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   263108篇
  免费   16556篇
  国内免费   5480篇
耳鼻咽喉   3128篇
儿科学   9412篇
妇产科学   3952篇
基础医学   32944篇
口腔科学   6840篇
临床医学   22954篇
内科学   45587篇
皮肤病学   5111篇
神经病学   14825篇
特种医学   8965篇
外国民族医学   22篇
外科学   35719篇
综合类   25919篇
现状与发展   11篇
一般理论   25篇
预防医学   16474篇
眼科学   6665篇
药学   20606篇
  17篇
中国医学   8545篇
肿瘤学   17423篇
  2023年   5050篇
  2022年   7668篇
  2021年   10329篇
  2020年   8464篇
  2019年   15615篇
  2018年   12896篇
  2017年   8544篇
  2016年   5903篇
  2015年   6594篇
  2014年   9985篇
  2013年   9777篇
  2012年   7989篇
  2011年   12379篇
  2010年   8410篇
  2009年   8753篇
  2008年   8917篇
  2007年   9496篇
  2006年   8619篇
  2005年   9162篇
  2004年   8178篇
  2003年   7054篇
  2002年   6811篇
  2001年   7262篇
  2000年   7322篇
  1999年   7353篇
  1998年   6200篇
  1997年   4859篇
  1996年   3917篇
  1995年   3182篇
  1994年   2844篇
  1993年   2347篇
  1992年   2169篇
  1991年   1844篇
  1990年   1670篇
  1989年   1415篇
  1988年   1417篇
  1987年   1027篇
  1985年   3274篇
  1984年   4532篇
  1983年   3172篇
  1982年   3236篇
  1981年   3001篇
  1980年   2642篇
  1979年   2456篇
  1978年   2027篇
  1977年   1740篇
  1976年   1903篇
  1975年   1562篇
  1974年   1371篇
  1973年   1312篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
PurposeTo compare morphological imaging features and CT texture histogram parameters between grade 3 pancreatic neuroendocrine tumors (G3-NET) and neuroendocrine carcinomas (NEC).Materials and methodsPatients with pathologically proven G3-NET and NEC, according to the 2017 World Health Organization classification who had CT and MRI examinations between 2006-2017 were retrospectively included. CT and MRI examinations were reviewed by two radiologists in consensus and analyzed with respect to tumor size, enhancement patterns, hemorrhagic content, liver metastases and lymphadenopathies. Texture histogram analysis of tumors was performed on arterial and portal phase CT images. images. Morphological imaging features and CT texture histogram parameters of G3-NETs and NECs were compared.ResultsThirty-seven patients (21 men, 16 women; mean age, 56 ± 13 [SD] years [range: 28-82 years]) with 37 tumors (mean diameter, 60 ± 46 [SD] mm) were included (CT available for all, MRI for 16/37, 43%). Twenty-three patients (23/37; 62%) had NEC and 14 patients (14/37; 38%) had G3-NET. NECs were larger than G3-NETs (mean, 70 ± 51 [SD] mm [range: 18 - 196 mm] vs. 42 ± 24 [SD] mm [range: 8 - 94 mm], respectively; P = 0.039), with more tumor necrosis (75% vs. 33%, respectively; P = 0.030) and lower attenuation on precontrast (30 ± 4 [SD] HU [range: 25-39 HU] vs. 37 ± 6 [SD] [range: 25-45 HU], respectively; P = 0.002) and on portal venous phase CT images (75 ± 18 [SD] HU [range: 43 - 108 HU] vs. 92 ± 19 [SD] HU [range: 46 - 117 HU], respectively; P = 0.014). Hemorrhagic content on MRI was only observed in NEC (P = 0.007). The mean ADC value was lower in NEC ([1.1 ± 0.1 (SD)] × 10−3 mm2/s [range: (0.91 - 1.3) × 10−3 mm2/s] vs. [1.4 ± 0.2 (SD)] × 10−3 mm2/s [range: (1.1 - 1.6) × 10−3 mm2/s]; P = 0.005). CT histogram analysis showed that NEC were more heterogeneous on portal venous phase images (Entropy-0: 4.7 ± 0.2 [SD] [range: 4.2-5.1] vs. 4.5 ± 0.4 [SD] [range: 3.7-4.9]; P = 0.023).ConclusionPancreatic NECs are larger, more frequently hypoattenuating and more heterogeneous with hemorrhagic content than G3-NET on CT and MRI.  相似文献   
92.
