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   8812篇
  免费   678篇
  国内免费   290篇
电工技术   372篇
综合类   353篇
化学工业   1605篇
金属工艺   415篇
机械仪表   618篇
建筑科学   747篇
矿业工程   241篇
能源动力   239篇
轻工业   632篇
水利工程   105篇
石油天然气   543篇
武器工业   60篇
无线电   1049篇
一般工业技术   1297篇
冶金工业   442篇
原子能技术   100篇
自动化技术   962篇
  2024年   33篇
  2023年   170篇
  2022年   269篇
  2021年   362篇
  2020年   286篇
  2019年   255篇
  2018年   273篇
  2017年   333篇
  2016年   305篇
  2015年   316篇
  2014年   471篇
  2013年   538篇
  2012年   547篇
  2011年   667篇
  2010年   531篇
  2009年   511篇
  2008年   500篇
  2007年   424篇
  2006年   417篇
  2005年   359篇
  2004年   256篇
  2003年   225篇
  2002年   185篇
  2001年   174篇
  2000年   161篇
  1999年   254篇
  1998年   180篇
  1997年   175篇
  1996年   123篇
  1995年   99篇
  1994年   84篇
  1993年   58篇
  1992年   40篇
  1991年   43篇
  1990年   28篇
  1989年   25篇
  1988年   18篇
  1987年   21篇
  1986年   12篇
  1985年   7篇
  1984年   8篇
  1983年   3篇
  1982年   5篇
  1981年   5篇
  1980年   5篇
  1977年   2篇
  1976年   5篇
  1975年   2篇
  1972年   2篇
  1968年   2篇
排序方式: 共有9780条查询结果,搜索用时 0 毫秒
71.
This paper proposes an extremum seeking control (ESC) scheme based on particle swarm optimization (PSO). In the proposed scheme, the controller steers the system states to the optimal point based on the measurement, and the explicit form of the performance function is not needed. By measuring the performance function value online, a sequence, generated by PSO algorithm, guides the regulator that drives the state of system approaching to the set point that optimizes the performance. We also propose an algorithm that first reshuffles the sequence, and then inserts intermediate states into the sequence, in order to reduce the regulator gain and oscillation induced by population-based stochastic searching algorithms. The convergence of the scheme is guaranteed by the PSO algorithm and state regulation. Simulation examples demonstrate the effectiveness and robustness of the proposed scheme.  相似文献   
72.
提出一种新的基于证据理论的数据融合的双效水印算法.首先应用水印公式构造特殊的水印嵌入后条件,根据嵌入系数之间的定性分析提取鲁棒水印;利用嵌入系数之间的定量分析能提取脆弱水印,并能准确定位篡改的区域.其次在嵌入过程中还使用纠错码对水印信息进行调和,把水印重复嵌入到图像信息的不同位置,以便利用纠错码的辅助信息来估计出提取的...  相似文献   
73.
74.
The research issues of intelligent information integration have become ubiquitous and critically important in e-business (EB) with the increasing dependence on Internet/Intranet and information technology (IT). Accessing the intelligent information sources separately without integration may lead to the chaos of information requested. It is also not cost-effective in EB settings. A common general way to deal with heterogeneity problems in traditional III is to create a common data model. The eXtensible Markup Language (XML) has been the standard data document format for exchanging information on the Web. XML only deals with the structural heterogeneity; it can barely handle the semantic heterogeneity. Ontologies are regarded as an important and natural means to represent the implicit semantics and relationships in the real world. And they are used to assist to reach semantic interoperability in III in this research. In this paper, we provide a generic construct orientation no ad hoc method to generate the global schema to enable the web-based alternative to traditional III. We provide a wiser query method over multiple intelligent information sources by applying global-as-view (GAV) and local-as-view (LAV) approach with the use of ontology to enhance both structural and semantic interoperability of the underlying intelligent information sources. We construct a prototype implementing the method to provide a proof on the validity and feasibility.  相似文献   
75.
