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   586682篇
  免费   7353篇
  国内免费   1242篇
电工技术   11365篇
综合类   1474篇
化学工业   90301篇
金属工艺   24611篇
机械仪表   19451篇
建筑科学   13456篇
矿业工程   4790篇
能源动力   14574篇
轻工业   46304篇
水利工程   7293篇
石油天然气   15832篇
武器工业   50篇
无线电   64008篇
一般工业技术   119533篇
冶金工业   97990篇
原子能技术   14878篇
自动化技术   49367篇
  2021年   7148篇
  2020年   5463篇
  2019年   6850篇
  2018年   9866篇
  2017年   9822篇
  2016年   10049篇
  2015年   6211篇
  2014年   10497篇
  2013年   26620篇
  2012年   16144篇
  2011年   22352篇
  2010年   17932篇
  2009年   19877篇
  2008年   19582篇
  2007年   19277篇
  2006年   16904篇
  2005年   15452篇
  2004年   15503篇
  2003年   14902篇
  2002年   14004篇
  2001年   13215篇
  2000年   12262篇
  1999年   11924篇
  1998年   27579篇
  1997年   20001篇
  1996年   15375篇
  1995年   12253篇
  1994年   11155篇
  1993年   10833篇
  1992年   8549篇
  1991年   8243篇
  1990年   8159篇
  1989年   7988篇
  1988年   7652篇
  1987年   6851篇
  1986年   6716篇
  1985年   7537篇
  1984年   6790篇
  1983年   6558篇
  1982年   5879篇
  1981年   5957篇
  1980年   5683篇
  1979年   5769篇
  1978年   5787篇
  1977年   6318篇
  1976年   7769篇
  1975年   5218篇
  1974年   4976篇
  1973年   5025篇
  1972年   4335篇
排序方式: 共有10000条查询结果,搜索用时 28 毫秒
1.
Photonic Network Communications - In the present work, a high-speed optical encoder is proposed based on two-dimensional photonic crystal ring resonator using coupled mode theory and resonance...  相似文献   
2.
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   
3.
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...  相似文献   
4.
Journal of Materials Science: Materials in Electronics - Non-volatile organic memory devices were fabricated using polystyrene sulfonate (PSS)?+?nitrogen-doped multi-walled carbon...  相似文献   
5.
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   
6.
Journal of Materials Science: Materials in Electronics - A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium...  相似文献   
7.
Journal of Engineering Physics and Thermophysics - The generalized nonlocal thermoelastic model in the context of Eringen’s nonlocal elasticity is applied to investigate the...  相似文献   
8.
This study was conducted to evaluate the effect of red-wine grape pomaces on the quality and sensory attributes of beef hamburger patties. Both phenolic content and antioxidant activity were assessed using Syrah, Merlot and Cabernet Sauvignon pomaces. Following the assessment, hamburger patties were prepared with Merlot pomace at 0%, 2% and 4% for the patty quality and sensory attributes. Grape seeds possessed significantly higher phenolics and antioxidant activities over the seedless pomace (P < 0.05), whereas no significant difference was found for phenolics and antioxidant activities within the seeds and seedless pomaces. The patty pH decreased as the pomace was added for 2% and 4%. Colour values (L*, a* and b*) of patties lowered as the pomace was added. Allo-Kramer shear force and hardness values increased while cooking yield decreased (P < 0.05) with the addition of pomace. No significant difference between control and Merlot patties was found for flavour, juiciness and colour, whereas lower sensory attributes were observed for texture, taste and overall acceptability. It is observed that the addition of fermented red-wine grape pomace provides hamburger patties with health promoting factors such as antioxidant and other functional components, but it also provided darker, sourer and lower cooking yield.  相似文献   
9.

Real-time continuous and remote health monitoring has become widespread due to the developments in Wireless body area networks (WBANs). Based on the criticality of health data to be transmitted, regular healthcare data and critical emergency health data must be provided differential service. In this paper, we consider the beyond WBAN communication in a system comprising multiple WBANs with different quality of service (QoS) requirements and multiple access points (APs), and propose two hybrid approaches for resource allocation. In the first approach, the AP association to the WBANs and channel allocation to the APs are done jointly and is modelled as an optimization problem, which is computationally complex and it also requires global network information. In order to reduce the involvement of APs in making decisions for resource allocations of WBANs, the problem is reformulated as a Stackelberg game with price update, which guarantees QoS of the critical users. A learning based algorithm, namely distributed learning for Pareto optimality, is used by the normal users, in this second approach. The performance of both the proposed approaches are evaluated and compared, in terms of the throughput of the critical and normal users as well as the QoS guarantee of the critical users.

  相似文献   
10.
Inorganic Materials - We have studied the effect of annealing on the chemical and physical properties of mineral-like host matrices for immobilization of the rare-earth–actinide fraction from...  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