首页 | 官方网站   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   28818篇
  免费   1079篇
  国内免费   110篇
工业技术   30007篇
  2024年   52篇
  2023年   153篇
  2022年   497篇
  2021年   785篇
  2020年   538篇
  2019年   605篇
  2018年   700篇
  2017年   770篇
  2016年   721篇
  2015年   555篇
  2014年   862篇
  2013年   1425篇
  2012年   1263篇
  2011年   1606篇
  2010年   1158篇
  2009年   1226篇
  2008年   1111篇
  2007年   976篇
  2006年   790篇
  2005年   849篇
  2004年   917篇
  2003年   821篇
  2002年   799篇
  2001年   693篇
  2000年   545篇
  1999年   528篇
  1998年   2028篇
  1997年   1330篇
  1996年   924篇
  1995年   606篇
  1994年   478篇
  1993年   534篇
  1992年   216篇
  1991年   284篇
  1990年   230篇
  1989年   193篇
  1988年   207篇
  1987年   165篇
  1986年   168篇
  1985年   187篇
  1984年   129篇
  1983年   92篇
  1982年   119篇
  1981年   126篇
  1980年   117篇
  1979年   96篇
  1978年   77篇
  1977年   143篇
  1976年   227篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
BACKGROUND: We assessed the utility of scintigraphy with indium 111-labeled polyclonal human IgG scintigraphy in patients with fever of unknown origin that fulfilled the criteria of temperature of 38.3 degrees C or more for at least 3 weeks and no diagnosis during 1 week of hospital admission. We compared the utility of this technique with results of scintigraphic techniques reported in the literature. METHODS: Data for all patients seen at our university hospital in whom 111In-IgG scanning was performed were analyzed and checked for the criteria for fever of unknown origin. The literature on the utility of scintigraphic techniques in patients with fever of unknown origin was reviewed. RESULTS: We studied 24 patients with fever of unknown origin. In 13 patients, focal 111In-IgG accumulation was observed. In nine (38%) of those, the positive 111In-IgG scintigram led to the final diagnosis; in the other four patients (17%), the scintigraphic findings were not helpful. In the 11 patients with negative 111In-IgG scans, extensive diagnostic workup produced no infection as the final diagnosis in nine patients (38%), one had an abscess in a renal cyst that was detected several months later, and in the other the cause of fever was an infected intravenous line. The overall sensitivity and specificity of 111In-IgG scintigraphy were 81% and 69%, respectively. The positive predictive value was 69% and the negative predictive value was 82%. CONCLUSIONS: Our results show that 111In-IgG scintigraphy significantly contributed to the diagnostic process in patients with fever of unknown origin. A positive scan increased the likelihood of finding the cause of the fever, and a negative scan ruled out an inflammatory component with a high degree of certainty. These data compare favorably with data in the literature concerning other radiopharmaceuticals; a larger prospective evaluation of this technique is indicated.  相似文献   
105.
106.
107.
The seroprevalence of HIV-1 and HIV-2 among pregnant women in Maputo, the capital of Mozambique, was compared between the years 1982/83, 1988 and 1990. None of the 432 serum samples collected in 1982/83 was positive for HIV antibodies whereas in 1988 the HIV-1 and HIV-2 seroprevalence was 0.4% (2/500) and 0.6% (3/500), respectively, and in 1990 0.6% (12/2014) and 0.2% (4/2014), respectively. These results indicate that HIV infection has been introduced recently in Maputo and is spreading at a slow rate among women.  相似文献   
108.
109.
A method for identifying a set of candidate words that matches well with a given utterance is discussed. The method uses precomputed groups of acoustically similar words. Given a vocabulary, for each word a short list of words that are acoustically similar to it is computed. These groups are constructed using training utterances recorded by several speakers and used in an isolated utterance recognition system to construct candidate word lists during recognition. Experiments show that the correct word appears on the short list of candidate words constructed during recognition using this scheme over 98% of the time  相似文献   
110.
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-23

京公网安备 11010802026262号