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   170608篇
  免费   14499篇
  国内免费   7434篇
电工技术   10425篇
技术理论   14篇
综合类   11053篇
化学工业   29113篇
金属工艺   9205篇
机械仪表   10418篇
建筑科学   13461篇
矿业工程   4881篇
能源动力   5157篇
轻工业   11008篇
水利工程   3159篇
石油天然气   9930篇
武器工业   1470篇
无线电   19903篇
一般工业技术   20497篇
冶金工业   8305篇
原子能技术   1934篇
自动化技术   22608篇
  2024年   788篇
  2023年   2825篇
  2022年   5200篇
  2021年   7144篇
  2020年   5404篇
  2019年   4526篇
  2018年   4904篇
  2017年   5569篇
  2016年   4788篇
  2015年   6821篇
  2014年   8231篇
  2013年   9998篇
  2012年   10802篇
  2011年   11571篇
  2010年   10097篇
  2009年   9689篇
  2008年   9373篇
  2007年   8879篇
  2006年   9164篇
  2005年   7869篇
  2004年   5537篇
  2003年   4834篇
  2002年   4671篇
  2001年   4279篇
  2000年   4203篇
  1999年   4423篇
  1998年   3790篇
  1997年   3204篇
  1996年   2867篇
  1995年   2450篇
  1994年   1949篇
  1993年   1471篇
  1992年   1180篇
  1991年   935篇
  1990年   664篇
  1989年   611篇
  1988年   491篇
  1987年   327篇
  1986年   253篇
  1985年   172篇
  1984年   98篇
  1983年   76篇
  1982年   98篇
  1981年   73篇
  1980年   58篇
  1979年   31篇
  1977年   16篇
  1976年   19篇
  1974年   13篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In this article, we present a detailed theoretical analysis and a prototype implementation of a family of cameras designed with the explicit goal of detecting and removing interfering dynamic occluders in real time, during live capture, as opposed to fixing the resulting artifacts a posteriori. Such an early-acquisition approach improves efficiency: more valid samples are acquired faster without worrying about moving occluders. One option for designing a camera to be unaffected by moving occluders is to sample through the occluder, but true x-ray-like vision is technically impractical. Another option is to sample around the occluder using a camera with a large effective aperture, but such an approach requires a bulky acquisition device. Yet another possibility of sampling around an occluder is to rely on second and higher order reflected rays that indirectly sample surfaces not directly visible. However, devising an acquisition device sufficiently sensitive and efficient to capture large environments using reflected rays will remain challenging for the foreseeable future.  相似文献   
22.
23.
A configurable nonlinear filter generator is proposed. The nonlinear function employed is key controllable. By changing the key, a different sequence will be obtained. Simulated results show that an optimal linear complexity profile of the sequence can be generated  相似文献   
24.
川东地区长兴组缝洞型储层的识别   总被引:1,自引:0,他引:1  
本文针对四川东部地区上二叠统长兴组(P_2~2)缝洞型储层的低孔、低渗及非均质性等特点,分析了影响这类储层识别的主要因素,提出了利用现有的地球物理测井手段定性识别储层的指标和定量综合识别储层的方法,这可望提高测试成功率。  相似文献   
25.
The effect of the atomic mobility on a film surface has been studied by using a three-dimensional atomistic thin-film deposition model which simulates three-dimensional thin-film images, surface profiles and cross-sectional area pictures. In addition, quantitative results of surface RMS roughness, average film thickness, atomic coordination number and its distribution, and solid fraction of the deposited thin films, were obtained from the simulations. When the film surface mobility increased from 0.3 to 3.0, RMS roughness decreased from 6.5 to 1.1, solid fraction increased from 0.27 to 0.56 and average film thickness decreased from 40 to 28, due to the reduction of the voids within the film. The full-width half magnitude of the atomic coordination distribution became narrower indicating the increased degree of crystallization. With increase in surface mobility crossing the boundary to 1.5, the film evolved from a porous or loose columnar structure with voids, to a densely packed fibrous grain structure which can be categorized by the zone structure models.  相似文献   
26.
27.
Images stored in resist for soft X-ray lithography or microradiography were found to show a background noise which limits the resolution. This is due to the statistically variable spatial distribution of the photons incident on the resist surface. An estimate of the fundamental noise-limited resolution has been made from the experimental measurement of photon flux incident on the surface and the accurate development rate curves. Monochromatic radiation from a synchrotron source was used.  相似文献   
28.
详细介绍了R-113流体管外上升流动的沸腾换热试验,包括试验台架、流量计和温度测量的修正,以及试验数据。拟合的换热关系式为q=528(Tw─Ts)1.33。  相似文献   
29.
本文实验研究了BHP的浓度对产生O2(1△)的影响。实验结果表明:当BHP浓度大于3.5M时,Cl2利用率以及O2(1△)的产率将不依赖于BHP浓度的变化而变化,同时,实验结果表明,使用低浓度的BHP对COIL的操作是可行的。  相似文献   
30.
The effect of DC flux on the core loss is examined for the practical range of power and frequency. Relevant core loss equations are derived and applied to an optimization algorithm to determine the minimum core loss at a given ratio of s (DC flux density to AC peak flux density). It has been found that the curves of hysteresis loss density versus the ratio of s exhibit a peak at a critical ratio. Below or above this critical ratio, the loss density decreases drastically. On the other hand, the curves of eddy-current loss density versus the ratio of s exhibits a minimum point at a critical ratio. Below or above this critical ratio, the loss density increases gradually  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