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   2456篇
  免费   105篇
  国内免费   22篇
耳鼻咽喉   65篇
儿科学   180篇
妇产科学   81篇
基础医学   190篇
口腔科学   90篇
临床医学   178篇
内科学   569篇
皮肤病学   118篇
神经病学   230篇
特种医学   77篇
外科学   376篇
综合类   32篇
预防医学   71篇
眼科学   146篇
药学   90篇
中国医学   6篇
肿瘤学   84篇
  2024年   2篇
  2023年   20篇
  2022年   40篇
  2021年   50篇
  2020年   44篇
  2019年   47篇
  2018年   66篇
  2017年   45篇
  2016年   63篇
  2015年   78篇
  2014年   102篇
  2013年   138篇
  2012年   204篇
  2011年   186篇
  2010年   139篇
  2009年   91篇
  2008年   136篇
  2007年   214篇
  2006年   198篇
  2005年   185篇
  2004年   129篇
  2003年   118篇
  2002年   93篇
  2001年   25篇
  2000年   15篇
  1999年   23篇
  1998年   11篇
  1997年   10篇
  1996年   16篇
  1995年   5篇
  1994年   9篇
  1993年   2篇
  1992年   5篇
  1991年   9篇
  1990年   7篇
  1989年   5篇
  1988年   7篇
  1987年   2篇
  1986年   5篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1980年   3篇
  1979年   2篇
  1975年   2篇
  1974年   4篇
  1972年   2篇
  1971年   2篇
  1970年   5篇
  1960年   2篇
排序方式: 共有2583条查询结果,搜索用时 31 毫秒
51.
Body position and obstructive sleep apnea syndrome   总被引:1,自引:0,他引:1  
In adults, influence of body position on the occurrence of respiratory events during sleep is recognized, and increased numbers of respiratory events occur when the supine position is assumed.1-4 In 1985, Orr et al. showed that body position did not influence respiratory events during sleep in children.5 Recently, Fernandes do Prado et al. showed that children had a lower obstructive apnea hypopnea index (AHI) in supine position.6 Results of these two studies are different from others performed on adults. Moreover, upper airway abnormalities were not considered in these studies.The aim of the present study was to evaluate the effect of body position on obstructive respiratory events in children with different upper airway findings.  相似文献   
52.
The implantation of heparin-coated stents was reported to be well tolerated, but there are conflicting results about acute in-hospital complications. (sub)acute thrombosis rates, and long-term follow-up compared to uncoated stents. We compared the angiographic and clinical results after coronary placement of two stent models: the heparin-coated premounted Jostent and the uncoated premounted NIR stent. Of 710 patients revascularized, a total of 426 patients received Jostent (n = 230) or NIR stent (n = 196) implantation. The primary end points were acute or subacute thrombosis, urgent CABG, AMI or death, while the secondary end points were the comparison of the restenosis rates of the stents at the 6th month and of the functional angina classification of the stent groups at the 1st, 6th and 12th months. There were no significant differences between the Jostent and NIR stent groups regarding angiographic and procedural success. Acute thrombosis rates in the Jostent and NIR stent groups were similar while no subacute thrombosis was observed in either group. The major adverse cardiac event rates of the groups also did not differ. Angiographic restenosis occurred in 17% of the Jostent group and 16% of the NIR stent group (NS). The combined clinical and angiographic restenosis rate was also similar between the Jo and NIR groups (19% and 18%, respectively). Comparison of functional angina classes at the 1st, 6th and 12th months revealed no significant difference between the study groups. In conclusion, when compared with implantation of an uncoated premounted NIR stent, implantation of a heparin-coated premounted Jostent does not provide any more benefit with respect to initial efficacy, sub(acute) thrombosis and 6-month restenosis rates and 12-month clinical outcomes.  相似文献   
53.

OBJECTIVES:

The aim of our study was to evaluate the total atrial conduction time and its relationship to subclinical atherosclerosis, inflammation and echocardiographic parameters in patients with type 2 diabetes mellitus.

METHODS:

A total of 132 patients with type 2 diabetes mellitus (mean age 54.5±9.6 years; 57.6% male) and 80 age- and gender-matched controls were evaluated. The total atrial conduction time was measured by tissue-Doppler imaging and the carotid intima-media thickness was measured by B-mode ultrasonography.

