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   4740篇
  免费   271篇
  国内免费   70篇
耳鼻咽喉   23篇
儿科学   196篇
妇产科学   69篇
基础医学   564篇
口腔科学   258篇
临床医学   534篇
内科学   997篇
皮肤病学   71篇
神经病学   325篇
特种医学   329篇
外科学   589篇
综合类   75篇
一般理论   3篇
预防医学   335篇
眼科学   48篇
药学   324篇
肿瘤学   341篇
  2022年   27篇
  2021年   52篇
  2020年   48篇
  2019年   60篇
  2018年   62篇
  2017年   62篇
  2016年   68篇
  2015年   77篇
  2014年   122篇
  2013年   186篇
  2012年   254篇
  2011年   237篇
  2010年   130篇
  2009年   154篇
  2008年   175篇
  2007年   213篇
  2006年   209篇
  2005年   195篇
  2004年   175篇
  2003年   144篇
  2002年   126篇
  2001年   143篇
  2000年   121篇
  1999年   130篇
  1998年   103篇
  1997年   106篇
  1996年   117篇
  1995年   90篇
  1994年   81篇
  1993年   67篇
  1992年   110篇
  1991年   73篇
  1990年   77篇
  1989年   104篇
  1988年   81篇
  1987年   114篇
  1986年   71篇
  1985年   83篇
  1984年   52篇
  1983年   64篇
  1982年   48篇
  1981年   35篇
  1980年   48篇
  1979年   45篇
  1978年   30篇
  1977年   38篇
  1976年   23篇
  1975年   36篇
  1974年   36篇
  1973年   27篇
排序方式: 共有5081条查询结果,搜索用时 0 毫秒
11.
A simple, rapid, and accurate method for measuring limb-length discrepancies with computerized axial tomographic equipment is described. With this method less irradiation is delivered and some of the errors of computation are eliminated, compared with conventional methods. The costs of the technique are comparable with those of scanograms. The method is particularly applicable in the patient who has contracture of a joint.  相似文献   
12.
13.
Cross-sectional studies have not consistently shown a positive association between milk drinking and serum cholesterol. We studied this relationship in a cohort of 7506 men and women aged 40-42 years in the county of Nordland in northern Norway (72% of all subjects in the age-bracket living in the county). We found a positive relationship between the percentage of fat in the milk and total serum cholesterol, but no positive relationship between whole fat milk consumption (number of glasses per day) and serum cholesterol. The findings were, however, to some extent influenced by effects of present atherosclerotic disease, or perceived threat of this.  相似文献   
14.
A prospectively recorded series of 107 patients with clinical neck node metastases from head and neck squamous cell carcinomas, treated in 1983-1988, and with initial local control, is evaluated. Eighty-eight patients received preoperative, and were operated 4-6 weeks after radiotherapy, and 19 received postoperative radiotherapy. Forty-four of the neck specimens in the preoperatively treated patients showed vital tumor tissue, 7 with positive and 37 with negative resection margins. Nine of the latter 37 patients died due to regional recurrence. Twenty-three of the preoperatively treated patients had no palpable residual tumor following radiotherapy, but histological examination showed vital tumor tissue in five, of whom two had N1 neck disease. The overall regional failure rate was 19%. Eleven patients (10%) died from local recurrence and 11 from distant metastases. Forty-one patients (38%) are alive without evidence of disease and three (3%) alive with disease (mean observation time 30 months). Combined treatment is recommended for all cases of neck node metastases.  相似文献   
15.
16.
