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   200994篇
  免费   2777篇
  国内免费   612篇
电工技术   3493篇
综合类   149篇
化学工业   29317篇
金属工艺   8078篇
机械仪表   6088篇
建筑科学   4862篇
矿业工程   1306篇
能源动力   5196篇
轻工业   17449篇
水利工程   2309篇
石油天然气   4045篇
武器工业   8篇
无线电   23181篇
一般工业技术   40279篇
冶金工业   37530篇
原子能技术   5095篇
自动化技术   15998篇
  2021年   1636篇
  2019年   1625篇
  2018年   2630篇
  2017年   2688篇
  2016年   2832篇
  2015年   1840篇
  2014年   3146篇
  2013年   9042篇
  2012年   5145篇
  2011年   7125篇
  2010年   5686篇
  2009年   6430篇
  2008年   6531篇
  2007年   6581篇
  2006年   5659篇
  2005年   5277篇
  2004年   5052篇
  2003年   4934篇
  2002年   4566篇
  2001年   4684篇
  2000年   4606篇
  1999年   4762篇
  1998年   11465篇
  1997年   8202篇
  1996年   6443篇
  1995年   4710篇
  1994年   4280篇
  1993年   4103篇
  1992年   3234篇
  1991年   3085篇
  1990年   2877篇
  1989年   2963篇
  1988年   2828篇
  1987年   2404篇
  1986年   2316篇
  1985年   2724篇
  1984年   2510篇
  1983年   2349篇
  1982年   2093篇
  1981年   2204篇
  1980年   2030篇
  1979年   2124篇
  1978年   2122篇
  1977年   2367篇
  1976年   3194篇
  1975年   1836篇
  1974年   1763篇
  1973年   1773篇
  1972年   1443篇
  1971年   1340篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs.  相似文献   
42.
43.
44.
45.
46.
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   
47.
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   
48.
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   
49.
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   
50.
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