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   159篇
  免费   8篇
电工技术   5篇
化学工业   31篇
金属工艺   2篇
机械仪表   6篇
建筑科学   1篇
能源动力   7篇
轻工业   2篇
石油天然气   1篇
无线电   15篇
一般工业技术   48篇
冶金工业   28篇
原子能技术   3篇
自动化技术   18篇
  2023年   2篇
  2022年   4篇
  2020年   4篇
  2019年   3篇
  2018年   4篇
  2017年   4篇
  2016年   3篇
  2015年   5篇
  2014年   7篇
  2013年   5篇
  2012年   5篇
  2011年   10篇
  2010年   10篇
  2009年   11篇
  2008年   9篇
  2007年   7篇
  2006年   8篇
  2005年   1篇
  2004年   10篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1997年   5篇
  1996年   2篇
  1995年   1篇
  1993年   4篇
  1990年   1篇
  1986年   4篇
  1985年   3篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1976年   3篇
  1975年   2篇
  1972年   1篇
  1969年   1篇
  1962年   1篇
排序方式: 共有167条查询结果,搜索用时 31 毫秒
1.
L Bünger  N Remus  D Roschlau 《Die Nahrung》1985,29(6):549-560
Body composition and organ weights were determined in male mice sampled from 4 different lines of a selection experiment: DU-6P (selected for high protein amount), DU-6 (selected for high body weight), DU-6 + LB (selected for an index combining body weight and endurance fitness) and DU-K (unselected control line). Selection was carried out under the conditions of ad libitum feeding and standardization of litter size at birth. In all 3 selection lines a significant direct selection response was shown. While fat in lines DU-6P and DU-6 + LB remained normal, it increased after selection for body weight (DU-6) significantly. Up to generation 13 the average increase of fat was 0.32% per generation. Investigations on 28 to 80 days old mice showed, that males of this line were fatter before, at and after the age of selection (42 days). After 9 generations the body weight of selected mice was significantly increased by 23 to 29%. The absolute organ weights of hearts, livers and kidneys were also significantly higher, while the relative weights of hearts and kidneys decreased. The relative liver weights were in the selected lines higher, but only the difference DU-6 vs. DU-K was significant.  相似文献   
2.
Photovoltaic (PV) and other sources of renewable energy are being used increasingly in grid-connected systems, for which stronger power quality requirements are being issued. Continuous grid monitoring should be considered so as to provide safe connections and disconnections from the grid. This letter gives an overview of the methods used for online grid measurement with PV inverters. Emphasis is placed on a method based on the injection of a noncharacteristic harmonic in the grid. Since this injection is regarded as a disturbance for the grid, different issues, i.e., the influence on total harmonic distortion (THD), the accuracy of line impedance measurement and the ENS (German abbreviation of Main Monitoring units with allocated Switching Devices) detection are studied. Laboratory results conducted on an existing PV inverter are presented to demonstrate the behavior of the PV inverter under different grid conditions. Some of the injection parameters are tuned in order to get an accurate measurement of line impedance.  相似文献   
3.
4.
We report the deposition of Si-N films by multipulse excimer laser ( = 308 nm, FWHM = 30 ns) ablation of Si wafers placed in a slow flow of NH3 in the pressure range (1 bar-1 mbar). The films are deposited on to a Si collector placed parallel to the Si target. We succeeded in depositing pure amorphous Si3N4 films at a pressure of 1 mbar of NH3. The deposition rate reached a maximum value of 0.2–0.3 nm per pulse. At lower pressures, the deposited films consist of a fine mixture of three amorphous phases (amorphous stoichiometric silicon nitride, amorphous non-stoichiometric silicon nitride and amorphous silicon). The amorphous silicon is prevalent in films deposited at a pressure of several to several tens of bars. Droplets of polycrystalline -Si are sometimes visible on the film surface. The experimental evidence, is analysed with a view to elucidating the participation in the chemical synthesis of the three main stages of the process: the substance expulsion from the target by laser ablation, the transition through the gas of the expulsed substance and it's final impact on the collector. We conclude that silicon nitride is mostly synthesized during the impact on the collector of the flow of the ablated substance.  相似文献   
5.
Ion bombardment of iron surfaces produced an ion eroded surface microtopography strongly dependent on the incidence angle and specimen temperature. For bombardment temperatures exceeding the self-diffusion temperature, T d, a microstructural smoothing process due to the thermally activated diffusion effects, assisted by ion bombardment, can be observed by SEM. The role of migrational processes which should be taken into account for a correct interpretation of the final surface topography formed by hot sputtering, was also considered.  相似文献   
6.
Meta-analysis was used to aggregate results from studies examining the relationship between intelligence and leadership. One hundred fifty-one independent samples in 96 sources met the criteria for inclusion in the meta-analysis. Results indicated that the corrected correlation between intelligence and leadership is .21 (uncorrected for range restriction) and .27 (corrected for range restriction). Perceptual measures of intelligence showed stronger correlations with leadership than did paper-and-pencil measures of intelligence. Intelligence correlated equally well with objective and perceptual measures of leadership. Additionally, the leader's stress level and the leader's directiveness moderated the intelligence-leadership relationship. Overall, results suggest that the relationship between intelligence and leadership is considerably lower than previously thought. The results also provide meta-analytic support for both implicit leadership theory and cognitive resource theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
8.
Technologies that accelerate the delivery of reliable battery-based energy storage will not only contribute to decarbonization such as transportation electrification, smart grid,but also strengthen the battery supply chain. As battery inevitably ages with time, losing its capacity to store charge and deliver it efficiently. This directly affects battery safety and efficiency,making related health management necessary. Recent advancements in automation science and engineering raised interest in A...  相似文献   
9.
The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKaMAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs.  相似文献   
10.
The paper presents an improved context-based denoising method for gray scale images affected by impulse noise. The proposed algorithm is using Markov chains to replace the detected noise with the intensity having the highest number of occurrences in similar contexts. The context of a noisy pixel consists in its neighbor pixels and is searched in a larger but limited surrounding area. We have analyzed different search methods and different context shapes. The experimental results obtained on the test images have shown that the most efficient model applies the search in form of   “*”  of contexts in form of   “+”. Besides the better denoising performance obtained on all the noise levels, the computational time has been also significantly improved with respect to our previous context-based filter which applied full search of full context. We have also compared this improved Markov filter with other denoising techniques existing in the literature, most of them being significantly outperformed.  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