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   2240篇
  免费   70篇
电工技术   21篇
综合类   2篇
化学工业   211篇
金属工艺   31篇
机械仪表   31篇
建筑科学   93篇
矿业工程   28篇
能源动力   40篇
轻工业   154篇
水利工程   16篇
石油天然气   23篇
武器工业   1篇
无线电   294篇
一般工业技术   252篇
冶金工业   637篇
原子能技术   12篇
自动化技术   464篇
  2023年   10篇
  2021年   28篇
  2020年   25篇
  2019年   28篇
  2018年   34篇
  2017年   44篇
  2016年   49篇
  2015年   37篇
  2014年   61篇
  2013年   108篇
  2012年   89篇
  2011年   125篇
  2010年   102篇
  2009年   94篇
  2008年   118篇
  2007年   106篇
  2006年   93篇
  2005年   81篇
  2004年   73篇
  2003年   72篇
  2002年   43篇
  2001年   48篇
  2000年   27篇
  1999年   47篇
  1998年   115篇
  1997年   68篇
  1996年   94篇
  1995年   47篇
  1994年   29篇
  1993年   43篇
  1992年   23篇
  1991年   14篇
  1990年   19篇
  1989年   16篇
  1988年   20篇
  1987年   23篇
  1986年   16篇
  1985年   23篇
  1984年   19篇
  1983年   13篇
  1981年   17篇
  1980年   13篇
  1979年   11篇
  1978年   19篇
  1977年   8篇
  1976年   27篇
  1975年   15篇
  1974年   7篇
  1973年   11篇
  1971年   7篇
排序方式: 共有2310条查询结果,搜索用时 15 毫秒
1.
High-efficiency filtration in residential forced-air heating, ventilation, and air conditioning (HVAC) systems protects equipment and can reduce exposure to particulate matter. Laboratory tests provide a measure of the nominal efficiency, but they may not accurately reflect the in situ efficiency of the filters because of variations in system conditions and changes in filter performance over time. The primary focus of this paper is to evaluate the effective filtration efficiency, which is inclusive of any loading and system impacts, in 21 occupied residential homes through in-duct concentration measurements. We considered the role of filter media by testing both electret and non-electret media, as well as the role of loading by considering new and used filters. The results show that filters with higher nominal efficiency generally had higher effective filtration efficiency in the same home. In terms of performance change, there is no significant difference in efficiency between initial and 3-month non-electret filters, but the efficiency of electret filters generally decreased over time. However, both nominal efficiency and performance change were vastly overshadowed by the wide variety in loading and system conditions across homes, making it hard to predict filter efficiency in a given home without in situ measurements.  相似文献   
2.
112 children (aged 7-13 yrs) were randomly assigned to one of three treatments: problem-solving skills training (PSST), problem-solving skills training with in vivo practice (PSST-P), which included therapeutically planned activities to extend training to settings outside of treatment, or client-centered relationship therapy (RT). PSST and PSST-P children showed significantly greater reductions in antisocial behavior and overall behavior problems, and greater increases in prosocial behavior than RT children. These effects were evident on measures obtained immediately after treatment and at a 1-year follow-up, and on measures of child performance at home and at school. PSST-P children showed greater changes than PSST children on measures of functioning at school at posttreatment, but these differences were no longer evident at follow-up. Children in both PSST conditions showed significant reductions in deviant behavior and improvements in prosocial behavior from pretreatment to follow-up, whereas RT children tended to remain at their pretreatment level of functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Efficient data layout is an important aspect of the compilation process. A model for the creation of perfect memory maps for large-scale parallel machines capable of user-controlled partitionable single-instruction-multiple data/single-program-multiple data (SIMD/SPMD) operation is developed. The term perfect implies that no memory fragmentation occurs and ensures that the memory map size is kept to a minimum. A major constraint on solving this problem is based on the single program nature of both the SIMD and SPMD modes of parallelism. It is assumed that all processors within the same submachine used identical addresses to access corresponding data items in each of their local memories. Necessary and sufficient conditions are derived for being able to create perfect memory maps, and results are applied to several partitionable interconnection networks  相似文献   
4.
This paper discusses the future requirements of integrated construction management systems and the need to support the management of large volumes of information on several levels. The solution proposes a combination of an efficient user interface and methods to partially automate the creation of the required information through access to stored information from past projects. The research follows the path being established for integrated construction management systems that rely on a standard representation of the industry's information requirements. By exploring the comprehensive aspects of construction planning for an integrated construction management system, the research demonstrates the usefulness of applying sound information representation structures. Through the application of case-based reasoning, the research advances the concepts of planning tools as they apply to integrated systems. The resulting prototype construction management system has the primary characteristic of assisting the user in the manipulation of information in order to generate the initial information requirements of an integrated construction management system.  相似文献   
5.
消费电子和通信产业正见证着I/O解决方案从并行到高速串行的转变:能够降低成本、简化设计,并具备可延展性,满足全新带宽的要求。这类接口I/O技术的市场潜力巨大,包括移动电话、DVD-RW和高清晰度LCD电视机,而低功耗、低电磁干扰(EMI)和高数据吞吐量在这些应用中极为重要。因此,业界一直致力于设计和开发这些串行I/O,以低功耗提供高速的数据速  相似文献   
6.
Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO2 dielectric with various interfacial layers were studied with time dependent sensing measurements: DC IV, pulse IV, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (Vt) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on Vt.  相似文献   
7.
8.
9.
When the projecting point of saphenous nerve in second somatosensory cortex (S II) of cat was stimulated, the evoked potentials elicited by C-fiber inputs of saphenous nerve recorded in the primary somatosensory cortex (C-CEP) might be either inhibited or facilited according to whether the superficial and/or the deeper layer of the cortex was stimulated. The inhibition was expressed as a decrease of amplitude and prolongation of latency of C-CEP; while the facilitation, as an increase of amplitude and duration of C-CEP. When the superfaicial layer of S II was stimulated by weaker current, both inhibitory and facilitatory effects could be observed, but only inhibitory effect was observed, when the deep layer was stimulated. With the same intensity of stimulation, inhibitory effect was more pronounced when the deep layer rather than the superficial layer was stimulated. It is suggested that S II may play a role in the modulation of C-CEP of S I.  相似文献   
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