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   202914篇
  免费   979篇
  国内免费   509篇
电工技术   3498篇
综合类   180篇
化学工业   29210篇
金属工艺   8071篇
机械仪表   6088篇
建筑科学   4855篇
矿业工程   1304篇
能源动力   5199篇
轻工业   17391篇
水利工程   2381篇
石油天然气   4158篇
武器工业   8篇
无线电   23223篇
一般工业技术   40254篇
冶金工业   37365篇
原子能技术   5269篇
自动化技术   15948篇
  2021年   1684篇
  2019年   1718篇
  2018年   2590篇
  2017年   2655篇
  2016年   2831篇
  2015年   1823篇
  2014年   3110篇
  2013年   8979篇
  2012年   5081篇
  2011年   7076篇
  2010年   5620篇
  2009年   6376篇
  2008年   6510篇
  2007年   6538篇
  2006年   5602篇
  2005年   5253篇
  2004年   5020篇
  2003年   4912篇
  2002年   4571篇
  2001年   4675篇
  2000年   4599篇
  1999年   4752篇
  1998年   11421篇
  1997年   8160篇
  1996年   6444篇
  1995年   4691篇
  1994年   4291篇
  1993年   4089篇
  1992年   3231篇
  1991年   3084篇
  1990年   2879篇
  1989年   2967篇
  1988年   2842篇
  1987年   2409篇
  1986年   2316篇
  1985年   2724篇
  1984年   2511篇
  1983年   2351篇
  1982年   2100篇
  1981年   2210篇
  1980年   2037篇
  1979年   2129篇
  1978年   2125篇
  1977年   2372篇
  1976年   3192篇
  1975年   1837篇
  1974年   1766篇
  1973年   1774篇
  1972年   1443篇
  1971年   1339篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A wideband wattmeter for measuring active power over a frequency range of dc to 500 kHz is described. The wattmeter is based on the three-voltmeter method in which three rms voltage measurements are used to calculate power. The wattmeter active power uncertainty is estimated to be within 0.03% from dc to 20 kHz and within 1.5% to 500 kHz  相似文献   
62.
Recent studies have identified molecules that interact with integrins and appear to participate in the signaling pathways that regulate integrin adhesiveness. Clues provided by studies of these molecules point to the integration by integrins of signal transduction pathways implicated in cell division and activation.  相似文献   
63.
MineSet aids knowledge discovery and supports decision making based on relational data. It uses visualization and data mining to arrive at interesting results. Providing diverse visualization tools lets users choose the most appropriate method for a given problem. The client-server architecture performs most of the computationally intensive tasks on a server, while the processed results return to the client for visualization. The paper discusses MineSet database visualization and data mining visualization  相似文献   
64.
65.
A simplified flash EEPROM process was developed using high-temperature LPCVD oxide both as flash cells interpoly dielectrics and as peripheral transistors gate oxide (decoding logic). An O2 anneal at 850°C lowers charge trapping and interface trap density induced by Fowler-Nordheim injection. However, electron trapping remains slightly higher than with dry thermal oxide. Similar memory charge loss and write-erase endurance are obtained as for ONO-insulated cells. HTO thus proves to have the required quality and reliability to be used in flash EEPROMs  相似文献   
66.
A value-based test is presented for economic screening of electric utility demand-side management (DSM) programs. The widely used least cost test is valid if the programs do not alter the amount or value of energy services provided to customers. But, in general, DSM programs have such effects and, as a result, the value consumers receive is changed. A more general economic efficiency test, the most value test, provides a practical method for considering the effects of DSM on customer value. The version presented allows for multiple load periods and can account for rate impacts on several customer classes. Four typical DSM programs are evaluated as illustrations  相似文献   
67.
For multiuser packet communications with unpredictable user demands (e.g., in a local or metropolitan area network), coordination and control of access to the frequency-division multiplexing (FDM) channels are difficult. B. Glance (J. Lightwave Technol., vol.10, pp.1323-1328, Sep 1992) proposed using a simple protection-against-collision (PAC) circuit to solve this media access problem and achieve full optical connectivity. The PAC system has the potential to interconnect hundreds of ports, each transmitting at several gigabits per second. Performance aspects of the PAC optical packet network are discussed here. The delay-throughout performance of this network is analyzed for uniform traffic patterns. The results show that in geographically distributed applications the maximum achievable throughput (normalized to the transmission rate) is typically between 0.4 and 0.5 per channel. In a centralized switch the (normalized) maximum achievable throughput can approach 0.8 per channel  相似文献   
68.
Bowers  B. 《IEE Review》1995,41(6):239
Of all the products of electrical technology, none has made a more profound difference to our way of life than the humble light bulb. The author describes the history of the light bulb from the time it was introduced and started to replace gas lamps to the present day. In particular the author discusses the early developments in arc lighting and incandescent filament lamps. The author also discusses the introduction of mercury vapour lamps, fluorescent lamps, and evacuation of the lamps  相似文献   
69.
70.
Giving a case example of an male adolescent with radical right-wing attitudes, the lack of male identification as well as in unresolved dyadic fixation to the mother will be shown. Though the radical right-wing orientation the adolescent tries on the basis of a phallic narcissistic conflict to establish bordes against an unresolved dyadic fixation to his mother.  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