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   1667291篇
  免费   28587篇
  国内免费   7234篇
电工技术   35705篇
综合类   6651篇
化学工业   281001篇
金属工艺   67407篇
机械仪表   48807篇
建筑科学   49730篇
矿业工程   12080篇
能源动力   50712篇
轻工业   131522篇
水利工程   17027篇
石油天然气   38711篇
武器工业   173篇
无线电   202424篇
一般工业技术   310970篇
冶金工业   237005篇
原子能技术   34878篇
自动化技术   178309篇
  2021年   15908篇
  2020年   12264篇
  2019年   15006篇
  2018年   20491篇
  2017年   20316篇
  2016年   23945篇
  2015年   18084篇
  2014年   29220篇
  2013年   88908篇
  2012年   40372篇
  2011年   56566篇
  2010年   47692篇
  2009年   55044篇
  2008年   51585篇
  2007年   49883篇
  2006年   48234篇
  2005年   44406篇
  2004年   45291篇
  2003年   44803篇
  2002年   43196篇
  2001年   40275篇
  2000年   38224篇
  1999年   38520篇
  1998年   67637篇
  1997年   53080篇
  1996年   44281篇
  1995年   36057篇
  1994年   33027篇
  1993年   32925篇
  1992年   27476篇
  1991年   24793篇
  1990年   25023篇
  1989年   24122篇
  1988年   22661篇
  1987年   20803篇
  1986年   20196篇
  1985年   23510篇
  1984年   22983篇
  1983年   20952篇
  1982年   19791篇
  1981年   19976篇
  1980年   18627篇
  1979年   18943篇
  1978年   18225篇
  1977年   19097篇
  1976年   21841篇
  1975年   16335篇
  1974年   15749篇
  1973年   15900篇
  1972年   13352篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
22.
23.
Multimedia Tools and Applications - Recently, many concepts in technology has been changed. According to the digital transformation trends, Internet of Things (IoT) represents an interested...  相似文献   
24.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
25.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
26.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
27.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
28.
Forschung im Ingenieurwesen - Das Arbeitsmittel in Wärmepumpen unterliegt einer Vielzahl von Anforderungen, welche für einen effizienten und sicheren Betrieb eingehalten werden...  相似文献   
29.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  相似文献   
30.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses.  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