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   603篇
  免费   35篇
  国内免费   1篇
耳鼻咽喉   1篇
儿科学   15篇
妇产科学   8篇
基础医学   84篇
口腔科学   5篇
临床医学   100篇
内科学   104篇
皮肤病学   8篇
神经病学   72篇
特种医学   31篇
外科学   67篇
综合类   6篇
一般理论   1篇
预防医学   62篇
眼科学   2篇
药学   49篇
中国医学   1篇
肿瘤学   23篇
  2023年   3篇
  2022年   8篇
  2021年   16篇
  2020年   7篇
  2019年   7篇
  2018年   18篇
  2017年   13篇
  2016年   20篇
  2015年   19篇
  2014年   24篇
  2013年   33篇
  2012年   48篇
  2011年   44篇
  2010年   24篇
  2009年   25篇
  2008年   44篇
  2007年   39篇
  2006年   41篇
  2005年   42篇
  2004年   39篇
  2003年   19篇
  2002年   23篇
  2001年   10篇
  2000年   5篇
  1999年   7篇
  1998年   4篇
  1997年   4篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1992年   4篇
  1991年   2篇
  1989年   5篇
  1988年   2篇
  1986年   2篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
  1972年   2篇
  1971年   4篇
  1967年   1篇
  1966年   2篇
  1965年   4篇
  1959年   1篇
  1910年   1篇
  1903年   1篇
  1902年   1篇
排序方式: 共有639条查询结果,搜索用时 31 毫秒
11.
The discourse of leaderism in health care has been a subject of much academic and practical debate. Recently, distributed leadership (DL) has been adopted as a key strand of policy in the UK National Health Service (NHS). However, there is some confusion over the meaning of DL and uncertainty over its application to clinical and non‐clinical staff. This article examines the potential for DL in the NHS by drawing on qualitative data from three co‐located health‐care organisations that embraced DL as part of their organisational strategy. Recent theorising positions DL as a hybrid model combining focused and dispersed leadership; however, our data raise important challenges for policymakers and senior managers who are implementing such a leadership policy. We show that there are three distinct forms of disconnect and that these pose a significant problem for DL. However, we argue that instead of these disconnects posing a significant problem for the discourse of leaderism, they enable a fantasy of leadership that draws on and supports the discourse.  相似文献   
12.
13.
BACKGROUND: Folic acid is assumed to have favourable effects on vascular endothelium, directly as well as indirectly through its effect on homocysteine metabolism. However, the clinical value of folic acid in secondary prevention after acute myocardial infarction (MI) has never been tested. Thus, a randomised, open-label, multicentre trial was performed in order to study the effect of folic acid 5 mg o.d. when added to statin therapy on the incidence of recurrent major clinical events up to 1 year post-MI. METHODS: A total of 283 patients with a total cholesterol >6.5 mmol/l (251 mg/dl) (mean 7.3 mmol/l) were included. All patients received 40 fluvastatin. In 140 of the 283 patients, folic acid (5 mg o.d.) was instituted at discharge, and the remaining 143 patients served as controls. Other secondary prevention measures for both groups were advocated. The primary endpoint was a composite consisting of all vascular events, including death, recurrent MI, strokes, and unplanned invasive coronary interventions. RESULTS: At baseline, the two groups were well-matched for all clinical and demographic parameters. After 1 year of treatment, no difference was noticed in the primary endpoint between the two groups. These endpoints occurred in 43 patients (31%) in the folic acid group, as opposed to 45 patients (31%) in the control group. All separate cardiovascular events were also equally distributed between both groups. Total cholesterol levels decreased to a similar extent in the two groups (to 5.5 and 5.7 mmol/l, in folic acid and control groups, respectively). CONCLUSIONS: In this medium-size pilot study, folic acid did not demonstrate any beneficial additive effects on cardiovascular mortality or morbidity in post-MI patients with hypercholesterolemia who were treated with statin therapy. Larger trials, possibly targeting at selected populations, must be awaited before definitive conclusions regarding the potentially favourable effects of folic acid supplementation in secondary prevention can be drawn.  相似文献   
14.
Erythrocyte aggregation is known to be affected by a number of factors including the concentration of various plasma proteins. This study was performed to examine the in vivo effect of hemodilution of plasma proteins on erythrocyte aggregation in patients undergoing cardiopulmonary bypass (CPB) surgery. Blood samples were taken before, during, and after operation from 40 coronary artery bypass grafting patients who were operated with CPB and concomitant hemodilution (CPB, n=20) and who without (nonCPB, n=20). Erythrocyte aggregation was determined with a LORCA aggregometer, during which all samples were standardized to a hematocrit level of 40%. Results showed that in the CPB patients the aggregation index (AI) dropped to 44% of its preoperative baseline level 5 minutes after the start of hemodilution (from 47.7+/-10.1 to 26.6+/-11.4, p<0.01). Meanwhile, plasma concentration of fibrinogen (Fb) dropped to 55%, haptoglobin to 85%, ceruloplasmin to 55%, and albumin to 67%. In the nonCPB patients, however, there was only a slight drop in AI and the concentrations of plasma proteins during the similar period of time. On postoperative day 1, AI was rebounded to 37.1+/-12.4 in CPB patients compared with 44.3+/-11.7 in nonCPB patients. At baseline, AI was correlated only with Fb. During CPB and hemodilution, AI was correlated not only with Fb but also with haptoglobin and ceruloplasmin. Postoperatively, significant correlationship was found between AI and Fb, CRP, haptoglobin, ceruloplasmin, as well as albumin. These results indicate that hemodilution of plasma proteins significantly reduces the aggregability of erythrocytes in patients undergoing CPB. Besides Fb, other plasma proteins also contribute to AI during the early postoperative period when patients are recovering from CPB surgery.  相似文献   
15.
