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   1083篇
  免费   34篇
电工技术   27篇
化学工业   207篇
金属工艺   18篇
机械仪表   21篇
建筑科学   58篇
矿业工程   3篇
能源动力   13篇
轻工业   95篇
无线电   106篇
一般工业技术   215篇
冶金工业   131篇
原子能技术   21篇
自动化技术   202篇
  2023年   10篇
  2022年   11篇
  2021年   25篇
  2020年   20篇
  2019年   16篇
  2018年   16篇
  2017年   17篇
  2016年   34篇
  2015年   21篇
  2014年   41篇
  2013年   50篇
  2012年   51篇
  2011年   65篇
  2010年   44篇
  2009年   39篇
  2008年   48篇
  2007年   58篇
  2006年   40篇
  2005年   40篇
  2004年   34篇
  2003年   27篇
  2002年   26篇
  2001年   18篇
  2000年   16篇
  1999年   29篇
  1998年   49篇
  1997年   46篇
  1996年   28篇
  1995年   20篇
  1994年   11篇
  1993年   11篇
  1992年   17篇
  1991年   4篇
  1990年   6篇
  1989年   6篇
  1988年   9篇
  1987年   6篇
  1986年   10篇
  1985年   7篇
  1983年   6篇
  1981年   10篇
  1980年   8篇
  1978年   6篇
  1977年   5篇
  1976年   11篇
  1973年   9篇
  1972年   3篇
  1968年   6篇
  1967年   4篇
  1966年   4篇
排序方式: 共有1117条查询结果,搜索用时 15 毫秒
1.
2.
3.
Eingegangen am 13.11.1996, in überarbeiteter Form am 12.5.1997  相似文献   
4.
The boreal forest contains almost half the total carbon pool of world forest ecosystems, and so has a very significant role in global biogeochemical cycles. The flux of greenhouse gases in and out of these forests is influenced strongly by disturbances such as diseases, logging and predominantly fire. It is important to quantify these disturbances to enable the modelling of major greenhouse gases. However, because of the remoteness and vastness of the boreal forest, little data is available on the type, extent, frequency and severity of these disturbances in Siberia. For burnt areas, two of the more responsive wavelengths are the short wave infra-red (SWIR) and the near infra-red (NIR). These produce a vegetation index, the normalised difference SWIR (NDSWIR) capable of detecting retrospective disturbances. Here we combine the NDSWIR from MODIS imagery acquired in the summer of 2003 with thermal anomaly data from 1992 to 2003 to detect and date areas which burnt at some point between 1992 and 2003. The semi-automated method is called SWIR and Thermal ANomalies for Detecting Disturbances (STANDD) and is complemented by an Normalised Difference Vegetation Index (NDVI) differencing method using MODIS 2002 and 2003 imagery to ensure reliable detection of area burnt in the year of image acquisition (i.e. 2003). The area of this study covers approximately 3 million km2 stretching from Lake Baikal in the south to the Laptev Sea in the north, above the Arctic Circle. Landsat ETM+ images were used to validate the shape and areal extent of the burnt areas resulting in an 81% overall accuracy with a kappa coefficient of agreement of 0.63.  相似文献   
5.
In this paper, we discuss a particular topology of a fiber-optic pressure transducer, developed recently at the Laboratory of the Photonics Research Center, University of Quebec en Outaouais. The sensor, which is an extension of our previous polarimetric configuration, was designed to operate using typical telecommunications components at the wavelength of 1300 nm. The pressure sensor is temperature compensated in an innovative way and has no polarizer between the LD and the sensor. The absolute accuracy of this sensor can be less than 1% in a wide range of temperatures, and including all types of metrological errors such as hysteresis and unrepeatability.  相似文献   
6.
This paper introduces DILIGENT, a digital library infrastructure built by integrating digital library and Grid technologies and resources. This infrastructure allows different communities to dynamically build specialised digital libraries capable to support the entire e-Science knowledge production and consumption life-cycle by using shared computing, storage, content, and application resources. The paper presents some of the main software services that implement the DILIGENT system. Moreover, it exemplifies the provided features by presenting how the DILIGENT infrastructure is being exploited in supporting the activity of user communities working in the Earth Science Environmental sector. This work is partially funded by the European Commission in the context of the DILIGENT project, under the 2nd call of FP6 IST priority.  相似文献   
7.
8.
Aerodynamic modelling of HAWT rotors by means of “engineering methods” has reached a saddle point, where no further development can be expected without a breakthrough in understanding the physics of unsteady, rotating three‐dimensional flows. However, such a breakthrough becomes ever more necessary, as the size of the wind turbines increases. With the experimental work in that direction being mostly limited to observing the phenomena and interpreting the associated mechanisms, and its increased cost, alternatives are being sought. The use of CFD techniques and state‐of‐the‐art Navier–Stokes solvers is considered a very serious contender, a belief shared by the members of the present consortium, which has worked on the VISCEL JOR3‐CT98‐0208 Joule III project. This project's goal was to determine the aerodynamic characteristics as well as the aeroelastic behaviour of wind turbine blades across their broad range of operational conditions, from attached to highly separated flow regimes. The work programme included specific tasks for the validation and assessment of existing 3D solvers, for the parametric study of 3D flow around realistic blades and for the investigation of aeroelastic stability, at the blade section level. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
9.
10.
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