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   1600521篇
  免费   28284篇
  国内免费   8113篇
电工技术   35906篇
技术理论   3篇
综合类   7868篇
化学工业   278683篇
金属工艺   66666篇
机械仪表   46499篇
建筑科学   49344篇
矿业工程   12514篇
能源动力   51192篇
轻工业   121893篇
水利工程   16664篇
石油天然气   39284篇
武器工业   290篇
无线电   201208篇
一般工业技术   298816篇
冶金工业   200366篇
原子能技术   34485篇
自动化技术   175237篇
  2021年   16626篇
  2020年   12707篇
  2019年   15400篇
  2018年   18203篇
  2017年   17757篇
  2016年   23035篇
  2015年   18436篇
  2014年   29987篇
  2013年   89487篇
  2012年   38994篇
  2011年   52964篇
  2010年   45691篇
  2009年   53553篇
  2008年   48586篇
  2007年   46198篇
  2006年   47321篇
  2005年   42421篇
  2004年   43818篇
  2003年   43565篇
  2002年   42209篇
  2001年   39474篇
  2000年   37507篇
  1999年   37443篇
  1998年   58091篇
  1997年   46860篇
  1996年   40249篇
  1995年   33642篇
  1994年   31142篇
  1993年   30988篇
  1992年   26793篇
  1991年   24006篇
  1990年   24239篇
  1989年   23237篇
  1988年   21878篇
  1987年   19975篇
  1986年   19403篇
  1985年   22716篇
  1984年   22653篇
  1983年   20597篇
  1982年   19479篇
  1981年   19628篇
  1980年   18225篇
  1979年   18693篇
  1978年   17896篇
  1977年   18038篇
  1976年   19469篇
  1975年   16140篇
  1974年   15606篇
  1973年   15747篇
  1972年   13138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.
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   
993.
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   
994.
995.
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   
996.
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   
997.
998.
999.
The objective of this study is to determine the economic and operational impact on energy cost of incorporating large photovoltaic (PV) and wind energy conversion systems (WECS) into the electric utility generation mix. In most cases, PV and WECS power outputs are subtracted from the utility load with the expectation that conventional generation would meet the residual load. This approach is valid for small penetration levels and/or for PV and WECS facilities connected near load centers, However, several constraints such as thermal generation characteristics, fuel supply and delivery, spinning reserve requirements, and hydro availability are not adequately represented in this process. To determine the optimal value of large-scale PV and WECS applications, a new methodology that would take into account the aforementioned constraints as well as a more global penetration is developed. Results indicate that while high hydro availability increases PV penetration levels, high ramping rates can also significantly increase penetration levels  相似文献   
1000.
Roos  G. Hoefflinger  B. 《Electronics letters》1993,29(24):2103-2104
A process-inherent NAND2 device is presented for a three-dimensional CMOS integration with epitaxial lateral overgrowth and chemo-mechanical polishing. The required 'OR' function of the two PMOS transistors is achieved by one silicon volume, which is controlled by a back gate and a conventional front gate. Almost symmetrical characteristics are measured for the front and the back gates.<>  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