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   597126篇
  免费   8674篇
  国内免费   1747篇
电工技术   10930篇
综合类   595篇
化学工业   92602篇
金属工艺   21850篇
机械仪表   17600篇
建筑科学   15763篇
矿业工程   2184篇
能源动力   14874篇
轻工业   60276篇
水利工程   5309篇
石油天然气   6771篇
武器工业   45篇
无线电   72582篇
一般工业技术   110612篇
冶金工业   112162篇
原子能技术   10443篇
自动化技术   52949篇
  2021年   4387篇
  2019年   4113篇
  2018年   6772篇
  2017年   6778篇
  2016年   7293篇
  2015年   5287篇
  2014年   8807篇
  2013年   27154篇
  2012年   14837篇
  2011年   20970篇
  2010年   16315篇
  2009年   18482篇
  2008年   19595篇
  2007年   20044篇
  2006年   17816篇
  2005年   16311篇
  2004年   15758篇
  2003年   15316篇
  2002年   15022篇
  2001年   14975篇
  2000年   14077篇
  1999年   14508篇
  1998年   33600篇
  1997年   24373篇
  1996年   19093篇
  1995年   14868篇
  1994年   13226篇
  1993年   12799篇
  1992年   9853篇
  1991年   9282篇
  1990年   9151篇
  1989年   8741篇
  1988年   8346篇
  1987年   7128篇
  1986年   7128篇
  1985年   8557篇
  1984年   8035篇
  1983年   7078篇
  1982年   6653篇
  1981年   6679篇
  1980年   6384篇
  1979年   6142篇
  1978年   5940篇
  1977年   6921篇
  1976年   9225篇
  1975年   5027篇
  1974年   4833篇
  1973年   4852篇
  1972年   3945篇
  1971年   3524篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
51.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  相似文献   
52.
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st  相似文献   
53.
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   
54.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  相似文献   
55.
Journal of Communications Technology and Electronics - Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave...  相似文献   
56.
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   
57.
The Fourth Industrial Revolution – also known as Industry 4.0 (i4.0) – comprises the digitalisation of the industrial sector. This paper uses the theoretical lens of supply chain innovation (SCI) to investigate the implications of i4.0 on supply chain management. For these purposes, the method of structured content analysis is applied to more than 200 use cases of i4.0-enabled SCI introduced by both established and startup companies. i4.0-enabled SCI manifests along three dimensions: process, technology, and business architecture. The key findings of this study can be summarised as follows: first, i4.0-enabled SCI extends the initial focus on productivity improvements in SC processes towards scalability and flexibility. Second, extant i4.0 solutions rely mostly on analytics and smart things while omitting smart people technology and the human-centric approach associated with the i4.0 paradigm. Third, established companies adopt i4.0 merely to sustain their existing business architectures while startup companies radically change their operating models, relying heavily on data analytics and the platform economy. Consequently, established companies pursue a problem-driven, engineering-based approach to SCI while startup companies follow an ‘asset-light’, business-driven approach. Lastly, there are two distinct approaches to digitalising operational SC processes: platform-based crowdsourcing of standard processes and on-demand provision of customised services.  相似文献   
58.
59.
60.
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