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   22615篇
  免费   1705篇
  国内免费   2166篇
电工技术   821篇
技术理论   2篇
综合类   1084篇
化学工业   549篇
金属工艺   506篇
机械仪表   1449篇
建筑科学   514篇
矿业工程   253篇
能源动力   330篇
轻工业   148篇
水利工程   122篇
石油天然气   136篇
武器工业   136篇
无线电   3408篇
一般工业技术   634篇
冶金工业   304篇
原子能技术   81篇
自动化技术   16009篇
  2024年   21篇
  2023年   225篇
  2022年   473篇
  2021年   688篇
  2020年   579篇
  2019年   384篇
  2018年   389篇
  2017年   393篇
  2016年   425篇
  2015年   585篇
  2014年   1131篇
  2013年   1114篇
  2012年   1374篇
  2011年   1967篇
  2010年   1229篇
  2009年   1303篇
  2008年   1503篇
  2007年   1710篇
  2006年   1636篇
  2005年   1529篇
  2004年   1290篇
  2003年   1235篇
  2002年   1034篇
  2001年   752篇
  2000年   676篇
  1999年   625篇
  1998年   479篇
  1997年   430篇
  1996年   346篇
  1995年   249篇
  1994年   178篇
  1993年   151篇
  1992年   106篇
  1991年   50篇
  1990年   53篇
  1989年   28篇
  1988年   33篇
  1987年   12篇
  1986年   17篇
  1985年   10篇
  1984年   19篇
  1983年   11篇
  1982年   12篇
  1981年   8篇
  1980年   4篇
  1979年   6篇
  1978年   4篇
  1977年   3篇
  1976年   3篇
  1974年   2篇
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
991.
Arectangular graph is a plane graph where all regions are four-sided and all edges are oriented in either the vertical or the horizontal direction. In addition the graph enclosure must also be rectangular. Given a plane graph representing a desired component connectivity, itsrectangular dual can be used to build afloorplan. This indicates that a system implementation can allocate rectangular floorplan regions to components that can be pairwise connected through common borders.This paper proves that constructing a rectangular dual graph is equivalent to a matching problem in a bipartite graph derived from the given plane graph. A simple existence theorem in terms of the graph structure is obtained as a corollary.This work was supported by the National Science Council, Taiwan, Republic of China, under Contract NSC 78-0404-E006-14.  相似文献   
992.
This paper addresses the problem of scheduling a set of independent jobs with sequence-dependent setups and distinct due dates on non-uniform multi-machines to minimize the total weighted earliness and tardiness, and explores the use of artificial neural networks as a valid alternative to the traditional scheduling approaches. The objective is to propose a dynamical gradient neural network, which employs a penalty function approach with time varying coefficients for the solution of the problem which is known to be NP-hard. After the appropriate energy function was constructed, the dynamics are defined by steepest gradient descent on the energy function. The proposed neural network system is composed of two maximum neural networks, three piecewise linear and one log-sigmoid network all of which interact with each other. The motivation for using maximum networks is to reduce the network complexity and to obtain a simplified energy function. To overcome the tradeoff problem encountered in using the penalty function approach, a time varying penalty coefficient methodology is proposed to be used during simulation experiments. Simulation results of the proposed approach on a scheduling problem indicate that the proposed coupled network yields an optimal solution which makes it attractive for applications of larger sized problems.  相似文献   
993.
In this paper, the modular combination of artificial neural nets is considered. A modular approach to combining can be contrasted with an ensemble-based approach in that it implies individual modules, each responsible for some specialist aspect of a task, as opposed to each approximating the same function. It is possible to characterize modular systems in terms of (i) reasons for the task decomposition, (ii) the method for accomplishing the decomposition and (iii) the relationship between the modules. These characteristics are considered in brief outlines of the papers in the issue. Reasons for task decomposition include the exploitation of specialist capabilities of individual nets, performance improvement, and making the system easier to understand and modify. Task decomposition may be either automatic (based on the blind application of a data partitioning algorithm) or explicit (based on prior knowledge of the task or the specialist capabilities of the modules), and the relationship between the modules may be successive, cooperative or supervisory.  相似文献   
994.
