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   16825篇
  免费   1246篇
  国内免费   691篇
电工技术   849篇
技术理论   7篇
综合类   1476篇
化学工业   2961篇
金属工艺   335篇
机械仪表   543篇
建筑科学   2929篇
矿业工程   816篇
能源动力   828篇
轻工业   1511篇
水利工程   1094篇
石油天然气   453篇
武器工业   100篇
无线电   743篇
一般工业技术   2043篇
冶金工业   957篇
原子能技术   156篇
自动化技术   961篇
  2024年   46篇
  2023年   253篇
  2022年   432篇
  2021年   580篇
  2020年   564篇
  2019年   456篇
  2018年   403篇
  2017年   494篇
  2016年   516篇
  2015年   496篇
  2014年   1251篇
  2013年   1197篇
  2012年   1289篇
  2011年   1260篇
  2010年   1020篇
  2009年   974篇
  2008年   799篇
  2007年   1095篇
  2006年   974篇
  2005年   819篇
  2004年   703篇
  2003年   543篇
  2002年   506篇
  2001年   372篇
  2000年   332篇
  1999年   259篇
  1998年   171篇
  1997年   160篇
  1996年   121篇
  1995年   107篇
  1994年   82篇
  1993年   63篇
  1992年   56篇
  1991年   49篇
  1990年   45篇
  1989年   39篇
  1988年   26篇
  1987年   17篇
  1986年   16篇
  1985年   20篇
  1984年   26篇
  1983年   19篇
  1982年   39篇
  1981年   7篇
  1979年   8篇
  1976年   8篇
  1965年   5篇
  1961年   6篇
  1960年   6篇
  1958年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The NIST 0:45 reflectometer measures the spectral reflectance factor at an influx angle of 0° and an efflux angle of 45° of colored, nonfluorescent specimens at room temperature, with widths ranging from 3 to 10 cm and heights from 3 to 20 cm and with an uncertainty of less than 0.5 in color difference units. Published in 2008 by John Wiley & Sons, Inc. Col Res Appl, 33, 94–99, 2008  相似文献   
92.
Sets of color tiles are available from the National Institute of Standards and Technology calibrated using the NIST 0:45 Reflectometer. The uncertainties associated with the measured values for the color tiles are an indispensable component of the calibration report that accompanies these tiles. A systematic, analytical approach developed previously was applied to the particular case of the reference instrument and color tile set, taking into account the operation and characteristics of the instrument and the spectral properties of the set. The primary sources of uncertainty were identified, and the resulting uncertainties in the color space values L*, a*, and b* were determined. In general, the uncertainties are lowest for those color tiles whose reflectance factors are nearly constant with wavelength. Published in 2008 by John Wiley & Sons, Inc. Col Res Appl, 33, 100–107, 2008  相似文献   
93.
福州万象商业广场的绿色施工技术   总被引:1,自引:0,他引:1  
绿色施工包括节能、节地、节材、节水,保护环境和保证职业健康等方面内容,本文介绍福州万象商业广场的绿色施工综合技术。  相似文献   
94.
苏道源 《钢铁研究》2004,32(1):46-48
介绍了武钢热轧厂烟气中残氧量自动监测技术及燃烧工艺试验 ,评述该项技术研究动态 ,指出它对节能降耗和环境保护的作用  相似文献   
95.
Exposure to turbulence, an environmental stimulus, produces behavioral adaptation in the Aplysia siphon-withdrawal response (SWR). The authors show that the duration and spatial extent of turbulence influence adaptation recovery. In terms of duration, recovery in whole animals and reduced preparations (tail, siphon, and CNS) was more rapid after longer exposures to turbulence (10 min) than after briefer exposures (10 s-5 min). In terms of spatial extent, recovery in reduced preparations was more rapid after diffuse turbulence (tail and siphon together) compared with focal turbulence (siphon alone). Furthermore, spatial extent and duration interact: Duration regulates recovery only when turbulence is diffuse. Results suggest that SWR adaptation reflects a composite of cellular processes, including short-term synaptic enhancement in L30 inhibitory interneurons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
Capital cost correlations are given for oil-water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars. To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data.  相似文献   
97.
The broadband integrated services digital networks (B-ISDN) based on asynchronous transfer mode (ATM) technology can support a wide range of applications such as voice, video, still images, and data. Compression techniques increase the effective bandwidth utilization, but the bursty and asynchronous nature of the traffic can still lead to congestion in the network, and degradation of image quality and quality of service (QOS). Some of the features to provide better coding schemes for ATM networks are layered coding, resynchronization, buffering, interleaved schemes, constrained bit rate due to buffers, encapsulation with the RTP or AAL1 for clock recovery, lapped transforms, motion compensation, and optimal bit allocation for coders based on wavelet transforms. We review various techniques forimage and video coding such as transforms, motion compensation, vector quantization, and subband coding. We outline the impact of the cell loss ratio (CLR), delay and cell delay variation (CDV) on video coding: blocking effects, loss of frame synchronization, motion vectors, and vector quantization codewords. The open problems include tuning coding parameters to the available QOS provided by the network.  相似文献   
98.
Electricity is a fundamental requirement for economic growth, and hydro-electric power is often thought to be environmentally benign. However, the construction and operation of many hydro-power dams in Africa have had significant negative impacts on the environment and rural economies. Reduced downstream flooding has destroyed fisheries and starved the floodplain soils of moisture and nutrients. Often the worst-affected areas have no electrification and therefore do not benefit from power generation. New dams which are planned in Kenya and Tanzania have been specifically designed to make flood releases. This will allow electricity to be generated whilst maintaining a dynamic flooding pattern for the short-term economic importance of fisheries and agriculture and the longer-term importance of soil fertility and biodiversity. Involvement of local community representatives in deciding when flood waters should be released on the Phongolo River in South Africa has resulted in substantial benefits to floodplain users.  相似文献   
99.
勘探开发数据管理已经成为当今油气勘探工程不可缺少的重要组成部分,为多学科综合研究提供了工具。本文简要地论述了勘探开发数据管理的背景、含义、现状以及面临的挑战,讨论了相关技术的发展,介绍了POSC标准及其内容,分析了当前数据管理存在的问题,并对未来几年的发展前景作了展望。  相似文献   
100.
Within its Automated Manufacturing Research Facility (AMRF), the U.S. National Bureau of Standards (NBS) is addressing research issues in interface standards for the fully automated factory of the future for the production of small batches of discrete parts. Consisting of robots, machine tools and computers, the AMRF is being integrated using a real-time, sensory-feedback, data-driven hierarchical control architecture. As such, the AMRF is a research tool for investigating the manufacturing enterprise as a system of intelligent machines. This paper: (1) describes the AMRF in terms of its real-time control system architecture; (2) notes the role of symbolic languages, knowledge-representation, sensory-processing and other aspects of artificial intelligence in its development; and (3) speculates on further application of AI in future intelligent manufacturing systems similar in form to the AMRF.  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