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   3028篇
  免费   2篇
综合类   3篇
化学工业   11篇
建筑科学   1篇
轻工业   1篇
水利工程   1篇
石油天然气   2篇
无线电   1篇
一般工业技术   9篇
冶金工业   2994篇
自动化技术   7篇
  2024年   1篇
  2021年   1篇
  2014年   2篇
  2013年   1篇
  2012年   4篇
  2011年   2篇
  2010年   1篇
  2008年   1篇
  2007年   1篇
  2005年   3篇
  2004年   1篇
  2003年   5篇
  2002年   1篇
  2001年   1篇
  1999年   88篇
  1998年   885篇
  1997年   492篇
  1996年   314篇
  1995年   169篇
  1994年   149篇
  1993年   171篇
  1992年   25篇
  1991年   36篇
  1990年   38篇
  1989年   45篇
  1988年   53篇
  1987年   54篇
  1986年   35篇
  1985年   34篇
  1983年   11篇
  1982年   14篇
  1981年   20篇
  1980年   38篇
  1979年   5篇
  1978年   12篇
  1977年   94篇
  1976年   215篇
  1975年   6篇
  1974年   1篇
  1955年   1篇
排序方式: 共有3030条查询结果,搜索用时 15 毫秒
11.
机械科学研究总院北京机电研究所承担“2000KN立式冷摆动辗压机开发研究”项目通过验收,研发的2000kN矿式冷摆动辗压机具有自主知识产权,填补了国内空白,达到国际先进水平,人选“2013度中关村科技园区首台(套)重大技术装备试验、示范项目。  相似文献   
12.
OBJECTIVE: Occupational skin changes in hairdressers are very common. Morbidity, however, has not yet been quantified precisely. METHODS: A cohort of 2,352 hairdressing apprentices (of the 2,570 invited to participate, i.e., 91.5% response) was prospectively followed for the duration of their vocational training (3 years) by three examinations. Three waves (years) were recruited in 1992, 1993, and 1994 from 15 vocational training schools in northwestern Germany. RESULTS: The point prevalence of (mostly slight) irritant skin changes of the hands increased from 35.4% in the initial examination to 47.5% in the intermediate examination and to 55.1% in the final examination. Given a more conservative definition of a case of "hand dermatitis," these estimates were 12.9%, 23.5%, and 23.9%, respectively. Altogether, 34.3 and 15.2 cases of "skin changes (any degree)" and "hand dermatitis," respectively, in 100 person-years were observed during the study period. The incidence rate, i.e., the number of newly diseased study participants in relation to the person-time at risk contributed, decreased in the course of the study. The proportion of dropouts until final follow-up was 51.8%. CONCLUSION: The present results appear to lie in a range with those found in other, much smaller cohort studies. However, comparison of the results is hampered either by the lack of a clear definition or by a different definition of "person-time at risk" or "a case of hand dermatitis." As compared with an external control group of office apprentices, the incidence was several times higher in hairdressing apprentices, which points to the high risk for skin damage in this occupation.  相似文献   
13.
Double contrast examination constitutes an important element in radiological gastric examination. The author examines the history of the term "double contrast" and defines the designation of "double contrast examination". The exclusive use of the double contrast method reduces the diagnostic value of gastric X-ray examinations. Thus a method is suggested that will avoid the disadvantages of exclusive double contrast examination while adequately including double contrast in the gastric examination. This is done by using various methods - according to the problem posed - in order to achieve the double contrast.  相似文献   
14.
15.
16.
A 23-year-old woman suffering from multiple sclerosis (MS) was given a course of 6 injections (0.5 U) of mumps transfer factor (TF) at 2-weekly intervals. The patient's symptoms improved dramatically and during the 10 months since treatment was instituted, no exacerbations have occurred. The possible aetiological role of paramyxoviruses in MS and the use of TF in the treatment of the disease are discussed. MS is however, a disease of exacerbations and spontaneous remissions, and despite our promising findings in this patient we wish to refrain from hailing mumps TF as a possible cure for this notorious disease.  相似文献   
17.
In the Public Salughter-House of Utrecht, a percentage increase in the number of pigs with inflammation of the tail, which had or had not healed, was observed during the period from 1972 to 1974 inclusive. The most common secondary symptoms of inflammation consisted in embolic pneumonia, osteomyelitis of the vertebrae and abscess formation in other parts of the body, particularly the semimebranosus muscles. Osteomyelitis was found to be the most common complication in pigs in which the inflammation of the tail had healed, whereas this usually consisted in embolic pneumonia in those cases in which the inflammation of the tail had not healed. The bacteriological examination carried out in accordance with the Meat Inspection Regulations was positive in 21.7 per cent, 13.5 per cent of the cases respectively in 1972, 1973 and 1974. Micro-organisms were isolated much more frequently from the kidney than they were from the spleen and meat. There was no relationship between the presence of inflammation of the tail and climatological conditions during the fattening period. The losses at slaughter from inflammation of the tail in the Netherlands are estimated at 3-4 million guilders per annum.  相似文献   
18.
19.
20.
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