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   15886篇
  免费   1281篇
  国内免费   588篇
电工技术   851篇
技术理论   1篇
综合类   1120篇
化学工业   2717篇
金属工艺   1042篇
机械仪表   1059篇
建筑科学   1216篇
矿业工程   577篇
能源动力   443篇
轻工业   876篇
水利工程   250篇
石油天然气   1174篇
武器工业   127篇
无线电   1457篇
一般工业技术   1901篇
冶金工业   926篇
原子能技术   151篇
自动化技术   1867篇
  2024年   84篇
  2023年   324篇
  2022年   470篇
  2021年   705篇
  2020年   549篇
  2019年   410篇
  2018年   517篇
  2017年   540篇
  2016年   463篇
  2015年   611篇
  2014年   736篇
  2013年   889篇
  2012年   963篇
  2011年   1075篇
  2010年   888篇
  2009年   841篇
  2008年   832篇
  2007年   796篇
  2006年   828篇
  2005年   732篇
  2004年   489篇
  2003年   474篇
  2002年   510篇
  2001年   442篇
  2000年   362篇
  1999年   408篇
  1998年   331篇
  1997年   270篇
  1996年   254篇
  1995年   231篇
  1994年   166篇
  1993年   107篇
  1992年   106篇
  1991年   72篇
  1990年   63篇
  1989年   53篇
  1988年   45篇
  1987年   25篇
  1986年   13篇
  1985年   16篇
  1984年   20篇
  1983年   3篇
  1982年   17篇
  1981年   7篇
  1980年   9篇
  1979年   4篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Semantic Web Services (SWS) were introduced to facilitate the publication, discovery, and execution of web services. A semantic matchmaker enhances the capability of UDDI service registries in the SWS architecture and it is able to recognize various degrees of matching for web services. On the basis of SWS and fuzzy-set theory, a fuzzy matching approach for semantic web services is proposed, to support a more automated and veracious service discovery process.  相似文献   
102.
Quantum size ZnO crystals have been synthesized successfully by a room temperature sol-gel process. Oleic acid (OA) has been used as capping agent to control the particle size of ZnO. The crystal structure and size of the ZnO are characterized by the X-ray diffraction (XRD) and transmission electron microscope (TEM). The XRD results show the as-synthesized ZnO has hexagonal wurtzite structure and the average crystallite size is 5.7 nm which is little less than TEM result. It is testified by photoluminescence (PL) and Raman spectra that the quantum size ZnO keeps the crystal structure of the bulk ZnO and possesses more surface defects. The quantum size ZnO has the highest response of 280 to NO2 and the highest selectivity of 31 and 49 corresponding to CO and CH4 at operating temperature of 290 °C. The effect of calcination temperatures on sensing property and transient response of the ZnO sensor are also investigated.  相似文献   
103.
DCS电源供电系统的可靠性定量分析   总被引:2,自引:0,他引:2  
根据DCS电源系统的现状,对目前几种不同的电源设计方案进行可靠性定量分析.通过建立不同DCS电源系统可靠性框图并估算相关的可靠性指标,比较了不同方案下的平均无故障工作时间 (MTBF),给出了系统可靠性的分析结果和改进措施,定量分析了改进后的方案.结果表明电源系统的MTBF有了明显的改善.  相似文献   
104.
基于WinCE的电梯监控系统多串口通信实现   总被引:2,自引:0,他引:2  
提出了一种基于WinCE的多串口电梯远程监控系统的实现方法.该方法以S3C2440微处理器为核心构建硬件平台,实现了与其他设备的串口通信;同时以WinCE5.0为软件平台,完成多串口分层流驱动的设计.通过文件映射,解决了访问多串口设备时产生的竞态问题.测试结果表明,该系统通信正常、数据稳定,能充分满足电梯监控对串行通信的要求.  相似文献   
105.
