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   3378篇
  免费   145篇
  国内免费   26篇
耳鼻咽喉   41篇
儿科学   49篇
妇产科学   47篇
基础医学   336篇
口腔科学   141篇
临床医学   209篇
内科学   821篇
皮肤病学   46篇
神经病学   185篇
特种医学   246篇
外科学   550篇
综合类   7篇
一般理论   1篇
预防医学   182篇
眼科学   65篇
药学   227篇
中国医学   2篇
肿瘤学   394篇
  2023年   22篇
  2022年   37篇
  2021年   53篇
  2020年   26篇
  2019年   41篇
  2018年   51篇
  2017年   40篇
  2016年   39篇
  2015年   41篇
  2014年   71篇
  2013年   88篇
  2012年   120篇
  2011年   141篇
  2010年   85篇
  2009年   66篇
  2008年   127篇
  2007年   142篇
  2006年   144篇
  2005年   154篇
  2004年   150篇
  2003年   140篇
  2002年   168篇
  2001年   145篇
  2000年   174篇
  1999年   136篇
  1998年   57篇
  1997年   37篇
  1996年   31篇
  1995年   39篇
  1994年   28篇
  1993年   26篇
  1992年   93篇
  1991年   85篇
  1990年   61篇
  1989年   80篇
  1988年   58篇
  1987年   58篇
  1986年   70篇
  1985年   59篇
  1984年   43篇
  1983年   36篇
  1982年   15篇
  1979年   32篇
  1978年   20篇
  1977年   23篇
  1976年   17篇
  1975年   24篇
  1974年   21篇
  1973年   19篇
  1972年   21篇
排序方式: 共有3549条查询结果,搜索用时 46 毫秒
11.
Obesity is a risk factor for cardiovascular disease and thromboembolic events. We investigated the effects of weight reduction by a 12-week calorie-restricted diet with or without aerobic exercise (diet group and diet plus exercise group) on leptin and anticoagulation proteins levels. Forty-two obese nondiabetic individuals were evaluated for blood levels of leptin, protein C activity, free protein S antigen and for body fat area calculated on computerized tomography before and after intervention. Before intervention, serum levels of leptin and free protein S antigen correlated positively with several adiposity-related parameters. After the program, body weight and fat area were significantly decreased in both groups. Body mass index and leptin levels decreased in both groups, with a larger change in the diet plus exercise group than in the diet group. Although protein C activity levels did not change in both groups, free protein S antigen levels decreased significantly in the diet plus exercise group. In conclusion, the 12-week programs had significant effects on the initial weight reduction and body fat mass, decreasing lepin levels in obese nondiabetic individuals. To clarify whether aerobic exercise has additional or direct effects on the anticoagulation system, a study in a large number of individuals is needed.  相似文献   
12.
13.
Electrocardiogram in a 15-year-old girl showed persistent supraventricular tachycardia at rates of 130 to 140 bpm. Electrophysiological study confirmed left atrial automatic tachycardia, which was transferred to sinus rhythm by intravenous infusion of aprindine (100 mg/10 min). Therefore, aprindine (60 mg/day) was administered orally, and neither recurrence of left atrial automatic tachycardia nor side effects were observed during subsequent follow-up period of 16 months.  相似文献   
14.
Hepatitis B virus (HBV), with a G-to-A point mutation at nucleotide 83 in the precore region (mutant HBV83), accounts for most cases of hepatitis B e antigen (HBeAg)-defective HBV. However, it is still not clear how mutant HBV83 is associated with HBe seroconversion. Twenty-six HBeAgpositive patients with chronic hepatitis B who received oral prednisolone (30 mg/day) for 3 weeks were studied to clarify the prevalence of mutant HBV83 during the treatment using polymerase chain reaction with a restriction fragment length polymorphism assay. Twelve (46%) patients seroconverted to anti-HBe 1 year after treatment, whereas 14 (54%) did not. The proportion of mutant HBV83 to whole HBV remained unchanged in both groups during an acute exacerbation induced by withdrawal of corticosteroids. Among 12 anti-HBe-0seroconverted patients, five (56%) of nine patients with only wild-type HBV at baseline developed detectable levels of mutant HBV83 while all three patients with a mixed viral population of wild-type HBV and mu tant HBV83 at baseline developed a higher pro portion of mutant HBV83 one year after treat ment. In contrast, these changes were observed in only one (14%) of seven who failed to seroconvert. The results indicate that a flare-up of hepa titis precedes emergence or selection of mutant HBV83, followed by HBe seroconversion in patients with chronic hepatitis B. © 1995 WiIey-Liss, Inc.  相似文献   
15.
