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   704302篇
  免费   11047篇
  国内免费   2222篇
电工技术   12555篇
综合类   691篇
化学工业   105116篇
金属工艺   25649篇
机械仪表   20241篇
建筑科学   17683篇
矿业工程   2757篇
能源动力   19779篇
轻工业   65502篇
水利工程   6617篇
石油天然气   10906篇
武器工业   41篇
无线电   83008篇
一般工业技术   133682篇
冶金工业   139275篇
原子能技术   12799篇
自动化技术   61270篇
  2021年   6053篇
  2020年   4458篇
  2019年   5649篇
  2018年   9502篇
  2017年   9331篇
  2016年   9905篇
  2015年   7017篇
  2014年   11642篇
  2013年   32912篇
  2012年   18949篇
  2011年   26552篇
  2010年   20808篇
  2009年   23326篇
  2008年   24126篇
  2007年   23753篇
  2006年   21116篇
  2005年   19285篇
  2004年   18478篇
  2003年   18270篇
  2002年   17278篇
  2001年   17495篇
  2000年   16215篇
  1999年   17300篇
  1998年   44446篇
  1997年   31038篇
  1996年   23591篇
  1995年   17750篇
  1994年   15454篇
  1993年   15190篇
  1992年   10819篇
  1991年   10149篇
  1990年   9878篇
  1989年   9534篇
  1988年   8971篇
  1987年   7734篇
  1986年   7553篇
  1985年   8722篇
  1984年   8087篇
  1983年   7205篇
  1982年   6752篇
  1981年   6898篇
  1980年   6466篇
  1979年   6250篇
  1978年   5909篇
  1977年   7152篇
  1976年   9353篇
  1975年   5100篇
  1974年   4788篇
  1973年   4984篇
  1972年   3953篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Tian  J. Y.  Xu  G.  Hu  H. J.  Zhou  M. X. 《Strength of Materials》2019,51(3):439-449
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,...  相似文献   
182.
Micro Aerial Vehicles (MAVs) have great potentials to be applied for indoor search and rescue missions. In this paper, we propose a modular lightweight design of an autonomous MAV with integrated hardware and software. The MAV is equipped with the 2D laser scanner, camera, mission computer and flight controller, running all the computation onboard in real time. The onboard perception system includes a laser‐based SLAM module and a custom‐designed visual detection module. A dual Kalman filter design provides robust state estimation by multiple sensor fusion. Specifically, the fusion module provides robust altitude measurement in the circumstance of surface changing. In addition, indoor‐outdoor transition is explicitly handled by the fusion module. In order to efficiently navigate through obstacles and adapt to multiple tasks, a task tree‐based mission planning method is seamlessly integrated with path planning and control modules. The MAV is capable of searching and rescuing victims from unknown indoor environments effectively. It was validated by our award‐winning performance at the 2017 International Micro Air Vehicle Competition (IMAV 2017), held in Toulouse, France. The performance video is available on https://youtu.be/8H19ppS_VXM .  相似文献   
183.
184.

Floods are common and recurring natural hazards which damages is the destruction for society. Several regions of the world with different climatic conditions face the challenge of floods in different magnitudes. Here we estimate flood susceptibility based on Analytical neural network (ANN), Deep learning neural network (DLNN) and Deep boost (DB) algorithm approach. We also attempt to estimate the future rainfall scenario, using the General circulation model (GCM) with its ensemble. The Representative concentration pathway (RCP) scenario is employed for estimating the future rainfall in more an authentic way. The validation of all models was done with considering different indices and the results show that the DB model is most optimal as compared to the other models. According to the DB model, the spatial coverage of very low, low, moderate, high and very high flood prone region is 68.20%, 9.48%, 5.64%, 7.34% and 9.33% respectively. The approach and results in this research would be beneficial to take the decision in managing this natural hazard in a more efficient way.

  相似文献   
185.
In this work, the sintering behaviour of fluorapatite (FAp)–silicate composites prepared by mixing variable amounts of natural quartz (2.5 wt% to 20 wt%) and FAp was studied. The composites were pressureless sintered in air at temperatures from 1000 °C to 1350 °C. The effects of temperatures on the densification, phase formation, chemical bonding and Vickers hardness of the composites were evaluated. All the samples exhibited mixed phase, comprising FAp and francolite as the major constituents along with some minor phases of cristobalite, wollastonite, dicalcium silicate and/or whitlockite dependent on the quartz content and sintering temperature. The composite containing 2.5 wt% quartz exhibited the best sintering properties. The highest bulk density of 3 g/cm3 and a Vickers hardness of >4.2 GPa were obtained for the 2.5 wt% quartz–FAp composite when sintered at 1100 °C. The addition of quartz was found to alter the microstructure of the composites, where it exhibited a rod-like morphology when sintered at 1000 °C and a regular rounded grain structure when sintered at 1350 °C. A wetted grain surface was observed for composites containing high quartz content and was believed to be associated with a transient liquid phase sintering.  相似文献   
186.
187.
188.
189.
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated.  相似文献   
190.
International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...  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