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   5574篇
  免费   370篇
  国内免费   22篇
电工技术   81篇
综合类   16篇
化学工业   1438篇
金属工艺   128篇
机械仪表   149篇
建筑科学   138篇
矿业工程   15篇
能源动力   151篇
轻工业   949篇
水利工程   70篇
石油天然气   27篇
武器工业   4篇
无线电   344篇
一般工业技术   923篇
冶金工业   658篇
原子能技术   42篇
自动化技术   833篇
  2024年   20篇
  2023年   51篇
  2022年   142篇
  2021年   262篇
  2020年   164篇
  2019年   213篇
  2018年   222篇
  2017年   233篇
  2016年   205篇
  2015年   154篇
  2014年   207篇
  2013年   370篇
  2012年   325篇
  2011年   350篇
  2010年   231篇
  2009年   269篇
  2008年   213篇
  2007年   188篇
  2006年   178篇
  2005年   154篇
  2004年   132篇
  2003年   133篇
  2002年   121篇
  2001年   74篇
  2000年   138篇
  1999年   83篇
  1998年   163篇
  1997年   100篇
  1996年   91篇
  1995年   62篇
  1994年   67篇
  1993年   51篇
  1992年   50篇
  1991年   23篇
  1990年   25篇
  1989年   45篇
  1988年   31篇
  1987年   22篇
  1986年   30篇
  1985年   24篇
  1984年   21篇
  1982年   22篇
  1981年   17篇
  1980年   18篇
  1979年   18篇
  1978年   23篇
  1977年   20篇
  1976年   32篇
  1975年   17篇
  1974年   23篇
排序方式: 共有5966条查询结果,搜索用时 15 毫秒
1.
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   
2.
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C.  相似文献   
3.

Both water balance (WB) and rating curve (RC) are methods for estimating streamflow. The first is mostly used to estimate reservoir outflows, while the second is usually adopted in hydrometeorological network streamflow gauges. While WB uses hourly collected data, the RC estimates streamflow using current water level and extrapolation techniques. The objective of this study was to analyze variations in the reservoir’s hourly outflow at Queimado Hydroelectric Power Plant (HPP Queimado) and to propose a method to evaluate whether the estimate of the daily outflows, obtained by the WB method, is similar to the flow values obtained at a conventional station. The logistic regression (LR) model was used because it is a method that adopts binary, categorically dependent variables to identify the event of interest. The results showed that the values of streamflow, obtained from an average of two daily readings, were a good representation of the flows in the region. The LR was able to identify atypical data, especially in the rainy season. This means that data consistency analysis can be faster and safer, when adequately employed and considering the proposed conditions, contributing to both management policies and the management of water resources.

  相似文献   
4.
5.
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations...  相似文献   
6.
7.
8.
9.
10.
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