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   546105篇
  免费   7420篇
  国内免费   2158篇
电工技术   9386篇
综合类   1294篇
化学工业   81894篇
金属工艺   21276篇
机械仪表   16116篇
建筑科学   13029篇
矿业工程   3472篇
能源动力   12907篇
轻工业   45375篇
水利工程   6150篇
石油天然气   11500篇
武器工业   60篇
无线电   60075篇
一般工业技术   105126篇
冶金工业   108280篇
原子能技术   13152篇
自动化技术   46591篇
  2021年   3969篇
  2019年   3708篇
  2018年   6952篇
  2017年   7190篇
  2016年   8023篇
  2015年   5281篇
  2014年   8098篇
  2013年   22280篇
  2012年   14355篇
  2011年   19288篇
  2010年   14302篇
  2009年   16458篇
  2008年   16798篇
  2007年   16671篇
  2006年   14634篇
  2005年   16214篇
  2004年   15095篇
  2003年   14149篇
  2002年   12950篇
  2001年   12739篇
  2000年   11687篇
  1999年   12192篇
  1998年   32310篇
  1997年   23067篇
  1996年   17561篇
  1995年   13086篇
  1994年   11525篇
  1993年   11508篇
  1992年   8199篇
  1991年   8115篇
  1990年   7807篇
  1989年   7747篇
  1988年   7426篇
  1987年   6528篇
  1986年   6480篇
  1985年   7322篇
  1984年   6798篇
  1983年   6286篇
  1982年   5952篇
  1981年   6116篇
  1980年   5992篇
  1979年   5675篇
  1978年   5747篇
  1977年   6904篇
  1976年   9468篇
  1975年   5148篇
  1974年   4897篇
  1973年   4906篇
  1972年   4229篇
  1971年   3859篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
2.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  相似文献   
3.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
4.
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   
5.
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   
6.

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   
7.
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   
8.
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   
9.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration.  相似文献   
10.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  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