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   1607694篇
  免费   26830篇
  国内免费   7183篇
电工技术   34922篇
综合类   6517篇
化学工业   276823篇
金属工艺   66211篇
机械仪表   45864篇
建筑科学   48006篇
矿业工程   11668篇
能源动力   50711篇
轻工业   121601篇
水利工程   16383篇
石油天然气   38127篇
武器工业   137篇
无线电   200507篇
一般工业技术   300232篇
冶金工业   215601篇
原子能技术   34455篇
自动化技术   173942篇
  2021年   15862篇
  2020年   12108篇
  2019年   14881篇
  2018年   18164篇
  2017年   17727篇
  2016年   22696篇
  2015年   17787篇
  2014年   29087篇
  2013年   88646篇
  2012年   38221篇
  2011年   52421篇
  2010年   45131篇
  2009年   53147篇
  2008年   48192篇
  2007年   45919篇
  2006年   46429篇
  2005年   41945篇
  2004年   43600篇
  2003年   43232篇
  2002年   41903篇
  2001年   39316篇
  2000年   37396篇
  1999年   37620篇
  1998年   62365篇
  1997年   49359篇
  1996年   41939篇
  1995年   34572篇
  1994年   31823篇
  1993年   31765篇
  1992年   26890篇
  1991年   24244篇
  1990年   24527篇
  1989年   23569篇
  1988年   22086篇
  1987年   20265篇
  1986年   19673篇
  1985年   22991篇
  1984年   22778篇
  1983年   20672篇
  1982年   19515篇
  1981年   19746篇
  1980年   18333篇
  1979年   18753篇
  1978年   18018篇
  1977年   18482篇
  1976年   20559篇
  1975年   16220篇
  1974年   15667篇
  1973年   15787篇
  1972年   13221篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Vaccination with peptides that induce a specific immune response is a potential prophylactic or therapeutic strategy against viral infections and tumors. Because of the extensive polymorphism of the HLA loci, synthetic peptide vaccines must consist of a cocktail of peptides that bind specifically to different HLA molecules. Such cocktails should be optimized for the target population as each population has its specific HLA gene frequencies. To achieve maximum population coverage with a minimum number of peptides, information is needed on the ranking of the most frequent HLA phenotypes. We introduce the minimal phenotype panel, which is the smallest combination of HLA antigens selected so that the proportion of individuals in a population that express at least one of the antigens in the panel exceeds a desired minimum value. We developed a method for assembling minimal phenotype panels based on known HLA class I gene frequencies. We give an example based on a set of 2446 well-defined HLA-typed, random, healthy, unrelated, Dutch Caucasoid individuals. In addition, we discuss the possibility of assembling minimal phenotype panels based on two-locus haplotypes, which enables the assembly of phenotype panels from the antigens of both loci.  相似文献   
992.
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   
993.
994.
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   
995.
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   
996.
997.
998.
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   
999.
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   
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