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   504845篇
  免费   6006篇
  国内免费   1815篇
电工技术   9472篇
综合类   2674篇
化学工业   70262篇
金属工艺   23014篇
机械仪表   19397篇
建筑科学   12077篇
矿业工程   2409篇
能源动力   12038篇
轻工业   38466篇
水利工程   4957篇
石油天然气   5403篇
武器工业   20篇
无线电   64044篇
一般工业技术   102082篇
冶金工业   76374篇
原子能技术   8146篇
自动化技术   61831篇
  2021年   2737篇
  2019年   2673篇
  2018年   23223篇
  2017年   22854篇
  2016年   16643篇
  2015年   4121篇
  2014年   5824篇
  2013年   17608篇
  2012年   13559篇
  2011年   27058篇
  2010年   23186篇
  2009年   21758篇
  2008年   23077篇
  2007年   25594篇
  2006年   11199篇
  2005年   14099篇
  2004年   12155篇
  2003年   12011篇
  2002年   9956篇
  2001年   9296篇
  2000年   8527篇
  1999年   8909篇
  1998年   21648篇
  1997年   15451篇
  1996年   12056篇
  1995年   9664篇
  1994年   8738篇
  1993年   8488篇
  1992年   6422篇
  1991年   6284篇
  1990年   6039篇
  1989年   5752篇
  1988年   5528篇
  1987年   4782篇
  1986年   4708篇
  1985年   5346篇
  1984年   4893篇
  1983年   4654篇
  1982年   4347篇
  1981年   4222篇
  1980年   4017篇
  1979年   3909篇
  1978年   3630篇
  1977年   4384篇
  1976年   5792篇
  1975年   3110篇
  1974年   2957篇
  1973年   2943篇
  1972年   2510篇
  1971年   2169篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...  相似文献   
2.
Journal of Materials Science: Materials in Electronics - In the recent years, metal oxides have attracted more interest for researchers because of their applications in energy and...  相似文献   
3.
4.
The micro-powder injection molding (micro-PIM) process has the potential to bridge the gap between the design and manufacturing of micro-components that are often used in small and handy devices. Numerical modeling helps to analyze and overcome various difficulties of micro-PIM. In the present work, a numerical model is developed to predict the powder–binder separation (a common defect in PIM and especially severe in micro-PIM) during the injection of an alumina feedstock. A powder–binder separation criterion is proposed dealing with applied injection pressure and friction force between the powder and binder. An indirect comparison of feedstock travel time between two locations is used to validate the model. The predicted segregation from the simulated result is supported by a qualitative experimental measurement. The developed model can be used to optimize injection parameters to get a defect-free product.  相似文献   
5.

We review the literature describing the use of interleaves to increase interlaminar fracture toughness in fibre-reinforced polymer composites and hence to improve damage tolerance. From an analysis of data provided in the literature from the use of microfibre and nanofibre interleaves, we show that the performance of these widely researched systems is clearly differentiated when plotted against the mean coverage of the interleaf. Using a simple analysis, we suggest that this can be attributed to the influence of their porous architectures on the infusion of resin. We show also that the superior toughening performance of microfibre interleaves is only weakly influenced by the choice of fibre. We find also that the inclusion of carbon nanotubes within interleaves to deliver multifunctional composites can be optimised by using a hybrid system with microfibres.

Graphical abstract
  相似文献   
6.
Telecommunication Systems - Internet of Things (IoT) has changed the way people live by transforming everything into smart systems. Wireless Sensor Network (WSN) forms an important part of IoT....  相似文献   
7.
Chemistry and Technology of Fuels and Oils - This article considers the alternatives for treatment of the raffinate produced at a unit for the extraction of benzene-containing fractions and the...  相似文献   
8.
Novel inks were formulated by dissolving polycaprolactone (PCL), a hydrophobic polymer, in organic solvent systems; polyethylene oxide (PEO) was incorporated to extend the range of hydrophilicity of the system. Hydroxyapatite (HAp) with a weight ratio of 55–85% was added to the polymer-based solution to mimic the material composition of natural bone tissue. The direct ink writing (DIW) technique was applied to extrude the formulated inks to fabricate the predesigned tissue scaffold structures; the influence of HAp concentration was investigated. The results indicate that in comparison to other inks containing HAp (55%, 75%, and 85%w/w), the ink containing 65% w/w HAp had faster ink recovery behavior; the fabricated scaffold had a rougher surface as well as better mechanical properties and wettability. It is noted that the 65% w/w HAp concentration is similar to the inorganic composition of natural bone tissue. The elastic modulus values of PCL/PEO/HAp scaffolds were in the range of 4–12 MPa; the values were dependent on the HAp concentration. Furthermore, vancomycin as a model drug was successfully encapsulated in the PCL/PEO/HAp composite scaffold for drug release applications. This paper presents novel drug-loaded PCL/PEO/HAp inks for 3D scaffold fabrication using the DIW printing technique for potential bone scaffold applications.  相似文献   
9.
Wireless Personal Communications - Wireless sensor network is gaining popularity due to its large-scale deployment in Internet of Things. The constraints of resources influence the protocol design...  相似文献   
10.
Chemistry and Technology of Fuels and Oils - The review examines biomass of animal origin in terms of a potential renewable raw material for obtaining CO2-neutral fuel unaffecting the carbon...  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