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   1479996篇
  免费   25739篇
  国内免费   6978篇
电工技术   34192篇
综合类   6373篇
化学工业   269164篇
金属工艺   63834篇
机械仪表   41250篇
建筑科学   45398篇
矿业工程   11319篇
能源动力   50233篇
轻工业   108102篇
水利工程   14807篇
石油天然气   37415篇
武器工业   132篇
无线电   195589篇
一般工业技术   279252篇
冶金工业   154269篇
原子能技术   33863篇
自动化技术   167521篇
  2021年   15550篇
  2020年   11805篇
  2019年   14568篇
  2018年   15174篇
  2017年   14462篇
  2016年   20979篇
  2015年   17250篇
  2014年   28622篇
  2013年   87795篇
  2012年   34449篇
  2011年   46329篇
  2010年   41814篇
  2009年   50326篇
  2008年   43536篇
  2007年   40419篇
  2006年   43795篇
  2005年   38254篇
  2004年   40690篇
  2003年   40747篇
  2002年   39789篇
  2001年   36692篇
  2000年   35260篇
  1999年   34296篇
  1998年   42423篇
  1997年   37438篇
  1996年   34161篇
  1995年   30057篇
  1994年   28390篇
  1993年   28206篇
  1992年   25914篇
  1991年   23006篇
  1990年   23324篇
  1989年   22396篇
  1988年   20931篇
  1987年   19206篇
  1986年   18589篇
  1985年   21828篇
  1984年   22161篇
  1983年   20139篇
  1982年   19187篇
  1981年   19293篇
  1980年   17879篇
  1979年   18410篇
  1978年   17638篇
  1977年   17302篇
  1976年   18159篇
  1975年   15936篇
  1974年   15437篇
  1973年   15510篇
  1972年   12973篇
排序方式: 共有10000条查询结果,搜索用时 15 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