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   25372篇
  免费   3084篇
  国内免费   639篇
耳鼻咽喉   90篇
儿科学   473篇
妇产科学   1240篇
基础医学   1382篇
口腔科学   184篇
临床医学   8005篇
内科学   3704篇
皮肤病学   301篇
神经病学   905篇
特种医学   1669篇
外国民族医学   6篇
外科学   2890篇
综合类   4068篇
现状与发展   3篇
预防医学   1125篇
眼科学   451篇
药学   1092篇
  51篇
中国医学   235篇
肿瘤学   1221篇
  2024年   115篇
  2023年   555篇
  2022年   1033篇
  2021年   1240篇
  2020年   1513篇
  2019年   1289篇
  2018年   1247篇
  2017年   1276篇
  2016年   1244篇
  2015年   1251篇
  2014年   2115篇
  2013年   1926篇
  2012年   1430篇
  2011年   1533篇
  2010年   1205篇
  2009年   1109篇
  2008年   1152篇
  2007年   1187篇
  2006年   981篇
  2005年   776篇
  2004年   652篇
  2003年   627篇
  2002年   484篇
  2001年   416篇
  2000年   323篇
  1999年   322篇
  1998年   263篇
  1997年   269篇
  1996年   223篇
  1995年   184篇
  1994年   169篇
  1993年   142篇
  1992年   113篇
  1991年   105篇
  1990年   85篇
  1989年   65篇
  1988年   62篇
  1987年   48篇
  1986年   58篇
  1985年   86篇
  1984年   62篇
  1983年   20篇
  1982年   45篇
  1981年   29篇
  1980年   23篇
  1979年   21篇
  1978年   9篇
  1977年   5篇
  1976年   3篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The paternal uniparental disomy 14 is a rare malformation syndrome whose postnatal pathognomonic sign is the deformation of the rib as coat hanger. In prenatal, ultrasonographic signs are major recurrent polyhydramnios, a narrow thorax and deformed long bones short and sometimes other anomalies including ends. The authors report one rare case of prenatal paternal uniparental disomy 14 with the deformation of the rib as coat hanger. Prenatally, the narrow deformed thorax can be searched by ultrasound three-dimensional (3D) and/or helical CT and thus represent an aid to prenatal diagnosis.  相似文献   
992.
ObjectiveCongenital heart disease is one of the most common types of structural fetal abnormalities and a major cause of perinatal morbidity and mortality. Fetal echocardiography aids in the diagnosis of congenital heart disease, which allows management planning for parents and physicians, including continuation or termination of the pregnancy and triaging for location of delivery. This is a key component of planning, as transport of neonates entails risks, costs, and parental stress. In this study, we examined the outcomes of pregnancies with fetal cardiac anomalies diagnosed at a single tertiary care centre. We aimed to assess whether the system of directing affected pregnancies to either a tertiary and quaternary care centre is effective.MethodsWe identified pregnancies with fetal cardiac anomalies diagnosed on fetal echocardiography between 2005 and 2009. Information about diagnosis, pregnancy outcome, delivery location, and surgical management was collected. This information was analyzed retrospectively.ResultsAnomalies were demonstrated in 120 fetal echocardiography studies. Four of the babies (3.3%) were stillborn, and 27 (22.5%) pregnancies were terminated. There were 89 live born babies, and 74 of these (61.7%) survived the neonatal period. Fifteen babies (12.5%) died as neonates. Thirty-two pregnant women were triaged to deliver at the quaternary centre with pediatric cardiac surgery services, and 20 of these babies underwent surgery. Two of the 89 live born babies (2.2%) required emergency transfer.ConclusionFetal echocardiography is an important contributor to efficient use of pediatric cardiac services and minimizes need for neonatal transfer. Contemporary use of fetal echocardiography is associated with optimized delivery location.  相似文献   
993.

Objective

To compare clinical data and transperineal ultrasound results for the diagnosis of fetal head engagement.

Methods

The present prospective longitudinal study enrolled 100 term women attending the Mongi Slim Hospital, La Marsa, Tunisia, between July and September 2012. The clinical assessment of fetal engagement was compared with ultrasound measurements. Ultrasound examination was performed in the delivery room. The probe was placed on the ano-vulvar area. The measure used was the distance between the perineum and external table of fetal skull.