OBJECTIVES: The purpose of this study was to evaluate the hypothesis that presumed reversion of electrical remodeling after cardioversion of atrial fibrillation (AF) restores the efficacy of flecainide. BACKGROUND: Flecainide loses its efficacy to cardiovert when AF has been present for more than 24 hours. Most probably, the loss is caused by atrial electrical remodeling. Studies suggest electrical remodeling is completely reversible within 4 days after restoration of sinus rhythm (SR). METHODS: One hundred eighty-one patients with persistent AF (median duration 3 months) were included in this prospective study. After failure of pharmacologic cardioversion by flecainide 2 mg/kg IV (maximum 150 mg in 10 minutes) and subsequent successful electrical cardioversion, we performed intense transtelephonic rhythm monitoring three times daily for 1 month. In case of AF recurrence, a second cardioversion by flecainide was attempted as soon as possible. RESULTS: AF recurred in 123 patients (68%). Successful cardioversion by flecainide occurred only when SR had been maintained for more than 4 days (7/51 patients [14%]). Failure to cardiovert was associated with a prolonged duration of the recurrent AF episode and concurrent digoxin use. Multivariate logistic regression confirmed that successful cardioversion was determined by digoxin use (odds ratio [OR] 0.093, P = .047) and by the interaction between the duration of SR and the (inverse) duration of recurrent AF (OR 6.499, P < .001). When flecainide was administered within 10 hours after AF onset and the duration of SR was greater than 4 days, the success rate was 58%. CONCLUSIONS: Flecainide recovers its antiarrhythmic action after cardioversion of AF. However, successful pharmacologic cardioversion occurs only after SR has lasted at least 4 days and is expected only for recurrences having duration of a few hours. Immediate pharmacologic cardioversion of AF recurrence may be a worthwhile strategy for management of persistent AF.  相似文献   
16.
17.
ObjectiveTo investigate the influence of workload setting (speed at constant power, method to impose power) on the propulsion technique (i.e. force and timing characteristics) in handrim wheelchair propulsion.MethodTwelve able-bodied men participated in this study. External forces were measured during handrim wheelchair propulsion on a motor driven treadmill at different velocities and constant power output (to test the forced effect of speed) and at power outputs imposed by incline vs. pulley system (to test the effect of method to impose power). Outcome measures were the force and timing variables of the propulsion technique.ResultsFEF and timing variables showed significant differences between the speed conditions when propelling at the same power output (p < 0.01). Push time was reduced while push angle increased. The method to impose power only showed slight differences in the timing variables, however not in the force variables.ConclusionsResearchers and clinicians must be aware of testing and evaluation conditions that may differently affect propulsion technique parameters despite an overall constant power output.  相似文献   
18.
19.
20.
No previous research in squash has considered the time between shots or the proximity of the ball to a wall, which are two important variables that influence shot outcomes. The aim of this paper was to analyse shot types to determine the extent to which they are played in different court areas and a more detailed analysis to determine whether the time available had an influence on the shot selected. Ten elite matches, contested by fifteen of the world’s top right handed squash players (age 27 ± 3.2, height 1.81 ± 0.06 m, weight 76.3 ± 3.7 kg), at the men’s World Team Championships were processed using the SAGIT/Squash tracking system with shot information manually added to the system. Results suggested that shot responses were dependent upon court location and the time between shots. When these factors were considered repeatable performance existed to the extent that one of two shots was typically played when there was limited time to play the shot (< 1.20s). For example, it was clear that when players did not have a lot of time to hit the ball (low time i.e. < 1.06s, and mid time i.e. 1.06 - 1.20s) in the front left corner close to the side wall, the crosscourt lob was used frequently (44.30% and 36.31% respectively) whereas when there was more time this shot was seldom used (13.64%). Consequently variant and invariant behaviour were shown to exist in elite squash although for the first time it was suggested that the availability of time to play a shot contributed to which of these behaviours was evident. This analysis could be extended by adopting a case study approach to see how individual differences in strategy and tactics affect shot selections.

Key points

  • Previous research has suggested that a playing strategy, elements decided in advance of the match, may be evident for elite players by examining court location and preceding shot type, however these parameters alone are unlikely to be sufficient predictors.
  • At present there is no known analysis in squash, or indeed in any of the racket sports, that has quantified the time available to respond to different shot types. An understanding of the time interval between shots and the movement characteristics of the player responding to different shots according to the court positions might facilitate a better understanding of the dynamics that determine shot selection.
  • Some elements of a general playing strategy were evident e.g. predominately hitting to the back left of the court, but tactical differences in shot selection were also evident on the basis of court location and time available to play a shot.
Key words: Strategy, tactics, SAGIT, invariant behaviour.  相似文献   
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