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   1482990篇
  免费   27484篇
  国内免费   7024篇
电工技术   34581篇
综合类   6594篇
化学工业   268968篇
金属工艺   64212篇
机械仪表   42630篇
建筑科学   45766篇
矿业工程   11520篇
能源动力   50228篇
轻工业   110204篇
水利工程   14901篇
石油天然气   37858篇
武器工业   197篇
无线电   196363篇
一般工业技术   281882篇
冶金工业   148559篇
原子能技术   34002篇
自动化技术   169033篇
  2021年   15609篇
  2020年   11922篇
  2019年   14649篇
  2018年   16050篇
  2017年   15481篇
  2016年   21434篇
  2015年   17487篇
  2014年   28835篇
  2013年   87867篇
  2012年   35124篇
  2011年   47457篇
  2010年   42542篇
  2009年   51067篇
  2008年   44309篇
  2007年   41508篇
  2006年   44214篇
  2005年   39004篇
  2004年   41141篇
  2003年   41044篇
  2002年   40093篇
  2001年   36839篇
  2000年   35349篇
  1999年   34117篇
  1998年   40023篇
  1997年   36248篇
  1996年   33429篇
  1995年   29676篇
  1994年   27970篇
  1993年   27820篇
  1992年   26072篇
  1991年   23103篇
  1990年   23410篇
  1989年   22417篇
  1988年   20958篇
  1987年   19302篇
  1986年   18686篇
  1985年   21991篇
  1984年   22283篇
  1983年   20247篇
  1982年   19201篇
  1981年   19273篇
  1980年   17852篇
  1979年   18485篇
  1978年   17700篇
  1977年   17189篇
  1976年   17735篇
  1975年   15965篇
  1974年   15538篇
  1973年   15589篇
  1972年   13040篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
261.
262.
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   
263.
264.
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   
265.
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   
266.
267.
268.
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   
269.
270.

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   
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