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   608839篇
  免费   9744篇
  国内免费   2844篇
电工技术   11939篇
技术理论   5篇
综合类   1501篇
化学工业   94161篇
金属工艺   22783篇
机械仪表   17538篇
建筑科学   16669篇
矿业工程   2435篇
能源动力   15008篇
轻工业   60605篇
水利工程   5600篇
石油天然气   7528篇
武器工业   256篇
无线电   73877篇
一般工业技术   112889篇
冶金工业   113581篇
原子能技术   10024篇
自动化技术   55028篇
  2021年   4635篇
  2019年   4103篇
  2018年   6490篇
  2017年   6526篇
  2016年   7098篇
  2015年   5671篇
  2014年   9163篇
  2013年   27853篇
  2012年   15911篇
  2011年   22164篇
  2010年   17403篇
  2009年   19300篇
  2008年   20800篇
  2007年   21226篇
  2006年   18938篇
  2005年   17262篇
  2004年   16152篇
  2003年   15575篇
  2002年   15261篇
  2001年   15413篇
  2000年   14411篇
  1999年   14801篇
  1998年   33603篇
  1997年   24652篇
  1996年   19322篇
  1995年   14956篇
  1994年   13430篇
  1993年   13049篇
  1992年   9990篇
  1991年   9472篇
  1990年   9213篇
  1989年   8933篇
  1988年   8541篇
  1987年   7214篇
  1986年   7202篇
  1985年   8547篇
  1984年   8162篇
  1983年   7230篇
  1982年   6648篇
  1981年   6800篇
  1980年   6340篇
  1979年   6402篇
  1978年   6033篇
  1977年   6922篇
  1976年   9165篇
  1975年   5175篇
  1974年   4918篇
  1973年   4860篇
  1972年   4008篇
  1971年   3563篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
The proliferating need for sustainability intervention in food grain transportation planning is anchoring the attention of researchers in the interests of stakeholders and environment at large. Uncertainty associated with food grain supply further intensifies the problem steering the need for designing robust, cost-efficient and sustainable models. In line with this, this paper aims to develop a robust and sustainable intermodal transportation model to facilitate single type of food grain commodity shipments while considering procurement uncertainty, greenhouse gas emissions, and intentional hub disruption. The problem is designed as a mixed integer non-linear robust optimisation model on a hub and spoke network for evaluating near optimal shipment quantity, route selection and hub location decisions. The robust optimisation approach considers minimisation of total relative regret associated with total cost subject to several real-time constraints. A version of Particle Swarm Optimisation with Differential Evolution is proposed to tackle the resulting NP-hard problem. The model is tested with two other state-of the art meta-heuristics for small, medium, and large datasets subject to different procurement scenarios inspired from real time food grain operations in Indian context. Finally, the solution is evaluated with respect to total cost, model and solution robustness for all instances.  相似文献   
3.
4.
5.
6.
7.
8.
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   
9.
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   
10.
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