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   7288篇
  免费   538篇
  国内免费   18篇
耳鼻咽喉   36篇
儿科学   148篇
妇产科学   101篇
基础医学   1474篇
口腔科学   127篇
临床医学   655篇
内科学   1401篇
皮肤病学   175篇
神经病学   692篇
特种医学   293篇
外科学   951篇
综合类   31篇
一般理论   6篇
预防医学   599篇
眼科学   191篇
药学   386篇
中国医学   16篇
肿瘤学   562篇
  2023年   60篇
  2022年   114篇
  2021年   198篇
  2020年   137篇
  2019年   195篇
  2018年   185篇
  2017年   194篇
  2016年   205篇
  2015年   265篇
  2014年   298篇
  2013年   387篇
  2012年   561篇
  2011年   581篇
  2010年   341篇
  2009年   318篇
  2008年   450篇
  2007年   474篇
  2006年   408篇
  2005年   403篇
  2004年   362篇
  2003年   329篇
  2002年   280篇
  2001年   79篇
  2000年   72篇
  1999年   94篇
  1998年   60篇
  1997年   51篇
  1996年   29篇
  1995年   29篇
  1994年   33篇
  1993年   25篇
  1992年   23篇
  1989年   14篇
  1988年   15篇
  1987年   17篇
  1986年   16篇
  1985年   16篇
  1981年   13篇
  1974年   13篇
  1973年   13篇
  1971年   17篇
  1966年   13篇
  1935年   16篇
  1934年   34篇
  1931年   16篇
  1930年   15篇
  1925年   25篇
  1924年   27篇
  1923年   40篇
  1922年   28篇
排序方式: 共有7844条查询结果,搜索用时 15 毫秒
1.
2.
Objectives:To reassess the long-term camouflage effects of resin infiltration (Icon, DMG, Hamburg, Germany) of white spot lesions (WSL) and sound adjacent enamel (SAE) achieved in a previous trial. The null hypothesis was tested that there were no significantly different CIE-L*a*b*-ΔE-values between WSL and SAE areas of assessment after at least 24 months (T24) compared to those at baseline (T0).Materials and Methods:Of twenty subjects who received previous resin infiltration treatment of nteeth = 111 nonrestored, noncavitated postorthodontic WSL after multibracket treatment during a randomized controlled trial and were contacted 20 months after baseline, eight subjects (trial teeth nteeth = 40; m/f ratio 1/7; age range (mean; SD) 12–17 [15.25; 2.12] years); response rate: 40%) were available for follow-up after at least 24 months (T24). CIE-L*a*b* differences between summarized color and lightness values (ΔEWSL/SAE) of WSL and SAE were assessed using a spectrophotometer and compared to baseline data assessed prior to infiltration (T0), and those after 6 (T6), and 12 (T12) months using paired t tests at a significance level of α = 5%.Results:T24 assessments were performed after a mean 33.86 (SD: 8.64; Min: 24; Max: 45) months following T0. Mean (SD) ΔEWSL/SAE units of available teeth were 8.76 (5.33) at baseline; 5.5 (2.75) at T6; 5.2 (2.41) at T12; and 5.57 (2.6) at T24. Comparisons of T6, T12, and T24 with T0 yielded highly significant differences, whereas T6–T24 and T12–T24 differences were found to be not significant.Conclusions:Assimilation of infiltrated WSL to the color of adjacent enamel by resin infiltration is considered to be suitable for the long-term improvement in the esthetic appearance of postorthodontic WSL.  相似文献   
3.
4.
5.
AIMS: To evaluate the predictive accuracy of the Systematic Coronary Risk Evaluation (SCORE) project high-risk function in Norway. METHODS AND RESULTS: We included 57 229 individuals screened in 1985-1992 from two population-based surveys in Norway (age groups 40-49, 50-59, and 60-69 years). The data have been linked to the Norwegian Cause of Death Registry. The SCORE high-risk algorithm for the prediction of 10-year cardiovascular disease (CVD) mortality was applied, and the risk factors entered into the model were age, sex, total cholesterol, systolic blood pressure, and smoking (yes/no). The number of expected events estimated by the SCORE model (E) was compared with the observed numbers (O). The SCORE low-risk algorithm was studied for comparison. In men, the observed number of CVD deaths was 718, compared with 1464 estimated by the SCORE high-risk function (O/E ratios 0.53, 0.53 and 0.45, for age groups 40-49, 50-59 and 60-69, respectively). In women, the observed and expected numbers were 226 and 547. The O/E ratios decreased with age (ratios 0.60, 0.45 and 0.37, respectively), i.e. the overestimation increased with age. The low-risk function predicted reasonably well for men (ratios 0.85, 0.92 and 0.79, respectively), whereas an overestimation was found for women aged 50-59 and 60-69 years (ratios 0.69 and 0.56, respectively). CONCLUSION: The SCORE high-risk model overestimated the number of CVD deaths in Norway. Before implementation in clinical practice, proper adjustments to national levels are required.  相似文献   
6.
