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   282782篇
  免费   33064篇
  国内免费   11384篇
电工技术   15909篇
技术理论   14篇
综合类   16171篇
化学工业   54501篇
金属工艺   14923篇
机械仪表   16371篇
建筑科学   18300篇
矿业工程   6179篇
能源动力   6828篇
轻工业   22871篇
水利工程   5328篇
石油天然气   13240篇
武器工业   2191篇
无线电   33224篇
一般工业技术   44915篇
冶金工业   14428篇
原子能技术   5977篇
自动化技术   35860篇
  2024年   864篇
  2023年   3271篇
  2022年   6522篇
  2021年   9553篇
  2020年   8230篇
  2019年   8638篇
  2018年   9911篇
  2017年   10922篇
  2016年   10747篇
  2015年   12558篇
  2014年   15040篇
  2013年   18598篇
  2012年   18051篇
  2011年   18952篇
  2010年   17214篇
  2009年   16804篇
  2008年   16226篇
  2007年   15198篇
  2006年   14085篇
  2005年   11912篇
  2004年   9227篇
  2003年   8621篇
  2002年   8639篇
  2001年   7686篇
  2000年   6636篇
  1999年   5286篇
  1998年   3740篇
  1997年   3163篇
  1996年   2785篇
  1995年   2419篇
  1994年   1965篇
  1993年   1668篇
  1992年   1555篇
  1991年   1310篇
  1990年   1278篇
  1989年   1153篇
  1988年   1016篇
  1987年   893篇
  1986年   837篇
  1985年   754篇
  1984年   724篇
  1981年   692篇
  1979年   748篇
  1978年   782篇
  1977年   742篇
  1976年   764篇
  1975年   717篇
  1974年   721篇
  1973年   729篇
  1972年   706篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
95.
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis.  相似文献   
96.
97.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
98.
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage.  相似文献   
99.
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.  相似文献   
100.
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