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   28401篇
  免费   1070篇
  国内免费   114篇
电工技术   374篇
综合类   230篇
化学工业   5053篇
金属工艺   624篇
机械仪表   581篇
建筑科学   966篇
矿业工程   93篇
能源动力   929篇
轻工业   3840篇
水利工程   240篇
石油天然气   150篇
武器工业   6篇
无线电   2233篇
一般工业技术   4104篇
冶金工业   6210篇
原子能技术   241篇
自动化技术   3711篇
  2024年   50篇
  2023年   149篇
  2022年   491篇
  2021年   783篇
  2020年   530篇
  2019年   595篇
  2018年   683篇
  2017年   766篇
  2016年   716篇
  2015年   551篇
  2014年   848篇
  2013年   1401篇
  2012年   1246篇
  2011年   1572篇
  2010年   1150篇
  2009年   1198篇
  2008年   1092篇
  2007年   955篇
  2006年   770篇
  2005年   830篇
  2004年   900篇
  2003年   808篇
  2002年   789篇
  2001年   689篇
  2000年   538篇
  1999年   522篇
  1998年   2026篇
  1997年   1317篇
  1996年   919篇
  1995年   601篇
  1994年   471篇
  1993年   531篇
  1992年   217篇
  1991年   281篇
  1990年   224篇
  1989年   190篇
  1988年   205篇
  1987年   157篇
  1986年   163篇
  1985年   180篇
  1984年   130篇
  1983年   91篇
  1982年   117篇
  1981年   124篇
  1980年   114篇
  1979年   90篇
  1978年   74篇
  1977年   138篇
  1976年   225篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 0 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