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   38105篇
  免费   2843篇
  国内免费   1485篇
电工技术   1890篇
技术理论   2篇
综合类   2283篇
化学工业   6425篇
金属工艺   2181篇
机械仪表   2300篇
建筑科学   2996篇
矿业工程   923篇
能源动力   906篇
轻工业   2293篇
水利工程   538篇
石油天然气   2595篇
武器工业   206篇
无线电   4638篇
一般工业技术   4779篇
冶金工业   2064篇
原子能技术   421篇
自动化技术   4993篇
  2024年   117篇
  2023年   602篇
  2022年   863篇
  2021年   1398篇
  2020年   1043篇
  2019年   873篇
  2018年   967篇
  2017年   1142篇
  2016年   1045篇
  2015年   1372篇
  2014年   1740篇
  2013年   2233篇
  2012年   2203篇
  2011年   2489篇
  2010年   2254篇
  2009年   2079篇
  2008年   2071篇
  2007年   2056篇
  2006年   2079篇
  2005年   1807篇
  2004年   1240篇
  2003年   1062篇
  2002年   1030篇
  2001年   883篇
  2000年   914篇
  1999年   1112篇
  1998年   957篇
  1997年   834篇
  1996年   832篇
  1995年   640篇
  1994年   557篇
  1993年   386篇
  1992年   342篇
  1991年   258篇
  1990年   194篇
  1989年   166篇
  1988年   135篇
  1987年   106篇
  1986年   75篇
  1985年   57篇
  1984年   57篇
  1983年   25篇
  1982年   35篇
  1981年   24篇
  1980年   16篇
  1979年   11篇
  1977年   7篇
  1976年   7篇
  1973年   5篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
一种新型电荷放大器的设计与研究   总被引:4,自引:0,他引:4  
介绍了一种新颖电荷放大器的设计结构及其工作原理,阐述了实验样机的的工作模式,给出了实验样机的实验结果。  相似文献   
962.
The paper proposes a new text similarity computing method based on concept similarity in Chinese text processing. The new method converts text to words vector space model at first, and then splits words into a set of concepts. Through computing the inner products between concepts, it obtains the similarity between words. The new method computes the similarity of text based on the similarity of words at last. The contributions of the paper include: 1) propose a new computing formula between words; 2) propose a new text similarity computing method based on words similarity; 3) successfully use the method in the application of similarity computing of WEB news; and 4) prove the validity of the method through extensive experiments.  相似文献   
963.
964.
This paper develops robust stability theorems and robust H control theory for uncertain impulsive stochastic systems. The parametric uncertainties are assumed to be time varying and norm bounded. Impulsive stochastic systems can be divided into three cases, namely, the systems with stable/stabilizable continuous‐time stochastic dynamics and unstable/unstabilizable discrete‐time dynamics, the systems with unstable/unstabilizable continuous dynamics and stable/stabilizable discrete‐time dynamics, and the systems in which both the continuous‐time stochastic dynamics and the discrete‐time dynamics are stable/stabilizable. Sufficient conditions for robust exponential stability and robust stabilization for uncertain impulsive stochastic systems are derived in terms of an average dwell‐time condition. Then, a linear matrix inequality‐based approach to the design of a robust H controller for each system is presented. Finally, the numerical examples are provided to demonstrate the effectiveness of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
965.
Granular Neural Networks With Evolutionary Interval Learning   总被引:1,自引:0,他引:1  
To deal with different membership functions of the same linguistic term, a new interval reasoning method using new granular sets is proposed based on Yin Yang methodology. To make interval-valued granular reasoning efficiently and optimize interval membership functions based on training data effectively, a granular neural network (GNN) with a new high-speed evolutionary interval learning is designed. Simulation results in nonlinear function approximation and bioinformatics have shown that the GNN with the evolutionary interval learning is able to extract interval-valued granular rules effectively and efficiently from training data by using the new evolutionary interval learning algorithm.  相似文献   
966.
