收费全文 | 2543174篇 |
免费 | 183471篇 |
国内免费 | 3642篇 |
耳鼻咽喉 | 35242篇 |
儿科学 | 82924篇 |
妇产科学 | 69576篇 |
基础医学 | 375205篇 |
口腔科学 | 69020篇 |
临床医学 | 227747篇 |
内科学 | 492930篇 |
皮肤病学 | 56053篇 |
神经病学 | 199634篇 |
特种医学 | 95832篇 |
外国民族医学 | 527篇 |
外科学 | 384284篇 |
综合类 | 52859篇 |
现状与发展 | 13篇 |
一般理论 | 967篇 |
预防医学 | 196696篇 |
眼科学 | 59263篇 |
药学 | 188616篇 |
11篇 | |
中国医学 | 4989篇 |
肿瘤学 | 137899篇 |
2021年 | 20353篇 |
2019年 | 20942篇 |
2018年 | 29266篇 |
2017年 | 21932篇 |
2016年 | 24586篇 |
2015年 | 27735篇 |
2014年 | 38958篇 |
2013年 | 58558篇 |
2012年 | 80267篇 |
2011年 | 85080篇 |
2010年 | 50948篇 |
2009年 | 48085篇 |
2008年 | 79960篇 |
2007年 | 85310篇 |
2006年 | 86082篇 |
2005年 | 83229篇 |
2004年 | 79766篇 |
2003年 | 76790篇 |
2002年 | 74335篇 |
2001年 | 116401篇 |
2000年 | 119224篇 |
1999年 | 100251篇 |
1998年 | 28956篇 |
1997年 | 25448篇 |
1996年 | 25760篇 |
1995年 | 24317篇 |
1994年 | 22404篇 |
1993年 | 21120篇 |
1992年 | 77161篇 |
1991年 | 75300篇 |
1990年 | 73549篇 |
1989年 | 70805篇 |
1988年 | 65036篇 |
1987年 | 63825篇 |
1986年 | 59705篇 |
1985年 | 57384篇 |
1984年 | 42510篇 |
1983年 | 36198篇 |
1982年 | 21596篇 |
1979年 | 38993篇 |
1978年 | 27910篇 |
1977年 | 23177篇 |
1976年 | 22158篇 |
1975年 | 23912篇 |
1974年 | 28650篇 |
1973年 | 27325篇 |
1972年 | 25590篇 |
1971年 | 24292篇 |
1970年 | 22463篇 |
1969年 | 21270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Objectives
This study reported a hospital outbreak due to an extensively drug-resistant (XDR) OXA-72-producing strain of Acinetobacter baumannii (A. baumannii).Methods and Results
The isolates were found to be genotypically indistinguishable by whole-genome multiple locus sequence typing, and to belong to the international clonal complex CC2. One of these isolates sequentially developed a high resistance to colistin and rifampicin under treatment, as a result of mutations in genes pmrB and rpoB, respectively. The blaOXA-72 gene was localised on a 10-kb transferable plasmid, named pAB-STR-1, whose sequence is nearly identical to that of another plasmid previously found in Lithuanian strains, pAB120.Conclusion
This report highlighted the need to carefully monitor the emergence of colistin and rifampicin resistance in patients treated for infections with multidrug-resistant A. baumannii. 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
To qualitatively and quantitatively compare unenhanced ultra-low-dose chest computed tomography (ULD-CT) acquired at 80 kVp and 135 kVp.Materials and methods
Fifty-one patients referred for unenhanced chest CT were prospectively included. There were 29 men and 22 women, with a mean age of 64.7 ± 11.6 (SD) years (range: 35–91 years) and a mean body mass index of 26.2 ± 6.3 (SD) (range: 17–54.9). All patients underwent two different ULD-CT protocols (80 kVp-40 mA and 135 kVp-10 mA). Image quality of both ULD-CT examinations using a 5-level scale as well as assessability of 6 predetermined lung parenchyma lesions were blindly evaluated by three radiologists and compared using a logistic regression model. Image noise of the two protocols was compared with Wilcoxon signed-rank test.Results
The mean dose-length product at 80 kVp and at 135 kVp were 14.7 ± 1.8 (SD) mGy.cm and 15.6 ± 1.9 (SD) mGy.cm, respectively (P < 0.001). Image noise was significantly lower at 135 kVp (58.9 ± 12.4) than at 80 kVp (74.7 ± 14.5) (P < 0.001). For all readers and for all examinations, the 135 kVp protocol yielded better image quality than 80 kVp protocol, with a mean qualitative score of 4.5 ± 0.7 versus 3.9 ± 0.8 (P < 0.001). The 135 kVp protocol was significantly more often of diagnostic quality than the 80 kvp protocol (92.3% versus 77.8%, respectively) (P < 0.001) and was less prone to image quality deterioration in obese patients. Parenchymal lesions were never better depicted on the 80 kVp protocol than with the 135 kVp protocol.Conclusion
Unenhanced chest ULD-CT should be acquired at a high kilovoltage and low current, such as 135 kVp-10 mA, over a low kilovoltage and high current protocol. 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