收费全文 | 16552篇 |
免费 | 781篇 |
国内免费 | 127篇 |
耳鼻咽喉 | 156篇 |
儿科学 | 342篇 |
妇产科学 | 149篇 |
基础医学 | 1993篇 |
口腔科学 | 229篇 |
临床医学 | 1021篇 |
内科学 | 4559篇 |
皮肤病学 | 176篇 |
神经病学 | 1262篇 |
特种医学 | 671篇 |
外科学 | 3277篇 |
综合类 | 43篇 |
现状与发展 | 1篇 |
一般理论 | 1篇 |
预防医学 | 396篇 |
眼科学 | 185篇 |
药学 | 1003篇 |
中国医学 | 48篇 |
肿瘤学 | 1948篇 |
2023年 | 121篇 |
2022年 | 219篇 |
2021年 | 329篇 |
2020年 | 214篇 |
2019年 | 312篇 |
2018年 | 350篇 |
2017年 | 300篇 |
2016年 | 407篇 |
2015年 | 379篇 |
2014年 | 492篇 |
2013年 | 616篇 |
2012年 | 973篇 |
2011年 | 1082篇 |
2010年 | 630篇 |
2009年 | 553篇 |
2008年 | 944篇 |
2007年 | 1058篇 |
2006年 | 1042篇 |
2005年 | 1133篇 |
2004年 | 1107篇 |
2003年 | 1085篇 |
2002年 | 1083篇 |
2001年 | 195篇 |
2000年 | 179篇 |
1999年 | 203篇 |
1998年 | 264篇 |
1997年 | 206篇 |
1996年 | 189篇 |
1995年 | 173篇 |
1994年 | 176篇 |
1993年 | 155篇 |
1992年 | 159篇 |
1991年 | 116篇 |
1990年 | 137篇 |
1989年 | 100篇 |
1988年 | 113篇 |
1987年 | 90篇 |
1986年 | 74篇 |
1985年 | 68篇 |
1984年 | 63篇 |
1983年 | 49篇 |
1982年 | 39篇 |
1981年 | 30篇 |
1980年 | 36篇 |
1979年 | 27篇 |
1978年 | 27篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1975年 | 17篇 |
1974年 | 18篇 |
Methods: An original system composed of a new skinfold chamber and compression device allowed loading quantitative vertical stress to the skin. An intravital microscopic technique enabled direct visualization of the microcirculation in the physiological condition and in response to pressure application. To estimate the effect of ischemia‐reperfusion injury, animals were divided into two groups: the compression‐release group in which the animals received four cycles of compression‐release which consisted of 2 hours of compression followed by 1 hour of pressure release; and the compression alone group in which the animals underwent continuous compression for 8 hours. Functional capillary density was quantified before the compression procedure and on day1 (35 hours) after the first evaluation.
Results and Conclusions: The cyclic compression‐release procedure significantly decreased functional capillary density as compared to continuous compression, indicating that in our experimental setting repetition of ischemia‐reperfusion cycle more severely damaged the microcirculation than single prolonged ischemic insult. The finding supports the significant contribution of ischemia‐reperfusion injury to the pathophysiology of pressure ulcers at the level of dynamic in vivo microcirculation. 相似文献
Methods. Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator.
Results. Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O2 and CO2 transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability.
Conclusions. This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators. 相似文献