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   921771篇
  免费   92000篇
  国内免费   280篇
  2018年   9389篇
  2017年   8884篇
  2016年   12378篇
  2015年   15386篇
  2014年   18542篇
  2013年   26800篇
  2012年   30226篇
  2011年   31109篇
  2010年   21316篇
  2009年   19648篇
  2008年   27817篇
  2007年   28895篇
  2006年   27212篇
  2005年   26017篇
  2004年   25940篇
  2003年   24842篇
  2002年   24490篇
  2001年   39232篇
  2000年   38706篇
  1999年   31245篇
  1998年   11440篇
  1997年   11499篇
  1996年   10968篇
  1995年   10107篇
  1994年   9773篇
  1993年   9744篇
  1992年   25253篇
  1991年   24951篇
  1990年   24286篇
  1989年   23807篇
  1988年   21902篇
  1987年   20952篇
  1986年   19488篇
  1985年   19596篇
  1984年   16060篇
  1983年   13887篇
  1982年   10463篇
  1981年   9438篇
  1980年   8833篇
  1979年   14958篇
  1978年   11800篇
  1977年   10683篇
  1976年   10287篇
  1975年   11538篇
  1974年   12414篇
  1973年   12339篇
  1972年   11221篇
  1971年   10145篇
  1970年   8811篇
  1969年   8702篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
981.
Glycosylated haemoglobin (HbA1) was measured in seven insulin-dependent diabetic patients before, during, and after a seven-day period of monitored poor control. There was considerable individual variation in the pattern and degree of change in HbA1 concentration induced by poor control and the time when it occurred. Greater increases in HbA1 were seen during the period of metabolic derangement than in the subsequent two months. More information is required before HbA1 estimations are widely used clinically to monitor control in individual diabetics.  相似文献   
982.
Diagnostic test systems for the detection of IgG and IgM to Mycobacterium leprae in the blood sera of leprosy patients and armadillos experimentally infected with M. leprae have been developed on the basis of the indirect immunoperoxidase assay. The possibility has been shown of prognosing the activity of the leprotic process in leprosy patients and the results of the experimental infection of armadillos by the dynamic increase of antibody reactions with the development of the infection.  相似文献   
983.
The results of the phage typing of 5, 168 Staph. aureus strains isolated in a surgical hospital between 1959 and 1977 are analyzed for each year of this period. The wave of increase in the number of staphylococci belonging to phage group II which began, as discovered in this study, in 1965 and still showed no tendency towards decrease in 1977, as well as the periodicity of rises and falls in the number of staphylococci belonging to phage groups I and III are discussed and compared with the data contained in the literature. The authors come to the conclusion that Staph. aureus is subject to wave-like rises and falls in the number of strains belonging to the main phage groups of the species, and among them the strains belonging to phage groups I and III seem to be inversely related in respect of rises and falls in number, such changes occurring periodically at an interval of 10-12 years, while in the strains belonging to phage group II changes in number occur at a slower rate. The constant account of the percentage of phage groups I, II and III is recommended to ensure rational antibiotic therapy.  相似文献   
984.
985.
New olean-18(19)-ene triterpenoids were effectively synthesized by the interaction of allobetulin or its acetate with phosphorous oxychloride in refluxing pyridine. The structures of the synthesized 17-chloromethyloleane-18(19)-enes were confirmed by NMR spectroscopy and X-ray analysis.  相似文献   
986.
Two methods for the calculation of optimal trajectories for the input variables of a fed-batch culture of hybridoma cells are compared. It pointed out that a gradient method based on Pontryagins' minimum principle based yields a significant better performance with respect to computational effort and the calculated minimum than a dynamic programming approach which has been presented in a previous paper [1] as the most suitable method.  相似文献   
987.
The in vitro treatment of membranes isolated from different rat organs with a water-soluble synthetic antioxidant has resulted in the change of basal and stimulus-induced adenylate cyclase activity. It is believed that the antioxidant effect is realized rather at the level of signal transfer from activated receptor to adenylate cyclase than at the level of agonist-receptor interaction.  相似文献   
988.
As the result of the study of tetanolysin-producing Clostridium tetani strains, their populations have been found to be markedly heterogeneous with respect to the hemolytic activity of clone cultures. On the basis of normal and dialyzed cultures of selected variants with maximum activity the preparations of tetanolysin have been obtained, and their hemolytic activity and antigenic properties have been studied. Antihemolytic rabbit sera have also been obtained and characterized. Partially purified preparations of tetanolysin with high hemolytic activity have been obtained by the fractionation of C. tetani dialyzed cultures with ammonium sulfate.  相似文献   
989.
Abstract The natural product cyanobacterin has been shown to be toxic to most cyanobacteria at a concentration of approx. 5 μM. We demonstrate here that cyanobacterin will also inhibit the growth of most eukaryotic algae at a similar concentration. Some algae, such as Euglena gracilis , are resistant because they are able to maintain themselves by heterotrophic nutrition. Others, such as Chlamydomonas reinhardtii , can apparently induce a detoxification mechanism to maintain photosynthesis in the presence of low concentrations of the inhibitor. Non-photosynthetic microorganisms are not affected by cyanobacterin.  相似文献   
990.
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