In this paper, effects of the implant thread pitch on the maximum Von Mises stresses were evaluated in jaw bones and implant–abutment complex by a finite element method. The thread pitch ranged from 0.5 mm to 1.6 mm. Results suggested that under axial load, the maximum equivalent stresses in cortical bone, cancellous bone and implant–abutment complex decreased by 6.7%, 55.2% and 22.3%, respectively with the variation of thread pitch; and under buccolingual load, 2.7%, 22.4% and 13.0%, respectively. When thread pitch exceeded 0.8 mm, minimum stresses were obtained. Data indicated that cancellous bone was more sensitive to thread pitch than cortical bone did; thread pitch played a great role in protecting dental implant under axial load than under buccolingual load; and thread pitch exceeding 0.8 mm were optimal selection for a screwed implant by biomechanical consideration.  相似文献   
76.
重压缩检测是多级隐密分析中关键的预处理部分,高准确率的重压缩检测是隐密分析获得更高性能的重要前提条件.深入研究了重压缩对于JPEG图像各种特征的影响,基于此提出了一种融合直方图分布特征、Benford特征、DFT特征的重压缩检测算法.仿真实验表明,该算法具有更高的检测率,能够适用于JPEG多级隐密分析中的重压缩检测.  相似文献   
77.
78.
Universal Access in the Information Society - In recent years, researchers have attempted to shift patient decision aids (PDAs) from paper-based to web-based to increase its accessibility. Insulin...  相似文献   
79.
Kong YK  Lee KS  Kim DM  Jung MC 《Ergonomics》2011,54(11):1072-1080
The objective of this study was to evaluate individual finger force and contribution to a gripping force, the difference between actual and expected finger forces and subjective discomfort rating at 10 different submaximal voluntary contraction (%MVC) levels (10-100% in 10 increments). Seventy-two participants randomly exerted gripping force with a multi-finger force measurement system. The individual finger force, gripping force and discomfort increased as %MVC levels increased. The middle and ring fingers exerted more force and contributed to a gripping force more than the index and little fingers due to their larger mass fractions of the digit flexor muscles. It was apparent at <50% MVC; however, the index finger increased its contribution and exerted even more force than expected at more than 50% MVC. Subjective discomfort supported the results of the objective measures. This could explain the conflicting findings between index and ring fingers in previous finger contribution studies. STATEMENT OF RELEVANCE: Hand tool design is of special interest in ergonomics due to its association with musculoskeletal disorders in the hand. This study reveals a different contribution pattern of the fingers in submaximal voluntary contraction of gripping exertion.  相似文献   
80.
Suitability evaluation of urban construction land based on geo-environmental factors is the process of determining the fitness of a given tract of land for construction. This process involves a consideration of the geomorphology, geology, engineering geology, geological hazards, and other geological factors and is the basis of urban construction land planning and management. With the support of Geographic Information Systems (GIS), grid analysis, and geo-spatial analysis techniques, four factor groups comprising nine separate subfactors of geo-environmental attributes were selected to be used in the evaluation of the suitability level for construction land in Hangzhou. This was based on K-means clustering and back-propagation (BP) neural network methods due to their advantages in fast computing, unique adaptive capacity, and self-organization. Simultaneously, the evaluation results based on K-means clustering and BP neural network were compared and analyzed, and the accuracy evaluation was set. The results showed that the geo-environmental suitability evaluation results of construction land based on K-means clustering and BP neural network were similar in terms of the distribution and scale of construction land suitability level. At the same time, the results of the two evaluation methods were consistent with the variability in suitability level, engineering geology, and hydrogeology of Hangzhou. The results also showed that the real advantage of the methods proposed in this paper lies in their capacity to streamline the mapping process and to ensure that the results are consistent throughout. The suitability level of the urban construction land based on the geo-environment in Hangzhou was divided into four construction sites: land for building super high-rise and high-rise buildings, land for building multistorey buildings, land for low-rise buildings, and nonbuilding land. The results of the suitability evaluation for each category will provide a scientific basis for decision-making in urban development in Hangzhou.  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