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   7375篇
  免费   627篇
  国内免费   30篇
电工技术   83篇
综合类   37篇
化学工业   1872篇
金属工艺   308篇
机械仪表   446篇
建筑科学   148篇
矿业工程   9篇
能源动力   369篇
轻工业   652篇
水利工程   19篇
石油天然气   31篇
无线电   1247篇
一般工业技术   1746篇
冶金工业   322篇
原子能技术   70篇
自动化技术   673篇
  2024年   9篇
  2023年   121篇
  2022年   155篇
  2021年   259篇
  2020年   197篇
  2019年   230篇
  2018年   290篇
  2017年   263篇
  2016年   274篇
  2015年   228篇
  2014年   361篇
  2013年   463篇
  2012年   571篇
  2011年   641篇
  2010年   450篇
  2009年   430篇
  2008年   435篇
  2007年   312篇
  2006年   275篇
  2005年   230篇
  2004年   207篇
  2003年   210篇
  2002年   197篇
  2001年   156篇
  2000年   129篇
  1999年   131篇
  1998年   146篇
  1997年   107篇
  1996年   99篇
  1995年   75篇
  1994年   51篇
  1993年   47篇
  1992年   40篇
  1991年   21篇
  1990年   27篇
  1989年   22篇
  1988年   18篇
  1987年   20篇
  1986年   16篇
  1985年   23篇
  1984年   20篇
  1983年   6篇
  1982年   6篇
  1981年   7篇
  1980年   9篇
  1979年   6篇
  1978年   5篇
  1977年   8篇
  1976年   12篇
  1974年   5篇
排序方式: 共有8032条查询结果,搜索用时 15 毫秒
31.
Learning and prediction capability of the backpropagation neural network (BPNN) have been used to build the prediction model for the structural stability of a surface grinder. The Lagrange energy method is applied to derive the dynamic equation of the lumped parameter model of the surface grinder. The major factors influencing the structural stability of the system can be determined after the ratio of kinetic energy of the sub-structure and the ratio of potential energy of the sub-structure interface are obtained. An orthogonal rotatable central composite design is adopted to dispose the treatment combinations of the major factors. The BPNN model is constructed by the treatment combinations of the training patterns and verified by the treatment combinations of the test patterns. In this paper, a 3-layer BPNN model with a 10-neuron hidden layer which converged after 4,072 learning cycles is selected to predict the structural stability of a surface grinder within the planned ranges. The percentage residuals of both training patterns and test patterns are all within 3.41%, thus the prediction accuracy of the BPNN model is excellent so that the engineering demands are well satisfied.  相似文献   
32.
TheCubooctahedronShape──ASuboptimalCellShapefor3-DimensionalCellularSystemChaGuangming;LiZhengmao;LuFan(UniversityofElectroni...  相似文献   
33.
The bang-bang controlled capacitor coupled converter (C3) is described in this paper. Due to the converter's inherent commutating property, the C3 can accommodate thyristors as well as high-power gate turn-off switches, due to zero-current switching transitions. The zero-current switching is achieved at no current stress increase, therefore, the topology is considered appropriate for high-power processing. DC and small signal AC models are derived for the bang-bang controlled C3, a design procedure is proposed, and simulation results are discussed. Finally, oscillograms from a proof of principle prototype circuit are presented  相似文献   
34.
Modeling molecular interactions in signalling networks is important from various perspectives such as predicting side effects of drugs, explaining unusual cellular behavior and drug and therapy design. Various formal languages have been proposed for representing and reasoning about molecular interactions. The interactions are modeled as triggered events in most of the approaches. The triggering of events is assumed to be immediate: once an interaction is triggered, it should occur immediately. Although working well for engineering systems, this assumption poses a serious problem in modeling biological systems. Our knowledge about biological systems is inherently incomplete, thus molecular interactions are constantly elaborated and refined at different granularity of abstraction. The model of immediate triggers can not consistently deal with this refinement. In this paper we propose an action language to address this problem. We show that the language allows for refinements of biological knowledge, although at a higher cost in terms of complexity.   相似文献   
35.
36.
Understanding information sharing is an important challenge to modern organizations, and is likely to be increasingly considered when IT investment decisions are made world-wide. Our research study investigated the influence of cultural factors on information sharing in China. It was postulated that social network structures such as guanxi, Confucian dynamism, and collectivism could explain the degree to which information sharing took place between people in China. It was found that guanxi, Confucian dynamism, and collectivism all had a significant influence on information sharing.  相似文献   
37.
Long-term exposure to cocaine can cause persistent behavioral changes and alterations in neuronal function. One cocaine-regulated mRNA in the rat brain is the beta-1 subunit of the Na+/K(+)-ATPase pump. We examined both Na+/K(+)-ATPase function and expression after cocaine treatment of pheochromocytoma cells. One-hour exposure to cocaine did not alter Na+/K(+)-ATPase activity, as measured by the ouabain-sensitive component of rubidium uptake. Four days of cocaine resulted in an approximately 30% decrease in Na+/K(+)-ATPase activity. Western blot analyses demonstrated an approximately 25% decrease in levels of the beta-1 isoform, without changes in pump total alpha subunit levels. Treatment with dopamine type 1 or type 2 receptor agonists for the same period did not affect Na+/K(+)-ATPase activity. The serotonin-selective reuptake inhibitor paroxetine caused an approximately 45% decrease in rubidium uptake after 4 days, whereas pump function was not altered after treatment with either the dopamine-selective reuptake blocker nomifensine or the norepinephrine-selective reuptake blocker desipramine. Chronic treatment with both cocaine and LY 278,584, a serotonin type 3 receptor antagonist, did not replicate the cocaine-associated decrease in pump function. Long-term cocaine exposure regulates expression and function of the Na+/K(+)-ATPase pump in neuronal-like cells; this regulation is mediated in part via the serotonin type 3 receptor. Similar Na+/K(+)-ATPase pump regulation in vivo may selectively alter neuronal function in the mammalian brain.  相似文献   
38.
龚查 《自动化应用》2012,(11):42-44
介绍在发电厂锅炉运行过程中降低燃烧低挥发分高热值燃料飞灰含碳量的途径  相似文献   
39.
Artificial Intelligence Review - Visual object tracking has become one of the most active research topics in computer vision, and it has been applied in several commercial...  相似文献   
40.
Recently, watermarking based data transmission techniques using terrestrial digital TV signal have been proposed since they are also cost-free and can overcome the limitations of GPS. However, in the previous watermarking based methods, the detection accuracy is low and additional data rate is too low. Thus, we propose the throughput enhancement method by employing the TZCD-MBOK watermarking technique in T-DMB system. By applying the proposed scheme to T-DMB, it allows additional data transmission for disaster broadcasting and improves efficiency of data transmission in shadow region and indoor to mobile environment through watermarking spread code. From the simulation results, we confirm the proposed watermarking scheme affected on the existing T-DMB signal. Moreover, it was also confirmed that the system capacity increases as the power of additional watermarking signal rose. The results of the paper can be applied to wireless multimedia digital broadcasting systems.  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