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   1539423篇
  免费   28752篇
  国内免费   8589篇
电工技术   36384篇
技术理论   2篇
综合类   8616篇
化学工业   274920篇
金属工艺   65556篇
机械仪表   44577篇
建筑科学   48969篇
矿业工程   12263篇
能源动力   51026篇
轻工业   114549篇
水利工程   15782篇
石油天然气   38843篇
武器工业   431篇
无线电   200041篇
一般工业技术   287381篇
冶金工业   170251篇
原子能技术   34309篇
自动化技术   172864篇
  2021年   16983篇
  2020年   12871篇
  2019年   15405篇
  2018年   16537篇
  2017年   16018篇
  2016年   22120篇
  2015年   18493篇
  2014年   30180篇
  2013年   89440篇
  2012年   37202篇
  2011年   49720篇
  2010年   44242篇
  2009年   52448篇
  2008年   46190篇
  2007年   43167篇
  2006年   46194篇
  2005年   40497篇
  2004年   42260篇
  2003年   42104篇
  2002年   41108篇
  2001年   38264篇
  2000年   36539篇
  1999年   35823篇
  1998年   47700篇
  1997年   40810篇
  1996年   36702篇
  1995年   31592篇
  1994年   29499篇
  1993年   29264篇
  1992年   26453篇
  1991年   23535篇
  1990年   23842篇
  1989年   22822篇
  1988年   21303篇
  1987年   19607篇
  1986年   19005篇
  1985年   22240篇
  1984年   22378篇
  1983年   20365篇
  1982年   19315篇
  1981年   19408篇
  1980年   17966篇
  1979年   18550篇
  1978年   17786篇
  1977年   17451篇
  1976年   18380篇
  1975年   15999篇
  1974年   15554篇
  1973年   15618篇
  1972年   13056篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
31.
32.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  相似文献   
33.
34.
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   
35.
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   
36.
37.
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   
38.
39.

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   
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