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   1489267篇
  免费   26590篇
  国内免费   7020篇
电工技术   34372篇
综合类   6537篇
化学工业   270419篇
金属工艺   63981篇
机械仪表   42311篇
建筑科学   45801篇
矿业工程   11445篇
能源动力   50230篇
轻工业   111268篇
水利工程   14961篇
石油天然气   37578篇
武器工业   186篇
无线电   196244篇
一般工业技术   282061篇
冶金工业   152897篇
原子能技术   33925篇
自动化技术   168661篇
  2021年   15598篇
  2020年   11866篇
  2019年   14609篇
  2018年   15627篇
  2017年   14957篇
  2016年   21206篇
  2015年   17379篇
  2014年   28703篇
  2013年   87761篇
  2012年   35042篇
  2011年   47379篇
  2010年   42212篇
  2009年   50679篇
  2008年   44224篇
  2007年   41297篇
  2006年   44408篇
  2005年   39001篇
  2004年   41203篇
  2003年   41185篇
  2002年   40217篇
  2001年   37054篇
  2000年   35499篇
  1999年   34373篇
  1998年   41333篇
  1997年   37152篇
  1996年   34090篇
  1995年   30085篇
  1994年   28246篇
  1993年   28099篇
  1992年   26154篇
  1991年   23220篇
  1990年   23519篇
  1989年   22543篇
  1988年   21051篇
  1987年   19400篇
  1986年   18765篇
  1985年   22050篇
  1984年   22305篇
  1983年   20278篇
  1982年   19226篇
  1981年   19305篇
  1980年   17889篇
  1979年   18489篇
  1978年   17723篇
  1977年   17316篇
  1976年   18039篇
  1975年   15982篇
  1974年   15545篇
  1973年   15603篇
  1972年   13051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.

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