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   829篇
  免费   27篇
  国内免费   5篇
电工技术   87篇
综合类   1篇
化学工业   198篇
金属工艺   20篇
机械仪表   35篇
建筑科学   28篇
能源动力   38篇
轻工业   84篇
无线电   74篇
一般工业技术   172篇
冶金工业   41篇
原子能技术   13篇
自动化技术   70篇
  2023年   3篇
  2022年   8篇
  2021年   16篇
  2020年   9篇
  2019年   19篇
  2018年   14篇
  2017年   12篇
  2016年   18篇
  2015年   10篇
  2014年   17篇
  2013年   41篇
  2012年   32篇
  2011年   50篇
  2010年   45篇
  2009年   31篇
  2008年   37篇
  2007年   38篇
  2006年   40篇
  2005年   39篇
  2004年   31篇
  2003年   24篇
  2002年   30篇
  2001年   15篇
  2000年   14篇
  1999年   14篇
  1998年   18篇
  1997年   14篇
  1996年   19篇
  1995年   15篇
  1994年   6篇
  1993年   14篇
  1992年   6篇
  1991年   10篇
  1990年   10篇
  1989年   3篇
  1988年   14篇
  1987年   7篇
  1986年   7篇
  1985年   13篇
  1984年   15篇
  1983年   9篇
  1982年   8篇
  1981年   7篇
  1980年   9篇
  1979年   12篇
  1978年   5篇
  1977年   4篇
  1976年   8篇
  1975年   6篇
  1974年   4篇
排序方式: 共有861条查询结果,搜索用时 15 毫秒
81.
82.
This study investigated the growth performance and gene expression for muscle development between grass hay-fed (GH) and concentrate-fed (CT) steers. Daily gain and energy intake during the fattening period of the GH group were lower than those of the CT group. Analysis of C/EBPα, PPARγ2, myosin heavy chain (MHC), and myostatin gene expressions was performed by real-time PCR. Expressions of C/EBPα and myostatin in semitendinosus and longissimus lumborum (LL) muscles were higher in the CT group than in the GH group at the end of fattening. In LL muscle, MHC expression at the end of fattening was greater in the GH group than in the CT group. These results suggest that regulation of adipogenesis and myogenesis by the expression of genes involved in muscle development might have occurred in the skeletal muscle of the GH group by the feeding of grass hay and/or because of the low energy intakes.  相似文献   
83.
84.
The thermal conductivities of near-stoichiometric (U, Ce)C and (U, Pu, Ce)C solid solutions containing CeC up to 10 mol% were determined in the temperature range from 740 to 1600 K by the laser flash method. The thermal conductivity decreased with the cerium content in the solid solutions. The electrical resistivities were also measured for the purpose of analyzing the heat conduction mechanism. It was found that the decrease of electronic heat conduction caused by the addition of cerium resulted in decreasing the thermal conductivities of (U, Ce)C and (U, Pu, Ce)C compared with UC and (U, Pu)C.  相似文献   
85.
Electrochromic nickel oxide thin films were prepared in air by an atmospheric-pressure chemical vapor deposition method. The raw material was nickel acetylacetonate. Amorphous nickel oxide thin films were obtained at a substrate temperature 250°C. Reduction and oxidation of the films in 1 M KOH resulted in bleaching and coloration, respectively. Coulometry indicated that the coloration efficiency was 44 cm2/C.  相似文献   
86.
Recent preventive maintenance for equipment has grown to include diagnosis of the insulation of cables under hot-line conduction. Much of the equipment constructed during the high-growth period in the 1960s has become obsolete. Recent circumstances make it difficult to obtain a longer service interruption time. Results of a study of the method that measures the live-wire insulation resistance by superimposing dc 50 V to a high-voltage busbar through GPT and forms a bridge with the resistance of a cable insulation are discussed. It is clarified that this live-wire insulation diagnostic method is highly effective at detecting degradation of a cable insulation resistance and is, therefore, suitable for so-called trend monitoring as well.  相似文献   
87.
Researches on the unit commitment with transmission network have been reported recently. However, most of these researches mainly discussed the security constrained unit commitment, while the relationship between unit commitment and transmission losses was not considered. However, from the standpoint of operating reserve for ensuring power supply reliability, a unit commitment considering transmission losses is required. Further, under the deregulation and liberalization of the electric power industry, not only the line's security but also transmission losses are expected to play an important role in calculating the network access charge, and unit commitment taking into account transmission losses is also desired from this viewpoint. In this paper, a unit commitment approach with both transmission losses and line flow constraint is presented. Based on a heuristic iterative optimization method, first, an initial schedule is created by using a successively decommitting unit approach that is proposed in this paper. Then, we determine constraints included in the unit commitment schedule by a heuristic iterative optimization approach, in which an algorithm able to get rid of line overload by DC optimal power flow is developed. Through numerical simulations on two test power systems, the effectiveness of the proposed method is shown. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 9–19, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10116  相似文献   
88.
Microfabrication technique using SR ablation for 3-D polytetrafluoroethylene (PTFE) structure is reported in this work. First of all, we investigated necessary basic data for the fabricated structure like the processing depth and the etching rate, etc. And, the exposure energy distribution was given to the surface of polytetrafluoroethylene by using the plane pattern to cross-section transfer (PCT) technique, 3-D microstructures was fabricated. To establish three dimension of highly accurate PTFE processing technology, we are researching the application to the device.  相似文献   
89.
Small crystalline particles or precipitates are often formed comprising near polyhedral shapes with round edges. Using the anisotropy of the surface energy given by a simple broken-bond model for fcc crystals, a geometrical analysis is performed to consider the particle-shape dependence of surface energy. Polyhedral and nearly polyhedral particles composed of {100} and {111} planes are treated as examples. The effect of round edges on the variation of surface energy of the nearly polyhedral particles is discussed.  相似文献   
90.
这座建筑是大学的语言教育中心,设有500台计算机、影像和音响系统,主要用于语言教学、留学生教学及国际交流活动。作为建筑“外皮”的性能,设计满足以下三点要求:①充分考虑减少计算机显示器的光反射,营造照度对比小的均质柔和的光环境。②在影像放映时,光环境可渐变调节。③适度的外墙散热功能。教室分别布置在南北两侧,南面的波纹玻璃和合成树脂板材形成双层表皮,中间设计有可调控百叶,能根据日照的入射角度调节;夏季可排热,冬季则可让阳光照射进室内,从而既可获得柔和均质的采光效果又可对热负载进行有效的控制。在建筑北侧满铺的玻璃砖…  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