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   369368篇
  免费   3927篇
  国内免费   840篇
电工技术   6268篇
综合类   2584篇
化学工业   55310篇
金属工艺   18422篇
机械仪表   14901篇
建筑科学   8351篇
矿业工程   2512篇
能源动力   6721篇
轻工业   28564篇
水利工程   4305篇
石油天然气   6451篇
武器工业   32篇
无线电   38252篇
一般工业技术   73631篇
冶金工业   51953篇
原子能技术   6949篇
自动化技术   48929篇
  2021年   2115篇
  2019年   2032篇
  2018年   22341篇
  2017年   21851篇
  2016年   15832篇
  2015年   3144篇
  2014年   4179篇
  2013年   10399篇
  2012年   10738篇
  2011年   22715篇
  2010年   19755篇
  2009年   17382篇
  2008年   18426篇
  2007年   21000篇
  2006年   7059篇
  2005年   10038篇
  2004年   8364篇
  2003年   7961篇
  2002年   6678篇
  2001年   5707篇
  2000年   5650篇
  1999年   5374篇
  1998年   12643篇
  1997年   8934篇
  1996年   6919篇
  1995年   5354篇
  1994年   4777篇
  1993年   4656篇
  1992年   3691篇
  1991年   3435篇
  1990年   3594篇
  1989年   3475篇
  1988年   3312篇
  1987年   2895篇
  1986年   2933篇
  1985年   3376篇
  1984年   3219篇
  1983年   2892篇
  1982年   2738篇
  1981年   2822篇
  1980年   2723篇
  1979年   2624篇
  1978年   2686篇
  1977年   2950篇
  1976年   3809篇
  1975年   2368篇
  1974年   2242篇
  1973年   2377篇
  1972年   1970篇
  1971年   1859篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Protection of Metals and Physical Chemistry of Surfaces - In this work, a universal sorbent has been obtained that works according to the mechanisms of chemisorption and adsorption by impregnating...  相似文献   
72.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
73.
Theoretical Foundations of Chemical Engineering - Using chemical and XRD phase analysis, along with electron microscopy, the hydrolytic processing of metallic bismuth into high-purity citrate has...  相似文献   
74.
Russian Engineering Research - Improvement in the wear resistance of plunger-pump rods is considered. Hardening by high-frequency current is proposed.  相似文献   
75.
76.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms.  相似文献   
77.
78.
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection.  相似文献   
79.
80.
Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials.  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