全文获取类型
收费全文 | 21526篇 |
免费 | 5657篇 |
国内免费 | 128篇 |
专业分类
耳鼻咽喉 | 627篇 |
儿科学 | 649篇 |
妇产科学 | 696篇 |
基础医学 | 385篇 |
口腔科学 | 2650篇 |
临床医学 | 4156篇 |
内科学 | 5113篇 |
皮肤病学 | 456篇 |
神经病学 | 1821篇 |
特种医学 | 984篇 |
外科学 | 3825篇 |
综合类 | 54篇 |
现状与发展 | 12篇 |
预防医学 | 2694篇 |
眼科学 | 319篇 |
药学 | 220篇 |
中国医学 | 6篇 |
肿瘤学 | 2644篇 |
出版年
2024年 | 163篇 |
2023年 | 1091篇 |
2022年 | 354篇 |
2021年 | 636篇 |
2020年 | 1213篇 |
2019年 | 482篇 |
2018年 | 1322篇 |
2017年 | 1287篇 |
2016年 | 1499篇 |
2015年 | 1562篇 |
2014年 | 1962篇 |
2013年 | 2370篇 |
2012年 | 771篇 |
2011年 | 728篇 |
2010年 | 1363篇 |
2009年 | 1938篇 |
2008年 | 746篇 |
2007年 | 509篇 |
2006年 | 654篇 |
2005年 | 471篇 |
2004年 | 333篇 |
2003年 | 316篇 |
2002年 | 258篇 |
2001年 | 402篇 |
2000年 | 284篇 |
1999年 | 389篇 |
1998年 | 502篇 |
1997年 | 485篇 |
1996年 | 533篇 |
1995年 | 388篇 |
1994年 | 304篇 |
1993年 | 261篇 |
1992年 | 180篇 |
1991年 | 158篇 |
1990年 | 137篇 |
1989年 | 147篇 |
1988年 | 127篇 |
1987年 | 130篇 |
1986年 | 109篇 |
1985年 | 99篇 |
1984年 | 80篇 |
1983年 | 89篇 |
1982年 | 82篇 |
1981年 | 67篇 |
1980年 | 45篇 |
1979年 | 34篇 |
1978年 | 32篇 |
1977年 | 45篇 |
1976年 | 32篇 |
1975年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
995.
996.
Sharmistha Dev MD MPH Andrew A. Gonzalez MD JD MPH Jessica Coffing MPH James E. Slaven MS Shantanu Dev BS Stan Taylor MA Carrie Ballard S. Nicole Hastings MD MHSc Dawn M. Bravata MD 《Academic emergency medicine》2023,30(4):349-358
Objectives
Frailty is a clinical syndrome characterized by decreased physiologic reserve that diminishes the ability to respond to stressors such as acute illness. Veterans Health Administration (VA) emergency departments (ED) are the primary venue of care for Veterans with acute illness and represent key sites for frailty recognition. As questionnaire-based frailty instruments can be cumbersome to implement in the ED, we examined two administratively derived frailty scores for use among VA ED patients.Methods
This national retrospective cohort study included all VA ED visits (2017–2020). We evaluated two administratively derived scores: the Care Assessment Needs (CAN) score and the VA Frailty Index (VA-FI). We categorized all ED visits across four frailty groups and examined associations with outcomes of 30-day and 90-day hospitalization and 30-day, 90-day, and 1-year mortality. We used logistic regression to assess the model performance of the CAN score and the VA-FI.Results
The cohort included 9,213,571 ED visits. With the CAN score, 28.7% of the cohort were classified as severely frail; by VA-FI, 13.2% were severely frail. All outcome rates increased with progressive frailty (p-values for all comparisons < 0.001). For example, for 1-year mortality based on the CAN score frailty was determined as: robust, 1.4%; prefrail, 3.4%; moderately frail, 7.0%; and severely frail, 20.2%. Similarly, for 90-day hospitalization based on VA-FI, frailty was determined as prefrail, 8.3%; mildly frail, 15.3%; moderately frail, 29.5%; and severely frail, 55.4%. The c-statistics for CAN score models were higher than for VA-FI models across all outcomes (e.g., 1-year mortality, 0.721 vs. 0.659).Conclusions
Frailty was common among VA ED patients. Increased frailty, whether measured by CAN score or VA-FI, was strongly associated with hospitalization and mortality and both can be used in the ED to identify Veterans at high risk for adverse outcomes. Having an effective automatic score in VA EDs to identify frail Veterans may allow for better targeting of scarce resources. 相似文献997.
998.
999.
1000.
Carrie L. Peterson PhD Zachary A. Riley PhD Eileen T. Krepkovich MS Wendy M. Murray PhD Eric J. Perreault PhD 《Muscle & nerve》2014,49(5):716-723
Introduction: Withdrawal reflexes in the leg adapt in a context‐appropriate manner to remove the limb from noxious stimuli, but the extent to which withdrawal reflexes adapt in the arm remains unknown. Methods: We examined the adaptability of withdrawal reflexes in response to nociceptive stimuli applied in different arm postures and to different digits. Reflexes were elicited at rest, and kinetic and electromyographic responses were recorded under isometric conditions, thereby allowing motorneuron pool excitability to be controlled. Results: Endpoint force changed from a posterior–lateral direction in a flexed posture to predominantly a posterior direction in a more extended posture [change in force angle (mean ± standard deviation) 35.6 ± 5.0°], and the force direction changed similarly with digit I stimulation compared with digit V (change = 22.9 ± 2.9°). Conclusions: The withdrawal reflex in the human upper limb adapts in a functionally relevant manner when elicited at rest. Muscle Nerve 49 : 716–723, 2014 相似文献