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   5435篇
  免费   2篇
  国内免费   1篇
电工技术   1篇
综合类   2篇
化学工业   14篇
建筑科学   2篇
轻工业   7篇
水利工程   1篇
无线电   6篇
一般工业技术   8篇
冶金工业   5382篇
自动化技术   15篇
  2017年   1篇
  2013年   3篇
  2012年   2篇
  2011年   4篇
  2010年   1篇
  2009年   1篇
  2008年   1篇
  2007年   4篇
  2006年   7篇
  2005年   4篇
  2004年   4篇
  2003年   4篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   165篇
  1998年   1668篇
  1997年   918篇
  1996年   581篇
  1995年   334篇
  1994年   293篇
  1993年   311篇
  1992年   40篇
  1991年   61篇
  1990年   70篇
  1989年   61篇
  1988年   68篇
  1987年   69篇
  1986年   54篇
  1985年   62篇
  1984年   1篇
  1983年   10篇
  1982年   27篇
  1981年   27篇
  1980年   53篇
  1979年   3篇
  1978年   13篇
  1977年   157篇
  1976年   340篇
  1975年   3篇
  1973年   1篇
  1972年   1篇
  1969年   1篇
  1955年   4篇
排序方式: 共有5438条查询结果,搜索用时 546 毫秒
321.
322.
323.
324.
325.
326.
Insects rely on both humoral and cellular mechanisms to defend themselves against microbial infections. The humoral response involves synthesis of a battery of potent antimicrobial peptides by the fat body and, to a lesser extent, by blood cells. The cellular response on the other hand consists of phagocytosis of small microorganisms and melanization and encapsulation of larger parasites. The l(2)mbn cell line, established from tumorous larval hemocytes, represents a system of choice to dissect the molecular events controlling cellular immunity. We report here that l(2)mbn cells can be efficiently induced to differentiate in adherent, macrophage-like cells by treatment with 20-hydroxyecdysone. Ecdysone treatment increases both the phagocytic capacity of l(2)mbn cells and their competence to express antimicrobial genes in response to immune challenge. We also report that expression of several regulatory molecules thought to be involved in the immune response is up-regulated by ecdysone in l(2)mbn cells.  相似文献   
327.
328.
Torsades de pointes (TDP) is a ventricular tachycardia that can deteriorate into ventricular fibrillation. TDP has been associated with terfenadine use in cases of liver disease, electrolyte abnormalities, concomitant administration of drugs that inhibit cytochrome P-450, or deliberate overdose. This report describes the first case of TDP in a healthy patient taking the recommended therapeutic dosage of terfenadine.  相似文献   
329.
330.
BACKGROUND: Besides considering well-known risk factors for the development of gallbladder stones, such as age, sex, fecundity, and hereditary predisposition, efforts at prevention have focused increasingly on other factors, such as nicotine, alcohol, and caffeine consumption, as well as general nutrition, which may be modified. METHODS: A total of 1116 blood donors were examined between April 1994 and February 1995 in the central blood bank of the German Red Cross in Ulm, Germany. Each subject received a questionnaire and underwent to an upper abdominal ultrasound examination. RESULTS: Gallbladder stone disease (current cholecystolithiasis and history of cholecystectomy) was detailed in 5.8% of the men and 6.3% of the women. Neither regularity nor number of daily meals correlated with the frequency of gallstone disease. Vegetarians (n = 48), as a group, were not found to have gallstones. In relation to the consumption of alcohol, tobacco, or caffeine higher prevalence of cholecystolithiasis was found only in heavy drinkers of coffee (P = 0.051; odds ratio (OR), 1.083; 95% confidence interval (CI), 0.999, 1.174). CONCLUSION: Results of the present study do not show a definite relationship between nutritional factors and the consumption of alcohol, tobacco, or caffeine and an increased prevalence of gallbladder stone disease.  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