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   1477736篇
  免费   25815篇
  国内免费   7005篇
电工技术   34000篇
综合类   6365篇
化学工业   269001篇
金属工艺   63491篇
机械仪表   41176篇
建筑科学   45857篇
矿业工程   11298篇
能源动力   50107篇
轻工业   110541篇
水利工程   14982篇
石油天然气   37244篇
武器工业   130篇
无线电   194976篇
一般工业技术   278902篇
冶金工业   151146篇
原子能技术   33722篇
自动化技术   167618篇
  2021年   15485篇
  2020年   11786篇
  2019年   14584篇
  2018年   14442篇
  2017年   13645篇
  2016年   20723篇
  2015年   17181篇
  2014年   28576篇
  2013年   87514篇
  2012年   34699篇
  2011年   46353篇
  2010年   41338篇
  2009年   49870篇
  2008年   43537篇
  2007年   40544篇
  2006年   44331篇
  2005年   38635篇
  2004年   41024篇
  2003年   40993篇
  2002年   40096篇
  2001年   37083篇
  2000年   35484篇
  1999年   34353篇
  1998年   42128篇
  1997年   37299篇
  1996年   33916篇
  1995年   29884篇
  1994年   28131篇
  1993年   27965篇
  1992年   25884篇
  1991年   22960篇
  1990年   23285篇
  1989年   22294篇
  1988年   20885篇
  1987年   19124篇
  1986年   18514篇
  1985年   21880篇
  1984年   22213篇
  1983年   20211篇
  1982年   19190篇
  1981年   19269篇
  1980年   17855篇
  1979年   18467篇
  1978年   17657篇
  1977年   17159篇
  1976年   17580篇
  1975年   15943篇
  1974年   15469篇
  1973年   15559篇
  1972年   13003篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
This paper focuses on the hydrodynamics of third sound on a superfluid 3 He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range.  相似文献   
932.
An implicit assumption of several causal reasoning models is that readers adopt the goals of a narrative's protagonist during text comprehension. In apparent violation of this assumption, readers participating in Experiment 1 of the present study drew inferences relevant to a protagonist's goal even when that goal was already satisfied from the perspective of the protagonist. In Experiments 2 and 3, participants were explicitly asked to view the text situation from the point of view of the protagonist. In this case, the goals of the reader and the protagonist should be the same. In these experiments, participants focused on the goals of the protagonist only when those goals had not been satisfied from the perspective of the protagonist. These results are discussed in terms of reader- and character-based perspectives and in terms of text characteristics that cue perspective taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
933.
934.
本文概述了离子注入过程中污染产生的原因和防止污染的措施,特别强调了对微粒污染和金属污染的防护以满足ULSI加工对离子注入的要求。  相似文献   
935.
The paper covers a simple idea. If we sample an aperture, we can obtain valid patterns over a limited angular region about the normal to the aperture. The same expression can be used with near-field measurements. I reduced the expression to a nomograph. A nomograph allows one to rapidly test various choices. In the second half of the paper, I answer questions caused by the February column which discussed polarization (Milligan, IEEE Antennas. Propag. Mag., vol.38, no.1, p.56-8, 1996)  相似文献   
936.
The formation of mullite was investigated using microcomposite powders which consist of α-alumina cores and amorphous silica coatings. Differential thermal analysis and X-ray diffraction showed that the mullitization reaction was endothermic. In contrast, mullite forms exothermically in samples prepared by sol-gel processing. The results are shown to be consistent with available thermodynamic data for mullite formation from different alumina and silica phases.  相似文献   
937.
938.
939.
The objective of this study is to determine the economic and operational impact on energy cost of incorporating large photovoltaic (PV) and wind energy conversion systems (WECS) into the electric utility generation mix. In most cases, PV and WECS power outputs are subtracted from the utility load with the expectation that conventional generation would meet the residual load. This approach is valid for small penetration levels and/or for PV and WECS facilities connected near load centers, However, several constraints such as thermal generation characteristics, fuel supply and delivery, spinning reserve requirements, and hydro availability are not adequately represented in this process. To determine the optimal value of large-scale PV and WECS applications, a new methodology that would take into account the aforementioned constraints as well as a more global penetration is developed. Results indicate that while high hydro availability increases PV penetration levels, high ramping rates can also significantly increase penetration levels  相似文献   
940.
Roos  G. Hoefflinger  B. 《Electronics letters》1993,29(24):2103-2104
A process-inherent NAND2 device is presented for a three-dimensional CMOS integration with epitaxial lateral overgrowth and chemo-mechanical polishing. The required 'OR' function of the two PMOS transistors is achieved by one silicon volume, which is controlled by a back gate and a conventional front gate. Almost symmetrical characteristics are measured for the front and the back gates.<>  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