PurposeThe purpose of this study was to determine whether computed tomography (CT)-based machine learning of radiomics features could help distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).Materials and MethodsEighty-nine patients with AIP (65 men, 24 women; mean age, 59.7 ± 13.9 [SD] years; range: 21–83 years) and 93 patients with PDAC (68 men, 25 women; mean age, 60.1 ± 12.3 [SD] years; range: 36–86 years) were retrospectively included. All patients had dedicated dual-phase pancreatic protocol CT between 2004 and 2018. Thin-slice images (0.75/0.5 mm thickness/increment) were compared with thick-slices images (3 or 5 mm thickness/increment). Pancreatic regions involved by PDAC or AIP (areas of enlargement, altered enhancement, effacement of pancreatic duct) as well as uninvolved parenchyma were segmented as three-dimensional volumes. Four hundred and thirty-one radiomics features were extracted and a random forest was used to distinguish AIP from PDAC. CT data of 60 AIP and 60 PDAC patients were used for training and those of 29 AIP and 33 PDAC independent patients were used for testing.ResultsThe pancreas was diffusely involved in 37 (37/89; 41.6%) patients with AIP and not diffusely in 52 (52/89; 58.4%) patients. Using machine learning, 95.2% (59/62; 95% confidence interval [CI]: 89.8–100%), 83.9% (52:67; 95% CI: 74.7–93.0%) and 77.4% (48/62; 95% CI: 67.0–87.8%) of the 62 test patients were correctly classified as either having PDAC or AIP with thin-slice venous phase, thin-slice arterial phase, and thick-slice venous phase CT, respectively. Three of the 29 patients with AIP (3/29; 10.3%) were incorrectly classified as having PDAC but all 33 patients with PDAC (33/33; 100%) were correctly classified with thin-slice venous phase with 89.7% sensitivity (26/29; 95% CI: 78.6–100%) and 100% specificity (33/33; 95% CI: 93–100%) for the diagnosis of AIP, 95.2% accuracy (59/62; 95% CI: 89.8–100%) and area under the curve of 0.975 (95% CI: 0.936–1.0).ConclusionsRadiomic features help differentiate AIP from PDAC with an overall accuracy of 95.2%.  相似文献   
93.
This article was designed to provide a pediatric cardiac computed tomography angiography (CCTA) expert panel consensus based on opinions of experts of the Société Française d’Imagerie Cardiaque et Vasculaire diagnostique et interventionnelle (SFICV) and of the Filiale de Cardiologie Pédiatrique Congénitale (FCPC). This expert panel consensus includes recommendations for indications, patient preparation, CTA radiation dose reduction techniques, and post-processing techniques. The consensus was based on data from available literature (original papers, reviews and guidelines) and on opinions of a group of specialists with extensive experience in the use of CT imaging in congenital heart disease. In order to reach high potential and avoid pitfalls, CCTA in children with congenital heart disease requires training and experience. Moreover, pediatric cardiac CCTA protocols should be standardized to acquire optimal images in this population with the lowest radiation dose possible to prevent unnecessary radiation exposure. We also provided a suggested structured report and a list of acquisition protocols and technical parameters in relation to specific vendors.  相似文献   
94.