The predominant shapes of small opacities on the chest radiographs of 895 British coalminers have been studied. The aims were to determine whether irregular (as distinct from rounded) small opacities can be identified reproducibly, whether their occurrence is related to dust exposure, and whether they are associated with excess prevalence of respiratory symptoms or impairments of lung function. Six of the doctors responsible for regular radiological surveys of all British coalminers each classified all 895 radiographs twice and independently, using the International Labour Organisation's 1980 classification system. The majority view was that 39 films showed predominantly irregular small opacities, 131 showed predominantly small rounded opacities, and 587 showed no small opacities. Readers' opinions varied about the presence and shapes of shadows on the other 138 films. In general, consistency between readers (and within readers on repeated viewings) was satisfactory. The occurrence and profusion of irregular shadows were related significantly both to the men's ages and additionally to their cumulative exposure to respirable coalmine dust as determined from 15 years' dust monitoring close to where the miners had worked. For any given level of exposure, the average level of profusion of the small irregular opacities was less than the corresponding profusion of small rounded opacities. The prevalence rates of chronic cough and phlegm, and of breathlessness, were higher in those with small irregular opacities than in those with no small opacities (category 0/0), but the differences were not statistically significant after adjustment for other factors including smoking habits. The presence of irregular (but not rounded) small shadows was associated with an impairment in respiratory function averaging about 190 ml deficits in both FEV1 and FVC. These deficits were not explicable in terms of the men's ages, body sizes, and smoking habits and they were in addition to the lung function losses attributable to the miners' dust exposure as such. It is concluded that the presence and profusion of small irregular opacities should be taken into consideration when assessing the severity of coalworkers' simple pneumoconiosis.  相似文献   
17.
18.
For the past 45 years, there has been a great deal of debate regarding the health issues surrounding the fluoridation of public water supplies. In order to assess the association between fluoridation and hip fracture, we identified 129 counties across the United States considered to be exposed to public water fluoridation and 194 counties without exposure. Data from the Health Care Financing Administration and the Department of Veterans Affairs were used to calculate the incidence of hip fracture among white persons, aged 65 years or older, in fluoridated and nonfluoridated counties. There was a small statistically significant positive association between fracture rates and fluoridation. The relative risk (95% confidence interval) of fracture in fluoridated counties compared to nonfluoridated counties was 1.08 (1.06 to 1.10) for women and 1.17 (1.13 to 1.22) for men. As comparisons were made at the grouped level, it may be inappropriate at this time to draw inferences at the individual level. The relationship observed at the county level needs to be duplicated at the individual level with more precise measures of fluoride exposure.  相似文献   
19.
BACKGROUND. Previous studies in humans advanced the concept that cardiac filling pressure and contractility, the primary determinants of ventricular mechanoreceptor discharge, are important determinants of sympathetic outflow during orthostatic stress. Thus, intravenous propranolol greatly attenuated forearm vasoconstrictor response to venous pooling with lower body negative pressure (LBNP). The aim of this study was to reevaluate the experimental support for this concept by using direct measurements of sympathetic nerve activity. METHODS AND RESULTS. In 11 healthy humans, we recorded muscle sympathetic nerve activity (MSNA) with microelectrodes (peroneal nerve), as well as blood flow in the forearm and calf (venous occlusion plethysmography) at baseline and during graded LBNP. The same experiments were repeated after administration of propranolol (0.15 mg/kg i.v.), which is thought to decrease ventricular mechanoreceptor discharge. The major new findings are that propranolol neither increased baseline MSNA nor attenuated the increases in MSNA during graded orthostatic stress even though in the same subjects, propranolol simultaneously increased the baseline level of vascular resistance in both the forearm and calf and substantially attenuated the increases in regional vascular resistance during orthostatic stress. CONCLUSIONS. Systemic beta-blockade causes a marked dissociation between sympathetic outflow and vascular resistance that invalidates the use of intravenous propranolol as an experimental model to examine the reflex effects of ventricular mechanoreceptors on peripheral vascular resistance in humans.  相似文献   
20.
The objective of the study was to quantify the voluntary dynamic muscular endurance (DME) in patients with primary fibromyalgia (PF) since easy fatigability of muscles is one of the major symptoms in this syndrome. Consecutive outpatients referred to a rheumatology clinic specializing in PF were investigated. Thirty-six patients with PF were compared with 18 patients with chronic myofascial pain (CMP) syndrome. Subjects were matched according to gender, age, height, weight, peak torque, and contractional work. The DME was defined as the number of repeated knee extensions necessary for the contractional work in two successive knee extensions to be equal to or below 70% of the initial value measured with an isokinetic dynamometer. A significantly lower DME was found in the PF group than in the CMP group: 11 (7-13) and 18 (11-25), respectively (median and quartiles), p less than .005. Patients with PF have a low voluntary muscular endurance compared to CMP patients.  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