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   480845篇
  免费   4497篇
  国内免费   1030篇
电工技术   8247篇
综合类   247篇
化学工业   76052篇
金属工艺   23776篇
机械仪表   16472篇
建筑科学   10286篇
矿业工程   4766篇
能源动力   9912篇
轻工业   33563篇
水利工程   6405篇
石油天然气   16367篇
武器工业   36篇
无线电   47295篇
一般工业技术   105803篇
冶金工业   75768篇
原子能技术   15376篇
自动化技术   36001篇
  2021年   4351篇
  2019年   4145篇
  2018年   7973篇
  2017年   8145篇
  2016年   8608篇
  2015年   4933篇
  2014年   8451篇
  2013年   20137篇
  2012年   12687篇
  2011年   16325篇
  2010年   13288篇
  2009年   15020篇
  2008年   15446篇
  2007年   14997篇
  2006年   12775篇
  2005年   11625篇
  2004年   11143篇
  2003年   10711篇
  2002年   10656篇
  2001年   10388篇
  2000年   10069篇
  1999年   9582篇
  1998年   20548篇
  1997年   15682篇
  1996年   12051篇
  1995年   9431篇
  1994年   8618篇
  1993年   8666篇
  1992年   6933篇
  1991年   6990篇
  1990年   6940篇
  1989年   6816篇
  1988年   6616篇
  1987年   6021篇
  1986年   5937篇
  1985年   6637篇
  1984年   6399篇
  1983年   5980篇
  1982年   5644篇
  1981年   5807篇
  1980年   5685篇
  1979年   5798篇
  1978年   6044篇
  1977年   6490篇
  1976年   7927篇
  1975年   5458篇
  1974年   5389篇
  1973年   5481篇
  1972年   4832篇
  1971年   4447篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
This paper begins by examining the most energy-intensive industries and methods by which fuel efficiency can be improved. Next the author analyses the economics of energy conservation using specific case studies drawn from India. It is shown that investing in energy efficiency is more economical Btu per Btu than investing in the enhancement of domestic energy resources. The author also assesses changes in the economics of conservation for private firms when there are government incentives. Finally government policies that can overcome economic and non-economic disincentives for investing in energy conservation are examined.  相似文献   
993.
G. Kardaun 《Energy》1985,10(2):119-127
Worldwide demand and supply of natural gas may rise substantially between the years 1982 and 2000, but the rate of increase will decelerate after 1990. The rapid growth of potential demand in the first decade is expected to take place in the developing countries in particular. During this period, gas production potential will rise most rapidly in Eastern Europe (including the U.S.S.R.) and in the Third World countries of Latin America, Africa, the Middle East, and Asia. In the year which has passed since the Venice Conference, forecasts of future natural gas demand in Western Europe have been reduced from 300–350 × 109 m3 (in the year 2000) to 270 × 109 m3. This change has greatly diminished the expected need for gas imports into Western Europe. It has also had a positive effect on the reserve position, relative to anticipated demand, of the Netherlands, which now will consider making more gas available for Western European markets.  相似文献   
994.
995.
996.
The influence exerted by electric-spark spraying on the kinetics of mass transfer and the physicomechanical properties of coatings is investigated. It is shown that electric-spark spraying is determined by the dynamic properties of the cathode jets, which depend on the electrical parameters of the spark discharge, the size of the interelectrode interval, and the physical properties of the coatings, which vary during spraying.  相似文献   
997.
No longer satisfied with compromising and controlling individual computers, a new breed of hackers have set their sights on virtual networks of zombie systems, which they use in concert to accomplish various nefarious deeds. Beware the botnet.  相似文献   
998.
The possibility of obtaining chemically stable ceramics in plastic molding from pastes based on comprehensive use of mining by-products (plagioporphyry, quartz-biotite shale), alumina production wastes (red mud), and polymineral clay was demonstrated. The mechanism of enhancing paste sintering on addition of finely disperse grog-flux and increasing the alkali resistance of the material (to 95%) in molding of the crystalline hematite-anorthite-quartz system was examined. __________ Translated from Steklo i Keramika, No. 2, pp. 17–20, February, 2007.  相似文献   
999.
1000.
The authors studied the biochemical composition of the meat of broilers, eggs, liver and muscles of laying hens of 3 generations on a 5, 10, 25, 50 and 100% (broilers), 10 and 20% (laying hens) replacement of the animal protein quota in the diet by protein obtained from the hydrogen bacteria Alcaligenes eutrophus L-1. No deterioration of the quality of the produce was found from the standpoint of the main biochemical parameters.  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