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   2439493篇
  免费   177337篇
  国内免费   3650篇
耳鼻咽喉   33307篇
儿科学   78202篇
妇产科学   64243篇
基础医学   359308篇
口腔科学   65531篇
临床医学   220765篇
内科学   475396篇
皮肤病学   53078篇
神经病学   194130篇
特种医学   91123篇
外国民族医学   491篇
外科学   366298篇
综合类   49105篇
现状与发展   12篇
一般理论   997篇
预防医学   191293篇
眼科学   56442篇
药学   181470篇
  12篇
中国医学   4726篇
肿瘤学   134551篇
  2021年   20417篇
  2019年   20939篇
  2018年   28719篇
  2017年   21626篇
  2016年   24116篇
  2015年   27295篇
  2014年   38522篇
  2013年   57810篇
  2012年   79983篇
  2011年   85269篇
  2010年   50457篇
  2009年   47794篇
  2008年   80288篇
  2007年   85629篇
  2006年   86306篇
  2005年   83971篇
  2004年   80238篇
  2003年   77436篇
  2002年   74783篇
  2001年   109570篇
  2000年   112118篇
  1999年   94395篇
  1998年   28213篇
  1997年   24678篇
  1996年   24864篇
  1995年   23559篇
  1994年   21574篇
  1993年   20383篇
  1992年   72542篇
  1991年   70554篇
  1990年   68862篇
  1989年   66092篇
  1988年   60703篇
  1987年   59519篇
  1986年   55598篇
  1985年   53506篇
  1984年   39942篇
  1983年   34028篇
  1982年   20724篇
  1979年   36219篇
  1978年   26095篇
  1977年   21656篇
  1976年   20662篇
  1975年   22124篇
  1974年   26436篇
  1973年   25044篇
  1972年   23364篇
  1971年   22138篇
  1970年   20366篇
  1969年   19404篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
15.

Background and aims

Since accelerated atherosclerosis has been reported in systemic lupus erythematosus (SLE), predictive biomarkers of cardiovascular disease (CVD) are needed. Among non-traditional risk factors, bone mineral density (BMD) has been related to CVD. However, its role in SLE remains controversial. This study aims to analyze the associations of subclinical atherosclerosis with traditional and non-traditional CV risk factors.

Methods and results

In a cross-sectional study, atherosclerosis burden was compared between 112 female SLE patients and 31 controls. Plaque number and carotid intima-media wall thickness (cIMT) were assessed by ultrasonography. In a retrospective study, BMD determinations obtained 5-years before the ultrasonography assessment were analyzed in a subgroup of 62 patients. Plaque frequency was increased in SLE, even in patients without CV events or carotid wall thickening. cIMT was increased in patients with CVD, positively correlated with body mass index (BMI). Interestingly, a paradoxical effect of BMI on carotid parameters was observed. Whereas underweight patients (BMI < 20) showed increased prevalence of carotid plaques with low cIMT, those with BMI > 30 showed higher cIMT and plaque burden. Overweight patients (25 < BMI<30) exhibited both elevated cIMT and plaque number. BMI was an independent predictor of BMD. In our retrospective study, patients with either clinical or subclinical CVD exhibited lower BMD levels than their CV-free counterparts. A low lumbar spine BMD independently predicted CVD development after adjusting for confounders.

Conclusion

SLE was associated with a higher subclinical atherosclerosis burden, a bimodal effect being observed for BMI. Decreased BMD can be a CV risk biomarker in SLE.  相似文献   
16.

Introduction

In the United States there has been a large increase in participation in lacrosse for both males and females. The purpose of this study was to analyze the number of head injuries, injury rates (calculated using the reported number of participants) and types of head injuries that are seen in emergency departments in the United States.

Methods

We compared injuries between male and female lacrosse participants. This was a retrospective study using a publicly available database produced by the US Consumer Product Safety Commission and information about lacrosse participation from US Lacrosse.

Results

A linear regression was performed and showed a positive correlation between number of head injuries to males and time from 2002 to 2010 (R2?=?0.823; p?=?0.001). While the number of injuries to the head in female lacrosse participants was not significant. There was a negative correlation between the number of head injuries to males from 2010 to 2016 (R2?=?0.800; p?=?0.007), but again, there was no significance for female injury count (R2?=?0.417; p?=?0.117). Other significant differences between head injuries in males and females included the mechanism of injury and the type of injury recorded.

Conclusion

The most recent data from 2010 to 2016, suggest that both males and females have had a decrease in injury rate. However the total number of female head injuries is not significantly decreasing and as the sport continues to grow there will likely be more total head injuries and visits to the emergency department.  相似文献   
17.
According to the current nutritional recommendations issued by professional diabetes and nutrition associations, diabetic patients should keep to a diet consisting of 45–60% carbohydrates, 10–20% protein, and not more than 35% fat. However, not all of these nutritional recommendations are evidence based. For example, current studies show that the intake of insoluble roughage may be underrepresented. It is also possible that diabetic patients could benefit from keeping to the lower end of the recommended range for carbohydrates (45%) and the upper end of the range advised for protein (20%).  相似文献   
18.
19.
Zusammenfassung In Deutschland leiden 25% der über 70-Jährigen unter einem Diabetes mellitus. Biologisch ältere, multimorbide und in ihren Funktionen beeinträchtigte geriatrische Patienten benötigen spezielle Vorgehensweisen bei Zielplanung, Allgemeinmaßnahmen und Pharmakotherapie. Auf der Basis der vorhandenen Leitlinien werden gesicherte Erkenntnisse dargestellt und Empfehlungen zu den Besonderheiten der Therapie des geriatrischen Diabetespatienten gegeben. Besonderes Augenmerk liegt dabei auf der Interaktion von geriatrischen Syndromen und Diabetes sowie der Verbesserung der Lebensqualität.  相似文献   
20.
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