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   3125292篇
  免费   237407篇
  国内免费   5237篇
耳鼻咽喉   45491篇
儿科学   98284篇
妇产科学   82945篇
基础医学   439673篇
口腔科学   89905篇
临床医学   282963篇
内科学   603593篇
皮肤病学   65780篇
神经病学   255669篇
特种医学   124259篇
外国民族医学   1082篇
外科学   472775篇
综合类   72089篇
现状与发展   2篇
一般理论   1201篇
预防医学   244371篇
眼科学   73958篇
药学   238207篇
  11篇
中国医学   6379篇
肿瘤学   169299篇
  2018年   31869篇
  2017年   24657篇
  2016年   27370篇
  2015年   30813篇
  2014年   43946篇
  2013年   66245篇
  2012年   89799篇
  2011年   94884篇
  2010年   56009篇
  2009年   53289篇
  2008年   89432篇
  2007年   95564篇
  2006年   96830篇
  2005年   93667篇
  2004年   90232篇
  2003年   87043篇
  2002年   85577篇
  2001年   149221篇
  2000年   154535篇
  1999年   130426篇
  1998年   36510篇
  1997年   32863篇
  1996年   32648篇
  1995年   31292篇
  1994年   29253篇
  1993年   27348篇
  1992年   104103篇
  1991年   100364篇
  1990年   97260篇
  1989年   93908篇
  1988年   86886篇
  1987年   85205篇
  1986年   80830篇
  1985年   76986篇
  1984年   57614篇
  1983年   48973篇
  1982年   29067篇
  1981年   25694篇
  1979年   53665篇
  1978年   37258篇
  1977年   32029篇
  1976年   29396篇
  1975年   31657篇
  1974年   38540篇
  1973年   36662篇
  1972年   34497篇
  1971年   32053篇
  1970年   30107篇
  1969年   28258篇
  1968年   25542篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
ABSTRACT

Adolescents and young adults smoke waterpipe tobacco (WT) and cigarillos, at least in part, based on erroneous beliefs that these products are safer than cigarettes. To address this challenge, we used a systematic, three-phase process to develop a health communication campaign to discourage WT and cigarillo smoking among at-risk (tobacco users and susceptible non-users) 16- to 25-year-olds. In Phase 1, we used a national phone survey (N = 896) to determine salient message beliefs. Participants reported constituents (i.e., harmful chemicals) emitted by the products were worrisome. In Phase 2, we developed and evaluated four message executions, with varying imagery, tone, and unappealing products with the same constituents, using focus groups (N = 38). Participants rated one execution highly, resulting in our development of a campaign where each message: (1) identified a tobacco product and constituent in the smoke; (2) included an image of an unappealing product containing the constituent (e.g., pesticides, gasoline) to grab attention; and (3) used a humorous sarcastic tone. In Phase 3, we tested the campaign messages (17 intervention and six control) with a nationally representative online survey (N = 1,636). Participants rated intervention and control messages highly with few differences between them. Exposure to messages resulted in significant increases in all risk beliefs from pre to post (< 0.05). For WT, intervention messages increased beliefs about addiction more than control messages (p < 0.05). This systematic, iterative approach resulted in messages that show promise for discouraging WT and cigarillo use.  相似文献   
32.

Background and aims

It is not known whether non alcoholic fatty liver disease (NAFLD) is a risk factor for diabetes in non obese, non centrally-obese subjects. Our aim was to investigate relationships between fatty liver, insulin resistance and a biomarker score for liver fibrosis with incident diabetes at follow up, in subjects who were neither obese nor centrally-obese.

Methods and results

As many as 70,303 subjects with a body mass index (BMI) < 25 kg/m2 and without diabetes were followed up for a maximum of 7.9 years. At baseline, fatty liver was identified by liver ultrasound, insulin resistance (IR) by homeostatic model assessment of insulin resistance (HOMA-IR) ≥2.0, and central obesity by waist circumference (waist circumference ≥90 cm (men) and ≥85 cm (women). The Fibrosis-4 (FIB-4 score) was used to estimate extent of liver fibrosis. Cox proportional hazards models adjusted for confounders were used to estimate hazard ratios (aHRs) for incident diabetes. As many as 852 incident cases of diabetes occurred during follow up (median [IQR] 3.71 [2.03] years). Mean ± SD BMI was 22.8 ± 1.8 and 21.7 ± 2.0 kg/m2 in subjects with and without diabetes at follow up. In subjects without central obesity and with fatty liver, aHRs (95% CI) for incident diabetes at follow up were 2.17 (1.56, 3.03) for men, and 2.86 (1.50,5.46) for women. Similar aHRs for incident diabetes occurred with fatty liver, IR and the highest quartile of FIB-4 combined, in men; and there was a non significant trend toward increased risk in women.

Conclusions

In normal weight, non-centrally obese subjects NAFLD is an independent risk factor for incident diabetes.  相似文献   
33.
34.
35.

Introduction

The nature of community pharmacy is changing, shifting from the preparation and distribution of medicines to the provision of cognitive pharmaceutical services (CPS); however, often the provision of traditional services leaves little time for innovative services. This study investigated the time community pharmacists spend on the tasks and activities of daily practice and to what extent they are able to implement CPS-related services in daily practice.

Methods

Self-reporting work sampling was used to register the activities of community pharmacists. A smartphone application, designed specifically for this purpose, alerted participants to register their current activity five times per working day for 6 weeks. Participants also completed an online survey about baseline characteristics.

