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   14642篇
  免费   2206篇
  国内免费   1440篇
电工技术   4313篇
综合类   2061篇
化学工业   673篇
金属工艺   186篇
机械仪表   1095篇
建筑科学   713篇
矿业工程   351篇
能源动力   753篇
轻工业   271篇
水利工程   985篇
石油天然气   251篇
武器工业   238篇
无线电   943篇
一般工业技术   992篇
冶金工业   214篇
原子能技术   37篇
自动化技术   4212篇
  2024年   112篇
  2023年   246篇
  2022年   415篇
  2021年   507篇
  2020年   641篇
  2019年   536篇
  2018年   497篇
  2017年   659篇
  2016年   668篇
  2015年   691篇
  2014年   957篇
  2013年   978篇
  2012年   1102篇
  2011年   1069篇
  2010年   786篇
  2009年   879篇
  2008年   865篇
  2007年   1032篇
  2006年   843篇
  2005年   667篇
  2004年   608篇
  2003年   519篇
  2002年   409篇
  2001年   377篇
  2000年   354篇
  1999年   284篇
  1998年   191篇
  1997年   217篇
  1996年   200篇
  1995年   152篇
  1994年   135篇
  1993年   90篇
  1992年   107篇
  1991年   91篇
  1990年   81篇
  1989年   69篇
  1988年   55篇
  1987年   23篇
  1986年   9篇
  1985年   10篇
  1984年   22篇
  1983年   15篇
  1982年   21篇
  1981年   18篇
  1980年   18篇
  1979年   24篇
  1978年   12篇
  1977年   14篇
  1959年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
ROI-based Watermarking Scheme for JPEG 2000   总被引:1,自引:0,他引:1  
A new region of interest (ROI)-based watermarking method for JPEG 2000 is presented. The watermark is embedded into the host image based on the characteristics of the ROI to protect rights to the images. This scheme integrates the watermarking process with JPEG 2000 compression procedures. Experimental results have demonstrated that the proposed watermark technique successfully survives JPEG 2000 compression, progressive transmission, and principal attacks.  相似文献   
62.
潮州供水枢纽拦河闸计算机监控及运行调度   总被引:7,自引:7,他引:0  
介绍了潮州供水枢纽工程的概况及拦河闸计算机监控系统的结构和主要功能,着重讨论了闸门的控制过程和自动运行调度,可供其他闸门工程的自动化建设参考。  相似文献   
63.
一种按时间切换的最速控制方法   总被引:3,自引:1,他引:2  
基于初始状态空间下的子空间概念,提出了一种按时间进行切换的最速控制方法,不需要求取开关线或开关面。数字仿真结果表明,采用这一方法是完全可行的。  相似文献   
64.
矿井串联系统模糊可靠性理论的研究   总被引:1,自引:0,他引:1  
马云东  孙宝铮 《煤炭学报》1994,19(5):504-512
矿井系统不仅具有随机性,而且同时也具有模糊性,在系统分析与设计过程中应同时考虑这两种不确定性因素的影响。文中提出了模糊故障、模糊功能、系统模糊运营状态和广义可靠度等概念,并在此基础上提出了求单元及串联系统的生产能力、营运费用、应急维修费用、修理时间和广义可靠度等指标的方法,建立了使系统平均生产能力最大的系统最优运营策略的数学模型。  相似文献   
65.
采用奇异值分解设计广义系统的最优滤波器   总被引:6,自引:2,他引:4  
本文讨论广义离散随机线性系统的状态估计问题,通过矩阵奇值分解,本文给出了一种设计降阶最优滤波器的实用方法,该方法同时还得到了动态系统和量测系统的干扰噪声的估计。  相似文献   
66.
1IntroductionAlgorithmshavebeenproposedtosolvelinearrecurrencesinparallell1-13].Someofthemsupposeunlimitednumberofprocessorsbeingusedwhileothersuselimitednumberofprocessors.P-M.KoggeandH.S.Stoneproposedarecursivedou-blingalgorithmforthesolutionofageneraJclassofrecuxrenceequationsl1].Itisthefastestalgorithm(thetimeisO(log,N))whenthenumberofprocessingelemelltspiseqllaltoN.Howeveritisnotoptimalintermsofefficiency:itsspeedupisO(de),whileitsefficiencyisO(wt).TherecursivedoublingapproachcanPro…  相似文献   
67.
Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy.  相似文献   
68.
Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.  相似文献   
69.
A pseudohyperbolic problem of optimal control of intratumoral drug distribution is formulated. It takes into account the heterogeneity of tumor tissues and effects of convection diffusion in a fissured porous medium. A mathematical model constructed and the corresponding optimal control problem are shown to be correct. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 147–154, November–December 2007.  相似文献   
70.
The importance of studies of alternative (as compared to traditional) methods of nonlinear stochastic parametric identification is demonstrated. Synthesis of a procedure of identification of the parameter, “discrete observer,” with the use of the criterion, “minimum probability of estimation error,” is proposed for the first time. A model example that demonstrates the efficiency of the proposed approach is considered.  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