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   706998篇
  免费   10491篇
  国内免费   2084篇
电工技术   13164篇
综合类   827篇
化学工业   104658篇
金属工艺   27012篇
机械仪表   20936篇
建筑科学   17189篇
矿业工程   3094篇
能源动力   19089篇
轻工业   61592篇
水利工程   7003篇
石油天然气   12005篇
武器工业   100篇
无线电   83554篇
一般工业技术   135806篇
冶金工业   138559篇
原子能技术   14055篇
自动化技术   60930篇
  2021年   6175篇
  2020年   4539篇
  2019年   5898篇
  2018年   10016篇
  2017年   9882篇
  2016年   10356篇
  2015年   7105篇
  2014年   11837篇
  2013年   32247篇
  2012年   18813篇
  2011年   25954篇
  2010年   20453篇
  2009年   22965篇
  2008年   23860篇
  2007年   23476篇
  2006年   20700篇
  2005年   18971篇
  2004年   18262篇
  2003年   17976篇
  2002年   17082篇
  2001年   17069篇
  2000年   16082篇
  1999年   16904篇
  1998年   42927篇
  1997年   30179篇
  1996年   23238篇
  1995年   17576篇
  1994年   15370篇
  1993年   15078篇
  1992年   11150篇
  1991年   10390篇
  1990年   10141篇
  1989年   9740篇
  1988年   9129篇
  1987年   8122篇
  1986年   7989篇
  1985年   9005篇
  1984年   8443篇
  1983年   7516篇
  1982年   7096篇
  1981年   7240篇
  1980年   6835篇
  1979年   6668篇
  1978年   6344篇
  1977年   7635篇
  1976年   9809篇
  1975年   5618篇
  1974年   5352篇
  1973年   5488篇
  1972年   4437篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
92.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models.  相似文献   
93.
94.
95.
96.
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   
97.
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   
98.
99.
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   
100.
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