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   7030篇
  免费   38篇
  国内免费   2篇
电工技术   27篇
综合类   1篇
化学工业   230篇
金属工艺   23篇
机械仪表   49篇
建筑科学   29篇
矿业工程   11篇
能源动力   22篇
轻工业   74篇
水利工程   4篇
石油天然气   1篇
无线电   98篇
一般工业技术   152篇
冶金工业   6245篇
原子能技术   13篇
自动化技术   91篇
  2020年   9篇
  2018年   13篇
  2017年   17篇
  2016年   12篇
  2015年   9篇
  2014年   14篇
  2013年   63篇
  2012年   23篇
  2011年   39篇
  2010年   23篇
  2009年   31篇
  2008年   37篇
  2007年   44篇
  2006年   20篇
  2005年   45篇
  2004年   27篇
  2003年   33篇
  2002年   24篇
  2001年   23篇
  2000年   20篇
  1999年   225篇
  1998年   2046篇
  1997年   1174篇
  1996年   756篇
  1995年   415篇
  1994年   314篇
  1993年   392篇
  1992年   62篇
  1991年   63篇
  1990年   67篇
  1989年   60篇
  1988年   45篇
  1987年   58篇
  1986年   45篇
  1985年   56篇
  1984年   9篇
  1983年   20篇
  1982年   25篇
  1981年   48篇
  1980年   62篇
  1979年   16篇
  1978年   24篇
  1977年   135篇
  1976年   319篇
  1975年   23篇
  1973年   11篇
  1972年   6篇
  1971年   6篇
  1970年   8篇
  1969年   9篇
排序方式: 共有7070条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: To review epidemiological studies dealing with the temporal and geographic variability in the occurrence of rheumatoid arthritis (RA) and clinical studies that address the variability of severity and manifestations among populations. METHODS: An extensive search of the literature, including a Medline search, was completed. Studies addressing the origin, history, and trends in the occurrence of RA were reviewed first. Next, studies of the prevalence and incidence of RA in different populations were reviewed, and occurrence rates compared. Standardization was attempted by tabulating adult prevalence rates of studies using equivalent sets of criteria. Studies comparing RA patients from two populations were sought next. Finally, studies dealing with explanations of the presumed variability were reviewed. RESULTS: Temporal variability is indicated by paleopathological evidence that RA has existed in the New World since 4000 BC, whereas there is no evidence that it occurred in Europe before the 17th century, or in Africa before the 20th century. Epidemiological studies show a possible trend of decreasing incidence of RA in the United States and Western Europe, whereas reports from Africa note a rising incidence. In white populations of Europe and America, prevalence is approximately 1%, and incidence is 0.03%. Significantly higher rates are found in some North American Indians, and significantly lower rates in some Asian and African populations, even when the different population structures are taken into account. In the latter populations, different patterns of occurrence from those observed in whites emerge, such as greater female preponderance and a much younger peak age at onset. Direct standardized comparisons of two diverse populations of RA patients showed some differences in expression, severity, or manifestations of RA between populations. CONCLUSION: The occurrence and manifestations of RA are temporally and geographically variable.  相似文献   
42.
43.
44.
45.
Massachusetts provides diphtheria-tetanus toxoid-pertussis (DTP) vaccine, and since 1980 has monitored pertussis with a statewide diagnostic service. The incidence of bacteriologically confirmed pertussis was 104.5 per 100,000 person-years in 1-month-old infants and declined progressively thereafter. Infants < 6 months old experienced disproportionate morbidity: 44% of bacteriologically confirmed pertussis, 64% of hospitalizations, and 71% of hospital days. Most children with pertussis had received < 3 DTP doses during childhood, whereas 87% of adolescents with pertussis had received > or = 4 doses. Serodiagnosis by single serum anti-pertussis toxin antibody ELISA increased the incidence of confirmed pertussis in persons 11-19 years old from 3.0 to 12.9 per 100,000 and in persons > or = 20 years old from 0.16 to 0.56 per 100,000. Bacteriologic methods underestimate pertussis incidence, but a single serum anti-pertussis toxin antibody ELISA is a practical method for population-based diagnosis in adolescents and adults.  相似文献   
46.
Prognostic significance of cathepsin-D in patients with breast cancer   总被引:1,自引:0,他引:1  
The expression of the protease cathepsin-D has been evaluated using an immunohistochemical technique with a polyclonal antibody in paraffin-embedded tissue from 359 patients treated between the years 1975-1981 for Stage I and II breast cancer. One hundred and twenty seven patients (35%) have strongly positive, granular staining, 138 (38%) are intermediately stained in the cytoplasm, and in 94 (26%) no staining is observed. There is a strong positive association between expression of cathepsin-D and the presence of tumour in axillary lymph nodes (P < 0.006). Expression of the protease is associated with significantly poorer survival of patients in univariate analysis (P = 0.025); however, this is not independent of other tumour variables.  相似文献   
47.
Urinary incontinence is most frequently associated with the elderly, particularly women, and is often thought of as inevitable. However, orthopaedic nurses encounter incontinence as a response to alterations in orthopaedic health. This article reviews the types of urinary incontinence, with emphasis on those which may most directly result from orthopaedic problems. It will also help the nurse differentiate between types of incontinence in a way that will clarify appropriate interventions.  相似文献   
48.
BACKGROUND: In order to elaborate recommendations for the dietetic care of diabetic patients and other clinical disorders we have measured the concentration of carbohydrates and trace elements in a group of non alcoholic refreshments of current use in Spain. MATERIAL AND METHODS: Thirty refreshments were classified into 10 groups. Glucose and phosphate were measured by hexokinase and reduction of phospho-molybdate methods respectively in an autoanalyzer Dax-72. Glucose and fructose were analyzed by cellulose thin-layer chromatography; glucose, fructose and sucrose by gas chromatographys. Sodium and potassium by emission spectrophotometry and calcium, magnesium, iron, copper and zinc by atomic absorption spectrophotometry. RESULTS: Light refreshments and soft drinks have no carbohydrates. Isotonic beverages, fruit juices, cool tea and non alcoholic beers had less than 10 g/dl. Tonic waters, Fanta, different coles, non alcoholic bitter and others had more than 10 g/dl. Sodium levels between 15-20 mEq/l were found in the isotonic beverages and 7-Up and levels of 7 mEq/l in the others. Potassium values between 15-40 mEq/l were found in the fruit juices, 3-4 mEq/l in Gatorade and less than 1 mEq/l in the others. CONCLUSIONS: Light refreshments and soft drinks contain low concentrations of carbohydrates and sodium. Fruit juices have high potassium concentration. Such information can be especially useful for dietetic care of diabetic patients.  相似文献   
49.
50.
The rostral migratory stream consists of a large number of cells migrating from the lateral ventricles to the rostral telencephalon, primarily the olfactory bulb. The pathway continually provides neuro- and glioblasts throughout life. The present paper indicates that a considerable number of cells undergo apoptotic cell death en route, even in young (day 3) rats when presumably many vacant sites are still available in the developing brain.  相似文献   
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