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   1581638篇
  免费   26515篇
  国内免费   7064篇
电工技术   34473篇
综合类   6563篇
化学工业   273830篇
金属工艺   65012篇
机械仪表   44211篇
建筑科学   48179篇
矿业工程   11443篇
能源动力   50335篇
轻工业   123363篇
水利工程   16177篇
石油天然气   37336篇
武器工业   139篇
无线电   197852篇
一般工业技术   295483篇
冶金工业   203645篇
原子能技术   33921篇
自动化技术   173255篇
  2021年   15680篇
  2019年   14727篇
  2018年   15472篇
  2017年   14644篇
  2016年   21469篇
  2015年   17533篇
  2014年   28933篇
  2013年   88248篇
  2012年   37390篇
  2011年   50230篇
  2010年   43062篇
  2009年   50918篇
  2008年   46960篇
  2007年   44300篇
  2006年   46704篇
  2005年   41052篇
  2004年   43440篇
  2003年   43210篇
  2002年   42184篇
  2001年   39502篇
  2000年   37529篇
  1999年   37240篇
  1998年   57253篇
  1997年   46717篇
  1996年   40445篇
  1995年   33894篇
  1994年   31480篇
  1993年   31046篇
  1992年   27040篇
  1991年   24365篇
  1990年   24436篇
  1989年   23558篇
  1988年   22108篇
  1987年   20295篇
  1986年   19784篇
  1985年   23147篇
  1984年   22939篇
  1983年   20851篇
  1982年   19679篇
  1981年   19765篇
  1980年   18420篇
  1979年   18927篇
  1978年   18149篇
  1977年   18849篇
  1976年   21593篇
  1975年   16302篇
  1974年   15802篇
  1973年   15866篇
  1972年   13344篇
  1971年   11978篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
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   
74.
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   
75.
76.
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   
77.
78.

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   
79.
80.
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