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   251115篇
  免费   3476篇
  国内免费   1019篇
电工技术   4951篇
综合类   422篇
化学工业   34233篇
金属工艺   9521篇
机械仪表   7589篇
建筑科学   5852篇
矿业工程   1003篇
能源动力   7205篇
轻工业   20857篇
水利工程   2260篇
石油天然气   3304篇
武器工业   52篇
无线电   34664篇
一般工业技术   49817篇
冶金工业   48670篇
原子能技术   5205篇
自动化技术   20005篇
  2021年   2197篇
  2020年   1644篇
  2019年   1998篇
  2018年   3359篇
  2017年   3407篇
  2016年   3495篇
  2015年   2338篇
  2014年   4149篇
  2013年   11713篇
  2012年   6485篇
  2011年   8859篇
  2010年   7159篇
  2009年   8100篇
  2008年   8576篇
  2007年   8462篇
  2006年   7513篇
  2005年   6646篇
  2004年   6384篇
  2003年   6591篇
  2002年   5810篇
  2001年   6189篇
  2000年   5516篇
  1999年   6062篇
  1998年   16200篇
  1997年   11118篇
  1996年   8480篇
  1995年   6559篇
  1994年   5883篇
  1993年   5795篇
  1992年   4091篇
  1991年   3982篇
  1990年   3829篇
  1989年   3594篇
  1988年   3508篇
  1987年   2962篇
  1986年   2904篇
  1985年   3157篇
  1984年   2884篇
  1983年   2778篇
  1982年   2591篇
  1981年   2493篇
  1980年   2419篇
  1979年   2263篇
  1978年   2083篇
  1977年   2566篇
  1976年   3514篇
  1975年   1728篇
  1974年   1704篇
  1973年   1633篇
  1972年   1445篇
排序方式: 共有10000条查询结果,搜索用时 78 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.
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   
6.
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   
7.
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