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   1405篇
  免费   82篇
  国内免费   10篇
耳鼻咽喉   8篇
儿科学   31篇
妇产科学   26篇
基础医学   153篇
口腔科学   51篇
临床医学   112篇
内科学   355篇
皮肤病学   75篇
神经病学   104篇
特种医学   85篇
外科学   239篇
综合类   30篇
预防医学   110篇
眼科学   10篇
药学   52篇
肿瘤学   56篇
  2023年   6篇
  2022年   17篇
  2021年   37篇
  2020年   18篇
  2019年   31篇
  2018年   52篇
  2017年   29篇
  2016年   32篇
  2015年   27篇
  2014年   49篇
  2013年   56篇
  2012年   70篇
  2011年   73篇
  2010年   66篇
  2009年   54篇
  2008年   68篇
  2007年   78篇
  2006年   57篇
  2005年   64篇
  2004年   54篇
  2003年   45篇
  2002年   38篇
  2001年   49篇
  2000年   57篇
  1999年   34篇
  1998年   30篇
  1997年   12篇
  1996年   21篇
  1995年   21篇
  1994年   16篇
  1993年   9篇
  1992年   19篇
  1991年   17篇
  1990年   27篇
  1989年   17篇
  1988年   18篇
  1987年   15篇
  1986年   23篇
  1985年   18篇
  1984年   10篇
  1983年   5篇
  1982年   5篇
  1981年   4篇
  1980年   4篇
  1978年   8篇
  1977年   3篇
  1976年   6篇
  1973年   4篇
  1969年   3篇
  1967年   3篇
排序方式: 共有1497条查询结果,搜索用时 0 毫秒
41.
42.
43.
The viscacha (Lagostomus maximus maximus) is a rodent with photoperiod‐dependent seasonal reproduction. The aim of this work was to study the morphological variations of the prostate during periods of maximal (summer, long photoperiod) and minimal (winter, short photoperiod) reproductive activity. Prostates of adult male viscachas were studied by light and electron microscopy, immunohistochemistry for androgen receptor, and morphometric analysis. The prostate consisted of two regions: peripheral and central. The peripheral zone exhibited large adenomeres with a small number of folds and lined with a pseudostratified epithelium. The central zone had small adenomeres with pseudostratified epithelium and the mucosa showed numerous folds. The morphology of both zones showed variations during periods of maximal and minimal reproductive activity. The prostate weight, prostate‐somatic index, luminal diameter of adenomeres, epithelial height and major nuclear diameter decreased during the period of minimal reproductive activity. Principal cells showed variations in their shape, size and ultrastructural characteristics during the period of minimal reproductive activity in comparison with the active period. The androgen receptor expression in epithelial and fibromuscular stromal cells was different between the studied periods. Our results suggest a reduced secretory activity of viscacha prostate during the period of minimal reproductive activity. Thus, the morphological variations observed in both the central and peripheral zones of the viscacha prostate agree with the results previously obtained in the gonads of this rodent of photoperiod‐dependent reproduction. Additionally, the variations observed in the androgen receptors suggest a direct effect of the circulating testosterone on the gland. Anat Rec, 298:1919–1931, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
44.
45.
46.
47.
48.
49.
OBJECTIVE: Previous findings in labial salivary glands (LSGs) from patients with Sj?gren's syndrome (SS) suggest that increased activity and expression of matrix metalloproteinase 9 (MMP-9) and MMP-3 trigger the destruction of acinar structures in these glands. Tissue inhibitors of matrix metalloproteinases (TIMPs) tightly control MMP activity, and TIMP expression is an important modulator of effects attributed to MMPs. This study was undertaken to investigate the correlation between the balance of MMPs/TIMPs in the LSGs of SS patients and the degree of inflammatory infiltration and acinar structure integrity. METHODS: Three groups of SS patients classified according to focus score and residual tissue were studied. The expression of MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 was examined at the messenger RNA and protein levels. The ratio of MMP/TIMP expression (R value) was calculated. Focus score and acinar structure were evaluated by histologic analysis. RESULTS: In SS patients the MMP-3/TIMP-1 ratio was higher than 1 and the MMP-9/TIMP-1 ratio was much higher than 1 whereas the MMP-2/TIMP-2 ratio nearly equaled 1, suggesting elevated proteolytic activity due mainly to MMP-9. R values were independent of the focus score of inflammatory cells, but correlated well with the dramatic changes observed in morphologic integrity of acini, as revealed mainly by the lack of nuclear polarity. Acinar changes were more evident when R values for both MMP-9/TIMP-1 and MMP-3/TIMP-1 were higher. CONCLUSION: This study provides evidence that an altered balance between MMPs and their inhibitors is associated with acinar damage. Since salivary gland acinar cells express both MMPs and TIMPs, these cells may play an important role in extracellular matrix destruction and in the LSG pathophysiology in SS.  相似文献   
50.
In this study we report the effects of sunflower, virgin olive and fish oils on the progression of aortic lesions. A total of 24 male New Zealand rabbits (six per each group) were fed for 50 days on a diet containing 3% lard and 1.3% cholesterol, to induce atherosclerosis. An atherogenic control group (A) was killed after this period and three groups were fed for an additional period of 30 days with a diet composed of (1.75 g of supplemented oil and 98.25 of standard chow): sunflower oil (S), virgin olive oil (O) and fish oil (F). A control group (n=6) was fed with a standard chow diet for 80 days. LDL lipid composition and histological analysis of aortic atherosclerotic lesions were assayed. The atherogenic diet caused a significant increase of cholesterol levels in LDL and aorta tissue. Cholesterol ester content rose significantly in the aortic arch of groups S, O and F. Fatty streaks were found in all aortic sections, although only group S showed a significant progression of the lesion compared with group A. We conclude that the replacement of a high cholesterol-saturated fat diet by another cholesterol free-unsaturated fat diet does not regress atherosclerosis in rabbit. However, sunflower oil provokes a significant progression in lesion development, whereas diet enrichment with extra virgin olive oil and, to a lesser extent, fish oil, stops this progression.  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