This paper presents a new robust optimization method for supply chain network design problem by employing variable possibility distributions. Due to the variability of market conditions and demands, there exist some impreciseness and ambiguousness in developing procurement and distribution plans. The proposed optimization method incorporates the uncertainties encountered in the manufacturing industry. The main motivation for building this optimization model is to make tools available for producers to develop robust supply chain network design. The modeling approach selected is a fuzzy value-at-risk (VaR) optimization model, in which the uncertain demands and transportation costs are characterized by variable possibility distributions. The variable possibility distributions are obtained by using the method of possibility critical value reduction to the secondary possibility distributions of uncertain demands and costs. We also discuss the equivalent parametric representation of credibility constraints and VaR objective function. Furthermore, we take the advantage of structural characteristics of the equivalent optimization model to design a parameter-based domain decomposition method. Using the proposed method, the original optimization problem is decomposed to two equivalent mixed-integer parametric programming sub-models so that we can solve the original optimization problem indirectly by solving its sub-models. Finally, we present an application example about a food processing company with four suppliers, five plants, five distribution centers and five customer zones. We formulate our application example as parametric optimization models and conduct our numerical experiments in the cases when the input data (demands and costs) are deterministic, have fixed possibility distributions and have variable possibility distributions. Experimental results show that our parametric optimization method can provide an effective and flexible way for decision makers to design a supply chain network.  相似文献   
106.
Fire detection is an important task in many applications. Smoke and flame are two essential symbols of fire in images. In this paper, we propose an algorithm to detect smoke and flame simultaneously for color dynamic video sequences obtained from a stationary camera in open space. Motion is a common feature of smoke and flame and usually has been used at the beginning for extraction from a current frame of candidate areas. The adaptive background subtraction has been utilized at a stage of moving detection. In addition, the optical flow-based movement estimation has been applied to identify a chaotic motion. With the spatial and temporal wavelet analysis, Weber contrast analysis and color segmentation, we achieved moving blobs classification. Real video surveillance sequences from publicly available datasets have been used for smoke detection with the utilization of our algorithm. We also have conducted a set of experiments. Experiments results have shown that our algorithm can achieve higher detection rate of 87% for smoke and 92% for flame.  相似文献   
107.
we present a novel polarimetric synthetic aperture radar (PolSAR) image compression scheme. PolSAR data contains lots of similar redundancies in single-channel and massively correlation between polarimetric channels. So these features make it difficult to represent PolSAR data efficiently. In this paper, discrete cosine transform (DCT) is adopted to remove redundancies between polarimetric channels, simple but quite efficient in improving compressibility. Sparse K-singular value decomposition (K-SVD) dictionary learning algorithm is utilized to remove redundancies within each channel image. Double sparsity scheme will be able to achieve fast convergence and low representation error by using a small number of sparsity dictionary elements, which is beneficial for the task of PolSAR image compression. Experimental results demonstrate that both numerical evaluation indicators and visual effect of reconstructed images outperform other methods, such as SPIHT, JPEG2000, and offline method.  相似文献   
108.
The global skyline, as an important variant of the skyline, has been widely applied in multi-criteria decision making, business planning and data mining. In this paper, we extend our early work and propose the maintenance methods to process the subspace global skyline (SGS) queries in dynamic databases. In the previous work, we proposed the index structure RB-tree, which can effectively manage the data to accelerate the subspace global skyline calculation. Also, the basic single SGS algorithm based on RB-tree (SSRB) and the optimized single SGS algorithm (OSSRB) were proposed to process a single SGS query. In addition, the multiple SGS algorithm (MSRB) was proposed to calculate multiple SGS queries by sharing the scan spaces of different queries. In this paper, we design some data structures and propose the maintenance approaches of SSRB, OSSRB and MSRB to cope with updates that happen to data sets. Thus our extended algorithms can be adopted for dynamic data sets. Finally, the experimental results show that the proposed algorithms OSSRB and MSRB have good performance to process SGS queries and they can be easily maintained with dynamic datasets.  相似文献   
109.
A considerable part of the literature on fuzzy sets is devoted to the field of fuzzy control system. In this paper, an alternative control system is introduced to describe a dynamic system with fuzzy white noise. In order to find optimal ways to control such a system, fuzzy optimal control theory is further developed. Specifically, a linear quadratic model is formulated and solved as a fuzzy optimal control problem. The formulation and solution of this model provide an economic interpretation of a production planning model both in the finite horizon and in the infinite horizon.  相似文献   
110.
Many decision-makers in industry, government and academia routinely make decisions whose outcome depends on the evolution of software technology trends. Even though the stakes of these decisions are usually very high, decision makers routinely depend on expert opinions and qualitative assessments to model the evolution of software technology; both of these sources of decision-making information are subjective, are based on opinions rather than facts, and are prone to error. In this paper, we report on our ongoing work to build quantitative models of the evolution of software technology trends. In particular, we discuss how we took specific evolutionary models and merged them into a single (general-purpose) model. The original specific models are derived empirically using statistical methods on trend data we had collected over several years, and have been validated individually; in this paper we further validate the generic (general-purpose) model.  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