Results

The ultrasound measures of the perineum to external table of fetal skull ranged from 13 to 75 mm. The measures of the perineum to succedaneum bump ranged from 22 to 68 mm. A threshold of 55 mm was determined as the perineum to fetal head distance above which a diagnosis of engagement would be reversed. This proposed threshold had a positive predictive value of 98.6%, a sensitivity of 86.7%, and a specificity of 94.1%.

Conclusion

Transperineal ultrasound is a simple, rapid, and reproducible method for the diagnosis of fetal head engagement. It can be used in the delivery room in addition to clinical examination and when the latter is hampered by a succedaneum bump.  相似文献   
994.

Objectives

Management of women with pre-gestational diabetes continues to be challenging for clinicians. This study aims to determine if 3D power Doppler (3DPD) analysis of placental volume and flow, and calculation of placental calcification using a novel software method, differ between pregnancies with type 1 or type 2 diabetes and normal controls, and if there is a relationship between these ultrasound placental parameters and clinical measures in diabetics.

Methods

This was a prospective cohort study of 50 women with diabetes and 250 controls (12–40 weeks gestation). 3DPD ultrasound was used to evaluate placental volume, vascularisation index (VI), flow index (FI) and vascularisation-flow index (VFI). Placental calcification was calculated by computer analysis. Results in diabetics were compared with control values, and correlated with early pregnancy HbA1c, Doppler results and placental histology.

Results

Placental calcification and volume increased with advancing gestation in pre-gestational diabetic placentae. Volume was also found to be significantly higher than in normal placentae. VI and VFI were significantly lower in diabetic pregnancies between 35 and 40 weeks gestation. A strong relationship was seen between a larger placental volume and both increasing umbilical artery pulsatility index and decreasing middle cerebral artery pulsatility index. FI was significantly lower in cases which had a booking HbA1c level ≥6.5%. Ultrasound assessed placental calcification was reduced with a histology finding of delayed villous maturation. No other correlation with placental histology was found.

