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   1445721篇
  免费   27633篇
  国内免费   7059篇
电工技术   34059篇
综合类   6404篇
化学工业   268642篇
金属工艺   63274篇
机械仪表   40030篇
建筑科学   44623篇
矿业工程   11273篇
能源动力   50519篇
轻工业   102738篇
水利工程   14627篇
石油天然气   37393篇
武器工业   147篇
无线电   194796篇
一般工业技术   272521篇
冶金工业   139121篇
原子能技术   33715篇
自动化技术   166531篇
  2021年   15924篇
  2020年   12147篇
  2019年   15006篇
  2018年   14691篇
  2017年   13881篇
  2016年   20934篇
  2015年   17433篇
  2014年   29021篇
  2013年   88211篇
  2012年   33613篇
  2011年   44750篇
  2010年   40915篇
  2009年   49718篇
  2008年   41939篇
  2007年   38625篇
  2006年   42951篇
  2005年   37142篇
  2004年   39801篇
  2003年   39799篇
  2002年   39107篇
  2001年   35868篇
  2000年   34533篇
  1999年   33308篇
  1998年   37615篇
  1997年   34568篇
  1996年   32483篇
  1995年   28928篇
  1994年   27378篇
  1993年   27284篇
  1992年   25558篇
  1991年   22559篇
  1990年   23026篇
  1989年   22067篇
  1988年   20475篇
  1987年   18849篇
  1986年   18165篇
  1985年   21473篇
  1984年   21933篇
  1983年   19920篇
  1982年   19046篇
  1981年   19121篇
  1980年   17671篇
  1979年   18249篇
  1978年   17524篇
  1977年   16807篇
  1976年   17031篇
  1975年   15793篇
  1974年   15321篇
  1973年   15392篇
  1972年   12866篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
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   
23.
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   
24.
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   
25.
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   
26.
Wireless Networks - In order to satisfy the delay requirements of telecommunication systems, in this paper, we present a cooperative network with the short packet transmission in the Rayleigh...  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.

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   
29.
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   
30.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  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