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   1668900篇
  免费   27004篇
  国内免费   7239篇
电工技术   35705篇
综合类   6651篇
化学工业   281002篇
金属工艺   67412篇
机械仪表   48810篇
建筑科学   49729篇
矿业工程   12080篇
能源动力   50712篇
轻工业   131523篇
水利工程   17027篇
石油天然气   38711篇
武器工业   173篇
无线电   202427篇
一般工业技术   310975篇
冶金工业   237016篇
原子能技术   34877篇
自动化技术   178313篇
  2021年   15914篇
  2020年   12266篇
  2019年   15007篇
  2018年   20493篇
  2017年   20318篇
  2016年   23945篇
  2015年   18084篇
  2014年   29221篇
  2013年   88909篇
  2012年   40372篇
  2011年   56568篇
  2010年   47694篇
  2009年   55044篇
  2008年   51585篇
  2007年   49883篇
  2006年   48234篇
  2005年   44407篇
  2004年   45292篇
  2003年   44803篇
  2002年   43196篇
  2001年   40274篇
  2000年   38225篇
  1999年   38522篇
  1998年   67638篇
  1997年   53081篇
  1996年   44282篇
  1995年   36056篇
  1994年   33027篇
  1993年   32926篇
  1992年   27476篇
  1991年   24793篇
  1990年   25023篇
  1989年   24122篇
  1988年   22661篇
  1987年   20804篇
  1986年   20196篇
  1985年   23510篇
  1984年   22983篇
  1983年   20952篇
  1982年   19791篇
  1981年   19976篇
  1980年   18627篇
  1979年   18943篇
  1978年   18225篇
  1977年   19099篇
  1976年   21844篇
  1975年   16335篇
  1974年   15749篇
  1973年   15900篇
  1972年   13352篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  相似文献   
32.
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.  相似文献   
33.
34.
Programming and Computer Software - Image segmentation using a hierarchical sequence of piecewise constant approximations that minimally differ from the original image in terms of the total squared...  相似文献   
35.
36.

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

  相似文献   
37.
38.
39.
40.
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