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   13355篇
  免费   1119篇
  国内免费   315篇
耳鼻咽喉   95篇
儿科学   225篇
妇产科学   68篇
基础医学   1061篇
口腔科学   272篇
临床医学   1643篇
内科学   1121篇
皮肤病学   40篇
神经病学   853篇
特种医学   1015篇
外国民族医学   2篇
外科学   579篇
综合类   1643篇
现状与发展   1篇
预防医学   2463篇
眼科学   131篇
药学   2564篇
  13篇
中国医学   740篇
肿瘤学   260篇
  2024年   9篇
  2023年   182篇
  2022年   283篇
  2021年   567篇
  2020年   593篇
  2019年   530篇
  2018年   479篇
  2017年   491篇
  2016年   464篇
  2015年   491篇
  2014年   891篇
  2013年   1071篇
  2012年   872篇
  2011年   960篇
  2010年   728篇
  2009年   582篇
  2008年   661篇
  2007年   671篇
  2006年   559篇
  2005年   447篇
  2004年   363篇
  2003年   346篇
  2002年   267篇
  2001年   230篇
  2000年   235篇
  1999年   199篇
  1998年   143篇
  1997年   131篇
  1996年   99篇
  1995年   135篇
  1994年   106篇
  1993年   84篇
  1992年   99篇
  1991年   80篇
  1990年   72篇
  1989年   59篇
  1988年   77篇
  1987年   64篇
  1986年   55篇
  1985年   76篇
  1984年   70篇
  1983年   48篇
  1982年   52篇
  1981年   30篇
  1980年   22篇
  1979年   38篇
  1978年   20篇
  1977年   14篇
  1976年   16篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
AimsTreatment decisions for older patients with breast cancer are complex and evidence is largely extrapolated from younger populations. Frailty and comorbidity need to be considered. We studied the baseline characteristics and treatment decisions in older patients in Christchurch with breast cancer and assessed survival outcomes and prognostic/discriminatory performance of several tools.Materials and methodsWe searched the Canterbury Breast Cancer Registry and identified patients aged 70 years or older at diagnosis with invasive, non-metastatic breast cancer between 1 June 2009 and 30 June 2015. We retrieved demographics, treatment and outcome information. Overall survival and breast cancer-specific survival were estimated. Tools analysing performance status and comorbidity were assessed for their prognostic and discriminatory power.ResultsIn total, 440 patients were identified. Primary surgery was carried out for 362 patients (82.3%): breast-conserving surgery in 114 (of whom 88.6% received radiation therapy); mastectomy in 248 (of whom 24.6% received radiation). Hormone therapy was given for 265 (71.1%) patients with oestrogen receptor-positive cancers. Two hundred and seventy-four (62.3%) patients received full standard treatment, which was associated with significantly improved 5-year survival and 5-year breast cancer-specific survival. The median estimated overall survival was 8.2 years (95% confidence interval 7.3–9.1 years). Of those who died, 71.3% of deaths were due to causes other than breast cancer or unknown causes. The comorbidity-adjusted life expectancy (CALE) showed partial prognostic accuracy. CALE, Charlson and Eastern Cooperative Oncology Group tools all showed discriminatory value.ConclusionIn this population-based series of older patients with breast cancer, showing high levels of primary and adjuvant treatment, patients were more likely to die of causes other than breast cancer. Performance status and comorbidity tools showed prognostic and discriminatory potential in this population supporting their use in treatment decision making. CALE showed the most potential to improve treatment decisions but requires validation in this population to improve prognostic accuracy.  相似文献   
2.
目的 评价美国国家电器制造协会(National Electrical Manufactures Association, NEMA)最新标准(NU 2-2018)在正电子发射型计算机断层显像/电子计算机断层显像(positron emission tomography/computed tomography, PET/CT)设备性能检测中的作用。 方法 依据最新的NEMA NU 2-2018标准,检测西门子Biograph Vision PET/CT的空间分辨率、灵敏度、散射分数、计数丢失、随机符合、飞行时间分辨率、计数丢失率和随机符合校正精度、图像质量、衰减和散射校正精度及PET与CT配准精度指标。 结果 距视野中心1 cm处横向和轴向空间分辨率分别为3.75 mm和3.76 mm;在视野中心和轴向10 cm处的灵敏度分别为16.83 kcps/MBq和16.67 kcps/MBq;放射性浓度为27.37 kBq/mL时,最大等效噪声计数率为258.26 kcps,散射分数为38.58%;系统时间分辨率为209.82 ps;图像质量模型的对比度恢复系数范围为88.9%~96.2%,背景变异系数范围为2.05%~6.80%,平均肺插件残余误差为2.43%;计数丢失和随机符合校正最大误差为3.9%;距离床板末端 5 cm 和 100 cm处,在距视野中心Y轴1 cm处,PET和CT的配准精度分别为0.46 mm和1.07 mm,在距视野中心X轴20 cm处,PET和CT的配准精度分别为1.06 mm和1.45 mm,在距视野中心Y轴20 cm处PET和CT的配准精度分别为0.85 mm和1.15 mm。 结论 NEMA NU 2-2018标准检测条件更加接近临床,能更好地反映PET/CT设备的系统性能。  相似文献   
3.
