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   469228篇
  免费   6380篇
  国内免费   1689篇
电工技术   8620篇
综合类   519篇
化学工业   68651篇
金属工艺   16970篇
机械仪表   14354篇
建筑科学   11848篇
矿业工程   1554篇
能源动力   12486篇
轻工业   46002篇
水利工程   4283篇
石油天然气   5605篇
武器工业   73篇
无线电   61119篇
一般工业技术   87567篇
冶金工业   86695篇
原子能技术   7967篇
自动化技术   42984篇
  2021年   3529篇
  2020年   2701篇
  2019年   3448篇
  2018年   5577篇
  2017年   5670篇
  2016年   6136篇
  2015年   4150篇
  2014年   7086篇
  2013年   21471篇
  2012年   12150篇
  2011年   16907篇
  2010年   13220篇
  2009年   14880篇
  2008年   15985篇
  2007年   15924篇
  2006年   14541篇
  2005年   13182篇
  2004年   12783篇
  2003年   12467篇
  2002年   11824篇
  2001年   12103篇
  2000年   11182篇
  1999年   11850篇
  1998年   27950篇
  1997年   19821篇
  1996年   15279篇
  1995年   11793篇
  1994年   10415篇
  1993年   10198篇
  1992年   7738篇
  1991年   7271篇
  1990年   6931篇
  1989年   6506篇
  1988年   6305篇
  1987年   5367篇
  1986年   5119篇
  1985年   6242篇
  1984年   5675篇
  1983年   5165篇
  1982年   4821篇
  1981年   4940篇
  1980年   4605篇
  1979年   4352篇
  1978年   4061篇
  1977年   4802篇
  1976年   5932篇
  1975年   3640篇
  1974年   3520篇
  1973年   3589篇
  1972年   2789篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The effect of high oxide field stress is studied using capacitance-time (C-t) measurements of MOS capacitors. The stress results in parallel shifts of the C-t curve along the time axis. The flatband voltage shift ΔVFB obtained from the initial deep depletion capacitance C(t=0+) follows the same trend as that from the high-frequency C-V characteristics. However, the discrepancy between the two flatband voltages becomes larger as the stress increases due to the effect of interface charges on C-t characteristics. The flatband voltage difference is converted to interface trap density, showing a steady increase of interface trap density with stress, similar to that from low-frequency C-V measurements  相似文献   
62.
Communication network design is becoming increasingly complex, involving making networks more usable, affordable, and reliable. To help with this, we have proposed an expert network designer (END) for configuring, modeling, simulating, and evaluating large structured computer networks, employing artificial intelligence, knowledge representation, and network simulation tools. We present a neural network/knowledge acquisition machine-learning approach to improve the END's efficiency in solving the network design problem and to extend its scope to acquire new networking technologies, learn new network design techniques, and update the specifications of existing technologies  相似文献   
63.
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   
64.
65.
66.
67.
Approaches to using visual language in a cultural context can be placed on a continuum, with global (universal) on one end and culture-focused on the other. Each approach reveals contrasting assumptions about three central design issues: perception, aesthetics and pragmatics. The global approach is characterized by attempts to invent an objective, universal visual language or to define such a language through perceptual principles and empirical research. The culture-focused perspective is founded on the principle that visual communication is intimately bound to experience and hence can function only within a given cultural context, to which designers must be sensitive. While the modernist, universal approach has been losing ground to the postmodern, culture-focused approach, the two complement each other in a variety of ways and, depending on the rhetorical situation, offer pragmatic benefits and drawbacks  相似文献   
68.
69.
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   
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