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   2546篇
  免费   21篇
  国内免费   3篇
电工技术   7篇
综合类   4篇
化学工业   122篇
金属工艺   6篇
机械仪表   12篇
建筑科学   17篇
矿业工程   1篇
能源动力   5篇
轻工业   54篇
水利工程   4篇
石油天然气   4篇
武器工业   1篇
无线电   35篇
一般工业技术   91篇
冶金工业   2145篇
原子能技术   4篇
自动化技术   58篇
  2022年   5篇
  2021年   13篇
  2020年   5篇
  2019年   7篇
  2018年   11篇
  2017年   14篇
  2016年   16篇
  2015年   8篇
  2014年   12篇
  2013年   33篇
  2012年   13篇
  2011年   29篇
  2010年   9篇
  2009年   31篇
  2008年   32篇
  2007年   17篇
  2006年   16篇
  2005年   15篇
  2004年   24篇
  2003年   21篇
  2002年   12篇
  2001年   13篇
  2000年   10篇
  1999年   65篇
  1998年   652篇
  1997年   381篇
  1996年   216篇
  1995年   127篇
  1994年   116篇
  1993年   140篇
  1992年   18篇
  1991年   39篇
  1990年   33篇
  1989年   36篇
  1988年   28篇
  1987年   39篇
  1986年   27篇
  1985年   31篇
  1984年   7篇
  1983年   6篇
  1982年   14篇
  1981年   20篇
  1980年   14篇
  1979年   8篇
  1978年   13篇
  1977年   53篇
  1976年   82篇
  1975年   5篇
  1974年   7篇
  1973年   5篇
排序方式: 共有2570条查询结果,搜索用时 31 毫秒
101.
BACKGROUND: An epidemic of bilateral optic neuropathy is affecting large numbers of people aged between 10 and 40 in Dar es Salaam, the capital city of Tanzania. The disease is characterised by acute onset of bilateral visual impairment, bilateral impairment of colour vision, and a characteristic temporal pallor of the optic discs. The disease often occurs in association with peripheral neuropathy and sensorineural hearing loss. This report presents the first data on disease prevalence in adolescents, based on a rapid assessment of schoolchildren. METHODS: Three schools in Dar es Salaam were visited and all children aged between 10 and 16 were screened for the disease. RESULTS: The prevalence of bilateral optic neuropathy among the schoolchildren is estimated to be 1.0% (95% CI 0.5-1.4%). This suggests that 5000 children (95% CI 2600-7300) aged 10-16 in Dar es Salaam may have the disease. CONCLUSION: The results of this rapid assessment indicate this epidemic is a major public health problem. The prevalence of the disease in the community is likely to be far higher than found in this survey because children with the disease may have withdrawn from school. As the disease predominantly affects young adults, resulting in impaired vision and hearing, the economic and social consequences are enormous.  相似文献   
102.
A series of 9-(N4-substituted acetaldehyde thiosemicarbazone) adenines were synthesized and evaluated for antiherpes virus activity. Compounds 4a-l were prepared by condensation of 9-(acetaldehyde) adenine(6) and the corresponding N4-substituted thiosemicarbazides (10). The antiviral effects of all compounds 4a-l were tested in vitro in primary rabbit kidney cell cultures infected with herpes simplex virus type 1 (HSV-1) and varicella-herpes zoster virus (VZV), and in primary human embryo cell cultures infected with herpes simplex virus type 2 (HSV-2). The results showed that the minimum inhibitory concentrations (MIC) of 4e and 4f for HSV-1 and VZV were 20, 40, 20 and 20 micrograms.ml-1, respectively, and other compounds were 200 micrograms.ml-1. For HSV-2, the MIC of all tested compounds were 300 micrograms.ml-1. We also evaluated the antiherpetic effect of 4e (and 4f) by combination with acyclovir (ACV) in the ratio of 1:1 in vitro. The MIC of the combined compounds were 2 micrograms.ml-1 for 4e and 6 micrograms.ml-1 for 4f, while their minimum cytotoxicities (MCC) in the cell were markedly reduced compared with the individual compounds.  相似文献   
103.
104.
105.
The behavioral effects were studied of monoclonal antibodies (MA) against A3G7 protein, which is known to be associated with the processes of nervous cell differentiation. Elaboration, storage, and retention of acoustic startle (ASR) habituation and freezing behavior were tested in adult rats. The MA applied in a dose of 50 ng on cerebellar vermis selectively impaired only the ASR long-term habituation storage whereas its dose of 5 mcg impaired both long-term habituation storage and fear-conditioned freezing. Application of 10 mcg of MA disrupted the elaboration and storage of the ASR short- and long-term habituation as well as fear-conditioned freezing. The results are considered as experimental verification of systemogenesis theory and hypothesis about a common molecular basis of learning and development.  相似文献   
106.
Osteomyelitis in childhood is common and causes serious morbidity. X-rays and bone scans are the primary tools of radiological investigation. Other imaging techniques, including ultrasound, computed tomography, magnetic resonance imaging and white cell scintigraphy have a valuable role in difficult cases.  相似文献   
107.
108.
Reviews major activities of the Editor and changes in the Journal of Pediatric Psychology (JPP) for issues published in 1993 through 1997. Significant trends and accomplishments are reviewed, including the increased use of Special Issues and Special Sections to highlight current pediatric psychological research. Articles published during the term are analyzed in terms of article type and population type. Comparisons are made to earlier trends in JPP publications, as reported by Roberts (1992).  相似文献   
109.
All 2,617 children who received midazolam and meperidine for a variety of endoscopic procedures were monitored for the development of adverse behavioral problems. Thirty-six (1.4%) of the children (ages 1-17 years) experienced a paradoxical behavioral reaction, which consisted of inconsolable crying, combativeness, disorientation, dysphoria, tachycardia, agitation, and restlessness. The reaction occurred at a mean of 17 minutes after the administration of midazolam. Following treatment with flumazenil, the reaction dissipated within a mean of 14 minutes. Three of the 36 patients underwent additional endoscopic procedures utilizing only meperidine. No similar reaction was observed in these patients. Awareness of the reaction and prompt administration of flumazenil decreased the duration of the reaction.  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