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   1627篇
  免费   11篇
  国内免费   1篇
电工技术   5篇
综合类   1篇
化学工业   101篇
金属工艺   2篇
机械仪表   1篇
建筑科学   1篇
能源动力   9篇
轻工业   17篇
石油天然气   6篇
无线电   26篇
一般工业技术   46篇
冶金工业   1388篇
原子能技术   1篇
自动化技术   35篇
  2024年   4篇
  2023年   9篇
  2022年   45篇
  2021年   39篇
  2020年   13篇
  2019年   14篇
  2018年   9篇
  2017年   14篇
  2016年   6篇
  2015年   3篇
  2014年   6篇
  2013年   6篇
  2012年   8篇
  2011年   8篇
  2010年   7篇
  2009年   3篇
  2008年   6篇
  2007年   4篇
  2006年   4篇
  2005年   6篇
  2004年   4篇
  2003年   12篇
  2002年   5篇
  2001年   2篇
  2000年   2篇
  1999年   45篇
  1998年   466篇
  1997年   267篇
  1996年   167篇
  1995年   83篇
  1994年   70篇
  1993年   78篇
  1992年   6篇
  1991年   18篇
  1990年   11篇
  1989年   23篇
  1988年   23篇
  1987年   26篇
  1986年   16篇
  1985年   17篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   4篇
  1980年   5篇
  1978年   2篇
  1977年   22篇
  1976年   43篇
  1975年   2篇
  1955年   1篇
排序方式: 共有1639条查询结果,搜索用时 15 毫秒
91.
92.
93.
In this study the desizing, scouring, bleaching and slack mercerising of cotton fabric by a one–step process at different sodium hydroxide concentrations, impregnation temperatures and curing times were examined. The results indicate that when the fabrics are mercerised at lower temperature, the strength retention and colour strength are enhanced. When the sodium hydroxide concentration is increased, these properties also increase. When cotton fabrics are mercerised for 3 min at 40C and cured for 30 s at 120C, their physical properties are similar to those obtained using a conventional two–step approach.  相似文献   
94.
95.
96.
97.
AIMS: To establish trends in frequency of serious spinal cord injuries in rugby and rugby league over a 20 year period and to elucidate patterns of injury from retrospective analysis of cases admitted to New Zealand's two spinal injuries units. METHODS: A detailed survey of unit records with follow-up of selected patients; statistical analysis of data. RESULTS: During the 20 years 1976 to 1995, 119 rugby and 22 rugby league players (total 141) were admitted to New Zealand's two spinal injuries units suffering serious spinal injuries and 47 of these became permanently confined to wheelchairs. There was a steady increase in frequency throughout the period studied. Of the injuries 83% occurred in forwards and 17% in backs. In rugby it was the scrum which produced most injuries, and in rugby league it was the tackle. The early season month of April produced most spinal injuries. In the eighteen months since intense compulsory educational programmes on safety were introduced by the New Zealand Rugby Union there have been no serious spinal cord injuries from rugby scrums. CONCLUSION: Contrary to widespread belief, there has not been a decrease in spinal cord injuries in rugby following rule changes in the mid 1980s. The information produced by this retrospective study has been an effective educational platform to make rugby and rugby league safer.  相似文献   
98.
99.
An enzyme-linked immunosorbent assay for the detection of Shiga toxins (Premier EHEC assay; Meridian Diagnostics, Inc.) was compared to conventional sorbitol-MacConkey culture for the recovery of enterohemorrhagic Escherichia coli. A total of 74 enteric pathogens, including 8 E. coli O157:H7 isolates, were recovered from 974 stool specimens. Two of these specimens were not tested by Premier assaying due to insufficient sample and are not considered in the data analysis. The Premier EHEC assay detected the 6 evaluable specimens which were culture positive for E. coli O157:H7 and identified an additional 10 specimens as containing Shiga toxin. Seven isolates were recovered from these 10 specimens by an immunoblot assay and were confirmed as toxin producers by a cytotoxin assay. Of these seven, four isolates were serotype O157:H7, one was O26:NM, one was O6:H-, and one was O untypeable:H untypeable. Three specimens contained Shiga toxin by both EHEC immunoassaying and cytotoxin testing; however, no cytotoxin-producing E. coli could be recovered. The sorbitol-MacConkey method had a sensitivity and a specificity of 60 and 100%, respectively, while the Premier EHEC assay had a sensitivity and a specificity of 100 and 99.7%, respectively, for E. coli O157:H7 only. The Premier EHEC assay also detected an additional 20% Shiga toxin-producing E. coli (STEC) that were non-O157:H7. Thus, the Premier EHEC assay is a sensitive and specific method for the detection of all STEC isolates. Routine use would improve the detection of E. coli O157:H7 and allow for determination of the true incidence of STEC other than O157:H7. The presence of blood in the stool and/or the ages of the patients were poor predictors of the presence of STEC. Criteria need to be determined which would allow for the cost-effective incorporation of this assay into the routine screen for enteric pathogens in high-risk individuals, especially children.  相似文献   
100.
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