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   590篇
  免费   20篇
  国内免费   4篇
电工技术   5篇
综合类   2篇
化学工业   125篇
金属工艺   27篇
机械仪表   19篇
建筑科学   14篇
矿业工程   1篇
能源动力   26篇
轻工业   33篇
水利工程   2篇
石油天然气   4篇
无线电   38篇
一般工业技术   111篇
冶金工业   127篇
原子能技术   4篇
自动化技术   76篇
  2023年   8篇
  2022年   15篇
  2021年   16篇
  2020年   17篇
  2019年   17篇
  2018年   18篇
  2017年   19篇
  2016年   19篇
  2015年   17篇
  2014年   19篇
  2013年   38篇
  2012年   26篇
  2011年   26篇
  2010年   23篇
  2009年   32篇
  2008年   18篇
  2007年   16篇
  2006年   12篇
  2005年   11篇
  2004年   12篇
  2003年   10篇
  2002年   9篇
  2001年   5篇
  2000年   9篇
  1999年   16篇
  1998年   14篇
  1997年   4篇
  1996年   20篇
  1995年   12篇
  1994年   4篇
  1993年   11篇
  1992年   13篇
  1991年   9篇
  1990年   9篇
  1989年   9篇
  1988年   8篇
  1987年   11篇
  1986年   7篇
  1985年   4篇
  1984年   6篇
  1983年   3篇
  1982年   3篇
  1981年   6篇
  1980年   3篇
  1979年   8篇
  1978年   4篇
  1976年   7篇
  1971年   2篇
  1965年   1篇
  1964年   1篇
排序方式: 共有614条查询结果,搜索用时 15 毫秒
1.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
2.
Xanthohumol (XH) is an important prenylated flavonoid that is found within the inflorescence of Humulus lupulus L. (Hop plant). XH is an important ingredient in beer and is considered a significant bioactive agent due to its diverse medicinal applications, which include anti-inflammatory, antimicrobial, antioxidant, immunomodulatory, antiviral, antifungal, antigenotoxic, antiangiogenic, and antimalarial effects as well as strong anticancer activity towards various types of cancer cells. XH acts as a wide ranging chemopreventive and anticancer agent, and its isomer, 8-prenylnaringenin, is a phytoestrogen with strong estrogenic activity. The present review focuses on the bioactivity of XH on various types of cancers and its pharmacokinetics. In this paper, we first highlight, in brief, the history and use of hops and then the chemistry and structure–activity relationship of XH. Lastly, we focus on its prominent effects and mechanisms of action on various cancers and its possible use in cancer prevention and treatment. Considering the limited number of available reviews on this subject, our goal is to provide a complete and detailed understanding of the anticancer effects of XH against different cancers.  相似文献   
3.
4.
5.
6.
7.
Real-time payments for mobile IP   总被引:2,自引:0,他引:2  
The mobile IP protocol has evolved from providing mobility support for portable computers to support for wireless handheld devices with high mobility patterns. A new category of micromobility protocols has been proposed to deal with the increased signaling loads that will be generated with large populations of such devices on a network. We argue that the authentication schemes presently employed in these networks do not scale well for large numbers of nodes, and that the lack of accounting procedures prevents the mass deployment of these networks. We envisage that future access networks will be operated by independent service providers, who will charge users for access to services in the fixed network but may not have long-term contractual relationships with them. These access networks may also employ a variety of micromobility protocols for fast handover support. We present a scheme based on hash chains, which allows for fast authentication of datagrams for secure updating of router entries within the access network, and real-time accounting of network usage by mobile nodes. Such a system will alleviate problems of fraud in mobile networks and eliminate the need for interoperator billing agreements.  相似文献   
8.
9.
The occurrence of a significant amount of age hardening, due to the precipitation of the γ′ phase, has been demonstrated in the nickel-copper base alloy MONEL K 500. The microstructure of the precipitation-hardened and deformed alloy has been examined in peak-aged underaged and overaged conditions. An attempt has been made to compare the observed increments in strength in these three aged conditions to those predicted on the basis of relevant theoretical models.  相似文献   
10.
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