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   461380篇
  免费   5388篇
  国内免费   1211篇
电工技术   8679篇
综合类   579篇
化学工业   70784篇
金属工艺   18077篇
机械仪表   14381篇
建筑科学   10729篇
矿业工程   2322篇
能源动力   10744篇
轻工业   42874篇
水利工程   4668篇
石油天然气   8158篇
武器工业   98篇
无线电   54371篇
一般工业技术   86700篇
冶金工业   86188篇
原子能技术   10184篇
自动化技术   38443篇
  2021年   3760篇
  2019年   3651篇
  2018年   6275篇
  2017年   6275篇
  2016年   6654篇
  2015年   4205篇
  2014年   7189篇
  2013年   19833篇
  2012年   11565篇
  2011年   15737篇
  2010年   12467篇
  2009年   13932篇
  2008年   14856篇
  2007年   14913篇
  2006年   13446篇
  2005年   12059篇
  2004年   11633篇
  2003年   11328篇
  2002年   11075篇
  2001年   10944篇
  2000年   10564篇
  1999年   10572篇
  1998年   24938篇
  1997年   17753篇
  1996年   13931篇
  1995年   10860篇
  1994年   9686篇
  1993年   9460篇
  1992年   7510篇
  1991年   6981篇
  1990年   7002篇
  1989年   6663篇
  1988年   6421篇
  1987年   5614篇
  1986年   5560篇
  1985年   6421篇
  1984年   6085篇
  1983年   5485篇
  1982年   5186篇
  1981年   5376篇
  1980年   5085篇
  1979年   4905篇
  1978年   4800篇
  1977年   5481篇
  1976年   6880篇
  1975年   4338篇
  1974年   4198篇
  1973年   4342篇
  1972年   3550篇
  1971年   3296篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
BACKGROUND: Home parenteral nutrition (HPN) is used to treat intestinal failure. A minority of HPN patients are dependent on opiates and benzodiazepines to control pain and anxiety. The aim of this study was to determine what effects such drug dependence had on patient outcomes. METHODS: Ten dependent patients were prospectively compared with 10 well-matched, nondependent HPN patients for the same 12-month period. Episodes of line sepsis and other complications were documented and the cost of treatment estimated. Health status was measured using the SF36 and EuroQol instruments. RESULTS: The dependent group had significantly more episodes of central line sepsis (p = .0007) as well as other complications (p = .0002). This led to significantly longer periods of inpatient care (p = .0004) and therefore higher costs of treatment. Health status was lower in the dependent group; they reported more pain (p = .04) and less energy (p = .04). CONCLUSIONS: The complication rate and increased cost of treatment for opiate- and sedative-dependent patients receiving HPN significantly detract from the overall outcome of this therapy.  相似文献   
62.
63.
64.
65.
The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency  相似文献   
66.
67.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included  相似文献   
68.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information technologies and systems by the Ukrainian State Committee, of Science and Technology.  相似文献   
69.
70.
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