OBJECTIVES: To assess prospectively the early time course of Transforming Growth Factor beta-1 (TGFbeta-1), basic Fibroblast Growth Factor (bFGF) and Tumor Necrosis Factor alpha (TNFalpha) as possible contributors to restenosis development after angioplasty. DESIGN: Prospective Study. METHODS: The levels of the soluble forms of these factors in the early response to Percutaneous Transluminal Angioplasty (PTA) in the arteries of the lower limb were prospectively assessed. 32 patients with peripheral arterial occlusive disease (PAOD), presenting with intermittent claudication (Fontaine stage IIb) were scheduled for angioplasty treatment. Serum levels of TGFbeta-1, TNFalpha and bFGF were assessed before intervention, 15 and 60 minutes after, 24 hours after as well as 2 and 4 weeks after intervention. We compared the distribution patterns between patients treated with balloon angioplasty and patients who required secondary stent implantation. Endpoint was the development of restenosis within 6 months after interventional treatment, defined as a lumen diameter reduction of more than 50% by ultrasound measurement compared to the result after PTA. RESULTS: The patients who later developed restenosis had significantly higher levels of TGFbeta-1 at 15 minutes, 24 hours and 2 weeks after PTA (p<0.05). TNFalpha and bFGF were only detected in a few patients and no significant change of serum levels was observed. CONCLUSION: The results demonstrate a possible role of TGFbeta-1 in the formation of restenosis after PTA.  相似文献   
7.
OBJECTIVES: Prompt diagnosis of subsequent dilatation of the dissected aorta is crucial to reduce late mortality in these patients. This study focuses on risk factors for dilatation of the aorta after type A aortic dissection (AADA) affecting a normal-sized or slightly dilated aorta. METHODS: Overall 531 CT scans were analysed. Patients were included in the study if at least 3 CT scans were available after operative repair. 64 patients (59.8%) out of 107 patients full-field the inclusion criteria. Volumetric analyses of the aorta were performed. Patients were divided in 3 groups: group A included 26 patients (40.6%) without progression of the aortic diameter, group 2, 27 patients (42.2%) with slight progression and group 3, 11 patients (17.2%) with important progression, requiring surgery in 9 patients (81.8%). Risk-factors for progression of the aortic size were analysed and compared between the groups. RESULTS: Patients from group 3 were younger 57.7+/-13.4 vs. 61.9+/-11.6 in group 1 (P<0.05) and were more frequent female (45.4 vs. 23.1%; P<0.05). Dissection of the supraaortic branches (100 vs. 80.8%; P<0.05), the presence of preoperative cerebral, visceral or peripheral malperfusion (54.6 vs. 26.9%; P<0.05) and contrast enhancement in the false lumen during the follow-up (72.7 vs. 57.7%; P=0.07) were additional risk factors for late aortic dilatation in these patients. CONCLUSIONS: Acute type A aortic dissection in younger patients, involving the supraaortic branches and/or combined with malperfusion syndrome favour secondary dilatation. A close follow-up is mandatory to prevent acute complications of the diseased downstream aorta following repair of a AADA.  相似文献   
8.
We tested the hypothesis that bone mineral density (BMD) and bone mineral content (BMC) in proximal human femur specimens in the upper neck region of interest (ROI) and femoral neck axis length (FNAL) provide a significantly better prediction of femoral bone strength than standard ROIs in vitro. BMD and BMC were measured in 110 proximal femur specimens using a standard dual-energy X-ray absorptiometry (DXA) scanner. The analysis included a new ROI in the upper neck as well as the standard ROIs. FNAL was obtained from the scan images. The specimens' failure-load was measured in a mechanical loading device, simulating a fall on the greater trochanter. For the standard ROIs, correlations between failure-load and BMD ranged from R2 = 0.64 (shaft ROI) to R2 = 0.70, p < 0.001 (femoral neck). Prediction of strength by BMD did not significantly differ from those of BMC (R2 ranging from 0.65 to 0.75, p < 0.001). In the upper neck ROI, for both BMD and BMC correlations with failure-load were higher (R2 = 0.76 and 0.81, respectively; p < 0.001). A lower, yet still significant, correlation was found between FNAL and bone strength (R2 = 0.23, p < 0.001). Normalization of failure-load with respect to FNAL did not significantly increase the correlations with densitometric measures. This study provides in vitro evidence indicating that among the ROIs of the proximal femur the newly defined upper neck ROI provides the best prediction of bone strength. Only a weak association was observed between failure load and FNAL.  相似文献   
9.
10.
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