively.  相似文献   
2.
The rat magnocellular basal forebrain (MNBF) is homologous to the human nucleus basalis of Meynert, a structure implicated in the cholinergic hypothesis of cognitive impairment in Alzheimer's disease (AD). In the present study, 18 male Sprague-Dawley rats with kainic acid lesions in the MNBF were compared with 6 unoperated controls, 10 sham-operated controls, and 6 controls injected with kainic acid in the cortical area directly above the MNBF. MNBF lesions depleted choline acetyltransferase in cortex but not in striatum or hippocampus. Cortical dopamine levels were unchanged; serotonin levels were unchanged in hippocampus and parietal cortex but decreased in frontal cortex. Compared with controls, MNBF-lesioned Ss were impaired in 24-hr retention, but not acquisition, of a passive avoidance task with escapable footshock. The groups did not differ in mean number of daily avoidances on a barpress active avoidance task, although learning was slower in MNBF-lesioned Ss. In a serial spatial discrimination reversal test, MNBF-lesioned Ss performed significantly worse than controls. This model may be useful for studying the role of the cholinergic system in memory and possibly for developing treatment strategies to alleviate the cognitive dysfunction of AD. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Several clinical disorders are strongly influenced by hormones involved in appetite and weight regulation. Obesity and eating disorders are of major importance, because they are associated with severe morbidity and considered to be among the greatest health problems in the Western world today. This review describes recent findings in hormonal regulation of food intake by substances acting both centrally, such as corticotropin-releasing factor, neuropeptide Y and leptin, and peripherally, such as cholecystokinin and somatostatin. Sex hormones and glucocorticoids play an important role in long-term regulation of metabolism. The role of these hormones in appetite and weight changes during life as well as during pregnancy and lactation is discussed. Furthermore, the development of obesity and eating disorders is influenced, in particular, by steroid hormones. Treatment with sex hormones, as in hormone replacement therapy, affects appetite and weight and may have beneficial effects in preventing android obesity. Currently, there is great effort in developing endogenous neurohumoral substances into effective drugs for the treatment of obesity and eating disorders. Leptin and neuropeptide Y analogues are of interest as potential antiobesity agents.  相似文献   
4.
A new design of optical antennas consisting of zinc oxide (ZnO) nanorods covered by a thin metal film is proposed. Arrays of highly oriented ZnO nanorods perpendicular to a substrate and covered by a thin silver film have been obtained using methods of carbothermal synthesis and magnetron sputtering. The problems of electromagnetic wave diffraction on a single metal/dielectric nanovibrator (situated at the interface of dielectrics) and on a two-dimensional periodic array of these nanovibrators have been solved. The results of calculations of the electrodynamic characteristics of optical antennas with various lengths have been compared to experimental data.  相似文献   
5.
Space-time integral equations describing diffraction of ultrashort electromagnetic pulses by slots in a screen located on a media interface are solved. The solution is based on separation of the static components of the kernels of the integral equations and the subsequent application of the collocation method.  相似文献   
6.
The problem of diffraction by planar metal nanodipoles is solved. The permittivity of metal in the optical band is taken into account. The proposed mathematical model is based on approximate boundary conditions for thin dielectric films. The characteristics of copper and golden nanoantennas are theoretically investigated. It is noted that the wavelength dependence of the scattered field has a resonance character and that the resonance wavelengths of nanodipoles are larger than the resonance wavelengths of a perfectly conducting dipole of the same dimension.  相似文献   
7.
We report a new optical metal-dielectric diffraction grating that absorbs almost 100% of the incident energy during resonance of the surface wave propagating along a metal (solid plasma)-dielectric interface.  相似文献   
8.
The mutations 185delAG, 188del11, and 5382insC in the BRCA1 gene and 6174delT in the BRCA2 gene were analyzed in 199 Ashkenazi and 44 non-Ashkenazi Jewish unrelated patients with breast and/or ovarian cancer. Of the Jewish Ashkenazi women with ovarian cancer, 62% (13/21) had one of the target mutations, as did 30% (13/43) of women with breast cancer alone diagnosed before the age 40 years and 10% (15/141) of those with breast cancer diagnosed after the age 40 years. Age at ovarian cancer diagnosis was not associated with carrier status. Of 99 Ashkenazi patients with no family history of breast and/or ovarian cancer, 10% carried one of the mutations; in two of them the mutation was proved to be paternally transmitted. One non-Ashkenazi Jewish ovarian cancer patient from Iraq carried the 185delAG mutation. Individual mutation frequencies among breast cancer Ashkenazi patients were 6.7% for 185delAG, 2.2% for 5382insC, and 4.5% for 6174delT, among ovarian cancer patients; 185delAG and 6174delT were about equally common (33% and 29%, respectively), but no ovarian cancer patient carried the 5382insC. More mutations responsible for inherited breast and ovarian cancer probably remain to be found in this population, since 79% of high-incidence breast cancer families and 35% of high-incidence breast/ovarian cancer families had none of the three known founder mutations.  相似文献   
9.
10.
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