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   12703篇
  免费   644篇
  国内免费   238篇
耳鼻咽喉   56篇
儿科学   366篇
妇产科学   414篇
基础医学   517篇
口腔科学   93篇
临床医学   4439篇
内科学   902篇
皮肤病学   47篇
神经病学   225篇
特种医学   1586篇
外科学   1394篇
综合类   1896篇
预防医学   443篇
眼科学   124篇
药学   611篇
  9篇
中国医学   88篇
肿瘤学   375篇
  2023年   173篇
  2022年   455篇
  2021年   562篇
  2020年   534篇
  2019年   483篇
  2018年   507篇
  2017年   521篇
  2016年   332篇
  2015年   426篇
  2014年   949篇
  2013年   799篇
  2012年   766篇
  2011年   717篇
  2010年   621篇
  2009年   643篇
  2008年   630篇
  2007年   590篇
  2006年   584篇
  2005年   423篇
  2004年   351篇
  2003年   277篇
  2002年   185篇
  2001年   202篇
  2000年   181篇
  1999年   161篇
  1998年   127篇
  1997年   139篇
  1996年   105篇
  1995年   97篇
  1994年   90篇
  1993年   56篇
  1992年   66篇
  1991年   57篇
  1990年   40篇
  1989年   48篇
  1988年   43篇
  1987年   43篇
  1986年   60篇
  1985年   53篇
  1984年   36篇
  1983年   45篇
  1982年   70篇
  1981年   62篇
  1980年   33篇
  1979年   36篇
  1978年   64篇
  1977年   25篇
  1976年   41篇
  1975年   23篇
  1974年   22篇
排序方式: 共有10000条查询结果,搜索用时 535 毫秒
1.

Background

Purulent bacterial pericarditis is a rare and potentially fatal disease. The course may be fulminant, and the presentation may pose a diagnostic challenge.

Case report

An otherwise healthy 75-year-old male was brought to the emergency department in a state of general deterioration, confusion, and shock. Bedside ultrasound showed a significant pericardial effusion. His condition quickly deteriorated and the resuscitation included emergent bedside pericardiocentesis. The drainage was purulent and later cultures grew out Streptococcus pneumoniae.

Why should an emergency physician be aware of this?

Purulent pericarditis is extremely rare but should be considered in the patient with a fulminant infectious process (particularly pneumonia) and signs of pericardial effusion. Treatment should include appropriate antibiotics and early drainage.  相似文献   
2.
Dynamic contrast-enhanced ultrasound (DCE-US) has been proposed as a powerful tool for cancer diagnosis by estimation of perfusion and dispersion parameters reflecting angiogenic vascular changes. This work was aimed at identifying which vascular features are reflected by the estimated perfusion and dispersion parameters through comparison with acoustic angiography (AA). AA is a high-resolution technique that allows quantification of vascular morphology. Three-dimensional AA and 2-D DCE-US bolus acquisitions were used to monitor the growth of fibrosarcoma tumors in nine rats. AA-derived vascular properties were analyzed along with DCE-US perfusion and dispersion to investigate the differences between tumor and control and their evolution in time. AA-derived microvascular density and DCE-US perfusion exhibited good agreement, confirmed by their spatial distributions. No vascular feature was correlated with dispersion. Yet, dispersion provided better cancer classification than perfusion. We therefore hypothesize that dispersion characterizes vessels that are smaller than those visible with AA.  相似文献   
3.
In the work described here, our aim was to determine, in an elderly population, changes in muscle thickness (MT), cross-sectional area (CSA) and echo intensity (EI) of the quadriceps muscles at four time points (0, 5, 10 and 15 min; i.e., T0, T5, T10 and T15, respectively) after changing from a standing to supine position. Twenty-one elderly participants (14 men: 68.1 ± 4.6 y; 8 women: 66.8 ± 4.1 y) were evaluated at four time points. Rectus femoris CSA (RFCSA), MT and EI of the quadriceps femoris (QF) muscles were assessed. EI significantly increased from T0 to T5, T10 and T15 (p < 0.001), whereas no differences were observed between T5 and T15 in the rectus femoris (RFEI), vastus intermedius (VIEI) and quadriceps femoris (QFEI). No differences were observed between any time points in the RFCSA and MT of QF muscles. In summary, these results suggest that periods >5 min are not necessary to obtain consistent MT and EI measurements of quadriceps femoris muscles in the elderly population.  相似文献   
4.

Background

In the emergency department, rib fractures are a common finding in patients who sustain chest trauma. Rib fractures may be a sign of significant, underlying pathology, especially in the elderly patients where rib fractures are associated with significant morbidity and mortality. To date, no studies have evaluated the ability of ultrasound to detect rib fractures using cadaver models and subsequently use this model as a teaching tool.

Objectives

The purpose of this study was to determine if it is possible to generate rib fractures on cadaver models which could be accurately identified using ultrasound.

Methods

This was a cross-sectional study performed during one session at a cadaver lab. A single hemithorax from four adult cadavers were used as models. Single rib fractures on each of rib five through eight were created. Four subjects, blinded to the normal versus fractured ribs, were asked to identify the presence of a fracture on each rib.

Results

A total of 8 of 16 potential ribs had fractured induced by study staff. Mean accuracy was 55% for all subjects. The overall sensitivity and specificity for detecting rib fractures was 50% (CI: 31.89–68.11) and 59.38% (CI: 35.69–73.55) respectively. The overall PPV and NPV was 55.17% and 54.29% respectively.