再谈水质稳定、管网改造及运行管理的相互关系   总被引:1,自引:0,他引:1  
何维华 《给水排水》2004,30(12):21-25
针对当前在改善管网水质上,偏重于管道的更新改造,忽略水质稳定及管网运行管理的问题,从腐蚀、结垢机理、水质稳定性等方面,论述了影响管网水质的诸多因素,并提出了制定供水企业出厂水稳定性要求,加强管网技术改造及管网运行管理科学化等具体建议。  相似文献   
995.
对20CrMnTi钢压力渗碳工艺研究结果表明,在保证产品质量的前提下,显著提高渗碳速度,缩短工艺周期,降低 生产成本。同时,对压力渗碳工艺的机理进行了初步探讨。  相似文献   
996.
The characteristics of networks formed in cured ‘reworkable’ epoxy thermosets capable of controlled thermal degradation were studied. Dynamic mechanical thermal analysis, swelling measurements, and glass transition temperature measurements were used to obtain information regarding the time and temperature dependence of the crosslink densities of these materials. By applying isothermal conditions, networks containing up to 36 mol% non-degradable components could be completely degraded, i.e. progress from a network of infinite molecular weight to a finite one with zero crosslink density. Percolation theory was used to facilitate the interpretation of these results. The degradation behavior of the reworkable thermosets were well-described by gel degradation theory, i.e. the reverse of the gelation process, and the experimental results were in good agreement with calculated values obtained by replacing the extent of reaction, p, in Macosko and Miller's branching theory with the extent of degradation, 1−p.  相似文献   
997.
常用温度控制法的对比   总被引:3,自引:0,他引:3  
常用温度控制包括常规PID、模糊、神经网络、Fuzzy-PID、神经网络PID、模糊神经网络、遗传PID及广义预测等控制方法.常规PID控制易于建立线性温度控制系统被控对象模型.模糊控制基于规则库,并以绝对或增量形式给出控制决策.神经网络控制采用数理模型模拟生物神经细胞结构,并用简单处理单元连接成复杂网络;Fuzzy-PID为线性控制,且结合模糊与PID控制优点.并给出了各方法的控制特性、功能及主要应用场合.  相似文献   
998.
Integrated Satellite Information Network (ISIN) includes those nodes in space and those on ground. It is the way to realize the fusion of satellite communication and traditional network technology. A satellite network management system based on Multiplex Network Management Protocol (MNMP) has accomplished traditional management, such as configuration, performance and fault management. An architecture of Service Level Management (SLM) in ISIN is proposed, and a service topology management and Service Level Agreement (SLA) are deeply researched. At last, service security and fault management are briefly discussed, and a simulation system is accomplished.  相似文献   
999.
The paper describes the implementation of a systolic array for a multilayer perceptron with a hardware-friendly learning algorithm. A pipelined modification of the on-line backpropagation algorithm is shown and explained. It better exploits the parallelism because both the forward and backward phases can be performed simultaneously. The neural network performance for the proposed modification is discussed and compared with the standard so-called on-line backpropagation algorithm in typical databases and with the various precisions required. Although the preliminary results are positive, subsequent theoretical analysis and further experiments with different training sets will be necessary. For this reason our VLSI systolic architecture—together with the combination of FPGA reconfiguration properties and a design flow based on generic VHDL—can create a reusable, flexible, and fast method of designing a complete ANN on a single FPGA and can permit very fast hardware verifications for our trials of the Pipeline On-line Backpropagation algorithm and the standard algorithms.  相似文献   
1000.
Tool wear is a dynamic process, as a tool progresses from sharp to worn state and possibly to breakage. Thus the multiclassification of tool states is preferred, which can provide more timely and accurate estimation of tool states. Based on acoustic emission (AE) sensing, this paper proposes a new performance evaluation function for tool condition monitoring (TCM) by considering manufacturing loss. Firstly, two types of manufacturing loss due to misclassification (loss caused by under prediction and loss caused by over prediction) are analyzed, and both are utilized to compute corresponding weights of the proposed performance evaluation function. Then the expected loss of future misclassification is introduced to evaluate the recognition performance of TCM. Finally, a revised support vector machine (SVM) approach coupled with one-versus-one method is implemented to carry out the multiclassification of tool states. With this approach, a tool is replaced or continued not only based on the tool condition alone, but also the risk in cost incurred due to underutilized or overused tool. The experimental results show that the proposed method can reliably perform multiclassificaion of tool flank wear, and reduce the potential manufacturing loss.  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