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   2087篇
  免费   54篇
  国内免费   7篇
电工技术   156篇
综合类   7篇
化学工业   609篇
金属工艺   41篇
机械仪表   81篇
建筑科学   37篇
能源动力   70篇
轻工业   181篇
水利工程   6篇
石油天然气   2篇
无线电   148篇
一般工业技术   389篇
冶金工业   192篇
原子能技术   48篇
自动化技术   181篇
  2022年   12篇
  2021年   19篇
  2019年   16篇
  2018年   16篇
  2017年   14篇
  2016年   32篇
  2015年   30篇
  2014年   50篇
  2013年   88篇
  2012年   64篇
  2011年   96篇
  2010年   65篇
  2009年   91篇
  2008年   95篇
  2007年   94篇
  2006年   94篇
  2005年   78篇
  2004年   77篇
  2003年   61篇
  2002年   73篇
  2001年   44篇
  2000年   52篇
  1999年   59篇
  1998年   83篇
  1997年   76篇
  1996年   46篇
  1995年   42篇
  1994年   30篇
  1993年   31篇
  1992年   21篇
  1991年   26篇
  1990年   20篇
  1989年   28篇
  1988年   34篇
  1987年   31篇
  1986年   32篇
  1985年   32篇
  1984年   23篇
  1983年   20篇
  1982年   32篇
  1981年   24篇
  1980年   25篇
  1979年   24篇
  1978年   15篇
  1977年   23篇
  1976年   16篇
  1974年   10篇
  1967年   14篇
  1966年   11篇
  1965年   13篇
排序方式: 共有2148条查询结果,搜索用时 203 毫秒
71.
1 Introduction There are two ways ,the multi-wire sawslicing method and the inner-diameter blade slicing method,re-cently used for cutting wafers froma single crystal ingot . Multi-wire sawbecomes more popular iningot slicingprocesses ,because it has an advantage for slicinglarge diameter or long siliconingot and has efficiency for massproduction.However ,this method is difficult to control the wire cutting the ingot along its crystal orientationandit is less correspond to the request of some …  相似文献   
72.
A tunable optical notch filter was realized by thermally shifting the TM-like (the light's electric field perpendicular to the substrate) bandgap of a silicon photonic crystal slab W1 line-defect waveguide with silica cladding. This device is compact-its footprint is 340times16 mum2, excluding the electrode pads. The 3-dB bandwidth of the device was about 5 nm, and the extinction ratio at the center wavelength was as high as 40 dB. A maximum center wavelength shift of 17.9 nm was attained at a heating power of 0.7W, with a tuning efficiency of 25.5 nm/W. The tuning response time was less than 100 mus  相似文献   
73.
Plastic deformation is an unlikely process by which to mould pristine silicon wafers into three-dimensional shapes owing to the inevitable detrimental impact that the resulting mechanically induced defects would have on their electrical properties. However, if one were to find a way of doing so without substantial degradation of these properties, a range of new applications might be opened up. Here we report on the successful plastic deformation of silicon crystal wafers for the preparation of wafers with various shapes. A silicon wafer was set between dies and pressed at high temperatures. One application of shaped wafers is as well-shaped concave silicon crystal lenses or mirrors. The lattice plane of such a crystal lens has a curvature exactly along the surface. A concave spheroidal X-ray lens, in the form of two-dimensional Johann and Johansson's monochromators, is proposed for an X-ray optical component system. We propose and demonstrate a new solar cell system with the concave silicon crystal mirror used as both a solar cell and a focused mirror. This system can make use of the reflected photons from solar cells.  相似文献   
74.
Suppose that some particular link in the Internet is currently congested. A natural solution is to try to make packets bypass that link. This can be done by increasing the cost of that link intentionally, say from a 1 to a 2, since the Internet uses shortest-path routing. Unfortunately, however, this often causes temporary loops for packet traveling, called routing loops. In this paper we show that routing loops can be avoided by increasing the cost of the link not directly from a 1 to a 2 but through an intermediate value, a 3, i.e., from a 1 to a 3 and then to a 2. We may need several intermediate values. We show that in this case the greedy strategy, namely, raising the cost as much as possible in each step, is optimal.  相似文献   
75.
We present a methodology of controlling machines using spoken language commands. The two major problems relating to the speech interfaces for machines, namely, the interpretation of words with fuzzy implications and the out-of-vocabulary (OOV) words in natural conversation, are investigated. The system proposed in this paper is designed to overcome the above two problems in controlling machines using spoken language commands. The present system consists of a hidden Markov model (HMM) based automatic speech recognizer (ASR), with a keyword spotting system to capture the machine sensitive words from the running utterances and a fuzzy-neural network (FNN) based controller to represent the words with fuzzy implications in spoken language commands. Significance of the words, i.e., the contextual meaning of the words according to the machine's current state, is introduced to the system to obtain more realistic output equivalent to users' desire. Modularity of the system is also considered to provide a generalization of the methodology for systems having heterogeneous functions without diminishing the performance of the system. The proposed system is experimentally tested by navigating a mobile robot in real time using spoken language commands.  相似文献   
76.
Pure Fe with coverage of 0.5-2.0 nm was deposited on Si (111) 7×7 surfaces by reactive deposition epitaxy (RDE) in an integrated ultrahigh vacuum (UHV) system. Transmission electron microscopy (TEM) confirmed that the as-deposited epitaxial phase exhibits rod-like and equilateral triangular morphology. The as-deposited phase was identified as c-FeSi2 by electron diffraction and high-resolution transmission electron microscopy. It was found that there exists lattice distortion in epitaxial c-FeSi2 phase. Upon annealing at 1073 K, the metastable c-FeSi2 transforms into equilibrium β-FeSi2 phase, the latter inherits completely the morphology of c-FeSi2 phase. Based on RDE and subsequent annealing, a new fabrication technique to grow rod-like semiconducting β-FeSi2 on a Si substrate has been proposed in the present work.  相似文献   
77.
The use of a sodium film as a filter for wavelengths between 40 and 80 nm is discussed, and a technique to prepare these films is described. Sodium films of 230 nm thickness were demonstrated to have a transmission of 55% at 100 degrees K at a wavelength 41 nm. The transmission decreased to 40% after 18 h in a vacuum of 5x10(-8) Torr. Films of this thickness were shown to attenuate 20.5-nm radiation appearing in second order at 41 nm by at least a factor of 50.  相似文献   
78.
79.
80.
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