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   1559702篇
  免费   27762篇
  国内免费   6971篇
电工技术   34583篇
综合类   6452篇
化学工业   272387篇
金属工艺   64965篇
机械仪表   44180篇
建筑科学   47339篇
矿业工程   11552篇
能源动力   50388篇
轻工业   119848篇
水利工程   15695篇
石油天然气   37834篇
武器工业   150篇
无线电   197942篇
一般工业技术   292113篇
冶金工业   193379篇
原子能技术   34234篇
自动化技术   171394篇
  2021年   15533篇
  2020年   11950篇
  2019年   14690篇
  2018年   17156篇
  2017年   16482篇
  2016年   22054篇
  2015年   17544篇
  2014年   28787篇
  2013年   88084篇
  2012年   37060篇
  2011年   50643篇
  2010年   43930篇
  2009年   51842篇
  2008年   46918篇
  2007年   44292篇
  2006年   45874篇
  2005年   40874篇
  2004年   42777篇
  2003年   42525篇
  2002年   41360篇
  2001年   38518篇
  2000年   36727篇
  1999年   36376篇
  1998年   54833篇
  1997年   45154篇
  1996年   39056篇
  1995年   32875篇
  1994年   30510篇
  1993年   30462篇
  1992年   26680篇
  1991年   23775篇
  1990年   24072篇
  1989年   23157篇
  1988年   21650篇
  1987年   19918篇
  1986年   19232篇
  1985年   22544篇
  1984年   22508篇
  1983年   20452篇
  1982年   19442篇
  1981年   19611篇
  1980年   18201篇
  1979年   18621篇
  1978年   17908篇
  1977年   18074篇
  1976年   19711篇
  1975年   16070篇
  1974年   15543篇
  1973年   15659篇
  1972年   13122篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
261.
262.
263.
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   
264.
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   
265.
266.
267.
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   
268.
269.

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   
270.
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