RESULTS:

The total atrial conduction time was significantly longer in the patients with type 2 diabetes mellitus than in the control group (131.7±23.6 vs. 113.1±21.3, p<0.001). The patients with type 2 diabetes mellitus had significantly increased carotid intima-media thicknesses, neutrophil to lymphocyte ratios and high-sensitivity C-reactive protein levels than those of the controls. The total atrial conduction time was positively correlated with the high-sensitivity C-reactive protein level, neutrophil to lymphocyte ratio, carotid intima-media thickness and left atrial volume index and negatively correlated with the early diastolic velocity (Em), Em/late diastolic velocity (Am) ratio and global peak left atrial longitudinal strain. A multiple logistic regression analysis demonstrated that the neutrophil to lymphocyte ratio, carotid intima-media thickness and global peak left atrial longitudinal strain were independent predictors of the total atrial conduction time.

CONCLUSIONS:

We suggest that subclinical atherosclerosis and inflammation may represent a mechanism related to prolonged total atrial conduction time and that prolonged total atrial conduction time and impaired left atrial myocardial deformation may be represent early subclinical cardiac involvement in patients with type 2 diabetes mellitus.  相似文献   
54.
Objective:We aimed to investigate a possible role of the endocrine disruptors phthalates, di-2-ethylhexyl phthalate (DEHP) and mono (2-ethylhexyl) phthalate (MEHP), in polycystic ovary syndrome (PCOS) aetiopathogenesis. We also wished to evaluate the relationship between phthalates and metabolic disturbances in adolescents with PCOS.Methods:A total of 124 adolescents were included. Serum MEHP and DEHP levels were determined by high-performance liquid chromatography. Insulin resistance was evaluated using homeostasis model assessment-insulin resistance, quantitative Insulin Sensitivity Check Index, fasting glucose/insulin ratio, Matsuda index, and total insulin levels during oral glucose tolerance test. Participants were further subdivided into lean and obese subgroups according to body mass index (BMI).Results:Sixty-three PCOS and 61 controls, (mean age 15.2±1.5; range: 13-19 years) were enrolled. Serum DEHP and MEHP concentrations were not significantly different between PCOS and control groups. The mean (95% confidence interval) values of DEHP and MEHP were 2.62 (2.50-2.75) μg/mL vs 2.71 (2.52-2.90) μg/mL and 0.23 (0.19-0.29) μg/mL vs 0.36 (0.18-0.54) μg/mL in PCOS and the control groups respectively, p>0.05. Correlation analysis, adjusted for BMI, showed that both phthalates significantly correlated with insulin resistance indices and serum triglycerides in adolescents with PCOS.Conclusion:Serum DEHP and MEHP concentrations were not different between adolescents with or without PCOS. However, these phthalates are associated with metabolic disturbances such as dyslipidemia and insulin resistance, independently of obesity, in girls with PCOS.  相似文献   
55.
56.
57.

Background and Purpose

To evaluate the relationship between infarct location and QTc-prolongation in patients with posterior circulation strokes.

Methods

Admission electrocardiograms (ECG) of 131 patients among a prospective sample of 407 consecutive adult patients in the New England Medical Center Posterior Circulation Registry were retrospectively analyzed. The QT interval (ms) was measured and corrected using Bazett’s formula (QTcBazett) as well as linear regression functions (QTcLinear). QTcBazett > 440 ms and QTcLinear ≥ 450 ms for men (≥460 ms for women) were considered prolonged. Multivariable linear and logistic regression analyses were used to identify independent predictors of the QTc.

Results

Overall, 34 % of patients had a prolonged QTcBazett and 7 % had a prolonged QTcLinear noted on the admission ECG. There was a significant association between temporal lobe infarction and QTcBazett and QTcLinear (p < 0.001 for both) in multivariable linear regression analyses adjusting for demographics, ECG parameters, and preadmission medication use. In multivariable logistic regression analysis, temporal lobe infarction emerged as an independent predictor of prolonged QTcBazett (p = 0.009) and QTcLinear (p = 0.008), respectively. Sensitivity analyses excluding patients with transient ischemic attack yielded similar results. Exploratory analyses indicated that patients with temporal lobe infarction had worse functional 30-day outcomes in multivariable logistic regression (p = 0.022). However, there was no significant association between QTc and 30-day functional outcome.