4.
目的 探讨动态对比增强磁共振成像(DCE-MRI)检查诊断原发性肝癌(PLC)患者的效能及评价疗效的价值。方法 2017年1月~2021年6月我院诊治的肝占位性病变患者68例,均接受DCE-MRI检查,并行穿刺细胞学检查诊断,应用临床流行病学基本技术评估MRI诊断的效能。所有PLC患者接受经皮肝动脉化疗栓塞术(TACE)治疗,术后再次接受MRI检查,评估疗效。结果 DCE-MRI检查显示PLC患者肝内特征性恶性肿瘤表现,T1WI序列为低信号,T2WI序列为高信号,动脉期明显强化,门脉期快速消退,偶见明显的肿瘤包膜;在68例肝占位性病变患者,经穿刺细胞学检查,诊断PLC患者64例,非肿瘤病变4例;DCE-MRI检查诊断的灵敏度、特异度、准确率、阳性和阴性预测值分别为95.2%、75.0%、89.7%、93.8%和25.0%;在TACE术后,MRI检查发现肿瘤被完全灭活18例(28.1%),部分灭活25例(39.1%),肿瘤稳定15例(23.4%),疾病进展6例(9.3%)。结论 DCE-MRI检查在诊断PLC和治疗后疗效判断方面有独特的作用,可指导临床制定治疗方案,价值很大。  相似文献   
5.
《Radiography》2022,28(1):8-16
IntroductionLittle is known about the factors influencing clinical supervisor-assessors’ ratings of sonographer students’ performance. This study identifies these influential factors and relates them to professional competency standards, with the aim of raising awareness and improving assessment practice.MethodsThis study used archived written comments from 94 clinical assessors describing 174 sonographer students’ performance one month into their initial clinical practice (2015–6). Qualitative mixed method analysis revealed factors influencing assessor ratings of student performance and provided an estimate of the valency, association, and frequency of these factors.ResultsAssessors provided written comments for 93 % (n = 162/174) of students. Comments totaled 7190 words (mean of 44 words/student). One-third of comment paragraphs were wholly positive, two-thirds were equivocal. None were wholly negative. Thematic analysis revealed eleven factors, and eight sub-factors, influencing assessor impressions of five dimensions of performance. Of the factors mentioned, 84.6 % (n = 853/1008) related to professional competencies. While 15.4 % (n = 155/1008) were unrelated to competencies, instead reflecting humanistic factors such as student motivation, disposition, approach to learning, prospects and impact on supervisor and staff. Factors were prioritised and combined independently, although some associated.ConclusionClinical assessors formed impressions based on student performance, humanistic behaviours and personal qualities not necessarily outlined in educational outcomes or professional competency standards. Their presence, and interrelations, impact success in clinical practice, through their contribution to, and indication of, competence.Implications for practiceSonographer student curricula and assessor training should raise awareness of the factors influencing performance ratings and judgement of clinical competence, particularly the importance of humanistic factors. Inclusion of narrative comments, multiple assessors, and broad performance dimensions would enhance clinical assessment of sonographer student performance.  相似文献   
6.
BackgroundAnterior cruciate ligament (ACL) reconstruction is recommended in patients who intend to return to high-level sports. However, there is only a 55–80% return to pre-injury level of sports after ACL reconstruction, with a re-injury rate up to 20%. The aim of this study was to determine the percentage of patients passing the Back in Action (BIA) test 9 months after primary bone-patellar-tendon-bone (BPTB) ACL reconstruction, and evaluate the association between passing the BIA test and patient reported outcome measurements (PROMs).MethodsPatients underwent the BIA test 9 months after BPTB ACL reconstruction. In total 103 patients were included. Passing the BIA test (PASSED-group) was defined as a normal or higher score at all sub-tests with limb symmetry index (LSI) ≥90% for the dominant leg and LSI >80% for the non-dominant leg. Patients who did not meet these criteria were defined as the FAILED-group. PROMs included the International Knee Documentation Committee, Knee injury Osteoarthritis Outcome Score and Anterior Cruciate Ligament-Return to Sport after Injury.ResultsEighteen patients (17.5%) passed the BIA test 9 months after BPTB ACL reconstruction. PROMs were not statistically significant different between the PASSED- and FAILED-group.ConclusionLow percentage of patients passed the BIA test 9 months after BPTB ACL reconstruction. Although current PROMs cut-off values were met, the BIA test results show persistent functional deficits. Therefore, the BIA test could be of additional value in the decision-making process regarding return to sport (RTS). This study highlights the need for additional rehabilitation as RTS in a condition of incomplete recovery may increase the risk of re-injury.Level of evidenceII.  相似文献   
7.
