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   298243篇
  免费   17359篇
  国内免费   422篇
耳鼻咽喉   4245篇
儿科学   10355篇
妇产科学   10280篇
基础医学   45244篇
口腔科学   7638篇
临床医学   24305篇
内科学   56336篇
皮肤病学   6361篇
神经病学   21120篇
特种医学   11662篇
外国民族医学   43篇
外科学   46883篇
综合类   7779篇
现状与发展   1篇
一般理论   161篇
预防医学   20129篇
眼科学   6967篇
药学   20996篇
中国医学   826篇
肿瘤学   14693篇
  2019年   2331篇
  2018年   3708篇
  2017年   2706篇
  2016年   3130篇
  2015年   3560篇
  2014年   4662篇
  2013年   7305篇
  2012年   9216篇
  2011年   9617篇
  2010年   6206篇
  2009年   5606篇
  2008年   8780篇
  2007年   9623篇
  2006年   9451篇
  2005年   9047篇
  2004年   8721篇
  2003年   8212篇
  2002年   7828篇
  2001年   13352篇
  2000年   13691篇
  1999年   11438篇
  1998年   3031篇
  1997年   2798篇
  1996年   2639篇
  1995年   2550篇
  1994年   2349篇
  1992年   8329篇
  1991年   8457篇
  1990年   8274篇
  1989年   8092篇
  1988年   7320篇
  1987年   7088篇
  1986年   6729篇
  1985年   6531篇
  1984年   4774篇
  1983年   4128篇
  1982年   2474篇
  1979年   4435篇
  1978年   3231篇
  1977年   2738篇
  1976年   2507篇
  1975年   2836篇
  1974年   3357篇
  1973年   3372篇
  1972年   3123篇
  1971年   2958篇
  1970年   2840篇
  1969年   2589篇
  1968年   2548篇
  1967年   2377篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
72.
The work gives substantiation of using complete intestinal lavage for certain indications in the complex treatment of incompetent colonic anastomoses. The method was efficiently used in 6 patients.  相似文献   
73.
The caffeine content of all tea or coffee beverages consumed by 17 healthy adults over 24 hours was measured. Plasma caffeine, theophylline, theobromine, and paraxanthine concentrations were determined over the same 24 hours. The average caffeine content per drink was 60.4 +/- 21.8 mg for instant coffee (14-fold range), 80.1 +/- 19.2 mg for brewed coffee (2.8-fold range), and 28.8 +/- 13.7 mg for tea (5.5-fold range). The number of drinks of coffee and tea consumed was a poor index of actual caffeine intake (r2 = 0.42). Caffeine intake correlated poorly with the 24-hour average caffeine concentration (r2 = 0.41), but there was a very good correlation between a single plasma caffeine concentration measured at 5 PM and the 24-hour average concentration (r2 = 0.94). The same was true for paraxanthine (r2 = 0.86). Paraxanthine accounted for 67.3% of the total dimethylxanthines in plasma, while theobromine and theophylline accounted for 24.4% and 8.3%, respectively. Mean caffeine clearance was 1.2 +/- 0.3 ml/min/kg. Plasma caffeine concentration before the first drink in the morning correlated very poorly with caffeine clearance (r2 = 0.07), even when adjusted for caffeine intake (r2 = 0.21).  相似文献   
74.
75.
76.
'Gliosarcomas' have long been considered to be mixed gliomas and sarcomas. The present study failed to define criteria which clearly delineate 'gliosarcomas' from glioblastoma multiforme and suggests that 'gliosarcomas' should be considered as spindle cell glioblastomas. A total of six cases originally diagnosed as 'gliosarcomas' were compared with four cases of glioblastoma multiforme. No clinical or prognostic features were defined which would clearly separate 'gliosarcomas' from glioblastoma multiforme. Macroscopically, biopsies from 'gliosarcomas' ranged from firm, apparently well-circumscribed tumours to poorly circumscribed lesions with a soft consistency resembling glioblastoma multiforme. Histology revealed a continuous spectrum in which 'gliosarcomas' with large reticulin-rich areas of spindle cells merged with typical glioblastomas containing only small islands of spindle cells and reticulin staining. Immunocytochemistry for glial fibrillary acidic protein (GFAP); S100 protein and alpha-smooth muscle actin (ASMA) showed that the majority of cells in reticulin-poor areas of 'gliosarcoma' and glioblastomas expressed S100 protein and GFAP; many expressed ASMA and some expressed both GFAP and ASMA. Spindle cells in reticulin-rich areas of 'gliosarcomas' and glioblastomas most frequently expressed ASMA but many cells also expressed S100 protein and GFAP; some cells expressed both GFAP and ASMA. The results of this study and a review of the literature suggests that there is a clinical, radiological and pathological continuum with glioblastoma and 'gliosarcoma' at different ends of the spectrum. It is suggested, therefore, that most, if not all, 'gliosarcomas' be redesignated as spindle cell glioblastomas and not be considered as a mixture of glioma and sarcoma.  相似文献   
77.
78.
79.
80.
To evaluate the relative contribution of insulin binding and postbinding defects of glucose utilization in peripheral tissue during normal and diabetic pregnancy, we have studied the in vitro insulin action of isolated adipocytes from eight nondiabetic pregnant women and nine pregnant women with insulin-dependent diabetes mellitus who were undergoing cesarian section. The pregnant women were compared with a matched group of normal nonpregnant women undergoing gynecologic surgery. Insulin binding to adipocytes measured at tracer insulin concentration was reduced by 45% (P less than 0.01) in normal pregnant women and by 30% (P less than 0.02) in pregnant women with diabetes. In contrast, no changes were found between the three groups in insulin binding to pure monocytes and erythrocytes. The glucose transport system in fat cells from both groups of pregnant women was characterized by impaired maximal (P less than 0.05) and half-maximal (P less than 0.05) response to insulin. When fat cell glucose metabolism was studied, pregnant diabetic women exhibited decreased basal lipogenesis (P less than 0.05) and decreased maximal responses of lipogenesis and glucose oxidation to insulin stimulation (P less than 0.05). Similar but less pronounced abnormalities were seen in glucose metabolism of adipocytes from nondiabetic pregnant women. In conclusion, both in late normal and diabetic pregnancy, insulin binding to adipocytes is significantly reduced and accompanied by decreased insulin sensitivity and reduced maximal insulin responsiveness of glucose transport and by impaired basal and maximally insulin-stimulated glucose metabolism.  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