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   72353篇
  免费   7059篇
  国内免费   4027篇
电工技术   5450篇
技术理论   5篇
综合类   5652篇
化学工业   10629篇
金属工艺   4490篇
机械仪表   4187篇
建筑科学   6178篇
矿业工程   2271篇
能源动力   2111篇
轻工业   5309篇
水利工程   1571篇
石油天然气   3636篇
武器工业   694篇
无线电   8778篇
一般工业技术   8324篇
冶金工业   2993篇
原子能技术   932篇
自动化技术   10229篇
  2024年   424篇
  2023年   1373篇
  2022年   2359篇
  2021年   3278篇
  2020年   2380篇
  2019年   1879篇
  2018年   2080篇
  2017年   2407篇
  2016年   2126篇
  2015年   3002篇
  2014年   3559篇
  2013年   4297篇
  2012年   4878篇
  2011年   5094篇
  2010年   4646篇
  2009年   4337篇
  2008年   4543篇
  2007年   4364篇
  2006年   4199篇
  2005年   3422篇
  2004年   2438篇
  2003年   2111篇
  2002年   2132篇
  2001年   1961篇
  2000年   1655篇
  1999年   1613篇
  1998年   1169篇
  1997年   1024篇
  1996年   1007篇
  1995年   810篇
  1994年   670篇
  1993年   496篇
  1992年   438篇
  1991年   326篇
  1990年   218篇
  1989年   181篇
  1988年   159篇
  1987年   101篇
  1986年   66篇
  1985年   56篇
  1984年   35篇
  1983年   24篇
  1982年   33篇
  1981年   20篇
  1980年   22篇
  1979年   10篇
  1978年   2篇
  1959年   5篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
自从计算机被应用于交通运输业以来,计算机技术在交通运输规划与管理中就得到了越来越广泛的应用.本文分析了计算机技术在交通运输规划与管理中的应用领域,详细讨论了计算机技术在智能运输系统和道路交通系统仿真中的应用.  相似文献   
82.
对软件开发框架模型提出了一种新的构化的分析方法,同时介绍了常用的结构化分析的工具及其更实用情况。  相似文献   
83.
浅谈网络安全风险的评估方法   总被引:1,自引:0,他引:1  
本文通过分析网络系统风险的概念及评价体系建设原则,针对风险评估的流程进行探讨,并就应注意的几个问题提出几点建议。以期通过本文的阐述为网络管理人员更好地制定安全策略提供有效的技术支持。  相似文献   
84.
In this paper an efficient feature extraction method named as locally linear discriminant embedding (LLDE) is proposed for face recognition. It is well known that a point can be linearly reconstructed by its neighbors and the reconstruction weights are under the sum-to-one constraint in the classical locally linear embedding (LLE). So the constrained weights obey an important symmetry: for any particular data point, they are invariant to rotations, rescalings and translations. The latter two are introduced to the proposed method to strengthen the classification ability of the original LLE. The data with different class labels are translated by the corresponding vectors and those belonging to the same class are translated by the same vector. In order to cluster the data with the same label closer, they are also rescaled to some extent. So after translation and rescaling, the discriminability of the data will be improved significantly. The proposed method is compared with some related feature extraction methods such as maximum margin criterion (MMC), as well as other supervised manifold learning-based approaches, for example ensemble unified LLE and linear discriminant analysis (En-ULLELDA), locally linear discriminant analysis (LLDA). Experimental results on Yale and CMU PIE face databases convince us that the proposed method provides a better representation of the class information and obtains much higher recognition accuracies.  相似文献   
85.
A residual-based moving block bootstrap procedure for testing the null hypothesis of linear cointegration versus cointegration with threshold effects is proposed. When the regressors and errors of the models are serially and contemporaneously correlated, our test compares favourably with the Sup LM test proposed by Gonzalo and Pitarakis. Indeed, shortcomings of the former motivated the development of our test. The small sample performance of the bootstrap test is investigated by Monte Carlo simulations, and the results show that the test performs better than the Sup LM test.  相似文献   
86.
Three fifth grade highly aggressive students participated in a study examining effects of an aggression intervention game. Using single-subject multiple baseline research design, the effect of the game was measured across three domains: attribution of peer intent (cognitive), emotional response (affective) and behavior response (behavioral). The results indicate that, while there were observable individual differences, the game had an immediate impact on attribution of peer behavior across all participants, had a less predictable impact on reported behavioral reactions, and had no discernable impact on reported emotional response. Theoretical and practical implications of the study are discussed.  相似文献   
87.
为了改善车辆的操纵稳定性和行驶平顺性,提高汽车底盘控制的集成度,本文对底盘部分的半主动悬架SASS (Semi Active Suspension System)和电动动力转向EPS (Electric Power Steering)系统进行了集成控制研究.设计并试制出基于嵌入式系统ARM S3C44BOX的SASS和EPS集成控制器,并进行了台架试验,结果表明研制的集成控制器效果良好,可用于汽车底盘集成控制系统的开发研究.  相似文献   
88.
ACOMPLEX-TYPEFOCUSSEDMAGNETRONFORSPUTTERING¥ZhengSixiao(郑思孝)(InstituteofNuclearScienceandTechnology,SichuanUniversity,Chengdu...  相似文献   
89.
由于水的选择性吸收特性,辐射换热中水份波长匹配一直是一个有分歧的问题。文章通过理论与计算论证了这个问题,得出的结论否定了波长匹配的重要性。  相似文献   
90.
Lithium metal batteries (LMBs), due to their ultra-high energy density, are attracting tremendous attentions. However, their commercial application is severely impeded by poor safety and unsatisfactory cycling stability, which are induced by lithium dendrites, side reactions, and inferior anodic stability. Electrolytes, as the indispensable and necessary components in lithium metal batteries, play a crucial role in regulating the electrochemical performance of LMBs. Recently, the fluorinated electrolytes are widely investigated in high-performance LMBs. Thus, the design strategies of fluorinated electrolytes are thoroughly summarized, including fluorinated salts, fluorinated solvents, and fluorinated additives in LMBs, and insights of the fluorinated components in suppressing lithium dendrites, improving anodic stability and cycling stability. Finally, an outlook with several design strategies and challenges will be proposed for novel fluorinated electrolytes.  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