全文获取类型
收费全文 | 49416篇 |
免费 | 3861篇 |
国内免费 | 1093篇 |
专业分类
耳鼻咽喉 | 277篇 |
儿科学 | 896篇 |
妇产科学 | 1371篇 |
基础医学 | 4819篇 |
口腔科学 | 1004篇 |
临床医学 | 5769篇 |
内科学 | 8133篇 |
皮肤病学 | 292篇 |
神经病学 | 1948篇 |
特种医学 | 1859篇 |
外国民族医学 | 9篇 |
外科学 | 3781篇 |
综合类 | 7537篇 |
现状与发展 | 2篇 |
预防医学 | 7361篇 |
眼科学 | 353篇 |
药学 | 5166篇 |
100篇 | |
中国医学 | 1850篇 |
肿瘤学 | 1843篇 |
出版年
2024年 | 93篇 |
2023年 | 718篇 |
2022年 | 1399篇 |
2021年 | 2082篇 |
2020年 | 1947篇 |
2019年 | 1707篇 |
2018年 | 1734篇 |
2017年 | 1591篇 |
2016年 | 1675篇 |
2015年 | 1631篇 |
2014年 | 3248篇 |
2013年 | 3391篇 |
2012年 | 3016篇 |
2011年 | 3252篇 |
2010年 | 2453篇 |
2009年 | 2269篇 |
2008年 | 2215篇 |
2007年 | 2337篇 |
2006年 | 1909篇 |
2005年 | 1703篇 |
2004年 | 1484篇 |
2003年 | 1246篇 |
2002年 | 1121篇 |
2001年 | 976篇 |
2000年 | 847篇 |
1999年 | 778篇 |
1998年 | 646篇 |
1997年 | 651篇 |
1996年 | 627篇 |
1995年 | 530篇 |
1994年 | 526篇 |
1993年 | 410篇 |
1992年 | 424篇 |
1991年 | 393篇 |
1990年 | 326篇 |
1989年 | 311篇 |
1988年 | 274篇 |
1987年 | 232篇 |
1986年 | 213篇 |
1985年 | 282篇 |
1984年 | 242篇 |
1983年 | 150篇 |
1982年 | 199篇 |
1981年 | 170篇 |
1980年 | 153篇 |
1979年 | 137篇 |
1978年 | 102篇 |
1977年 | 101篇 |
1976年 | 93篇 |
1975年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
《Journal of the American College of Surgeons》2020,230(4):363-370
- Download : Download high-res image (207KB)
- Download : Download full-size image
22.
Breast Elastography: How to Perform and Integrate Into a “Best-Practice” Patient Treatment Algorithm
Breast elastography has been available for more than 15 years but is not widely incorporated into clinical practice. Many publications report extremely high accuracy for various breast elastographic techniques. However, results in the literature are extremely variable. This variability is most likely due to variations in technique, a relatively steep learning curve, and variability in methods between vendors. This article describes our protocol for performing breast elastography using both strain elastography and shear wave elastography, which produces high sensitivity and specificity. Additionally, we will describe the most commonly known false-positive and false-negative lesions as well as how to detect them. 相似文献
23.
Fayiqa Ahamed Bahkir Srinivasan Subramanian Grandee 《Indian journal of ophthalmology》2020,68(11):2378
Purpose:Since the declaration of the lockdown due to COVID-19, the usage of digital devices has gone up across the globe, resulting in a challenge for the visual systems of all ages. The purpose of this study is to assess the impact of the lockdown on digital device usage, and consequently, the ocular surface health implications and circadian rhythm abnormalities related to digital eye strain.Methods:An open online survey was sent through various social media platforms and was open for a period of 2 weeks.Results:A total of 407 usable responses were obtained; the average age of respondents was 27.4 years. Typically, 93.6% of respondents reported an increase in their screen time since the lockdown was declared. The average increase in digital device usage was calculated at about 4.8 ± 2.8 h per day. The total usage per day was found to be 8.65 ± 3.74 hours. Sleep disturbances have been reported by 62.4% of people. Typically, 95.8% of respondents had experienced at least one symptom related to digital device usage, and 56.5% said that the frequency and intensity of these symptoms increased since the lockdown was declared.Conclusion:The study highlighted the drastic increase in use of digital devices after the initiation of the COVID-19 lockdown, and along with it, the slow deterioration of ocular health across all age groups. Awareness about prevention of digital eye strain should be stressed, and going forward, measures to bring these adverse effects to a minimum should be explored. 相似文献
24.
25.
26.