Results

Ninety-one Dutch community pharmacists provided work-sampling data (7848 registered activities). Overall, 51.5% of their time was spent on professional activities, 35.4% on semi-professional activities, and 13.1% on non-professional activities. The proportion of time devoted to CPS decreased during the workweek, whereas the time spent on traditional task increased.

Discussion and conclusion

This study shows it is feasible to collect work-sampling data using smartphone technology. Community pharmacists spent almost half of their time on semi-professional and non-professional activities, activities that could be delegated to other staff members. In practice, the transition to CPS is hampered by competing traditional tasks, which prevents community pharmacists from profiling themselves as pharmaceutical experts in daily practice.  相似文献   
36.
37.

Background and aims

Since accelerated atherosclerosis has been reported in systemic lupus erythematosus (SLE), predictive biomarkers of cardiovascular disease (CVD) are needed. Among non-traditional risk factors, bone mineral density (BMD) has been related to CVD. However, its role in SLE remains controversial. This study aims to analyze the associations of subclinical atherosclerosis with traditional and non-traditional CV risk factors.

Methods and results

In a cross-sectional study, atherosclerosis burden was compared between 112 female SLE patients and 31 controls. Plaque number and carotid intima-media wall thickness (cIMT) were assessed by ultrasonography. In a retrospective study, BMD determinations obtained 5-years before the ultrasonography assessment were analyzed in a subgroup of 62 patients. Plaque frequency was increased in SLE, even in patients without CV events or carotid wall thickening. cIMT was increased in patients with CVD, positively correlated with body mass index (BMI). Interestingly, a paradoxical effect of BMI on carotid parameters was observed. Whereas underweight patients (BMI < 20) showed increased prevalence of carotid plaques with low cIMT, those with BMI > 30 showed higher cIMT and plaque burden. Overweight patients (25 < BMI<30) exhibited both elevated cIMT and plaque number. BMI was an independent predictor of BMD. In our retrospective study, patients with either clinical or subclinical CVD exhibited lower BMD levels than their CV-free counterparts. A low lumbar spine BMD independently predicted CVD development after adjusting for confounders.

Conclusion

SLE was associated with a higher subclinical atherosclerosis burden, a bimodal effect being observed for BMI. Decreased BMD can be a CV risk biomarker in SLE.  相似文献   
38.

Background

Lung ultrasound can accelerate the diagnosis of life-threatening diseases in adults with respiratory symptoms.

Objective

Systematically review the accuracy of lung ultrasonography (LUS) for emergency diagnosis of pneumonia, acute heart failure, and exacerbation of chronic obstructive pulmonary disease (COPD)/asthma in adults.

Methods

PubMed, Embase, Scopus, Web of Science, and LILACS (Literatura Latino Americana e do Caribe em Ciências da Saúde; until 2016) were searched for prospective diagnostic accuracy studies. Rutter-Gatsonis hierarchical summary receiver operating characteristic method was used to measure the overall accuracy of LUS and Reitsma bivariate model to measure the accuracy of the different sonographic signs. This review was previously registered in PROSPERO (Centre for Reviews and Dissemination, University of York, York, UK; CRD42016048085).

Results

Twenty-five studies were included: 14 assessing pneumonia, 14 assessing acute heart failure, and four assessing exacerbations of COPD/asthma. The area under the summary receiver operating characteristic curve of LUS was 0.948 for pneumonia, 0.914 for acute heart failure, and 0.906 for exacerbations of COPD/asthma. In patients suspected to have pneumonia, consolidation had sensitivity of 0.82 (95% confidence interval [CI] 0.74–0.88) and specificity of 0.94 (95% CI 0.85–0.98) for this disease. In acutely dyspneic patients, modified diffuse interstitial syndrome had sensitivity of 0.90 (95% CI 0.87–0.93) and specificity of 0.93 (95% CI 0.91–0.95) for acute heart failure, whereas B-profile had sensitivity of 0.93 (95% CI 0.72–0.98) and specificity of 0.92 (95% CI 0.79–0.97) for this disease in patients with respiratory failure. In patients with acute dyspnea or respiratory failure, the A-profile without PLAPS (posterior-lateral alveolar pleural syndrome) had sensitivity of 0.78 (95% CI 0.67–0.86) and specificity of 0.94 (95% CI 0.89–0.97) for exacerbations of COPD/asthma.

Conclusion

Lung ultrasound is an accurate tool for the emergency diagnosis of pneumonia, acute heart failure, and exacerbations of COPD/asthma.  相似文献   
39.

Introduction

In the United States there has been a large increase in participation in lacrosse for both males and females. The purpose of this study was to analyze the number of head injuries, injury rates (calculated using the reported number of participants) and types of head injuries that are seen in emergency departments in the United States.

Methods

We compared injuries between male and female lacrosse participants. This was a retrospective study using a publicly available database produced by the US Consumer Product Safety Commission and information about lacrosse participation from US Lacrosse.

Results

A linear regression was performed and showed a positive correlation between number of head injuries to males and time from 2002 to 2010 (R2?=?0.823; p?=?0.001). While the number of injuries to the head in female lacrosse participants was not significant. There was a negative correlation between the number of head injuries to males from 2010 to 2016 (R2?=?0.800; p?=?0.007), but again, there was no significance for female injury count (R2?=?0.417; p?=?0.117). Other significant differences between head injuries in males and females included the mechanism of injury and the type of injury recorded.

Conclusion

The most recent data from 2010 to 2016, suggest that both males and females have had a decrease in injury rate. However the total number of female head injuries is not significantly decreasing and as the sport continues to grow there will likely be more total head injuries and visits to the emergency department.  相似文献   
40.
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