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   406篇
  免费   3篇
综合类   2篇
化学工业   7篇
金属工艺   1篇
机械仪表   5篇
建筑科学   3篇
能源动力   2篇
轻工业   13篇
无线电   6篇
一般工业技术   30篇
冶金工业   336篇
自动化技术   4篇
  2022年   1篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2016年   4篇
  2015年   1篇
  2014年   4篇
  2013年   5篇
  2012年   3篇
  2011年   5篇
  2009年   1篇
  2008年   4篇
  2007年   3篇
  2006年   6篇
  2005年   2篇
  2004年   4篇
  2003年   2篇
  2002年   4篇
  2001年   2篇
  2000年   2篇
  1999年   9篇
  1998年   104篇
  1997年   58篇
  1996年   42篇
  1995年   34篇
  1994年   20篇
  1993年   14篇
  1992年   1篇
  1991年   3篇
  1989年   3篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1983年   1篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1979年   3篇
  1978年   1篇
  1977年   14篇
  1976年   26篇
  1975年   1篇
  1972年   2篇
  1955年   1篇
  1954年   1篇
排序方式: 共有409条查询结果,搜索用时 15 毫秒
311.
312.
313.
Infection and rejection remain the greatest threats to the survival of pulmonary allograft recipients. Furthermore, a relationship may exist between these events, because the occurrence of one may predispose to the other. By using multivariate analysis for repeated events, we analyzed the risk factors for bacterial, fungal, and viral infection, grade II or greater acute rejection, and death among 239 lung transplant recipients who received 250 allografts between January 1988 and September 1993. A total of 90 deaths, 491 episodes of acute rejection, and 542 infectious episodes occurred during a follow-up of 6 to 71 months. The hazard or risk patterns of death, infection, and rejection each followed an extremely high risk during the first 100 days after transplantation, a second modest risk period at 800 to 1200 days, and a lower constant risk. Infection and graft failure manifested by diffuse alveolar damage were the major causes of early death (< 100 days), whereas infection and chronic rejection were primary causes of later death after pulmonary transplantation. By multivariate analysis, cytomegalovirus mismatching risk for primary infection was the most significant risk factor for death, rejection, and infection. Absence of cytomegalovirus prophylaxis was also a risk factor for early and late death and late infection. Survival of recipients who received cytomegalovirus prophylaxis was significantly improved. Immunosuppression based on cyclosporine versus FK 506 was a risk factor for late death and late infection. Graft failure manifested by diffuse alveolar damage/adult respiratory distress syndrome was a significant risk for death late after transplantation. These data suggest the following: (1) The hazard for death, infection, and rejection after pulmonary transplantation appears biphasic; (2) lower survival is associated with ischemia-reperfusion lung injury represented by diffuse alveolar damage/adult respiratory distress syndrome; (3) cytomegalovirus mismatch, absence of cytomegalovirus prophylaxis, and development of cytomegalovirus disease are significant threats for death, rejection, and infection after pulmonary transplantation; (4) prevention of cytomegalovirus disease should improve survival by decreasing the prevalence of infection and rejection.  相似文献   
314.
A case is presented in which complete colonic duplication is associated with genitourinary and bone abnormalities including a complete duplication of the urethra. The etiology, appearance, clinical course, and classification of various large bowel duplications are discussed.  相似文献   
315.
Immunogrammes of 31 patients with grave forms of insulindependent diabetes mellitus were reviewed. The illness has been characterized as a systemic immunopathologic process combining autoimmune and infectious-and-allergic components realized by organ and tissue abnormalities; it evolves against the manifest background of allergy of both delayed anl immediate types, impairement of the humoral and cell-mediated immunity function, pathogenetic activity of endogenous proteases, the complement system components and interferon.  相似文献   
316.
317.
New design principles for visual acuity letter charts   总被引:2,自引:0,他引:2  
This paper intoduces new principles for the design and use of letter charts for the measurement of visual acuity. It is advocated that the test task should be essentially the same at each size level on the chart. Such standardization of the test task requires the use of letters of equal legibility, the same number of letters on each row, and uniform between-letter and between-row spacing. It is also advocated that, combined with the test task standardization, there should be a logarithmic progression of letter size. Charts incorporating these design features have been made. These charts facilitate the use of nonstandard testing distances which might be used when there is low visual acuity, when examination room layout prevents testing at the standard distance, or when it is necessary to validate visual acuity scores or detect malingering. Adjusting the visual acuity score according to the chosen testing distance is simplified by the use of logarithmic scaling.  相似文献   
318.
319.
The number of DNA synthesizing myocytes in the conductive system, as compared with the working myocardium, was determined by means of light autoradiography. At the same time the number of mitosing cells was counted. The indices of labelled nuclei in the sinoatrial and atrioventricular nodes of the embryos after the single and repeated 3H-thymidine injections were significantly lower than in the working ventricle and atrium. During the postnatal development (3-11 days) only in the sinoatrial node the index of labelled nuclei was significantly lower than in the working ventricle. The proliferative activity in all the myocardium parts fell markedly by the 13th day of development. Following 10 3H-thymidine injections with 12 hrs intervals, the indices of labelled nuclei varied from 0.03 to 0.67% in the working ventricle and atrium and from 0.13 to 1.0% in the conductive system of adult mice. During the embryogenesis the index of labelled nuclei in the sinoatrial node was significantly higher than in the atrioventricular one and during the postnatal development-vice versa.  相似文献   
320.
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