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   429784篇
  免费   48153篇
  国内免费   163篇
  478100篇
  2018年   4016篇
  2016年   5425篇
  2015年   7103篇
  2014年   8399篇
  2013年   11619篇
  2012年   13219篇
  2011年   13638篇
  2010年   9332篇
  2009年   8620篇
  2008年   12434篇
  2007年   12930篇
  2006年   12132篇
  2005年   11608篇
  2004年   11610篇
  2003年   10854篇
  2002年   10684篇
  2001年   17469篇
  2000年   17469篇
  1999年   13963篇
  1998年   5069篇
  1997年   5305篇
  1996年   4953篇
  1995年   4654篇
  1994年   4513篇
  1993年   4577篇
  1992年   11634篇
  1991年   11547篇
  1990年   11309篇
  1989年   10921篇
  1988年   10501篇
  1987年   10091篇
  1986年   9374篇
  1985年   9243篇
  1984年   7765篇
  1983年   6716篇
  1982年   5166篇
  1981年   4631篇
  1980年   4471篇
  1979年   7425篇
  1978年   5869篇
  1977年   5402篇
  1976年   5204篇
  1975年   5597篇
  1974年   6302篇
  1973年   6168篇
  1972年   5764篇
  1971年   5228篇
  1970年   4634篇
  1969年   4575篇
  1968年   4421篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
A 14-days' training of rats designed to adapt the animals to the procedure of blood-pressure measurement caused in the myocardium a decrease, in serum an increase in noradrenaline ( NA) content. The latter remained unchanged following 3 days of treatment with 2.5 mg depot angiotensin II (AII) but decreased by more than one-half in the myocardium of untreated animals, and increased in serum. Despite the considerable difference in myocardial NA content and blood-pressure behaviour, both trained and untrained rats showed the same morphological reactions following administration of A II. These myocardial alterations which largely correspond to the so-called epinephrine myocarditis should not therefore be due solely to NA action; rather, the involvement of A II should be considered also.  相似文献   
996.
Combined patch-clamp and fura-2 measurements were performed to study the calcium release properties of Chinese hamster ovary (CHO) cells transfected with the rabbit skeletal muscle ryanodine receptor cDNA carried by an expression vector. Both caffeine (1-50 mM) and ryanodine (100 microM) induced release of calcium from intracellular stores of transformed CHO cells but not from control (non-transfected) CHO cells. The calcium responses to caffeine and ryanodine closely resembled those commonly observed in skeletal muscle. Repetitive applications of caffeine produced characteristic all-or-none rises in intracellular calcium. Inositol 1,4,5-trisphosphate (IP3) neither activated the ryanodine receptor channel nor interfered with the caffeine-elicited calcium release. These results indicate that functional calcium release channels are formed by expression of the ryanodine receptor cDNA.  相似文献   
997.
998.
999.
Staphylococcus and Micrococcus populations were collected from the healthy skin of 10 infant subjects. Infants were sampled from 1 day to 32 weeks of age. Species were characterized by approximately 30 different morphological, physiological, and biochemical characters. Staphylococci were the predominant inhabitants of normal skin, whereas micrococci were found only occasionally in this environment. Staphylococcus epidermidid, S. haemolyticus, and S. hominis were the predominant and persistent staphylococci. These species constituted a high percentage of the total aerobic bacterial flora of infant skin. Micrococcus luteus and M. kristinae were the prevalent micrococci found on infant skin. Only limited correlation between Staphyloccus and Micrococcus populations and infant age or body area sampled was indicated by this study.  相似文献   
1000.
J. E. Devitt 《CMAJ》1979,120(11):1370-1372
Most reports advocating mammography have been written by radiologists rather than by clinicians who are frequently confronted by women with breast complaints. The value of mammography in managing patients with breast problems was studied by reviewing its role in 1026 breast consultations; there were 129 patients with cancer. Mammography was performed in 95 patients. The procedure hastened the diagnosis of one comedocarcinoma, and in another patient was suspicious 3 years before she presented with a locally advanced lesion. It missed six cancers. In seven patients it recognized clinically obvious cancers, though in one of these it had given negative results 10 months before the patient presented with a lesion 15 cm in diameter. It also falsely suggested the possibility of cancer in 28 women. In the other 52 patients the clinical diagnosis of a benign condition was usually fairly evident. The morbidity caused by mammography does not seem to have been widely appreciated, no doubt because of the hope that clinically unrecognized cancers would be found by it. Most breast problems can be diagnosed without mammography.  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