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   457923篇
  免费   6714篇
  国内免费   1665篇
电工技术   8759篇
综合类   1422篇
化学工业   69413篇
金属工艺   16627篇
机械仪表   14133篇
建筑科学   13265篇
矿业工程   1521篇
能源动力   11551篇
轻工业   45747篇
水利工程   3964篇
石油天然气   3092篇
武器工业   26篇
无线电   61315篇
一般工业技术   84740篇
冶金工业   80076篇
原子能技术   6034篇
自动化技术   44617篇
  2022年   4700篇
  2021年   6553篇
  2020年   4770篇
  2019年   6109篇
  2018年   5035篇
  2017年   4637篇
  2016年   4594篇
  2015年   3826篇
  2014年   6133篇
  2013年   20125篇
  2012年   10921篇
  2011年   16402篇
  2010年   12593篇
  2009年   14280篇
  2008年   14737篇
  2007年   15095篇
  2006年   13649篇
  2005年   12916篇
  2004年   13625篇
  2003年   13200篇
  2002年   12919篇
  2001年   12690篇
  2000年   11254篇
  1999年   11529篇
  1998年   24741篇
  1997年   18252篇
  1996年   14378篇
  1995年   11396篇
  1994年   10332篇
  1993年   9774篇
  1992年   7526篇
  1991年   7059篇
  1990年   6706篇
  1989年   6509篇
  1988年   6184篇
  1987年   5141篇
  1986年   5170篇
  1985年   6287篇
  1984年   5818篇
  1983年   5148篇
  1982年   4767篇
  1981年   4653篇
  1980年   4370篇
  1979年   4209篇
  1978年   3999篇
  1977年   4828篇
  1976年   6310篇
  1975年   3333篇
  1974年   3187篇
  1973年   2989篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
2.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
3.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  相似文献   
4.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
5.
6.
7.
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,...  相似文献   
8.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  相似文献   
9.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
10.
Objective

To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated.

Materials and methods

Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T1 mapping and visual control. Signal properties of the emulsifiers were investigated by 1H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T1 and T2) and ADC values of aqueous solutions.

Results

Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T1 maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in 1H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r1,lecithin = 0.11 wt.%−1 s−1, r2,lecithin = 0.57 wt.%−1 s−1) and ADC value (Δ(ADC)lecithin =  − 0.18 × 10–3 mm2/s⋅wt.%) with increasing concentration.

Conclusion

Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.

  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