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   515484篇
  免费   43067篇
  国内免费   23736篇
电工技术   32792篇
技术理论   46篇
综合类   35551篇
化学工业   82395篇
金属工艺   30092篇
机械仪表   33773篇
建筑科学   42741篇
矿业工程   17163篇
能源动力   14718篇
轻工业   33314篇
水利工程   10194篇
石油天然气   31817篇
武器工业   4710篇
无线电   57744篇
一般工业技术   57064篇
冶金工业   25320篇
原子能技术   5377篇
自动化技术   67476篇
  2024年   2210篇
  2023年   7848篇
  2022年   14533篇
  2021年   20380篇
  2020年   15329篇
  2019年   12500篇
  2018年   14123篇
  2017年   16317篇
  2016年   14345篇
  2015年   20506篇
  2014年   25852篇
  2013年   30757篇
  2012年   34127篇
  2011年   36732篇
  2010年   32848篇
  2009年   31051篇
  2008年   30404篇
  2007年   29438篇
  2006年   29519篇
  2005年   25115篇
  2004年   16784篇
  2003年   14541篇
  2002年   13829篇
  2001年   12299篇
  2000年   12006篇
  1999年   13038篇
  1998年   10225篇
  1997年   8586篇
  1996年   8075篇
  1995年   6614篇
  1994年   5650篇
  1993年   3918篇
  1992年   3144篇
  1991年   2378篇
  1990年   1743篇
  1989年   1406篇
  1988年   1165篇
  1987年   780篇
  1986年   579篇
  1985年   392篇
  1984年   267篇
  1983年   182篇
  1982年   210篇
  1981年   155篇
  1980年   124篇
  1979年   65篇
  1978年   16篇
  1977年   14篇
  1976年   15篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6.  相似文献   
3.
With the emergence of large-scale knowledge base, how to use triple information to generate natural questions is a key technology in question answering systems. The traditional way of generating questions require a lot of manual intervention and produce lots of noise. To solve these problems, we propose a joint model based on semi-automated model and End-to-End neural network to automatically generate questions. The semi-automated model can generate question templates and real questions combining the knowledge base and center graph. The End-to-End neural network directly sends the knowledge base and real questions to BiLSTM network. Meanwhile, the attention mechanism is utilized in the decoding layer, which makes the triples and generated questions more relevant. Finally, the experimental results on SimpleQuestions demonstrate the effectiveness of the proposed approach.  相似文献   
4.
本项目主要研究和实现了工业废白土在BAYAH燃煤自备电厂中的再利用,实现变废为宝,减少了环境污染,同时为企业创造了一定的经济效益。针对废白土的特性,对燃料输送系统给煤机、皮带机、煤仓、下料溜子和排渣系统进行了改造。通过修改操作规程消除废白土对锅炉运行的影响。  相似文献   
5.
6.
7.
8.
9.
10.
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active edge 1T‐MoS 2 / edge Ni ( OH ) 2 heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich edge 1T‐MoS 2 / edge Ni ( OH ) 2 sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions.  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