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   633篇
  免费   27篇
耳鼻咽喉   19篇
儿科学   39篇
妇产科学   23篇
基础医学   65篇
口腔科学   7篇
临床医学   63篇
内科学   196篇
皮肤病学   4篇
神经病学   41篇
特种医学   22篇
外科学   47篇
综合类   3篇
预防医学   88篇
眼科学   4篇
药学   14篇
肿瘤学   25篇
  2022年   5篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   4篇
  2016年   5篇
  2015年   4篇
  2014年   9篇
  2013年   15篇
  2012年   18篇
  2011年   26篇
  2010年   12篇
  2009年   21篇
  2008年   33篇
  2007年   37篇
  2006年   33篇
  2005年   40篇
  2004年   42篇
  2003年   46篇
  2002年   41篇
  2001年   7篇
  2000年   7篇
  1999年   6篇
  1998年   6篇
  1997年   9篇
  1996年   15篇
  1995年   9篇
  1994年   6篇
  1993年   7篇
  1992年   5篇
  1991年   3篇
  1990年   9篇
  1989年   10篇
  1988年   8篇
  1987年   10篇
  1986年   5篇
  1985年   7篇
  1984年   13篇
  1983年   17篇
  1982年   17篇
  1981年   7篇
  1980年   11篇
  1979年   11篇
  1978年   11篇
  1977年   8篇
  1976年   3篇
  1975年   5篇
  1974年   7篇
  1970年   4篇
排序方式: 共有660条查询结果,搜索用时 15 毫秒
31.
32.
OBJECTIVE: To investigate the association of retinopathy with the risk of all-cause, cardiovascular disease (CVD), and coronary heart disease (CHD) mortality in type 2 diabetic subjects in a population-based 18-year follow-up study with particular emphasis on sex differences. RESEARCH DESIGN AND METHODS: Our study cohort comprised 425 Finnish type 2 diabetic men and 399 type 2 diabetic women who were free of CVD at baseline. The findings were classified based on standardized clinical ophthalmoscopy to categories of no retinopathy, background retinopathy, and proliferative retinopathy. The study end points were all-cause, CVD, and CHD mortality. RESULTS: Adjusted Cox model hazard ratios (95% CIs) of all-cause, CVD, and CHD mortality in men were 1.34 (0.98-1.83), 1.30 (0.86-1.96), and 1.18 (0.74-1.89), respectively, for background retinopathy and 3.05 (1.70-5.45), 3.32 (1.61-6.78), and 2.54 (1.07-6.04), respectively, for proliferative retinopathy and in women 1.61 (1.17-2.22), 1.71 (1.17-2.51), and 1.79 (1.13-2.85), respectively, for background retinopathy and 2.92 (1.41-6.06), 3.17 (1.38-7.30), and 4.98 (2.06-12.06), respectively, for proliferative retinopathy. CONCLUSIONS: Proliferative retinopathy in both sexes and background retinopathy in women predicted all-cause, CVD, and CHD death. These associations were independent of current smoking, hypertension, total cholesterol, HDL cholesterol, glycemic control of diabetes, duration of diabetes, and proteinuria. This suggests the presence of common background pathways for diabetic microvascular and macrovascular disease other than those included in the conventional risk assessment of CVD. The sex difference observed in the association of background retinopathy with macrovascular disease warrants closer examination.  相似文献   
33.
OBJECTIVE: To study the occurrence and main causes of transient loss of consciousness in primary health care. DESIGN: A 4-month prospective survey. SETTING: Primary health care emergency room of the City of Tampere, Finland. SUBJECTS: Consecutive patients, aged over 15 years, admitted to the emergency room. MAIN OUTCOME MEASURES: The overall prevalence of loss of consciousness divided into three subgroups: seizure, syncope and uncertain, and their distribution by gender and age. The prevalence of epilepsy, coronary heart disease and alcohol abuse among these diagnostic subgroups. RESULTS: Of all emergency room visits, 1.2% were for loss of consciousness. Of these, 53% were diagnosed as seizures, 33% as syncope attacks and 14% as uncertain. In the seizure group, 75% of patients were men and 67% had a history of alcohol abuse. In the syncope group, 44% of patients had coronary heart disease and 68% were women. CONCLUSION: Loss of consciousness is a fairly frequent problem for the primary health care emergency room. A history of alcohol abuse is commonly associated with seizures.  相似文献   
34.
35.