《Value in health》2022,25(11):1805-1813
ObjectivesA significant indirect impact of COVID-19 has been the increasing elective waiting times observed in many countries. In England’s National Health Service, the waiting list has grown from 4.4 million in February 2020 to 5.7 million by August 2021. The objective of this study was to estimate the trajectory of future waiting list size and waiting times up to December 2025.MethodsA scenario analysis was performed using computer simulation and publicly available data as of November 2021. Future demand assumed a phased return of various proportions (0%, 25%, 50%, and 75%) of the estimated 7.1 million referrals “missed” during the pandemic. Future capacity assumed 90%, 100%, and 110% of that provided in the 12 months immediately before the pandemic.ResultsAs a worst-case scenario, the waiting list would reach 13.6 million (95% confidence interval 12.4-15.6 million) by Autumn 2022, if 75% of missed referrals returned and only 90% of prepandemic capacity could be achieved. The proportion of patients waiting under 18 weeks would reduce from 67.6% in August 2021 to 42.2% (37.4%-46.2%) with the number waiting over 52 weeks reaching 1.6 million (0.8-3.1 million) by Summer 2023. At this time, 29.0% (21.3%-36.8%) of patients would be leaving the waiting list before treatment. Waiting lists would remain pressured under even the most optimistic of scenarios considered, with 18-week performance struggling to maintain 60%.ConclusionsThis study reveals the long-term challenge for the National Health Service in recovering elective waiting lists and potential implications for patient outcomes and experience.  相似文献   
8.
目的:建立高效液相色谱-荧光检测法测定性早熟女童血浆中双酚A和4-壬基酚含量的方法。方法:采用Shim-pack VP-ODS C18色谱柱(150 mm×4.6 mm,5 μm),流动相为乙腈∶水=70∶30,流速1 mL/min,柱温30 ℃,检测激发波长275 nm,发射波长315 nm,外标法定量检测血浆中双酚A和4-壬基酚含量。结果:双酚A和4-壬基酚分别在1.45~5 937.50 ng/mL (r2=0.999 9,n=7),1.53~6 250.00 ng/mL(r2=0.998 8,n=7)范围内线性关系良好;日内、日间RSD均<7.83%,方法回收率均>94.6%。结论:本法简便、快速、灵敏、准确,适用于同时测定性早熟女童血浆中双酚A和4-壬基酚的含量和临床血样常规检测。  相似文献   
9.
目的:利用聚多巴胺(PDA)对丹参注射液中多成分进行负载,构建丹参注射液(SMI)缓释制剂(PDA-SMI)。方法:建立丹参注射液的原儿茶醛、迷迭香酸和丹酚酸B3种成分的分析方法并进行含量测定;制备PDA,在pH值2.5的条件下对SMI进行负载,制备PDA-SMI;对PDA-SMI体外释放行为进行考察。结果:SMI中原儿茶醛、迷迭香酸、丹酚酸B的浓度分别为0.344、0.214、0.262 mg/mL;PDA-SMI对原儿茶醛、迷迭香酸、丹酚酸B的载药量分别为8.59%,15.90%和20.57%;PDA-SMI中原儿茶醛、迷迭香酸、丹酚酸B体外累计释放率分别为84.05%,77.57%和63.12%。结论:PDA可以负载SMI的多种成分,载药量较高,并具有良好的缓释效应。  相似文献   
10.
In 2008, Brazil's conditional cash transfer program expanded to cover a wider range of ages. Poor families are now given stipends for their children's school attendance up to age seventeen, whereas prior the maximum age was fifteen. Using a nationally representative household survey, we estimate the impact of this policy on teen fertility with a triple difference analysis on the fertility outcomes of treated cohorts vs. non-treated cohorts based on income eligibility, age eligibility, and timing of program implementation. We find a three percentage point drop in fertility among eligible teens within five years of program implementation. This offsets the difference in fertility between poor and non-poor teens. The impact is concentrated in urban areas, with no program effects found in rural areas. We are able to replicate these findings using National Birth Registry Data.  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