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   1270375篇
  免费   95198篇
  国内免费   1626篇
耳鼻咽喉   16387篇
儿科学   41129篇
妇产科学   35220篇
基础医学   190221篇
口腔科学   34850篇
临床医学   118363篇
内科学   249311篇
皮肤病学   27377篇
神经病学   102425篇
特种医学   46977篇
外国民族医学   265篇
外科学   179587篇
综合类   25778篇
现状与发展   3篇
一般理论   572篇
预防医学   104983篇
眼科学   28209篇
药学   93049篇
  7篇
中国医学   2041篇
肿瘤学   70445篇
  2018年   13728篇
  2017年   10550篇
  2016年   11494篇
  2015年   13255篇
  2014年   18232篇
  2013年   27812篇
  2012年   38065篇
  2011年   40455篇
  2010年   23355篇
  2009年   22495篇
  2008年   38148篇
  2007年   40771篇
  2006年   40350篇
  2005年   39472篇
  2004年   37893篇
  2003年   36260篇
  2002年   35112篇
  2001年   56123篇
  2000年   57119篇
  1999年   48165篇
  1998年   13445篇
  1997年   12255篇
  1996年   12682篇
  1995年   11952篇
  1994年   11148篇
  1993年   10431篇
  1992年   38245篇
  1991年   37699篇
  1990年   36480篇
  1989年   35300篇
  1988年   32719篇
  1987年   32055篇
  1986年   30536篇
  1985年   28806篇
  1984年   21962篇
  1983年   19200篇
  1982年   11372篇
  1981年   10335篇
  1979年   20961篇
  1978年   15405篇
  1977年   12796篇
  1976年   11851篇
  1975年   12816篇
  1974年   15596篇
  1973年   15368篇
  1972年   14518篇
  1971年   13564篇
  1970年   12795篇
  1969年   12078篇
  1968年   11238篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
As many as 136 patients (76 with Bechterew's disease, 40 with Reiter's disease and 20 with psoriatic arthritic) and 35 practically healthy persons were examined by echocardiography combined with electro-, phonocardiographic and by clinical, x-ray and laboratory methods. 62 patients were examined over time (within a period from 1 to 4 years). Echocardiography was used to study in detail the central and intracardiac hemodynamics, the status of the valvular apparatus of the heart and of the aorta. The different clinical characteristics of the disease were established to make a concrete contribution to the development of cardial pathology. The disease duration is the most significant characteristics. A long-term prospective follow-up coupled with echocardiographic examinations made over time enabled one to specify the structure of heart damage in patients suffering from Bechterew's disease, Reiter's disease and psoriatic arthritis depending on the hypothetic nature of the damage.  相似文献   
994.
AIMS: To assess the association between abnormal stress myocardial perfusion imaging (MPI) and cardiac events (CE) in asymptomatic patients with diabetes and with > or = 1 additional risk factor. Predictors of abnormal stress MPI were also evaluated. METHODS: Four hundred and forty-seven consecutive patients who underwent stress MPI were prospectively followed for 2.1 [0.5-4.1] years for the subsequent occurrence of hard CE (myocardial infarction and sudden or coronary death) and soft CE (unstable angina and ischaemic heart failure requiring hospitalization). Re-vascularization procedures performed as a result of the screening protocol were not included in the analysis. RESULTS: Follow-up was successful in 419 of 447 patients (94%), of whom 71 had abnormal MPI at baseline. Medical therapy was intensified in all subjects and especially in those with abnormal MPI. Twenty-three patients with abnormal MPI underwent a re-vascularization procedure. CEs occurred in 14 patients, including six of 71 patients (8.5%) with abnormal MPI and eight of 348 patients (2.3%) with normal MPI (P < 0.005). Only two patients developed a hard CE and 12 a soft CE. In multivariate analysis, abnormal MPI was the strongest predictor for CEs [odds ratio (OR) (95% CI) = 5.6 (1.7-18.5)]. Low-density lipoprotein cholesterol > or = 3.35 mmol/l [OR (95% CI) = 7.3; 1.5-34.7] and age > median [OR (95% CI) = 6.0 (1.2-28.6)] were additional independent predictors for CE. The independent predictors for abnormal MPI were male gender, plasma triglycerides > or = 1.70 mmol/l, creatinine clearance < 60 ml/min and HbA1c > 8%, with male gender the strongest [OR (95% CI) = 4.0 (1.8-8.8)]. CONCLUSIONS: Asymptomatic patients with diabetes in this study had a very low hard cardiac event rate over an intermediate period. This could be explained by the effects of intervention or by the low event rate in the background population. Randomized studies of cardiac heart disease screening are required in asymptomatic subjects with diabetes to determine the effectiveness of this intervention.  相似文献   
995.
