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   425420篇
  免费   5818篇
  国内免费   1319篇
电工技术   7918篇
综合类   467篇
化学工业   61620篇
金属工艺   16827篇
机械仪表   13358篇
建筑科学   10258篇
矿业工程   2260篇
能源动力   10719篇
轻工业   36606篇
水利工程   4497篇
石油天然气   7353篇
武器工业   75篇
无线电   52815篇
一般工业技术   83060篇
冶金工业   78714篇
原子能技术   9389篇
自动化技术   36621篇
  2021年   3362篇
  2019年   3350篇
  2018年   5554篇
  2017年   5708篇
  2016年   5999篇
  2015年   3839篇
  2014年   6559篇
  2013年   18839篇
  2012年   10732篇
  2011年   14696篇
  2010年   11690篇
  2009年   13138篇
  2008年   13909篇
  2007年   13929篇
  2006年   12319篇
  2005年   11391篇
  2004年   10971篇
  2003年   10744篇
  2002年   10081篇
  2001年   10230篇
  2000年   9863篇
  1999年   10098篇
  1998年   23758篇
  1997年   17118篇
  1996年   13478篇
  1995年   10276篇
  1994年   9232篇
  1993年   9008篇
  1992年   7100篇
  1991年   6694篇
  1990年   6387篇
  1989年   6219篇
  1988年   5945篇
  1987年   5210篇
  1986年   5025篇
  1985年   5904篇
  1984年   5490篇
  1983年   5022篇
  1982年   4623篇
  1981年   4832篇
  1980年   4445篇
  1979年   4437篇
  1978年   4262篇
  1977年   4960篇
  1976年   6382篇
  1975年   3864篇
  1974年   3815篇
  1973年   3826篇
  1972年   3056篇
  1971年   2857篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
111.
112.
113.
Application of brown titanium dioxide (TiO2-x) and its modified composite forms in the photocatalytic decomposition of organic pollutants in the environment is a promising way to provide solutions for environmental redemption. Herein, we report the synthesis of effective and stable TiO2-x nanoparticles with g-C3N4, RGO, and multiwalled carbon nanotubes (CNTs) using a simple hydrothermal method. Among all the as-synthesized samples, excellent photocatalytic degradation activity was observed for RGO-TiO2-x nanocomposite with high rate constants of 0.075 min?1, 0.083 min?1 and 0.093 min?1 for methylene blue, rhodamine-B, and rosebengal dyes under UV–Visible light irradiation, respectively. The altered bandgap (1.8 eV) and the large surface area of RGO-TiO2-x nanocomposite impacts on both absorption of visible light and efficiency of photogenerated charge electron (e?)/hole (h+) pair separation. This resulted in enhanced photocatalytic property of carbon-based TiO2-x nanocomposites. A systematic study on the influence of different carbon nanostructures on the photocatalytic activity of brown TiO2-x is carried out.  相似文献   
114.
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   
115.
Mobile Networks and Applications - Public cloud system offers Infrastructure-as-a-Service (IaaS) to deliver the computational resources on demand. Resource requirements of a cloud environment are...  相似文献   
116.
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   
117.
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   
118.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  相似文献   
119.
120.
Anup Bhat B  Harish SV  Geetha M 《ETRI Journal》2021,43(6):1024-1037
Mining high utility itemsets (HUIs) from transaction databases considers such factors as the unit profit and quantity of purchased items. Two-phase tree-based algorithms transform a database into compressed tree structures and generate candidate patterns through a recursive pattern-growth procedure. This procedure requires a lot of memory and time to construct conditional pattern trees. To address this issue, this study employs two compressed tree structures, namely, Utility Count Tree and String Utility Tree, to enumerate valid patterns and thus promote fast utility computation. Furthermore, the study presents an algorithm called single-phase utility computation (SPUC) that leverages these two tree structures to mine HUIs in a single phase by incorporating novel pruning strategies. Experiments conducted on both real and synthetic datasets demonstrate the superior performance of SPUC compared with IHUP, UP-Growth, and UP-Growth+ algorithms.  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