OBJECTIVE: To investigate whether quantity or quality of dietary fat predicts coronary heart disease (CHD) events in middle-aged type 2 diabetic subjects. RESEARCH DESIGN AND METHODS: The dietary habits of 366 type 2 diabetic men and 295 women, aged 45-64 years and free from CHD, were assessed with a 53-item food frequency questionnaire. They were followed up for 7 years. RESULTS: Men in the highest tertile of the polyunsaturated/saturated fat (P/S) ratio (>0.28) had a significantly lower risk for CHD death than men in the two lowest tertiles (5.0 vs. 14.2%, P = 0.009). The risk for all CHD events was 14.2 vs. 23.2%, respectively (P = 0.044). P/S ratio did not predict CHD events in women. In Cox multiple regression analyses taking into account other cardiovascular risk factors, the highest P/S ratio tertile was associated with the lowest rate of CHD death in men (P = 0.048). CONCLUSIONS: Low P/S ratio in men predicted future CHD events in type 2 diabetic subjects independently of conventional CHD risk factors.  相似文献   
36.
In this paper, a new method intended for ERP denoising in multichannel EEG data is discussed. The denoising is done by separating ERP/noise subspaces in multidimensional EEG data by a linear transformation and the following dimension reduction by ignoring noise components during inverse transformation. The separation matrix is found based on the assumption that ERP sources are deterministic for all repetitions of the same type of stimulus within the experiment, while the other noise sources do not obey the determinancy property. A detailed derivation of the technique is given together with the analysis of the results of its application to a real high-density EEG data set. The interpretation of the results and the performance of the proposed method under conditions, when the basic assumptions are violated – e.g. the problem is underdetermined – are also discussed.Moreover, we study how the factors of the number of channels and trials used by the method influence the effectiveness of ERP/noise subspaces separation. In addition, we explore also the impact of different data resampling strategies on the performance of the considered algorithm. The results can help in determining the optimal parameters of the equipment/methods used to elicit and reliably estimate ERPs.  相似文献   
37.
38.
39.
PURPOSE: The purpose of this study was to investigate the effects of a progressive 10-wk aquatic resistance training on neuromuscular performance and muscle mass of the knee extensors and flexors in healthy women. METHODS: Twenty-four healthy women (34.2 +/- 3.9 yr) were randomly assigned into aquatic exercise (N = 12) and control group (N = 12). Maximum knee extension and flexion torques were measured isometrically and at constant angular velocities of 60 degrees x s(-1) and 180 degrees x s(-1) (isokinetic) with simultaneous electromyography (EMG) recordings of the quadriceps and hamstrings. The lean muscle mass (LCSA) of the quadriceps and hamstring muscles was determined by computed tomography scanning. RESULTS: Significant interaction of group by time was observed in each of the measured parameters. The change in extension and flexion isometric/isokinetic torque varied between 8 and 13% and in EMGs between 10 and 27% in the exercise group. The change in the quadriceps LCSA of the exercise group was 4% and in hamstrings 5.5%. CONCLUSIONS: The results of the present study showed that 10 wk of progressive aquatic resistance training resulted in significant improvement in muscle torque of the knee extensors and flexors accompanied with proportional improvement in neural activation and with significant increase in the LCSA of the trained muscles. Aquatic training can be recommended for neuromuscular conditioning in healthy persons.  相似文献   
40.
Brachial artery FMD (flow-mediated dilatation) is widely used as a marker of systemic arterial endothelial function. FMD, however, shows considerable 25% day-to-day variation that hinders its clinical use. The reasons for this variability are poorly characterized. Therefore the present study was designed to clarify factors responsible for the hourly variation in endothelial function, including consuming a low-fat meal and circadian rhythms in endogenous hormonal levels. Brachial artery FMD, along with serum glucose, triacylglycerols (triglycerides) and levels of several hormones were measured six times per day on two separate days 1 week apart. On one day, the subjects (healthy males: n=12, mean age, 24 years) ate a light breakfast and a standardized lunch (23.5% fat, 48.7% carbohydrate and 27.8% protein). On the other day, they had a similar breakfast after which they fasted. Postprandial FMD values (both after breakfast and after lunch) were similar to baseline FMD. FMD showed a 28% hourly variation and 27% weekly variation. Variation in plasma levels of insulin (P=0.02) associated negatively and DHPG (3,4-dihydroxyphenylglycol) (P=0.001), a marker of sympathetic nervous activation, associated positively with variation in FMD. The effects of DHPG and insulin on FMD were independent of changes in baseline brachial artery diameter, although DHPG was also inversely associated with baseline diameter. Eating a regular low-fat meal does not have any measurable effects on brachial artery endothelial function. These data suggest that strict requirements for fasting conditions may be unnecessary when measuring peripheral endothelial function using the ultrasound technique. Circadian variation in serum insulin and sympathetic tone are physiological determinants of endothelial function.  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