《Indian heart journal》2022,74(1):7-12
BackgroundThe relationship of atrial fibrillation (AF) with coronary artery disease (CAD) is well established, yet it is often missed. There is evidence of myocardial ischemia on stress imaging in AF patients in the absence of obstructive CAD. In this prospective cohort, we studied the angiographic profiles of non-valvular AF patients.MethodsThe study was a nonrandomized, prospective, single-center observational study of consecutive patients of persistent non-valvular AF. Patients symptomatic for AF despite optimal medical therapy for 3 months were recruited and all underwent coronary angiograms (CAG). Patients with prior history of CAD were excluded.ResultsA total of 70 patients were followed for a mean duration of 12 ± 1.4 months. The mean age of the study group was 66.07 (±11.49) years. Hypertension was the commonest comorbidity seen in 74% patients. Obstructive CAD was present in 32 (46%) patients, non-obstructive (<50% stenosis) CAD in 17 (24%) patients and normal coronaries in 21 (30%) patients. Overall 49 (70%) patients had evidence of CAD. Amongst patients without obstructive CAD, slow flow was seen in 16 (42%) patients. Lower baseline ejection fraction, lower haemoglobin & albumin levels and higher creatinine levels was associated with increased mortality. In patients without obstructive CAD, hospitalizations for fast ventricular rate were significantly increased in those having slow flow on CAG (p = 0.005).ConclusionsMajority (70%) of our patients had evidence of atherosclerotic CAD on CAG. A large proportion of patients without obstructive CAD had slow flow on CAG. 相似文献
27.
《Nutrition, metabolism, and cardiovascular diseases : NMCD》2022,32(10):2338-2347
Background and aimsResting heart rate variability (HRV) and maximal fat oxidation (MFO) during exercise are both considered as a noninvasive biomarkers for early detection of cardiovascular risk factors. Thus, this study aimed to analyze the relationship between resting HRV parameters and MFO during exercise, and the intensity of exercise that elicit MFO (Fatmax) in healthy sedentary adults.Methods and resultsA total of 103 healthy young adults (22.2 ± 2.3 years old, 67% female; from the ACTIBATE cohort) and 67 healthy middle-aged adults (53.1 ± 5.0 years old, 52% female; from the FIT-AGEING cohort) were included in this cross-sectional study. HRV was assessed using a Polar RS800CX heart rate monitor, while MFO and Fatmax were determined during a graded exercise treadmill test using indirect calorimetry. No significant associations were observed for healthy young adults (standardized β coefficients ranged from ?0.063 to 0.094, and all P ≥ 0.347) and for middle-aged adults (standardized β coefficients ranged from ?0.234 to 0.090, and all P ≥ 0.056). Nevertheless, only a weak association was observed between one HRV parameter in time-domain (the percentage of R-R intervals that shows a difference higher than 50 ms [pNN50]) and MFO in the cohort of middle-aged adults (β coefficient = ?0.279, and P = 0.033).ConclusionThe results of this study suggest that resting HRV parameters are not associated with MFO and Fatmax during exercise in two independent cohorts of healthy sedentary young and middle-aged adults, respectively. 相似文献
28.
Marginal rate-based analyses are widely used for the analysis of recurrent events in clinical trials. In many areas of application, the events are not instantaneous but rather signal the onset of a symptomatic episode representing a recurrent infection, respiratory exacerbation, or bout of acute depression. In rate-based analyses, it is unclear how to best handle the time during which individuals are experiencing symptoms and hence are not at risk. We derive the limiting value of the Nelson-Aalen estimator and estimators of the regression coefficients under a semiparametric rate-based model in terms of an underlying two-state process. We investigate the impact of the distribution of the episode durations, heterogeneity, and dependence on the asymptotic and finite sample properties of standard estimators. We also consider the impact of these features on power in trials designed to test intervention effects on rate functions. An application to a trial of individuals with herpes simplex virus is given for illustration. 相似文献
29.
30.
《Indian heart journal》2022,74(5):414-419
BackgroundLeft ventricular outflow tract obstruction (LVOTO) is commonly observed in patients with hypertrophic cardiomyopathy (HCM) or left ventricular hypertrophy (LVH). Some patients develop LVOTO provoked by physical exertion, and hence termed dynamic LVOTO (DLVOTO). However, its precise prevalence and mechanism are still unclear.AimTwo-dimensional speckle tracking echocardiography (2D STE) seems to be helpful for the detection of early LV structural abnormalities. This study aimed to examine the possible role of segmental as well as global longitudinal strain in identifying DLVOTO non-HCM patients as detected by dobutamine stress echocardiography (DSE).Methods and resultsTwo hundred and fifty patients without structural heart disease had undergone conventional transthoracic echocardiography, 2D STE, and DSE. All patients with non-ischemic evidence were divided into two groups according to the DSE results; DLVOTO (+) and DLVOTO (?).Among 250 patients, 50 patients (36%) had shown DLVOTO after DSE (15 males, 35 females; mean age 55±7years). They were compared with 90 non -LVOTO obstruction patients (43 males, 47 females; mean age 57±6years). Based on multivariate logistic regression analysis, the independent predictors of provoked DLVOTO during DSE were resting basal septal longitudinal strain BS-LS average (p < 0.001), resting LA reservoir strain (p < 0.001), and systolic LVOT diameter (p = 0.03). Resting BS-LS average with cut-off - 17.5% was recognized as a critical indicator of DLVOTO, with sensitivity 78%, and specificity 95% (better than systolic LVOT diameter of sensitivity 76%, and specificity 15% and resting LA reservoir strain which showed poor AUC at ROC curve 0.007).ConclusionWe demonstrate that provoked LVOTO during DSE in non HCM symptomatic patients is directly correlated to resting regional LS, where the increased BS-LS of ≥ ?17.5% was a key determinant of LVOT gradient provocation. Assessment of baseline BS-LS average might be a bedside simple tool for detection of patients with DLVOTO not able to do DSE. 相似文献