Conclusions

QTc-prolongation is common after posterior circulation stroke and associated with temporal lobe infarction. Prospective studies are needed to confirm these preliminary findings and to examine potential long-term consequences.  相似文献   
58.
The hypothalamic Arg-Phe-amide-related peptides, gonadotropin-inhibitory hormone and orthologous mammalian peptides of Arg-Phe-amide, may be important regulators of the hypothalamus-pituitary-gonadal reproductive axis. These peptides may modulate the effects of kisspeptins because they are presently recognized as the most potent activators of the hypothalamus-pituitary-gonadal axis. However, their effects on gonadotropin-releasing hormone neurons have not been investigated. In the current study, the GT1-7 cell line-expressing gonadotropin-releasing hormone was used as a model to explore the effects of Arg-Phe- amide-related peptides on kisspeptin activation. Intracellular calcium concentration was quantified using the calcium-sensitive dye, fura-2 acetoxymethyl ester. Gonadotropin-releasing hormone released into the medium was detected via enzyme-linked immunosorbent assay. Results showed that 100 nmol/L kisspeptin-10 significantly increased gonadotropin-releasing hormone levels (at 120 minutes of exposure) and intracellular calcium concentrations. Co-treatment of kisspeptin with 1 μmol/L gonadotropin-inhibitory hormone or 1 μmol/L Arg-Phe-amide-related peptide-1 significantly attenuated levels of kisspeptin-induced gonadotropin-releasing hormone but did not affect kisspeptin-induced elevations of intracellular calcium concentration. Overall, the results suggest that gonadotropin-inhibitory hormone and Arg-Phe-amide-related peptide-1 may have inhibitory effects on kisspeptin-activated gonadotropin-releasing hormone neurons independent of the calcium signaling pathway.  相似文献   
59.

OBJECTIVES:

Acute ST-elevation myocardial infarction is associated with ventricular dysfunction due to ischemia-induced progressive myocardial damage. The decrease in ventricular compliance causes left atrial dilatation and stretching of the atrial myocardium, which are the main stimuli for the secretion of atrial natriuretic peptide. The aim of this study was to evaluate left atrial dimensions and atrial natriuretic peptide levels in patients early after their first acute ST-elevation myocardial infarction and assess the probable interaction between coronary lesions and these measurements.

METHODS:

A total of 110 patients with acute myocardial infarction and 50 controls were studied. Plasma atrial natriuretic peptide was measured at admission. Left ventricular function, diameter, and volume index were evaluated using transthoracic echocardiography. Gensini and vessel scores of the patients who underwent coronary angiography were calculated.

RESULTS:

Plasma atrial natriuretic peptide in the patients with myocardial infarction was increased compared with that in controls (3.90±3.75 vs. 1.35±0.72 nmol/L, p<0.001). Although the left atrial diameter was comparable in patients and controls, the left atrial volume index was increased in patients with acute myocardial infarction (26.5±7.1 vs. 21.3±4.9 mL/m2, p<0.01). Multivariate regression analysis showed a strong independent correlation between the left atrial volume index and the plasma atrial natriuretic peptide level (β = 0.23, p = 0.03).

CONCLUSIONS:

The left atrial volume index and plasma atrial natriuretic peptide level were correlated in patients with acute myocardial infarction.  相似文献   
60.

Introduction

Near-infrared diode lasers can be used for several applications, which range from disinfection to smear layer removal in endodontics. This study evaluated the efficacy of agitation of 15% EDTA with an 808-nm diode laser on removal of the smear layer.

Methods

Sixty extracted human maxillary central incisor teeth were instrumented up to ProTaper F4 (Dentsply Maillefer, Ballagues, Switzerland) and then randomly divided into 6 groups (n = 10 for each group) according to the different final irrigating protocols as follows: 5% sodium hypochlorite for 120 seconds performed with the NaviTip (Dentsply Maillefer, Ballaigues, Switzerland) (control group); 15% EDTA for 120 seconds performed with the NaviTip; and agitation of 15% EDTA with an 808-nm diode laser for 10, 20, 30, and 40 seconds. Specimens were observed under a scanning electron microscope, and open dentinal tubules were counted using Adobe Photoshop software (Adobe Systems, San Jose, CA). The data were analyzed with 1-way analysis of variance and Tukey post hoc tests (P = .05).

Results

The number of open dentinal tubules was higher in the middle thirds than in the apical thirds. The differences between the apical and middle thirds were statistically significant (P < .05). Statistically significant differences were also found between the control group and the other groups in both the middle and apical thirds of the root canals (P < .05).

Conclusions

The results indicated that agitation of 15% EDTA with an 808-nm diode laser for 20 seconds was effective in removing the smear layer in the apical thirds of root canals.  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