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   126986篇
  免费   9597篇
  国内免费   3001篇
电工技术   7571篇
技术理论   12篇
综合类   7713篇
化学工业   21020篇
金属工艺   6977篇
机械仪表   7783篇
建筑科学   9771篇
矿业工程   3536篇
能源动力   3862篇
轻工业   8109篇
水利工程   2151篇
石油天然气   7474篇
武器工业   879篇
无线电   14564篇
一般工业技术   15411篇
冶金工业   5605篇
原子能技术   1486篇
自动化技术   15660篇
  2025年   367篇
  2024年   2997篇
  2023年   2716篇
  2022年   3801篇
  2021年   5162篇
  2020年   4377篇
  2019年   3800篇
  2018年   3593篇
  2017年   4071篇
  2016年   3639篇
  2015年   4848篇
  2014年   5841篇
  2013年   6833篇
  2012年   7408篇
  2011年   7968篇
  2010年   6949篇
  2009年   6637篇
  2008年   6437篇
  2007年   6109篇
  2006年   6342篇
  2005年   5515篇
  2004年   3763篇
  2003年   3288篇
  2002年   3078篇
  2001年   2797篇
  2000年   2946篇
  1999年   3173篇
  1998年   2685篇
  1997年   2284篇
  1996年   2100篇
  1995年   1827篇
  1994年   1476篇
  1993年   1061篇
  1992年   871篇
  1991年   687篇
  1990年   504篇
  1989年   447篇
  1988年   355篇
  1987年   251篇
  1986年   173篇
  1985年   102篇
  1984年   72篇
  1983年   52篇
  1982年   64篇
  1981年   46篇
  1980年   38篇
  1979年   10篇
  1959年   4篇
  1953年   9篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。  相似文献   
3.
Power distribution systems have been significantly affected by many outage-causing events. Good fault cause identification can help expedite the restoration procedure and improve the system reliability. However, the data imbalance issue in many real-world data sets often degrades the fault cause identification performance. In this paper, the E-algorithm, which is extended from the fuzzy classification algorithm by Ishibuchi to alleviate the effect of imbalanced data constitution, is applied to Duke Energy outage data for distribution fault cause identification. Three major outage causes (tree, animal, and lightning) are used as prototypes. The performance of E-algorithm on real-world imbalanced data is compared with artificial neural network. The results show that the E-algorithm can greatly improve the performance when the data are imbalanced  相似文献   
4.
For the first time, the surface metal on nonalloyed ohmic electrodes is found to significantly change the profiles of gate grooves, when resist openings are employed to monitor drain current during wet-chemical gate recess for sub-micron InAlAs/lnGaAs heterojunction field-effect transistors (HFETs). The surface metal of Ni enhances the etching rate in comparison with that in the absence of electrodes by a factor of 4 and 10, laterally and vertically, which is favorable to fabricate deep gate grooves with small side etching. The Pt surface metal, however, leads to preferential etching of InGaAs over InAlAs, which can be useful to realize large side etching. The existence of an electrochemistry-related etching component, which arises when the ohmic electrodes are present during recess etching, is considered to be responsible for these behaviors  相似文献   
5.
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   
6.
7.
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   
8.
9.
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   
10.
转移法色交换   总被引:1,自引:0,他引:1  
将图G的着色由一种变为中一种,通常用Kempe法以交换。但是,对于某些情况,用此法无效。针对这个问题,本文提出了一种转移法色交换,它适用于平面图着色,方法直观,清晰且有效。  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