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   206723篇
  免费   15836篇
  国内免费   208篇
电工技术   3298篇
综合类   135篇
化学工业   43404篇
金属工艺   9808篇
机械仪表   6473篇
建筑科学   4770篇
矿业工程   1889篇
能源动力   3571篇
轻工业   15749篇
水利工程   3032篇
石油天然气   8734篇
武器工业   13篇
无线电   21693篇
一般工业技术   49702篇
冶金工业   28786篇
原子能技术   6946篇
自动化技术   14764篇
  2020年   2642篇
  2019年   4709篇
  2018年   6048篇
  2017年   6474篇
  2016年   7177篇
  2015年   5565篇
  2014年   6781篇
  2013年   11298篇
  2012年   7002篇
  2011年   7762篇
  2010年   7058篇
  2009年   7463篇
  2008年   7051篇
  2007年   6821篇
  2006年   5857篇
  2005年   5240篇
  2004年   5035篇
  2003年   4860篇
  2002年   4732篇
  2001年   4593篇
  2000年   4451篇
  1999年   3714篇
  1998年   7216篇
  1997年   5298篇
  1996年   3912篇
  1995年   2977篇
  1994年   2664篇
  1993年   2774篇
  1992年   2283篇
  1991年   2333篇
  1990年   2436篇
  1989年   2351篇
  1988年   2341篇
  1987年   2216篇
  1986年   2285篇
  1985年   2322篇
  1984年   2226篇
  1983年   2146篇
  1982年   1991篇
  1981年   2207篇
  1980年   2067篇
  1979年   2273篇
  1978年   2440篇
  1977年   2443篇
  1976年   3107篇
  1975年   2246篇
  1974年   2309篇
  1973年   2347篇
  1972年   2155篇
  1971年   1914篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
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   
53.
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   
54.
55.
56.
57.
58.
59.
Bochkareva  N. I.  Ivanov  A. M.  Klochkov  A. V.  Kogotkov  V. S.  Rebane  Yu. T.  Virko  M. V.  Shreter  Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode...  相似文献   
60.
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits.  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