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   1589128篇
  免费   26223篇
  国内免费   7123篇
电工技术   35305篇
综合类   6470篇
化学工业   276719篇
金属工艺   66447篇
机械仪表   46694篇
建筑科学   48010篇
矿业工程   11891篇
能源动力   50484篇
轻工业   122155篇
水利工程   16197篇
石油天然气   38410篇
武器工业   147篇
无线电   200070篇
一般工业技术   299523篇
冶金工业   195494篇
原子能技术   34694篇
自动化技术   173764篇
  2021年   15623篇
  2020年   11931篇
  2019年   14721篇
  2018年   18939篇
  2017年   18741篇
  2016年   22944篇
  2015年   17602篇
  2014年   28745篇
  2013年   88101篇
  2012年   38045篇
  2011年   53259篇
  2010年   45967篇
  2009年   53774篇
  2008年   48845篇
  2007年   46828篇
  2006年   46488篇
  2005年   42505篇
  2004年   43654篇
  2003年   43245篇
  2002年   41961篇
  2001年   38646篇
  2000年   36890篇
  1999年   36326篇
  1998年   54403篇
  1997年   45166篇
  1996年   39213篇
  1995年   33079篇
  1994年   30607篇
  1993年   30422篇
  1992年   26722篇
  1991年   23974篇
  1990年   24306篇
  1989年   23383篇
  1988年   21909篇
  1987年   20141篇
  1986年   19479篇
  1985年   22844篇
  1984年   22639篇
  1983年   20647篇
  1982年   19494篇
  1981年   19596篇
  1980年   18271篇
  1979年   18755篇
  1978年   17987篇
  1977年   18263篇
  1976年   19939篇
  1975年   16203篇
  1974年   15663篇
  1973年   15810篇
  1972年   13261篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
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   
34.
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   
35.
36.
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   
37.
38.

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   
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