Conclusions

In this pilot study, subjects were not able to detect induced rib fractures using ultrasound on cadaver models. The use of this model as a teaching tool in the detection of rib fractures requires further investigation.  相似文献   
5.
ObjectivesTo compare fetal anterior abdominal wall thickness (AAWT) between women with and without GDM during third trimester and to determine accuracy of AAWT to predict large for gestational age (LGA) infants.Materials and methodsA total of 250 pregnant women, including 125 women with GDM and 125 women without GDM, were enrolled. Tansabdominal ultrasonographic examinations were performed at 28–30, 32–34 and 36–38 weeks. In addition to standard fetal biometries, AAWT was measured. Patient characteristics and ultrasonographic measurements were compared between groups. Sensitivity and specificity of AAWT for identifying LGA were evaluated.ResultsWhile standard fetal biometries were comparable, mean fetal AAWT in GDM women were significantly higher than those without GDM at 28–30 weeks (2.8 ± 0.8 vs. 2.6 ± 0.6, p = 0.006) and 32–34 weeks (4.0 ± 0.9 vs. 3.5 ± 0.8, p = 0.042). LGA infants had significantly higher fetal AAWT at each time point only in GDM women. Using cut off values of AAWT of ≥2.0, 3.0, and 4.0 mm at 28–30, 32–34, and 36–38 weeks, sensitivity for LGA diagnosis in GDM women were 94.4%, 93.9%, and 89.3%, respectively. The use of abdominal circumference (AC) at >90th percentile showed lower sensitivity but higher specificity, regardless of GDM status. Combination of both measurements increased sensitivity to approximately 90% or higher in every time point, especially among GDM women.ConclusionSignificant increase in fetal AAWT was observed in GDM women at 28–30 and 32–34 weeks. Fetal AAWT significantly increased among LGA infants and had higher sensitivity than AC in identifying LGA during third trimester. In GDM women at 28–30 weeks, AAWT ≥2.0 mm and AC >90th percentile had 97.2% sensitivity for LGA diagnosis.  相似文献   
6.
The primary aim of this study was to evaluate the accuracy of sonographic estimation of fetal weight when performed at due date by first-line sonographers. This was a prospective study including 500 singleton pregnancies. Ultrasound examinations were performed by residents on delivery day. Estimated fetal weights (EFWs) were calculated and compared with the corresponding birth weights. The median absolute difference between EFW and birth weight was 200 g (100–330). This difference was within ±10% in 75.2% of the cases. The median absolute percentage error was 5.53% (2.70%–10.03%). Linear regression analysis revealed a good correlation between EFW and birth weight (r = 0.79, p < 0.0001). According to Bland–Altman analysis, bias was −85.06 g (95% limits of agreement: −663.33 to 494.21). In conclusion, EFWs calculated by residents were as accurate as those calculated by experienced sonographers. Nevertheless, predictive performance remains limited, with a low sensitivity in the diagnosis of macrosomia.  相似文献   
7.
8.
《中国现代医生》2020,58(19):119-122+封三
目的 探讨实时超声引导微波消融术治疗子宫腺肌瘤的临床应用。方法 选取2015年1月~2019年1月收入我院子宫腺肌瘤患者37例为研究对象。采用超声造影评价患者的腺肌瘤消融率,常规超声评价瘤体缩小率。采用临床疗效评定标准来评价患者临床症状改善情况。结果 痛经改善率为78.9%(15/19),月经失调改善率为42.9%(9/21),贫血改善率为55.6%(10/18)。超声造影显示仅3例出现消融不完全,消融有效率为91.9%,术后行补充消融治疗,37例局限性子宫腺肌瘤平均消融率均达90%以上。与治疗前比较,治疗后3、6、12个月患者瘤体缩小率分别为60.8%、78.1%、93.1%,差异有统计学意义(P0.05)。与治疗前比较,治疗后临床症状有改善。结论实时超声引导微波消融术治疗子宫腺肌瘤患者,能够减小腺肌瘤体积,且能够明显改善患者临床症状,为子宫肌瘤患者提供新的治疗手段。  相似文献   
9.
10.
We prospectively evaluated the effectiveness of contrast-enhanced ultrasonography (CEUS) for differentiation of benign versus malignant portal vein thrombosis (PVT). We studied a total of 43 patients with chronic liver disease, hepatocellular carcinoma-suggestive nodules and confirmed PVT, in whom the nature of the PVT was confirmed by follow-up imaging (US, computed tomography and/or magnetic resonance imaging) performed up to 6 mo after CEUS. PVT was assessed by US, Doppler US and CEUS with respect to vessel wall disruption and/or invasion, color Doppler vascularization, pulsed Doppler vascularization pattern and CEUS enhancement and vascularization pattern, and thrombi were classified as benign or malignant based on these findings. Follow-up studies revealed malignant PVT in 22 of the 43 patients (51%) and benign PVT in 21 patients (49%). CEUS findings were consistent with follow-up studies in 41 of the 43 patients (95%), with κ?=?0.903 (p < 0.0001), sensitivity?=?91% and specificity?=?100%, indicating that CEUS can be confidently used to differentiate benign from malignant portal vein thrombosis in the setting of chronic liver disease.  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