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   1618934篇
  免费   26814篇
  国内免费   7095篇
电工技术   34893篇
综合类   6560篇
化学工业   277200篇
金属工艺   65955篇
机械仪表   46260篇
建筑科学   48643篇
矿业工程   11652篇
能源动力   50570篇
轻工业   126329篇
水利工程   16617篇
石油天然气   37940篇
武器工业   140篇
无线电   200138篇
一般工业技术   303941篇
冶金工业   216044篇
原子能技术   34325篇
自动化技术   175636篇
  2021年   15790篇
  2020年   12059篇
  2019年   14846篇
  2018年   17835篇
  2017年   17349篇
  2016年   22664篇
  2015年   17775篇
  2014年   29085篇
  2013年   88517篇
  2012年   38836篇
  2011年   53249篇
  2010年   45077篇
  2009年   52814篇
  2008年   48878篇
  2007年   46758篇
  2006年   47290篇
  2005年   42450篇
  2004年   44317篇
  2003年   44020篇
  2002年   42594篇
  2001年   39929篇
  2000年   37925篇
  1999年   37945篇
  1998年   61714篇
  1997年   49283篇
  1996年   42004篇
  1995年   34705篇
  1994年   32126篇
  1993年   31783篇
  1992年   27205篇
  1991年   24500篇
  1990年   24666篇
  1989年   23745篇
  1988年   22306篇
  1987年   20453篇
  1986年   19978篇
  1985年   23306篇
  1984年   23061篇
  1983年   20911篇
  1982年   19665篇
  1981年   19824篇
  1980年   18446篇
  1979年   18929篇
  1978年   18137篇
  1977年   18797篇
  1976年   21293篇
  1975年   16284篇
  1974年   15763篇
  1973年   15882篇
  1972年   13313篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis.  相似文献   
992.
993.
One month following the Great Hanshin Earthquake of January 17, 1995, we conducted a survey of 173 hospitals in Aichi Prefecture to pinpoint problems related to their actual disaster-readiness and the medical backup systems in place to deal with such disasters. This study revealed that staff at 50% of the surveyed hospitals could reach the hospital within an hour, but that communication is almost entirely dependent on phone lines, suggesting that cordless/portable/mobile phones, radio systems, Internet, communications satellites and the like should be studied in the days to come for possible use as effective communication alternatives in times of disaster. Whereas 92% of the surveyed hospitals had manuals dealing with fire outbreaks, other areas were less well represented. For example, only 36.9% of surveyed hospitals had manuals for earthquakes, 31.7% had manuals for power outages and 14.2% had manuals to deal with flooding and water disasters. New manuals must be developed incorporating the key points garnered from experience (especially Hanshin) and be ready for use immediately. It is the time for each hospital to seriously rethink the measures it should take to deal with disasters.  相似文献   
994.
本文概述了离子注入过程中污染产生的原因和防止污染的措施,特别强调了对微粒污染和金属污染的防护以满足ULSI加工对离子注入的要求。  相似文献   
995.
996.
This paper discusses the problem of violence and its expression upon mortality due to external causes. A few indicators are offered, which have been worked upon it to emphasise the importance of the theme. In a general way, the study demonstrates violent death has had its magnitude increased along the years, not only throughout Latin America but also in Brazil and in Santa Catarina.  相似文献   
997.
The paper covers a simple idea. If we sample an aperture, we can obtain valid patterns over a limited angular region about the normal to the aperture. The same expression can be used with near-field measurements. I reduced the expression to a nomograph. A nomograph allows one to rapidly test various choices. In the second half of the paper, I answer questions caused by the February column which discussed polarization (Milligan, IEEE Antennas. Propag. Mag., vol.38, no.1, p.56-8, 1996)  相似文献   
998.
The formation of mullite was investigated using microcomposite powders which consist of α-alumina cores and amorphous silica coatings. Differential thermal analysis and X-ray diffraction showed that the mullitization reaction was endothermic. In contrast, mullite forms exothermically in samples prepared by sol-gel processing. The results are shown to be consistent with available thermodynamic data for mullite formation from different alumina and silica phases.  相似文献   
999.
1000.
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