收费全文 | 21955篇 |
免费 | 6031篇 |
国内免费 | 127篇 |
耳鼻咽喉 | 635篇 |
儿科学 | 652篇 |
妇产科学 | 710篇 |
基础医学 | 434篇 |
口腔科学 | 2653篇 |
临床医学 | 4257篇 |
内科学 | 5286篇 |
皮肤病学 | 489篇 |
神经病学 | 1912篇 |
特种医学 | 1000篇 |
外科学 | 3913篇 |
综合类 | 58篇 |
现状与发展 | 12篇 |
一般理论 | 1篇 |
预防医学 | 2845篇 |
眼科学 | 344篇 |
药学 | 260篇 |
中国医学 | 6篇 |
肿瘤学 | 2646篇 |
2024年 | 137篇 |
2023年 | 1111篇 |
2022年 | 406篇 |
2021年 | 714篇 |
2020年 | 1262篇 |
2019年 | 535篇 |
2018年 | 1387篇 |
2017年 | 1329篇 |
2016年 | 1544篇 |
2015年 | 1595篇 |
2014年 | 2011篇 |
2013年 | 2411篇 |
2012年 | 847篇 |
2011年 | 810篇 |
2010年 | 1379篇 |
2009年 | 1973篇 |
2008年 | 787篇 |
2007年 | 549篇 |
2006年 | 669篇 |
2005年 | 499篇 |
2004年 | 344篇 |
2003年 | 318篇 |
2002年 | 272篇 |
2001年 | 385篇 |
2000年 | 284篇 |
1999年 | 386篇 |
1998年 | 502篇 |
1997年 | 482篇 |
1996年 | 536篇 |
1995年 | 387篇 |
1994年 | 301篇 |
1993年 | 259篇 |
1992年 | 177篇 |
1991年 | 155篇 |
1990年 | 142篇 |
1989年 | 142篇 |
1988年 | 128篇 |
1987年 | 125篇 |
1986年 | 98篇 |
1985年 | 94篇 |
1984年 | 76篇 |
1983年 | 93篇 |
1982年 | 82篇 |
1981年 | 69篇 |
1980年 | 48篇 |
1979年 | 38篇 |
1978年 | 34篇 |
1977年 | 43篇 |
1976年 | 31篇 |
1975年 | 27篇 |
Methods: An Intubation Difficulty Scale (IDS) was developed, based on parameters known to be associated with difficult intubation. It was then evaluated prospectively in a group of 311 consecutive prehospital intubations and 315 intubations in an operating room. In the operating room, the IDS was compared with two other parameters: the time to completion of intubation and the visual analog scale (VAS). Time was measured by an independent observer. Operators in both groups completed a checklist regarding the conditions of intubation.
Results: There is a good correlation between the IDS scale and the VAS assessment of difficulty and time to completion of intubation. VAS and time to completion have a significant but lesser correlation to each other. Comparison of IDS with operator-assessed subjective categorical impression of difficulty by Kruskall-Wallis was statistically significant. 相似文献
Methods. Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non-heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 μg/kg (n = 7) before initiation of apnea. Non-heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia.
Results. Phenylephrine 25 μg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 ± 0.5 versus 7.7 ± 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 ± 5.3 versus 41.0 ± 3.4 mm Hg; p = 0.04). Phenylephrine 25 μg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09).
Conclusions. Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest. 相似文献