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   1408094篇
  免费   25607篇
  国内免费   6896篇
电工技术   33845篇
综合类   6320篇
化学工业   266405篇
金属工艺   62663篇
机械仪表   38964篇
建筑科学   43922篇
矿业工程   11214篇
能源动力   50159篇
轻工业   99780篇
水利工程   13977篇
石油天然气   37226篇
武器工业   128篇
无线电   193451篇
一般工业技术   267103篇
冶金工业   116829篇
原子能技术   33653篇
自动化技术   164958篇
  2021年   15766篇
  2020年   11916篇
  2019年   14707篇
  2018年   13979篇
  2017年   13134篇
  2016年   20377篇
  2015年   17155篇
  2014年   28556篇
  2013年   87426篇
  2012年   32609篇
  2011年   43252篇
  2010年   40136篇
  2009年   49157篇
  2008年   40922篇
  2007年   37586篇
  2006年   42265篇
  2005年   36492篇
  2004年   39181篇
  2003年   39310篇
  2002年   38748篇
  2001年   34961篇
  2000年   33849篇
  1999年   32100篇
  1998年   29933篇
  1997年   30207篇
  1996年   29454篇
  1995年   27261篇
  1994年   26049篇
  1993年   25965篇
  1992年   25275篇
  1991年   22182篇
  1990年   22634篇
  1989年   21706篇
  1988年   20158篇
  1987年   18568篇
  1986年   17858篇
  1985年   21228篇
  1984年   21820篇
  1983年   19801篇
  1982年   18933篇
  1981年   18988篇
  1980年   17554篇
  1979年   18182篇
  1978年   17437篇
  1977年   16541篇
  1976年   16388篇
  1975年   15759篇
  1974年   15304篇
  1973年   15362篇
  1972年   12846篇
排序方式: 共有10000条查询结果,搜索用时 15 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