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   52359篇
  免费   2972篇
  国内免费   167篇
电工技术   729篇
综合类   308篇
化学工业   12165篇
金属工艺   1053篇
机械仪表   1221篇
建筑科学   1842篇
矿业工程   147篇
能源动力   1806篇
轻工业   8590篇
水利工程   536篇
石油天然气   264篇
武器工业   8篇
无线电   3544篇
一般工业技术   7741篇
冶金工业   8107篇
原子能技术   371篇
自动化技术   7066篇
  2024年   95篇
  2023年   341篇
  2022年   1173篇
  2021年   2144篇
  2020年   1203篇
  2019年   1341篇
  2018年   1559篇
  2017年   1663篇
  2016年   1705篇
  2015年   1304篇
  2014年   1863篇
  2013年   3135篇
  2012年   2851篇
  2011年   3430篇
  2010年   2454篇
  2009年   2545篇
  2008年   2297篇
  2007年   2100篇
  2006年   1631篇
  2005年   1577篇
  2004年   1554篇
  2003年   1473篇
  2002年   1348篇
  2001年   1112篇
  2000年   825篇
  1999年   828篇
  1998年   2581篇
  1997年   1736篇
  1996年   1238篇
  1995年   819篇
  1994年   647篇
  1993年   709篇
  1992年   337篇
  1991年   372篇
  1990年   322篇
  1989年   273篇
  1988年   299篇
  1987年   218篇
  1986年   239篇
  1985年   247篇
  1984年   183篇
  1983年   136篇
  1982年   145篇
  1981年   154篇
  1980年   155篇
  1979年   124篇
  1978年   102篇
  1977年   173篇
  1976年   273篇
  1975年   104篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
31.
Debittered trub (brewing waste) is an important source of protein source (70.26%). Trub and whey protein were used for 5% protein enrichment of ice cream frozen by liquid nitrogen. Three formulations were elaborated: ice cream standard (ICS), ice cream with whey protein (ICW) and ice cream with trub (ICT). Chemical composition, rheological properties, texture, overrun, melting rate, scanning electron microscopy and a sensorial test were performed. Results showed that ICT presented a higher viscosity, obtained on the upward curve up to 6.76 Pa s−1, consistency index (22.96 (Pa s−1)n), hysteresis area (140.40 mPa s−1) and hardness (31113.33 g) but a lower melting rate (0.38 g min−1), overrun (13.92%) and sensorial acceptability than the other formulations. The addition of trub debittered for protein enrichment improved ice cream properties and demonstrated that it could be used as a food ingredient.  相似文献   
32.
33.
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y...  相似文献   
34.
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   
35.
36.
The purpose of this research was to study the capacity of emulsions containing saturated monoglyceride self‐assembly structures to deliver omega‐3 fatty acids in fresh soft cheese. To this aim, fortified emulsions containing different ratios of milk, saturated monoglycerides (MGs) and cod liver oil were added to milk before cheese‐making. These emulsions were characterised by distinct microstructural features observed by polarised light microscopy and apparent viscosity values. The omega‐3 delivery performance of MG emulsions highlighted that this strategy allowed a good retention of the omega‐3‐rich oil in the curd (up to 75%). The fortified cheeses showed yield value and fat content higher than those of control samples. The enriched cheese showed hardness and cohesiveness obtained by texture profile analysis similar to those of the unfortified product. Only a slight decrease in gumminess was detected in fortified cheese.  相似文献   
37.
38.
39.
40.
ABSTRACT

This paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR. In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs.  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