Conclusions

This study shows a potential role for 3D placental evaluation, and computer analysis of calcification, in monitoring pre-gestational diabetic pregnancies.  相似文献   
995.
血管内超声(IVUS)图像是观测血管内部结构的首选影像学手段,基于IVUS图像的内膜和中外膜边界的提取是实现冠脉粥样硬化精准诊断的前提和关键。针对IVUS图像结构复杂、对比度低、边界提取困难等问题,本研究提出一种基于改进TransUnet网络的分割方法。首先,针对IVUS图像边界提取难点,对边血管、血管分叉、导丝伪像、阴影等4种图像结构进行建模,并基于建模结果予以定向数据增强;而后,结合IVUS图像的环状结构分布特点,在TransUnet网络中提出了Polar-bias归纳偏置的策略,并对IVUS图像进行像素级的分类;最后,基于分类结果优化GVF snake模型的外力场,进而提取IVUS图像的内膜和中外膜边界。采用国际标准IVUS图像数据集(两组不同中心频率,共512幅图像)对算法进行评测,引入JMard距离(JM),Hausdorff距离(HD)和面积差异百分比(PAD)等3个评测指标,在数据集A中JM为0.87, HD为0.87, PAD为0.18,数据集B中JM为0.91, HD为0.25, PAD为0.08。实验结果表明,所提出的算法在两组数据集的内膜及中外膜提取问题中的表现均...  相似文献   
996.
ObjectiveOur study aimed to build a normal reference range for routine mid-pregnancy cervical length screening for preterm birth (PTB) based on a large cross-section of Taiwanese singleton pregnancies. Based on our reference range findings, we aim to develop a Z-score and centile calculator.Materials and methodsWe performed a retrospective analysis of the routine mid-trimester cervical length measurement in low-risk singleton pregnancies (without known abnormal growth or karyotype, congenital malformation, history of preterm birth due to preterm premature rupture of the membranes, or history of cervical cerclage treatment). From November 2008 to June 2018, the cervical lengths of 51,644 Taiwanese low-risk pregnant women were measured by experienced sonographers via transvaginal ultrasound during second trimester fetal anatomical screening at 20–24 weeks of gestation. Kolmogorov–Smirnov test was used to assess the normality of the distribution. Cole's lambda, mu, sigma (LMS) method was applied to build mid-pregnancy cervical length reference range and calculate Z-scores. Cut-off values of 2.5, 2.0 and 1.5 cm were used to evaluate the number of pregnancies considered high-risk for PTB.ResultsKolmogorov–Smirnov test showed that the cervical length measurements did not follow a normal distribution (<0.001). Reference range constructed by LMS method was presented in our study. Mean cervical length was 3.82 cm (SD = 0.62 cm). Overall, less than 0.3% of women had a cervical length shorter than 1.5 cm.ConclusionWe are providing an open access calculator for z-score and centile calculation for use in clinical practice for assessing how CL measurement compares in normally developing singleton pregnancies. Further investigation is needed to determine if Z-scores can better assess risk for PTB compared to fixed cut-offs. Since Z-scores are used to assess large deviations from normal development, they may be a useful tool for risk assessment and can be the basis for future standardized screening protocol in Taiwan.  相似文献   
997.
宫颈妊娠是临床罕见的一种异位妊娠,由于胚胎种植于宫颈管黏膜内,可能造成大出血等不良结局,严重时需切除子宫,甚至危及患者生命。该疾病尚无特定治疗方法,需行个体化治疗。目前采用高强度聚焦超声治疗宫颈妊娠的报道极少,现回顾中国人民武装警察部队特色医学中心妇产科2020年收治的1例高强度聚焦超声联合清宫术成功治疗宫颈妊娠的病例,希望通过分享治疗经验引起妇产科医师的注意,为宫颈妊娠患者谋求更安全、有效、经济的治疗方案。  相似文献   
998.
平花  王英 《现代保健》2010,(1):10-11
目的探讨应用宫腔镜联合腹部B超处理难取的宫内节育器的临床价值。方法选择常规方法取器失败1~3次的病例78例,在官腔镜联合腹部B超监测下取器,观察疗效及并发症。结果所有患者一次性取器成功,成功率100%,无并发症。结论宫腔镜下联合腹部B超监测处理难取宫内节育器的方法是成功的。  相似文献   
999.
Patients with neuromuscular disorders often present with swallowing difficulties due to oral phase problems and pharyngeal residue after swallow. It is important to assess the underlying pathology and cause of the swallowing disturbance in this patient group, such as dystrophic changes in oral and masticatory muscles. This allows for more patient‐tailored recommendations, for example optimal compensation strategies to maintain function for longer. Ultrasound can show structural changes caused by dystrophy or denervation of muscles, detect involuntary movements such as fasciculations, and provide dynamic video images of tongue motion during swallowing attempts. This article, based on the authors' extensive experience with ultrasound in neuromuscular disease, explains the concepts of oral muscle ultrasound and its proven value in assessing neuromuscular mastication and swallowing problems. As a patient‐friendly and portable technique, we advocate its use as a standard tool for analyzing neuromuscular dysphagia. Clin. Anat. 30:183–193, 2017. © 2017 Wiley Periodicals, Inc.  相似文献   
1000.

Objective

The prevalence of musculoskeletal complications in diabetes mellitus (DM) increases with the duration of disease and with poor glycemic control. Our aim was to evaluate lower extremity musculoskeletal complications in patients with DM using the Glasgow Ultrasound Enthesitis Scoring System, and to reveal the relationship between clinical and sonographic findings.

Materials and methods

A total of 67 patients (25 men, 42 women) with DM were included in the study. All the diabetic patients were selected if they did not have any symptom of musculoskeletal system in the lower extremities. They were divided into four groups. Ultrasonographic assessment was performed according to the Glasgow Ultrasound Enthesitis Scoring System with an Esaote MyLab 5 device equipped with a 5–13 MHz linear transducer. Correlation between diabetes duration and lower extremity enthesopathy scores were evaluated.

Results

There was a significant correlation between duration of DM and total Glasgow Ultrasound Enthesitis Scoring System scores (p < 0.001). In addition, duration of DM was significantly correlated with enthesophyte scores and erosion scores (both p < 0.001). There was a significant difference among Groups 1–4 for the mean enthesophyte score and mean erosion score (both, p < 0.001).

Conclusion

Musculoskeletal ultrasonography is an effective, inexpensive, and useful tool without radiation for evaluating diabetic patients for the early diagnosis of musculoskeletal complications.  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