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   2443篇
  免费   142篇
  国内免费   20篇
耳鼻咽喉   20篇
儿科学   130篇
妇产科学   82篇
基础医学   230篇
口腔科学   41篇
临床医学   288篇
内科学   461篇
皮肤病学   36篇
神经病学   164篇
特种医学   255篇
外科学   288篇
综合类   48篇
一般理论   1篇
预防医学   265篇
眼科学   11篇
药学   141篇
  2篇
中国医学   1篇
肿瘤学   141篇
  2021年   26篇
  2020年   17篇
  2019年   24篇
  2018年   34篇
  2017年   25篇
  2016年   22篇
  2015年   32篇
  2014年   41篇
  2013年   69篇
  2012年   105篇
  2011年   107篇
  2010年   60篇
  2009年   47篇
  2008年   82篇
  2007年   119篇
  2006年   91篇
  2005年   109篇
  2004年   87篇
  2003年   88篇
  2002年   95篇
  2001年   63篇
  2000年   83篇
  1999年   73篇
  1998年   47篇
  1997年   35篇
  1996年   36篇
  1995年   40篇
  1994年   33篇
  1993年   40篇
  1992年   66篇
  1991年   54篇
  1990年   52篇
  1989年   73篇
  1988年   55篇
  1987年   64篇
  1986年   44篇
  1985年   53篇
  1984年   39篇
  1983年   28篇
  1982年   20篇
  1981年   28篇
  1980年   25篇
  1979年   28篇
  1978年   20篇
  1977年   31篇
  1976年   22篇
  1975年   18篇
  1974年   19篇
  1970年   14篇
  1969年   13篇
排序方式: 共有2605条查询结果,搜索用时 15 毫秒
31.
Study was made of 95 survivors of aortic valve replacement during the early years of this procedure (1964 to 1970). The average follow-up time was 50.2 months. Survival was not related to hemodynamic parameters, such as cardiac index or left ventricular pressure, and did not appear to be influenced by the type of preoperative valve lesion. A history of angina pectoris and a New York Heart Association Class IV grouping were associated with shorter survival. Associated coronary artery disease was a leading cause of death in those patients surviving less than 2 years and angina pectoris the leading cause of morbidity in the long-term survivors. Sudden death occurred in five patients. Once a patient survived 36 months after the operation, the prognosis was excellent.  相似文献   
32.
33.
34.
Epidemics of novel or re-emerging infectious diseases have quickly spread globally via air travel, as highlighted by pandemic H1N1 influenza in 2009 (pH1N1). Federal, state, and local public health responders must be able to plan for and respond to these events at aviation points of entry. The emergence of a novel influenza virus and its spread to the United States were simulated for February 2009 from 55 international metropolitan areas using three basic reproduction numbers (R(0)): 1.53, 1.70, and 1.90. Empirical data from the pH1N1 virus were used to validate our SEIR model. Time to entry to the U.S. during the early stages of a prototypical novel communicable disease was predicted based on the aviation network patterns and the epidemiology of the disease. For example, approximately 96% of origins (R(0) of 1.53) propagated a disease into the U.S. in under 75 days, 90% of these origins propagated a disease in under 50 days. An R(0) of 1.53 reproduced the pH1NI observations. The ability to anticipate the rate and location of disease introduction into the U.S. provides greater opportunity to plan responses based on the scenario as it is unfolding. This simulation tool can aid public health officials to assess risk and leverage resources efficiently.  相似文献   
35.
Abstract

Background: Accurate, reliable assessment of upper extremity muscular power in persons with paraplegia caused by spinal cord injury (SCI) would provide an objective indication of their ability to generate the forces necessary for the performance of daily activities. Wingate Anaerobic Testing (WAnT) consists of a 30-second sprint test on a cycle ergometer and has been used widely in both athletic and research settings.

Purpose: To examine test-retest reliability of arm WAnT performance in persons with complete SCI and paraplegia.

Methods: Forty-three participants with thoracic-level paraplegia (T2 through T12) performed 2 trials of arm WAnT with 2 to 7 days between each trial. Testing was performed using a Monarch 834E ergometer with participants seated in their wheelchairs. Participants were directed to crank at maximal pace for 30 seconds against a resistance load equivalent to 3.5% of their body mass. The SMI OptoSensor 2000 system was used to determine values of peak power (Ppeak), mean power (Pmean), minimum power, and rate of fatigue, which were compared between trials using 1-way analysis of variance for repeated measures. Coeffi cients of determination (r2) were calculated between trials for Ppeak and Pmean.

