收费全文 | 2127718篇 |
免费 | 158316篇 |
国内免费 | 6423篇 |
耳鼻咽喉 | 27565篇 |
儿科学 | 71594篇 |
妇产科学 | 59350篇 |
基础医学 | 311407篇 |
口腔科学 | 58831篇 |
临床医学 | 201790篇 |
内科学 | 407559篇 |
皮肤病学 | 45204篇 |
神经病学 | 174570篇 |
特种医学 | 78886篇 |
外国民族医学 | 653篇 |
外科学 | 303621篇 |
综合类 | 48945篇 |
现状与发展 | 1篇 |
一般理论 | 825篇 |
预防医学 | 177141篇 |
眼科学 | 48054篇 |
药学 | 155906篇 |
8篇 | |
中国医学 | 4837篇 |
肿瘤学 | 115710篇 |
2019年 | 17233篇 |
2018年 | 24287篇 |
2017年 | 18473篇 |
2016年 | 20494篇 |
2015年 | 23310篇 |
2014年 | 32092篇 |
2013年 | 49641篇 |
2012年 | 67004篇 |
2011年 | 71163篇 |
2010年 | 41915篇 |
2009年 | 38868篇 |
2008年 | 65620篇 |
2007年 | 69369篇 |
2006年 | 69932篇 |
2005年 | 67368篇 |
2004年 | 64795篇 |
2003年 | 61881篇 |
2002年 | 60038篇 |
2001年 | 95748篇 |
2000年 | 98225篇 |
1999年 | 82483篇 |
1998年 | 23613篇 |
1997年 | 21359篇 |
1996年 | 21173篇 |
1995年 | 20272篇 |
1994年 | 18787篇 |
1993年 | 17613篇 |
1992年 | 65934篇 |
1991年 | 64852篇 |
1990年 | 63062篇 |
1989年 | 60234篇 |
1988年 | 55508篇 |
1987年 | 54913篇 |
1986年 | 51869篇 |
1985年 | 49778篇 |
1984年 | 37645篇 |
1983年 | 31835篇 |
1982年 | 19235篇 |
1981年 | 17058篇 |
1979年 | 34466篇 |
1978年 | 24797篇 |
1977年 | 20568篇 |
1976年 | 19890篇 |
1975年 | 20554篇 |
1974年 | 25032篇 |
1973年 | 24347篇 |
1972年 | 22454篇 |
1971年 | 20956篇 |
1970年 | 19400篇 |
1969年 | 17855篇 |
Background
There are conflicting data regarding the relative effectiveness of renal sympathetic denervation (RSD) in patients with hypertension.Objectives
The purpose of this study was to evaluate the blood pressure (BP) response after RSD in sham-controlled randomized trials.Methods
Databases were searched through June 30, 2018. Randomized trials (RCTs) with ≥50 patients comparing catheter-based RSD with a sham control were included. The authors calculated summary treatment estimates as weighted mean differences (WMD) with 95% confidence intervals (CIs) using random-effects meta-analysis.Results
The analysis included 977 patients from 6 trials. The reduction in 24-h ambulatory systolic blood pressure (ASBP) was significantly greater for patients treated with RSD than sham procedure (WMD ?3.65 mm Hg, 95% CI: ?5.33 to ?1.98; p < 0.001). Compared with sham, RSD was also associated with a significant decrease in daytime ASBP (WMD ?4.07 mm Hg, 95% CI: ?6.46 to ?1.68; p < 0.001), office systolic BP (WMD ?5.53 mm Hg, 95% CI: ?8.18 to ?2.87; p < 0.001), 24-h ambulatory diastolic BP (WMD ?1.71 mm Hg, 95% CI: ?3.06 to ?0.35; p = 0.01), daytime ambulatory diastolic BP (WMD ?1.57 mm Hg, 95% CI: ?2.73 to ?0.42; p = 0.008), and office diastolic BP (WMD ?3.37 mm Hg, 95% CI: ?4.86 to ?1.88; p < 0.001). Compared with first-generation trials, a significantly greater reduction in daytime ASBP was observed with RSD in second-generation trials (6.12 mm Hg vs. 2.14 mm Hg; p interaction = 0.04); however, this interaction was not significant for 24-h ASBP (4.85 mm Hg vs. 2.23 mm Hg; p interaction = 0.13).Conclusions
RSD significantly reduced blood pressure compared with sham control. Results of this meta-analysis should inform the design of larger, pivotal trials to evaluate the long-term efficacy and safety of RSD in patients with hypertension. 相似文献Background
Physicians treating nonvalvular atrial fibrillation (AF) assess stroke and bleeding risks when deciding on anticoagulation. The agreement between empirical and physician-estimated risks is unclear. Furthermore, the association between patient and physician sex and anticoagulation decision-making is uncertain.Methods
We pooled data from 2 national primary care physician chart audit databases of patients with AF (Facilitating Review and Education to Optimize Stroke Prevention in Atrial Fibrillation and Coordinated National Network to Engage Physicians in the Care and Treatment of Patients with Atrial Fibrillation Chart Audit) with a combined 1035 physicians (133 female, 902 male) and 10,927 patients (4567 female and 6360 male).Results
