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   411122篇
  免费   10215篇
  国内免费   4165篇
电工技术   8989篇
技术理论   1篇
综合类   6349篇
化学工业   59057篇
金属工艺   20917篇
机械仪表   17761篇
建筑科学   13070篇
矿业工程   3862篇
能源动力   8762篇
轻工业   28497篇
水利工程   5635篇
石油天然气   7743篇
武器工业   477篇
无线电   44459篇
一般工业技术   80507篇
冶金工业   51876篇
原子能技术   7036篇
自动化技术   60504篇
  2022年   2407篇
  2021年   4246篇
  2020年   3123篇
  2019年   3484篇
  2018年   23975篇
  2017年   23632篇
  2016年   17212篇
  2015年   5564篇
  2014年   6964篇
  2013年   14666篇
  2012年   15024篇
  2011年   27777篇
  2010年   24297篇
  2009年   21997篇
  2008年   22626篇
  2007年   24929篇
  2006年   10300篇
  2005年   13256篇
  2004年   10495篇
  2003年   9653篇
  2002年   7804篇
  2001年   6552篇
  2000年   6178篇
  1999年   5987篇
  1998年   12333篇
  1997年   8993篇
  1996年   7222篇
  1995年   5424篇
  1994年   4956篇
  1993年   4726篇
  1992年   3802篇
  1991年   3474篇
  1990年   3305篇
  1989年   3350篇
  1988年   3167篇
  1987年   2749篇
  1986年   2621篇
  1985年   3106篇
  1984年   2897篇
  1983年   2652篇
  1982年   2372篇
  1981年   2463篇
  1980年   2269篇
  1979年   2353篇
  1978年   2333篇
  1977年   2551篇
  1976年   3355篇
  1975年   1995篇
  1974年   1896篇
  1973年   1908篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
The cover image is based on the Research Article V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification by Mohan, H et al., DOI: 10.1002/jctb.6238 .

  相似文献   

82.
83.
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed.  相似文献   
84.
Csáji  Balázs Cs.  Kis  Krisztián B. 《Machine Learning》2019,108(8-9):1677-1699
Machine Learning - We propose a data-driven approach to quantify the uncertainty of models constructed by kernel methods. Our approach minimizes the needed distributional assumptions, hence,...  相似文献   
85.
现有的时态网络可视化方法大多采用等量时间片来可视化网络的演变,不利于时态模式的快速挖掘和发现。为此,根据时态网络固有的特征提出自适应时间片划分方法(Adaptive Time Slice Partition method,ATSP)。在时态网络的两种表示方式(基于事件的表示方式和基于快照的表示方式)的基础上,构建了ATSP的基础模型,同时提出了一种改进模型用来描述事件间隔时间服从长尾分布的时态网络。为了实现时间片的不等量划分,针对探索任务的不同提出了基于时态模式的ATSP规则和基于中心节点的ATSP规则,并提出了实现算法--层次划分算法(Hierarchical Partition algorithm,HP)和增量划分算法(Incremental Partition algorithm,IP)。实验结果表明,ATSP方法比传统的时间片划分方法更能准确地表示网络的时态特征,且该方法应用于可视化时,能有效归纳并展示网络的特征,明显提高了视觉分析的效率。  相似文献   
86.
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics.  相似文献   
87.
Porous alumina with a highly textured microstructure was fabricated by pulse electric current sintering (PECS) using alumina platelets. Highly oriented porous alumina with a porosity of 3%–50% was obtained by a pressure-controlled method of PECS. The properties of the highly textured porous alumina were measured in two directions. The nitrogen gas permeance and thermal conductivity at room temperature were higher in the direction along the platelet length due to the higher continuity of pores and the connectivity of alumina platelets, respectively. The anisotropy of the thermal conductivity at room temperature was investigated and explained by the effect of grain size of platelets as well as morphology and orientation of pores. The bending strength was higher with the loading direction along the platelet thickness. The thermal shock strength was clearly different in the two directions. The difference in the thermal shock strength was investigated by the measurement of properties and thermal stress analysis.  相似文献   
88.
Radiation therapy is a technology-driven cancer treatment modality that has experienced significant advances over the last decades, due to multidisciplinary contributions that include engineering and computing. Recent technological developments allow the use of noncoplanar volumetric modulated arc therapy (VMAT), one of the most recent photon treatment techniques, in clinical practice. In this work, an automated noncoplanar arc trajectory optimization framework designed in two modular phases is presented. First, a noncoplanar beam angle optimization algorithm is used to obtain a set of noncoplanar irradiation directions. Then, anchored in these directions, an optimization strategy is proposed to compute an optimal arc trajectory. The computational experiments considered a pool of twelve difficult head-and-neck tumor cases. It was possible to observe that, for some of these cases, the optimized noncoplanar arc trajectories led to significant treatment planning quality improvements, when compared with coplanar VMAT treatment plans. Although these experiments were done in a research environment treatment planning software (matRad), the conclusions can be of interest for a clinical setting: automated procedures can simplify the current treatment workflow, produce high-quality treatment plans, making better use of human resources and allowing for unbiased comparisons between different treatment techniques.  相似文献   
89.
Journal of Inorganic and Organometallic Polymers and Materials - This work aimed to investigate the impact of Lead-fluoride based glasses via theoretical and simulation techniques on mechanical and...  相似文献   
90.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  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