Results: No significant diffe rence was found between trials for any of the power output variables. Regression analysis ind icat ed that Ppeak and Pmean were closely associated between the 2 trials (r2= 0.92 and 0.94, respectively).

Conclusion: Arm WAnT is a reliable measurement tool for the assessment of upper extremity muscular power in persons with complete paraplegia.  相似文献   
36.
Abstract

Background/Objective: This study examined magnitude and recovery of low-frequency fatigue (LFF) in the quadriceps after electrically stimulated contractions in spinal cord-injured (SCI) and able-bodied subjects.

Subjects: Nine SCI (ASIA A-C, levels C5-T9, injured 13.6 ± 12.2 years) and 9 sedentary able-bodied subjects completed this study.

Methods: Fatigue was evoked in 1 thigh, and the nonfatigued leg served as a control. The fatigue test for able-bodied subjects lasted 15 minutes. For SCI, stimulation was adjusted so that the relative drop in force was matched to the able-bodied group. Force was assessed at 20 (P20) and 100 Hz (PI 00), and the ratio of P20/P100 was used to evaluate LFF in thighs immediately after, at 10, 20, and 60 minutes, and at 2, 4, 6, and 24 hours after a fatigue test.

Results: The magnitude of LFF (up to 1 hour after fatigue) was not different between able-bodied and patients with SCI. However, recovery of LFF over 24 hours was greater in able-bodied compared with patients with SCI in both the experimental (P < 0.001) and control legs (P < 0.001). The able-bodied group showed a gradual recovery of LFF over time in the experimental leg, whereas the SCI group did not.

Conclusions: These results show that individuals with SCI are more susceptible to LFF than able-bodied subjects. In SCI, simply assessing LFF produced considerable LFF and accounted for a substantial portion of the response. We propose that muscle injury is causing the dramatic LFF in SCI, and future studies are needed to test whether “fatigue” in SCI is actually confounded by the effects of muscle injury.  相似文献   
37.
The focus on quality of life issues in wound care has justly taken a far greater importance. With the acceptance that pain can be a major factor to the patient, and in particular, pain at dressing change comes the opportunity for avoidance and/or reduction strategies. Whilst pain has been associated with wound infection for millennia, it is only much more recently that this has received due attention from research and clinical practice. In this study, the nature of pain, changes in pain and pain associated with infection are the focal points. A Delphi approach, now a frequently used tool in wound care research, has been used to obtain expert opinion on these aspects of management.  相似文献   
38.
Background: Previous research has shown that context improves aphasic individuals' auditory comprehension. The specific contextual information that has been identified as beneficial includes semantic constraints, semantic plausibility, both predictive and non‐predictive information, and familiar topics. However, context can also include familiar content such as the names of relatives, friends, local schools, and local stores.

Aims: The purpose of the present study was to assess the influence of familiar content on comprehension in individuals with aphasia. Specifically, it assessed whether individuals with aphasia answer questions about paragraphs more accurately when the paragraphs contain familiar content than when they do not.

Methods & Procedures: Eleven participants with aphasia and eleven participants without brain damage listened to short paragraphs that differed in the familiarity of the content included. In half of the paragraphs, the people and places were generic and not known specifically by the participants. In the other half, the people and places were known by the participants (as provided by a spouse or other close individual). Approximately half of the subsequent questions asked of the participants related to this targeted information and half related to other, more generic, information in the paragraphs.

Outcomes & Results: The questions relating to the paragraphs with the familiar content were answered more accurately than were the questions relating to the paragraphs with neutral content. For the participants with aphasia, this result occurred for the questions relating to both the targeted (and thus familiar) information and the non‐targeted or neutral information. The extent to which each participant with aphasia benefited from the familiar content did not relate to age, education, time‐post‐onset, or comprehension and naming skills.

Conclusions: These results suggest that familiar content may be another type of context that enhances comprehension skills in individuals with aphasia. The results are interpreted with respect to attention and domain knowledge concepts.  相似文献   
39.
International Journal of Legal Medicine - SYNBONE® spheres were impacted with 7.62 × 39 mm mild steel core ammunition at a mean impact velocity of 654&nbsp;m/s, SD...  相似文献   
40.
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