Male physicians underestimated stroke risk in female patients and overestimated risk in male patients. Female physicians estimated stroke risk well in female patients but underestimated the risk in male patients. Risk of bleeding was underestimated in all. Despite differences in risk assessment by physician and patient sex, > 90% of patients received anticoagulation across all subgroups. There was modest agreement between physician estimated and calculated (ie, CHADS2 score) stroke risk: Kappa scores were 0.41 (0.35-0.47) for female physicians and 0.34 (0.32-0.36) for male physicians.Conclusions
Our study is the first to examine the association between patient and physician sex influences and stroke and bleeding risk estimation in AF. Although there were differences in agreement between physician estimated stroke risk and calculated CHADS2 scores, these differences were small and unlikely to affect clinical practice; further, despite any perceived differences in the accuracy of risk assessment by sex, most patients received anticoagulation. 相似文献Background
Nutrition specialists are considered key members of multicomponent pediatric weight management intervention teams, but to date, their contribution has not been quantified.Objective
The purpose of this systematic review was to estimate the effectiveness of interventions provided by treatment teams that include a nutrition specialist on pediatric weight management outcomes, including body mass index (BMI), BMI z score, and waist circumference when compared with treatment teams that do not include a nutrition specialist.Methods
The results of a comprehensive literature search and a systematic and more targeted update of that search were included in the meta-analyses: a search of controlled trials published between July 2005 and April 2012, conducted during the 2015 Pediatric Weight Management Update Project of the Academy of Nutrition and Dietetics Evidence Analysis Library, and an update search of controlled trials published between May 2012 and December 2015 focusing on a more specific topic within the previous search. Studies included overweight and/or obese patients aged 6 to 18 years receiving outpatient weight management treatment. Data extraction of all studies identified was performed using a standardized tool. The resulting data from the search and the systematic update were merged. Ninety-nine studies and 209 study arms were included in the analysis. An exploratory meta-analysis using alternative meta-analytic methods designed for complex, heterogenous interventions was conducted to identify relative contributions by intervention provider category at selected time points. Meta-regression analyses were used to evaluate significant differences from the reference category for each provider category.Results
The nutrition specialist-only condition resulted in increased reductions in BMI z score compared with behavioralist-only, combined nutrition specialist and behavioralist, and neither nutrition specialist or behavioralist category (reference) throughout the analysis. Meta-regression analysis indicated that the difference in BMI z score between the nutrition specialist-only category and the reference category was significant at 3 to <6 months, 6 months to <1 year, and 1-year to 2-year time points (P=0.01, P=0.05, and P=0.01, respectively). There were smaller increases in BMI over time for the nutrition specialist-only provider category compared with reference categories, and this difference was significant at the 3 to <6 months and 1-year to 2-years time points (P=0.001 and P=0.05, respectively). There were no significant differences among provider categories for waist circumference at any time point.Conclusions
Indirect evidence indicated that pediatric weight management outcomes for BMI z score and BMI at selected time points appeared to be better when a nutrition specialist was involved in delivering care. 相似文献Introduction
There is an urgent need for new anti-tuberculosis (TB) drugs and optimization of current TB treatment. Moxifloxacin and linezolid are valuable options for the treatment of drug-resistant TB; however, it is crucial to find a dose at which these drugs not only show high efficacy but also suppress the development of further drug resistance.Methods