Video Annotation Based on Kernel Linear Neighborhood Propagation   总被引:1,自引:0,他引:1  
The insufficiency of labeled training data for representing the distribution of the entire dataset is a major obstacle in automatic semantic annotation of large-scale video database. Semi-supervised learning algorithms, which attempt to learn from both labeled and unlabeled data, are promising to solve this problem. In this paper, a novel graph-based semi-supervised learning method named kernel linear neighborhood propagation (KLNP) is proposed and applied to video annotation. This approach combines the consistency assumption, which is the basic assumption in semi-supervised learning, and the local linear embedding (LLE) method in a nonlinear kernel-mapped space. KLNP improves a recently proposed method linear neighborhood propagation (LNP) by tackling the limitation of its local linear assumption on the distribution of semantics. Experiments conducted on the TRECVID data set demonstrate that this approach outperforms other popular graph-based semi-supervised learning methods for video semantic annotation.  相似文献   
967.
The essence of intelligence is to use certain abilities to obtain knowledge, to use that knowledge, and to operate with that knowledge. New knowledge learned by a human is often related to old existing knowledge, and sometimes we could have more conceptual knowledge based on old knowledge. So, the knowledge in the brain exists in a related structural form, and this structure is dynamic, and therefore is evolvable. Based on the understanding of the real process of learning by a human being, we discuss how to make a model to describe the dynamic structure of knowledge. This model is also a principle of artificial brain design. Most of the knowledge a child learns is from natural language and perception information, and we define this as semantic knowledge. The model to describe the process and structure of knowledge growing in a network form is called a K-net. It is a dynamic network with two main dynamics: one is new knowledge added, and the other is aggregating knowledge existing in the network with some probability. Under these very natural conditions, we found that the network is originally a simple random net, and then some characteristics of a complex network gradually appear when more new knowledge is added and aggregated. A more interesting phenomenon is the appearance of a random hierarchical structure. Does this mean emergence?  相似文献   
968.
With few exceptions, most of the existing noise reduction and data segmentation algorithms are only suited to image data. Therefore, an adaptive smoothing algorithm, with model-based masks, within a scale space framework is proposed for range data in this paper. This algorithm smoothes range data that conform to predefined, geometric models, while leaving other data points unaffected. The convergence of the algorithm in yielding dominant features is shown based on its compliance with the anisotropic diffusion concept. The weights of the smoothing masks are adaptively calculated according to the Mahalanobis distances between range data and model-based predictions. These behave as the diffusion coefficient in the anisotropic diffusion equation, thus satisfying the requirements of the causality criterion that no new features are introduced from fine to coarse scales. The computational complexity of this algorithm is examined and compared to that of the well-known RANSAC feature extraction algorithm. Unlike RANSAC, it has the advantage that the computational complexity is less affected by increasing the order of the model, and is independent of the number of model outliers. The proposed algorithm can be used to smooth range data in multiscale space by increasing the number of smoothing iterations. Robust, robot-occlusion-invariant features are then easily extracted from the smoothed data by least squares fitting algorithms.  相似文献   
969.
有机薄膜器件的镀膜自动控制系统设计   总被引:1,自引:1,他引:0  
唐超  夏斯杰  徐慧  吴开红 《计算机测量与控制》2008,16(11):1619-1621,1634
设计了用于有机薄膜器件的镀膜自动控制系统;整个自动控制系统以单片机为核心,可分为3个功能模块:人机交互、强弱电转换、样品处理。人机交互由单片机来实现;强弱电转换由固体继电器来完成;样品处理包括镀膜速率自动控制和样品保护两个部分。控制系统体现了弱电控制强电的设计思路,系统采用了单片机、继电器、电磁阀和可调变阻器等器件以及程控可调电阻电路。所设计的控制系统能克服目前有机薄膜器件镀膜系统的一些弊端,实现镀膜和镀膜速率的自动控制,并且能够避免有机半导体材料在真空腔内的相互污染。  相似文献   
970.
基于ARM的人体脂肪测量仪的设计   总被引:1,自引:0,他引:1  
为解决传统的人体脂肪测量仪只测量人体的全身阻抗,不能反映人体各个部位的脂肪分布情况的问题,提出了人体阻抗分布模型和分段阻抗计算公式,进而测量人体不同部位的脂肪含量的方法,并设计完成了一种基于ARM处理器的人体脂肪测量仪;该仪器以ARM处理器S3C2410为核心,外扩激励信号源、信号采集和处理、放大电路及整流滤波等电路,在嵌入式linux操作系统下实现了对人体脂肪的测量和分析;实验结果表明,该仪器比传统的人体脂肪测量仪检测精度高,能反映人体脂肪分布状况。  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