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   93262篇
  免费   11239篇
  国内免费   6091篇
电工技术   7311篇
技术理论   1篇
综合类   9767篇
化学工业   13907篇
金属工艺   5706篇
机械仪表   6046篇
建筑科学   7422篇
矿业工程   2817篇
能源动力   2311篇
轻工业   11757篇
水利工程   2518篇
石油天然气   3152篇
武器工业   1007篇
无线电   10018篇
一般工业技术   9035篇
冶金工业   3271篇
原子能技术   1342篇
自动化技术   13204篇
  2025年   5篇
  2024年   1347篇
  2023年   1742篇
  2022年   3383篇
  2021年   4273篇
  2020年   3314篇
  2019年   2496篇
  2018年   2658篇
  2017年   3074篇
  2016年   2776篇
  2015年   3961篇
  2014年   5228篇
  2013年   6055篇
  2012年   7123篇
  2011年   7744篇
  2010年   7230篇
  2009年   6887篇
  2008年   6985篇
  2007年   6693篇
  2006年   6104篇
  2005年   4786篇
  2004年   3462篇
  2003年   2649篇
  2002年   2648篇
  2001年   2319篇
  2000年   1731篇
  1999年   1010篇
  1998年   583篇
  1997年   445篇
  1996年   408篇
  1995年   336篇
  1994年   228篇
  1993年   179篇
  1992年   139篇
  1991年   114篇
  1990年   84篇
  1989年   77篇
  1988年   63篇
  1987年   45篇
  1986年   38篇
  1985年   32篇
  1984年   15篇
  1983年   13篇
  1982年   17篇
  1981年   6篇
  1980年   28篇
  1979年   17篇
  1976年   4篇
  1959年   11篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
介绍了四光束激光扫描测量车身三维坐标的系统构成和基本原理,从系统PIN预处理输出的靶标回射信号的特点出发,为汽车车身测量传感器设计了基于条形码识别原理的合作靶标识别体系,最多可同时对27个测量点进行有效识别,确保传感器的精度要求和效率要求,达到了很好的实验效果。  相似文献   
52.
53.
Radiotherapy is identified as a crucial treatment for patients with glioblastoma, but recurrence is inevitable. The efficacy of radiotherapy is severely hampered partially due to the tumor evolution. Growing evidence suggests that proneural glioma stem cells can acquire mesenchymal features coupled with increased radioresistance. Thus, a better understanding of mechanisms underlying tumor subclonal evolution may develop new strategies. Herein, data highlighting a positive correlation between the accumulation of macrophage in the glioblastoma microenvironment after irradiation and mesenchymal transdifferentiation in glioblastoma are presented. Mechanistically, elevated production of inflammatory cytokines released by macrophages promotes mesenchymal transition in an NF-κB-dependent manner. Hence, rationally designed macrophage membrane-coated porous mesoporous silica nanoparticles (MMNs) in which therapeutic anti-NF-κB peptides are loaded for enhancing radiotherapy of glioblastoma are constructed. The combination of MMNs and fractionated irradiation results in the blockage of tumor evolution and therapy resistance in glioblastoma-bearing mice. Intriguingly, the macrophage invasion across the blood-brain barrier is inhibited competitively by MMNs, suggesting that these nanoparticles can fundamentally halt the evolution of radioresistant clones. Taken together, the biomimetic MMNs represent a promising strategy that prevents mesenchymal transition and improves therapeutic response to irradiation as well as overall survival in patients with glioblastoma.  相似文献   
54.
The Journal of Supercomputing - The incomplete enforcement of environmental regulation by local governments will lead to environmental degradation. While the strategy selection for local...  相似文献   
55.
International Journal of Computer Vision - Visual tracking of generic objects is one of the fundamental but challenging problems in computer vision. Here, we propose a novel fully convolutional...  相似文献   
56.
Ying C. MacNab 《TEST》2018,27(3):554-569
I thank the discussants, Miguel A. Martinez-Beneito, Fedel Greco, Carlo Trivisano, Stephan R Sain, and Reinhard Furrer, for their insightful and stimulating commentary. The rejoinder is organized in five sections: (1) the M-based models, (2) posterior sensitivity to prior choices for \({\varvec{C}}\) and \({\varvec{\varSigma }}\), (3) stationary and non-stationary (M)GMRFs, (4) various approaches to model formulation and related applications, and (5) statistical computation.  相似文献   
57.
The corrosion behavior of 2A02 Al alloy under simulated marine atmospheric environment has been studied using mass-gain, scanning electron microscope/energy dispersive spectroscopy (SEM/EDS), laser scanning confocal microscopy, X-ray diffraction spectroscopy and localized electrochemical methods. The results demonstrate that the relationship between the corrosion induced mass-gain and the corrosion time is in accordance with the power rule. The mass-gain increases gradually during the corrosion time, while the corrosion rate decreases. With ongoing of the corrosion, corrosion products film changed from a porous to a compact structure. The various spectroscopic data show that the corrosion products films composed mainly of Al(OH)3, Al2O3 and AlCl3. The electrochemical corrosion behavior of the 2A02 Al alloy was studied by electrochemical impedance spectroscopy (EIS).  相似文献   
58.
Meng  Fanbin  Wang  Ying  Wang  Qiang  Xu  Xiaoling  Jiang  Man  Zhou  Xuesong  He  Ping  Zhou  Zuowan 《Nano Research》2018,11(7):3958-3958
Nano Research - The first author, Fanbin Meng, and the second author, Ying Wang, contributed equally to this work was unfortunately forgotten to write on the first pages of the main text and the...  相似文献   
59.
Approximate dynamic programming (ADP) formulation implemented with an adaptive critic (AC)-based neural network (NN) structure has evolved as a powerful technique for solving the Hamilton-Jacobi-Bellman (HJB) equations. As interest in ADP and the AC solutions are escalating with time, there is a dire need to consider possible enabling factors for their implementations. A typical AC structure consists of two interacting NNs, which is computationally expensive. In this paper, a new architecture, called the ‘cost-function-based single network adaptive critic (J-SNAC)’ is presented, which eliminates one of the networks in a typical AC structure. This approach is applicable to a wide class of nonlinear systems in engineering. In order to demonstrate the benefits and the control synthesis with the J-SNAC, two problems have been solved with the AC and the J-SNAC approaches. Results are presented, which show savings of about 50% of the computational costs by J-SNAC while having the same accuracy levels of the dual network structure in solving for optimal control. Furthermore, convergence of the J-SNAC iterations, which reduces to a least-squares problem, is discussed; for linear systems, the iterative process is shown to reduce to solving the familiar algebraic Ricatti equation.  相似文献   
60.
基于网络的多媒体课堂教学模式的研究与实践   总被引:2,自引:1,他引:1  
计算机多媒体技术和网络技术应用于教学,给学生提供了一个开放的学习空间,使学生在新型学习环境中,不断充实自己、完善自我。本文从教学模式出发,探讨基于网络的多媒体课堂教学模式,并对该模式进行了分析。旨在将网络、多媒体这种现代教育技术运用于传统的课堂教学,提高素质教育水平。  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