Background Oxidative stress and increased inflammation have been reported to be increased in subjects with diabetes and to be involved in the pathogenesis of cardiovascular complications after myocardial infarction (MI). It is well recognized that red wine has antioxidant and anti‐inflammatory activities. We examined the effects of moderate red wine intake on echocardiographic parameters of functional cardiac outcome in addition to inflammatory cytokines and nitrotyrosine (oxidative stress marker), in subjects with diabetes after a first uncomplicated MI. Methods One hundred and fifteen subjects with diabetes who had sustained a first non‐fatal MI were randomized to receive a moderate daily amount of red wine (intervention group) or not (control group). Echocardiographic parameters of ventricular dys‐synchrony, circulating levels of nitrotyrosine, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐18 (IL‐18) and C‐reactive protein (CRP) were investigated at baseline and 12 months after randomization. Results After 1 year of diet intervention, concentrations of nitrotyrosine (P < 0.01), CRP (P < 0.01), TNF‐α (P < 0.01), IL‐6 (P < 0.01) and IL‐18 (P < 0.01) were increased in the control group compared with the intervention group. In addition, myocardial performance index (P < 0.02) was higher, and transmitral Doppler flow (P < 0.05), pulmonary venous flow analysis (P < 0.02) and ejection fraction (P < 0.05) were lower in the control group, indicating ventricular dys‐synchrony. The concentrations of nitrotyrosine, CRP, TNF‐α and IL‐6 were related to echocardiographic parameters of ventricular dys‐synchrony. Conclusions In subjects with diabetes, red wine consumption, taken with meals, significantly reduces oxidative stress and pro‐inflammatory cytokines as well as improving cardiac function after MI. Moderate red wine intake with meals may have a beneficial effect in the prevention of cardiovascular complications after MI in subjects with diabetes.  相似文献   
996.
The calculation of the extent of the ring scotoma around positive lenses, as conventionally taught to students of clinical optics, indicates that the scotoma is of a significant size. Using knife-edge lenses this study shows that the calculations are invalid due to the finite size of the eye's entrance pupil and in many instances the scotoma is shown not to exist. The effect noticed in clinical practice is probably largely due to the frame and the edging techniques used which add to the refractive scotoma which is present with high powered lenses, large apertures and/or small pupil sizes.  相似文献   
997.
998.
999.
The application of spin-echo magnetic resonance imaging sequences on non-invasive temperature imaging for temperature mapping of human limbs is investigated. In an in vitro expriment performed on a meat sample, the equilibrium magnetisation P and the spin-lattice relaxation time T1 are calculated from the values for the repetition time TR and the signal intensities obtained by a spin-echo sequence at different tissue temperatures tures as measured by a fibre-optic probe. T1 is linearly correlated to the tissue temperature, and P is linearly correlated to the reciprocal value of the absolute temperature. Both effects, taken together, lead to a non-linear dependency of the signal intensity on temperature. Therefore a TR leading to maximum temperature dependency of the signal intensity is calculated and used in the futher experiments. In the in vivo experiments, the lower legs of two volunteers are cooled from outside. Images are acquired with a spin-echo sequence (1.5T, TR=1200 ms, TE=10 ms). A rise in signal intensity in the muscle with falling skin temperature is observed, particularly in more peripheral muscle layers. This study shows that spin-echo sequences can be used to monitor temperature changes and temperature differences in living muscle tissue.  相似文献   
1000.
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