目的比较3%高渗盐水和20%甘露醇治疗重症动脉瘤性蛛网膜下腔出血所致颅内压增高的疗效.方法25例动脉瘤性蛛网膜下腔出血患者出现颅内压增高事件时, 随机交替接受等渗透剂量的160 mL 3%高渗盐水与150 mL 20%甘露醇进行降低颅内压治疗, 连续监测患者颅内压、平均动脉压、脑灌注压及中心静脉压.记录有效降低颅内压持续时间、颅内压最大降幅及其时间, 用药前及用药后1 h、3 h血钠水平及血浆渗透压.结果3%高渗盐水和20%甘露醇均可降低颅内压(均 P < 0.01), 两者的降低颅内压作用持续时间及颅内压降幅差异均无统计学意义(均 P >0.05).患者脑灌注压较用药前均上升(均 P < 0.01), 平均动脉压先上升后下降, 但差异无统计学意义( P >0.05).患者中心静脉压稍有波动, 但差异均无统计学意义(均 P >0.05).20%甘露醇治疗后患者血钠下降, 3%高渗盐水治疗后患者血钠值上升, 变化均有统计学意义(均 P < 0.05).20%甘露醇及3%高渗盐水治疗后患者血浆渗透压均先上升后下降, 变化均有统计学意义(均 P < 0.01). 结论3%高渗盐水可作为治疗动脉瘤性蛛网膜下腔出血所致颅内压增高患者的一线治疗药物.  相似文献   
95.
2015年中华医学会感染病学分会艾滋病学组发布了第三版《艾滋病诊疗指南》。新版指南强调抗病毒治疗时点前移:一旦成人确诊感染人类免疫缺陷病毒(HIV), 若无禁忌宜尽早启动抗HIV治疗。对于合并机会性感染的HIV感染者, 在感染控制、病情稳定后也应及早开始抗病毒治疗。尤其强调HIV合并结核患者在CD4阳性淋巴细胞数少于200/μL的情况下, 建议抗结核两周内即开始抗病毒治疗。在抗HIV治疗用药中, 淘汰了一些毒副作用大、依从性较差的药物, 如司他夫定、去羟肌苷、茚地那韦等, 优选抗病毒效力强、服药方便的组合, 如拉米夫定、替诺福韦、依非韦伦组合。对于HIV感染的婴幼儿, 亦主张及早抗HIV治疗。对于五岁以内的幼儿, 主张确诊后即启动抗病毒治疗。对于HIV感染的孕产妇, 建议尽快予以全程、联合抗HIV治疗, 寓防于治。  相似文献   
96.
97.
98.
PurposeTo investigate the safety of yttrium-90 radioembolization in combination with checkpoint inhibitor immunotherapy for the treatment of hepatocellular carcinoma (HCC).Materials and MethodsThis single-center retrospective study included 26 consecutive patients with HCC who received checkpoint inhibitor immunotherapy within 90 days of radioembolization from April 2015 to May 2018. Patients had preserved liver function (Child-Pugh scores A–B7) and either advanced HCC due to macrovascular invasion or limited extrahepatic disease (21 patients) or aggressive intermediate stage HCC that resulted in earlier incorporation of systemic immunotherapy (5 patients). Clinical documentation, laboratory results, and imaging results at 1- and 3-month follow-up intervals were reviewed to assess treatment-related adverse events and treatment responses.ResultsThe median follow-up period after radioembolization was 7.8 months (95% confidence interval [CI], 5.6–11.8). There were no early (30-day) mortality or grades 3/4 hepatobiliary or immunotherapy-related toxicities. Delayed grades 3/4 hepatobiliary toxicities (1–3 months) occurred in 2 patients in the setting of HCC disease progression. One patient developed pneumonitis. The median overall survival from first immunotherapy was 17.2 months (95% CI, 10.9–23.4). The median overall survival from first radioembolization was 16.5 months (95% CI, 6.6–26.4). From first radioembolization, time to tumor progression was 5.7 months (95% CI, 4.2–7.2), and progression-free survival was 5.7 months (95% CI, 4.3–7.1).ConclusionsRadioembolization combined with checkpoint inhibitor immunotherapy in cases of HCC appears to be safe and causes limited treatment-related toxicity. Future prospective studies are needed to identify the optimal combination treatment protocols and evaluate the efficacy of combination therapy.  相似文献   
99.
100.
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