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   147990篇
  免费   19797篇
  国内免费   9575篇
电工技术   13319篇
技术理论   15篇
综合类   18363篇
化学工业   11642篇
金属工艺   4640篇
机械仪表   10606篇
建筑科学   13822篇
矿业工程   4865篇
能源动力   6545篇
轻工业   5087篇
水利工程   9376篇
石油天然气   7657篇
武器工业   2053篇
无线电   11827篇
一般工业技术   12556篇
冶金工业   4770篇
原子能技术   1507篇
自动化技术   38712篇
  2025年   1618篇
  2024年   3838篇
  2023年   3552篇
  2022年   4765篇
  2021年   5321篇
  2020年   5757篇
  2019年   5048篇
  2018年   4646篇
  2017年   5515篇
  2016年   6394篇
  2015年   6528篇
  2014年   8454篇
  2013年   9077篇
  2012年   10012篇
  2011年   10620篇
  2010年   8413篇
  2009年   8678篇
  2008年   8681篇
  2007年   9743篇
  2006年   8442篇
  2005年   7415篇
  2004年   5988篇
  2003年   5216篇
  2002年   4129篇
  2001年   3410篇
  2000年   2963篇
  1999年   2263篇
  1998年   1915篇
  1997年   1580篇
  1996年   1489篇
  1995年   1292篇
  1994年   1052篇
  1993年   748篇
  1992年   620篇
  1991年   485篇
  1990年   390篇
  1989年   323篇
  1988年   200篇
  1987年   129篇
  1986年   99篇
  1985年   99篇
  1984年   105篇
  1983年   47篇
  1982年   66篇
  1981年   35篇
  1980年   48篇
  1979年   47篇
  1978年   16篇
  1959年   17篇
  1951年   15篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
We present a time-continuous identification method for nonlinear dynamic Volterra models of the form HX=f(u,X)+v with H, a causal convolution operator. It is mainly based on a suitable parameterization of H deduced from the so-called diffusive representation, which is devoted to state representations of integral operators. Following this approach, the complex dynamic nature of H can be summarized by a few numerical parameters on which the identification of the dynamic part of the model will focus. The method is validated on a physical numerical example.  相似文献   
72.
In this paper we describe an algorithm for distributed, BDD-based bounded property checking and its implementation in the verification tool SymC. The distributed algorithm verifies larger models and returns results faster than the sequential version.The core algorithm distributes partitions of the state set to computation nodes after reaching a threshold size. The nodes proceed with image computation on the nodes asynchronously. The main scalability problem of this scheme is the overlap of state set partitions. We present static and dynamic overlap reduction techniques.  相似文献   
73.
Rapid prototyping of software and hardware is recognized as a very important step in timely, cost-effective system development. The complexity inherent in designing distributed computing systems and distributed problem solutions emphasizes the need for effective rapid prototyping tools. ADL/ADS is a testbed user interface tool for experimentation with critical research and design issues pertaining to distributed data processing (DDP). The experimenter expresses a candidate distributed system in terms of experiment objects, along with attributes and relationships. The experiment objects represent hardware, software, and behavior. This paper provides a brief overview of ADL/ADS, and gives especial emphasis to the Behavior Prototyping Language (BPL) within ADL/ADS. BPL is designed for expressing Behavior Modules (B_MODULEs)—the most versatile of the behavior objects. BPL incorporates set-theoretical approaches, and provides syntax designed for effectively describing manipulations of experiment objects, and their attributes and relationships.  相似文献   
74.
水和甲醇存在下MAMS的消失反应动力学研究   总被引:1,自引:0,他引:1  
通过实验研究了甲基丙烯酰胺硫酸盐(MAMS)与甲醇、水进行反应的动力学,并对该反应的机理进行了探讨。  相似文献   
75.
《国际计算机数学杂志》2012,89(14):3236-3253
In this article, optimal error estimates of the penalty method for the linearized viscoelastic flows equations arising in the Oldroyd model are derived. Furthermore, error estimates for the backward Euler time discretization scheme in L 2 and H 1-norms are obtained.  相似文献   
76.
《国际计算机数学杂志》2012,89(11):2275-2284
The hypermeshes are a family of promising optical interconnection topologies for multiprocessor systems. In this paper, the conditional diagnosability of the hypermesh optical multiprocessor systems, under the PMC model, is determined. We derive that the conditional diagnosability of k n -hypermesh is 4n(k?1)?4k+1, where n≥3 and k≥5. This result shows that the hypermesh optical multiprocessor systems possess strong self-diagnosing abilities.  相似文献   
77.
A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence.In order to ensure the safety of the transmission towers and the safe operati...  相似文献   
78.
Many video-based techniques for assessing postures at work have been developed. Choosing the most appropriate technique should be based on an evaluation of different alternatives in terms of their ability to produce posture information at low input costs, i.e. their cost efficiency. This study compared four video-based techniques for assessing upper arm postures, using cost and error data from an investigation on hairdressers. Labour costs associated with the posture assessments from the video recordings were the dominant factor in the cost efficiency comparison. Thus, a work sampling technique associated with relatively large errors appeared, in general, to be the most cost-efficient because it was labour-saving. Measurement bias and other costs than labour cost for posture assessment influenced the ranking and economic evaluation of techniques, as did the applied measurement strategy, i.e. the numbers of video recordings and repeated assessments of them. PRACTITIONER SUMMARY: The cost efficiency of four video-based techniques for assessing upper arm postures was compared. Work sampling techniques were in general more cost efficient than continuous observations since they were labour-saving. Whilst a labour cost dominated the comparison, 'hidden costs', bias and measurement strategy also influenced this dominance.  相似文献   
79.
《Ergonomics》2012,55(3):398-406
This article describes the development and validation of a model for predicting multi-finger movements in grasping activities. The model builds upon a newly proposed approach that incorporates forward dynamics and a system identification procedure, and is amenable to empirical tests. A database of multi-fingered grasping movements performed by 28 subjects was established and divided into four sets, one for model development and three for model validation. In the development phase, model parameter values were estimated by the iterative system identification procedure through a physics-based heuristic algorithm. The estimated parameter values were then statistically synthesised and integrated into the prediction model. In the validation phase, the model was applied to three novel datasets containing different grasping movements involving objects of varied sizes and different subjects. The results demonstrated the model's ability to predict hand prehensile movements with error magnitudes comparable to the inter-person variability in performing such movements. New insights into the control of multi-fingered hand prehensile movements at the systems and joint levels emerged from the model development and validation process. The current study contributes to building a foundation for long-term development of realistic biodynamic simulation of multi-finger hand movements. Such simulation capabilities will aid in design of hand-operated tools, devices or hand-intensive work for proactive ergonomics and in evaluation as well as treatment of functional impairment of the hand.  相似文献   
80.
“就业导向、工学结合”已成为高等职业教育人才培养模式改革的重要切入点,这给作为主干专业课程的“地籍与房产测量”教学带来全新的课题.为了构建适应这种新形势的教学模式,分别从教材建设、教学内容、教学手段、实践教学和考试形式5个方面进行了探索.  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