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   6024篇
  免费   7篇
电工技术   6篇
化学工业   273篇
机械仪表   12篇
建筑科学   9篇
矿业工程   1篇
能源动力   5篇
轻工业   500篇
石油天然气   1篇
无线电   12篇
一般工业技术   48篇
冶金工业   5137篇
原子能技术   5篇
自动化技术   22篇
  2013年   76篇
  2011年   5篇
  2009年   5篇
  2006年   5篇
  2005年   7篇
  2004年   7篇
  2003年   7篇
  2000年   5篇
  1999年   138篇
  1998年   1521篇
  1997年   860篇
  1996年   581篇
  1995年   338篇
  1994年   312篇
  1993年   331篇
  1992年   58篇
  1991年   102篇
  1990年   73篇
  1989年   98篇
  1988年   105篇
  1987年   99篇
  1986年   91篇
  1985年   57篇
  1984年   25篇
  1983年   32篇
  1982年   46篇
  1981年   48篇
  1980年   67篇
  1979年   24篇
  1978年   50篇
  1977年   163篇
  1976年   362篇
  1975年   40篇
  1974年   24篇
  1973年   24篇
  1972年   29篇
  1971年   28篇
  1970年   22篇
  1969年   11篇
  1968年   10篇
  1967年   11篇
  1966年   11篇
  1965年   14篇
  1964年   11篇
  1963年   8篇
  1959年   6篇
  1958年   8篇
  1957年   5篇
  1956年   10篇
  1955年   7篇
排序方式: 共有6031条查询结果,搜索用时 359 毫秒
61.
62.
63.
The purpose of this study was to examine whether exposure of rat pups to alcohol postnatally over a period of brain development similar to that of the human 3rd trimester results in a permanent loss of cells in the inferior olivary nucleus. It was hypothesized that a deficit of neurons in the inferior olive, the sole source of climbing fibers, may contribute to the cerebellar dysfunction observed following exposure to alcohol during development. Sprague-Dawley rat pups were artificially reared and administered alcohol over postnatal days 4-9. One artificially reared group received a daily alcohol dose of 4.5 g/kg, administered as a 10.2% solution in 2 of 12 daily feedings (10.2% group). This pattern of alcohol administration resulted in high peak blood alcohol concentrations with near total clearance. The other artificially reared group was fed a diet made isocaloric to the alcohol-containing diet (gastrostomy control group). Pups were allowed to grow to adulthood and killed on postnatal day 115. The total number of neurons in the inferior olivary nucleus was estimated using unbiased stereological methods. Exposure to alcohol resulted in a significant deficit in the number of neurons in the inferior olive at 115 days of age. The total number of neurons in the alcohol-exposed group was 40.12 +/- 8.7 x 10(3), compared with 53.37 +/- 3.7 x 10(3) in the artificially reared controls. These results indicate that there is a permanent deficit of neurons in the inferior olive after postnatal exposure to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
64.
65.
66.
67.
68.
Patients with chlamydial infections (Ct) attending the outpatient Venereal Disease Clinic of Copenhagen from July 1-November 30 1995 were asked to fill in a questionnaire focusing upon knowledge, attitude and behaviour related to sexually transmitted diseases (STDs) in order to strengthen the future prevention of Ct. The questionnaire was answered by 37 men and 35 women with a median age of 27 and 21 years and a median number of three and two sexual partners within the last six months, respectively. Half of the patients had previously had an STD, and 92% had been tested for HIV, of whom one homosexual man was known HIV-positive. Notification about exposure from a partner was the reason for attending for 24%. All but one were in favour of partner notification, but only 6% wanted provider referral. During last intercourse condoms had neither been used with a steady partner by 75% especially by the young and women, who thought themselves safe, nor with a casual partner by 52% especially among the young and men, mainly because of thoughtlessness or perception of low risk. Before the actual STD diagnosis only 49% were able to name one symptom and 35% one complication related to Ct. A majority (79%) stated, that fear of catching another Ct would lead to better protection, and 70% found that more information would have a preventive effect. Future Ct prevention programs in Denmark should include intensified chlamydial screening and partner notification together with centrally produced mass media information supplemented by individual counselling.  相似文献   
69.
70.
Four sets of sweet potato clones obtained by meristem tip culture were used to investigate the effect of feathery mottle virus (FMV) infection on the appearance, sensory quality and chemical composition of the storage roots. This study, encompassing four generations, indicated that FMV infection had a slight effect on carbohydrate metabolism but no effect on the polyphenoloxidase-phenol system. Flavor and texture profile analyses indicated that for one clone, FMV-infected roots were more desirable when baked than healthy roots. Considering the study as a whole, FMV infection did not appear to adversely affect sweet potato sensory properties. Clones produced from the same parent by meristem tip culture might have different compositional and sensory properties.  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