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   1402455篇
  免费   104165篇
  国内免费   2139篇
耳鼻咽喉   17928篇
儿科学   44458篇
妇产科学   37325篇
基础医学   207693篇
口腔科学   37762篇
临床医学   131619篇
内科学   276738篇
皮肤病学   30206篇
神经病学   114720篇
特种医学   52913篇
外国民族医学   278篇
外科学   200554篇
综合类   27524篇
现状与发展   3篇
一般理论   671篇
预防医学   115026篇
眼科学   31014篇
药学   101461篇
  7篇
中国医学   2240篇
肿瘤学   78619篇
  2021年   12374篇
  2019年   12731篇
  2018年   16666篇
  2017年   12868篇
  2016年   14127篇
  2015年   16197篇
  2014年   22436篇
  2013年   33539篇
  2012年   46558篇
  2011年   49619篇
  2010年   28659篇
  2009年   27567篇
  2008年   46244篇
  2007年   49283篇
  2006年   48785篇
  2005年   47940篇
  2004年   45637篇
  2003年   43442篇
  2002年   42053篇
  2001年   57910篇
  2000年   58629篇
  1999年   49956篇
  1998年   15082篇
  1997年   13556篇
  1996年   13797篇
  1995年   13013篇
  1994年   12075篇
  1992年   39302篇
  1991年   38674篇
  1990年   37296篇
  1989年   36076篇
  1988年   33477篇
  1987年   32775篇
  1986年   31273篇
  1985年   29512篇
  1984年   22714篇
  1983年   19861篇
  1982年   12174篇
  1979年   21488篇
  1978年   15949篇
  1977年   13223篇
  1976年   12300篇
  1975年   13187篇
  1974年   16033篇
  1973年   15740篇
  1972年   14861篇
  1971年   13820篇
  1970年   13047篇
  1969年   12288篇
  1968年   11434篇
排序方式: 共有10000条查询结果,搜索用时 1 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.
995.
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   
996.
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   
997.
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   
998.
999.
1000.
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   
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