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   108898篇
  免费   13653篇
  国内免费   5464篇
电工技术   51855篇
技术理论   4篇
综合类   8603篇
化学工业   5202篇
金属工艺   2776篇
机械仪表   5457篇
建筑科学   3403篇
矿业工程   2271篇
能源动力   8112篇
轻工业   2323篇
水利工程   2851篇
石油天然气   1049篇
武器工业   857篇
无线电   15119篇
一般工业技术   4146篇
冶金工业   2009篇
原子能技术   2209篇
自动化技术   9769篇
  2024年   441篇
  2023年   1414篇
  2022年   2720篇
  2021年   3283篇
  2020年   3518篇
  2019年   2863篇
  2018年   2639篇
  2017年   3788篇
  2016年   4120篇
  2015年   4724篇
  2014年   7720篇
  2013年   6403篇
  2012年   8828篇
  2011年   9516篇
  2010年   6968篇
  2009年   7060篇
  2008年   6867篇
  2007年   8272篇
  2006年   7335篇
  2005年   5911篇
  2004年   4774篇
  2003年   3884篇
  2002年   2975篇
  2001年   2604篇
  2000年   2163篇
  1999年   1603篇
  1998年   1077篇
  1997年   853篇
  1996年   801篇
  1995年   615篇
  1994年   554篇
  1993年   352篇
  1992年   308篇
  1991年   193篇
  1990年   159篇
  1989年   128篇
  1988年   100篇
  1987年   69篇
  1986年   46篇
  1985年   45篇
  1984年   68篇
  1983年   54篇
  1982年   57篇
  1981年   25篇
  1980年   16篇
  1979年   13篇
  1978年   17篇
  1977年   8篇
  1959年   15篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
951.
Cognitive radios such as intelligent phones and Bluetooth devices have been considered essential goods in next-generation communication systems.Such devices will have to share the same frequency band owing to the limited bandwidth resource.To improve spectrum efciency,we formulate multi-channel power allocation as a market competitive equilibrium(CE)problem,and prove that its solution exists and is unique under the condition of weak interference.We then propose two distributed power allocation algorithms achieving CE,namely the fast convergent power allocation algorithm(FCPAA)and the social-fairness-aware FCPAA(SFAF).Theoretical analysis and simulation results demonstrate that the proposed algorithms lead to better system performance in terms of the guaranteed interference temperature constraint using the price mechanism instead of a strategy based on the Nash equilibrium.Moreover,it is shown that the FCPAA maximizes total utility,and converges more quickly than the method addressed in prior research with the help of improved round-robin rules.However,the FCPAA cannot ensure the same social fairness among secondary users as the SFAF scheme in both the non-fading channel and Rayleigh fading channel;the SFAF balances the individual utility by adjusting each user’s budget at the expense of a small quantity of system total throughput.  相似文献   
952.
Software systems can be represented as complex networks and their artificial nature can be investigated with approaches developed in network analysis.Influence maximization has been successfully applied on software networks to identify the important nodes that have the maximum influence on the other parts.However,research is open to study the effects of network fabric on the influence behavior of the highly influential nodes.In this paper,we construct class dependence graph(CDG)networks based on eight practical Java software systems,and apply the procedure of influence maximization to study empirically the correlations between the characteristics of maximum influence and the degree distributions in the software networks.We demonstrate that the artificial nature of CDG networks is reflected partly from the scale free behavior:the in-degree distribution follows power law,and the out-degree distribution is lognormal.For the influence behavior,the expected influence spread of the maximum influence set identified by the greedy method correlates significantly with the degree distributions.In addition,the identified influence set contains influential classes that are complex in both the number of methods and the lines of code(LOC).For the applications in software engineering,the results provide possibilities of new approaches in designing optimization procedures of software systems.  相似文献   
953.
With the technology scaling down, low power dissipation has become one of the research focuses in the field of integrated circuit design. Various types of adiabatic logics have been invented for low-power applications. However, the expanding leakage current degrades the performance of conventional adiabatic logics. In this article, a novel improved complementary pass-transistor adiabatic logic (ICPAL) based on fin-type field- effect transistor (FinFET) devices with ultra-low power dissipation has been presented. The proposed ICPAL takes full advantage of different FinFET operating modes, that is, shorted-gate mode, independent-gate mode, and low-power mode, to make a tremendous reduction in power dissipation. For explication and verification, the power dissipation of different ICPAL standard cells has been investigated and compared with other types of adiabatic circuits based on FinFETs. The results show that the ICPAL circuits have ultra-low power dissipation in a wide range of clock frequencies(30-800 MHz) under the condition of similar number of transistors, and the average reduction in power dissipation is about 23.1%, 75.0%, and 50.0% relative to 2N-2N2P, improved pass- transistor adiabatic logic, and complimentary pass-transistor adiabatic logic, respectively. Furthermore, ICPAL supports a better pre-evaluation of system power dissipation in VLSI design and has an intrinsic characteristic for the resistance to some types of side channel attacks.  相似文献   
954.
介绍贵港地区电网基于软分区的三级自动电压控制(AVC)系统,并对该系统的三级控制原理及区域变电站的控制规则进行说明。  相似文献   
955.
Epoxidized 10-undecenoic acid triglyceride, an experimental seed oil derivative that has a terminal epoxy group on each of the three acyl glyceride segments, has been found to have good reactivity with amine curatives and allows room temperature cures to be obtained. Coatings based on epoxidized 10-undercenoic acid triglyceride have also shown excellent UV stability. As an example, coatings samples placed in a QUVA chamber exhibit no loss in gloss after 3000 hr of a cycled exposure to high intensity UV lamps and moisture at temperatures of 50–60°C. In comparison, coatings based on standard liquid epoxy resins (LERs) and commercially available hydrogenated LERs lose gloss due to chalking/decomposition within 200–800 hr. Presented at the 81 st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.  相似文献   
956.
根据厂区所使用的调节阀自身具备的功能以及生产工艺需求,选择合适的(三断)保位方案,分析了所选择方案的工作原理及优、缺点及适用条件.  相似文献   
957.
介绍电力系统继电保护整定计算软件的相关问题,着重探讨了对该软件的改进措施.  相似文献   
958.
介绍无功补偿的作用、方法及原则,分析炼钢供配电系统负荷性质及无功补偿的必要性,并提出各供配电系统的无功补偿方案。  相似文献   
959.
对选定回路进行谐波测试,分析变流设备产生谐波的原因,并提出抑制方案.  相似文献   
960.
以IEC61312规范为指导,对岭澳#3/4机组烟囱流量信号DCS侧保险在雷暴天气期间被烧毁,同时机组出现异常报警信息的事件进行分析,明确雷电侵害DCS的途径及影响,并提出改进措施.  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