Leukocyte adhesion to vascular endothelial cells is an essential step in the development of inflammatory diseases. We have searched for inhibitors of leukocyte-endothelial cell adhesion that could be used as anti-inflammatory drugs and found that bruceine B (0.2 g/ml; 0.44 M) inhibited human neutrophil or T cell adhesion to tumor necrosis factor- (TNF) stimulated human umbilical vein endothelial cells (HUVEC). The inhibition of neutrophil adhesion to TNF-stimulated HUVEC by bruceine B was not derived from cytotoxic effects, as determined by measurement of the level of lactate dehydrogenase (LDH) activity in conditioned medium. The effect of bruceine B on neutrophil adhesion to HUVEC was not seen when the neutrophils were preincubated with bruceine B. However, inhibitory effects were evident when the HUVEC were preincubated with bruceine B. Bruceine B also inhibited neutrophil adhesion to lipopolysaccharide-stimulated HUVEC and T cell adhesion to TNF-stimulated HUVEC. These findings suggest that bruceine B may have anti-inflammatory activity.  相似文献   
16.
We often see perilobular necrosis of the pancreas in patients with liver disease at autopsy. This study was undertaken to determine the frequency and the mechanism of development of pancreatic perilobular necrosis in patients with liver disease. Pancreatic perilobular necrosis was seen in 21 per cent of 261 autopsied patients: in 41 per cent of 73 autopsied patients with liver disease and in 13 per cent of 188 autopsied patients without liver disease. Moreover, splanchnic congestion was present in 90 per cent of 30 pancreatic perilobular necrosis patients with liver disease. These data indicate that patients with liver disease develop perilobular necrosis of the pancreas more often than patients without liver disease, and that the high frequency may be a sequela of splanchnic congestion; that is, congestion of the pancreas and endotoxaemia due to congestion of the gut.  相似文献   
17.
The activities of RNase (RNase-U and RNase-C) were determined in the serum and leukocytes of 277 patients with 14 cases of various kinds of eosinophilia (not less than 10(3)/microliters), 28 cases of chronic myelocytic leukemia (CML), using polyuridylic acid and polycytidylic acid as synthetic substrates according to the method of Raddi et al. Serum RNase-U activity, serum RNase-C activity and the activity ratio (U/C x 10(-3)) were 55 +/- 14 U, 1,280 +/- 235 U and 44 +/- 11 (mean +/- SD), 196 +/- 137, 1,992 +/- 1,134 U and 97 +/- 38, and 110 +/- 50 U, 1,854 +/- 625 U and 65 +/- 13 for normal subjects, eosinophilia and CML (untreated), respectively. U/C ratio in eosinophilia and CML (untreated) showed a highly significant positive correlation (p less than 0.001) with peripheral eosinophil count; the activity of serum RNase-U per cells in the supernatant of eosinophil homogenate rose significantly (p less than 0.001) compared with that of lymphocytes or granulocytes. Besides, serum and eosinophil RNase-U had a similar optimal pH. These results suggested that serum RNase-U in eosinophilia originated mostly from eosinophils and its rise was correlated strongly with the increase in eosinophils.  相似文献   
18.
19.
We evaluated a novel method of computed tomography (CT) analysis using formalin-fixed lungs of autopsy cases with mild emphysema. Eight formalin-inflated lungs (FILs) obtained at autopsy were examined using CT after draining off the formalin and air inflation with an air pump, and subjected to pathological study including pathological scoring of emphysema and microscopic image analysis (MIA). Satisfactory CT examination was carried out within 5 h of lung fixation. The mean alveolar area determined by MIA correlated highly with the lung volume (r=0.845) and CT score (r=0.722). This method is simple compared with conventional polyethylene glycol fixation for CT and enables CT examination of resected lungs without anxiety about biohazards. Mild emphysema can be detected by MIA.  相似文献   
20.
To clarify the pathogenesis of hyaline globules in liver cells after partial hepatectomy, the present study was undertaken in rats. When partial hepatectomy was performed by the surgical procedure of Higgins and Anderson, the inferior vena cava pressure was raised, and many hyaline globules, which are very similar to those caused by condensation of the contents of vacuoles in liver cells after temporary pressure elevation of the inferior vena cava, were induced in liver cells. On the other hand, when the median lobe and the left lateral lobe were removed carefully one at a time to avoid operative narrowing of the inferior vena cava, the inferior vena cava pressure was not elevated, and only very few hyaline globules were formed. This suggests that hyaline globules in liver cells following partial hepatectomy in rats may be caused by elevation of inferior vena cava pressure due to narrowing of the inferior vena cava by surgical procedure.  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