Activity of moxifloxacin and linezolid against Mycobacterium tuberculosis was studied in the hollow-fiber infection model system in log-phase growth under neutral pH and slow growth in an acidic environment. Doses that achieved maximum bacterial kill while suppressing the emergence of drug resistance were determined. Through Monte Carlo simulations the quantitative output of this in vitro study was bridged to the human patient population to inform optimal dosage regimens while accounting for clinical minimum inhibitory concentration (MIC) distributions.Results and Discussion
Moxifloxacin activity was significantly decreased in an acidified environment. The loss of activity was compensated by accumulation of the drug in TB lung lesions; therefore, moderate efficacy can be expected. Moxifloxacin 800 mg/day is the dose that most likely leads to resistance suppression while exerting maximum bacterial kill. Linezolid demonstrated very good activity even at a reduced pH. Linezolid 900 mg once-daily (QD) is likely to achieve a maximum killing effect and prevent the emergence of drug resistance; 600 mg QD in a robust drug regimen may have similar potential. 相似文献Purpose
The purpose of this study was to assess the potential of a deep learning model to discriminate between benign and malignant breast lesions using magnetic resonance imaging (MRI) and characterize different histological subtypes of breast lesions.Materials and methods
We developed a deep learning model that simultaneously learns to detect lesions and characterize them. We created a lesion-characterization model based on a single two-dimensional T1-weighted fat suppressed MR image obtained after intravenous administration of a gadolinium chelate selected by radiologists. The data included 335 MR images from 335 patients, representing 17 different histological subtypes of breast lesions grouped into four categories (mammary gland, benign lesions, invasive ductal carcinoma and other malignant lesions). Algorithm performance was evaluated on an independent test set of 168 MR images using weighted sums of the area under the curve (AUC) scores.Results
We obtained a cross-validation score of 0.817 weighted average receiver operating characteristic (ROC)-AUC on the training set computed as the mean of three-shuffle three-fold cross-validation. Our model reached a weighted mean AUC of 0.816 on the independent challenge test set.Conclusion
This study shows good performance of a supervised-attention model with deep learning for breast MRI. This method should be validated on a larger and independent cohort. 相似文献Patients and methods — All cemented stems with > 100 implantations were identified in the National Joint Registry of England and Wales from April 1, 2003 to September 31, 2013 and categorised as taper-slip or composite beam. Survival analyses using Kaplan–Meier and Cox regression were performed.
Results — We identified 292,987 cemented arthroplasties, of which 16% (47,586) were composite beam stems, with taper-slip stems making up the remainder (n = 245,401). There was a statistically significant increased chance of revision in the composite beam group compared with the taper-slip group (1.7% vs 1.3%, p < 0.001) but statistically no significant differences of survival estimates (p = 0.06). When the 2 groups were segregated to delineate the most implanted model in each category, the differences became more profound with the most implanted taper-slip stem (Exeter V40) showing statistically and clinically significant superior 8-year survival: 97.9% compared with 97.6% for all other taper-slip; 97.5% for the most implanted composite beam (Charnley cemented stem); and 97.7% for all other composite beam.
Interpretation — There was an increased incidence of revision for composite beam stems. The most implanted taper-slip stem demonstrated significant survival advantage vs. all other stems. 相似文献