首页 | 官方网站   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   90378篇
  免费   5211篇
  国内免费   4999篇
医药卫生   100588篇
  2024年   76篇
  2023年   563篇
  2022年   879篇
  2021年   1701篇
  2020年   1352篇
  2019年   1130篇
  2018年   1236篇
  2017年   1198篇
  2016年   1143篇
  2015年   1593篇
  2014年   2175篇
  2013年   2197篇
  2012年   3423篇
  2011年   6258篇
  2010年   3816篇
  2009年   2734篇
  2008年   3632篇
  2007年   3364篇
  2006年   3385篇
  2005年   4536篇
  2004年   8462篇
  2003年   7722篇
  2002年   6113篇
  2001年   4881篇
  2000年   3183篇
  1999年   3793篇
  1998年   2651篇
  1997年   2324篇
  1996年   1600篇
  1995年   1463篇
  1994年   1401篇
  1993年   1933篇
  1992年   1700篇
  1991年   1452篇
  1990年   1094篇
  1989年   913篇
  1988年   729篇
  1987年   583篇
  1986年   597篇
  1985年   301篇
  1984年   171篇
  1983年   115篇
  1982年   85篇
  1981年   78篇
  1980年   62篇
  1979年   85篇
  1978年   54篇
  1977年   67篇
  1975年   68篇
  1974年   49篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
神经内分泌肿瘤(neuroendocrine neoplasm,NEN)是一类起源于肽能神经元和神经内分泌细胞,具有神经内分泌分化并表达神经内分泌标志物的少见肿瘤,可发生于全身各处,以肺及胃肠胰NEN(gastroenteropancreatic neuroendocrine neoplasm, GEP-NEN)最常见。国内外研究数据均提示,NEN的发病率在不断上升。美国流行病学调查结果显示,与其他类型肿瘤相比,NEN的发病率上升趋势更为显著。中国抗癌协会神经内分泌肿瘤专委会在现有循证医学证据基础上,结合已有国内外指南和共识,制订了首版中国抗癌协会神经内分泌肿瘤诊治指南,为临床工作者提供参考。  相似文献   
3.
Vegetation water content (VWC) is the key input parameter for a soil moisture retrieval algorithm based on microwave remote sensing, and VWC uncertainty can limit the estimated accuracy of soil moisture. There has been little research on VWC algorithm development and validation in China, and the uncertainty of the VWC estimation method has not been well evaluated. Therefore, the aim of this study is to evaluate the uncertainty of the VWC estimation method used in the SMAP (Soil Moisture Active Passive) algorithm on three spatial scales (the point-scale, 30 m scale, and 1 km scale) for maize in northeast China. Results from three ground experimental datasets showed that the SMAP VWC estimation method was strongly biased with an average overestimation of 1.16 kg m?2,1.04 kg m?2, and 1.13 kg m?2 for the point-scale, 30 m scale, and 1 km scale respectively, and maximum bias occurred in the mid-stage of maize. Also, a new power relationship between NDVI (Normalized Difference Vegetation Index) and VWC was proposed for the 30 m scale based on Sentinel 2 NDVI and field VWC values from 2017 experiment, with respective R2 (coefficient of determination) and Root Mean Squared Error (RMSE) values of 0.80 and 0.67 kg m?2. The results confirmed that this power relationship was still suitable for VWC estimation at the 1 km scale, and it has smaller bias than the original SMAP VWC method. Future work will be carried out to evaluate the applicability of this VWC estimation method over a lager region. It is expected that it can improve the accuracy of soil moisture by providing high precision VWC input parameters.  相似文献   
4.
5.
The specialty of emergency medicine in Australasia is coming of age. As part of this maturation there is a need for high‐quality evidence to inform practice. This article describes the development of the New Zealand Emergency Medicine Network, a collaboration of committed emergency care researchers who share the vision that New Zealand/Aotearoa will have a world‐leading, patient‐centred emergency care research network, which will improve emergency care for all, so that people coming to any ED in the country will have access to the same world‐class emergency care.  相似文献   
6.
Based on the physical randomization of completely randomized experiments, in a recent article in Statistics in Medicine, Rigdon and Hudgens propose two approaches to obtaining exact confidence intervals for the average causal effect on a binary outcome. They construct the first confidence interval by combining, with the Bonferroni adjustment, the prediction sets for treatment effects among treatment and control groups, and the second one by inverting a series of randomization tests. With sample size n, their second approach requires performing O(n4)randomization tests. We demonstrate that the physical randomization also justifies other ways to constructing exact confidence intervals that are more computationally efficient. By exploiting recent advances in hypergeometric confidence intervals and the stochastic order information of randomization tests, we propose approaches that either do not need to invoke Monte Carlo or require performing at most O(n2)randomization tests. We provide technical details and R code in the Supporting Information . Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
7.
改良超滤(MUF)技术作为心肺转流中节约用血的重要手段之一,具有浓缩血液、清除炎性介质、减轻组织水肿等优点,但随着微小化体外循环技术的应用,MUF在临床应用中的获益性和必要性开始受到各中心的重新审视。本文对近年来MUF的临床使用进展予以综述。  相似文献   
8.
Objective: To evaluate the effectiveness of a modified behavioral activation treatment (MBAT) intervention on reducing depressive symptoms in rural left-behind elderly.

Method: This is a randomized study registered in Chinese Clinical Trial Registry (ChiCTR-IOR-17011289). Eighty rural left-behind elderly people who had a Geriatric Depression Scale (GDS) score between 11 and 25 were randomly assigned to the intervention (n?=?40) and control group (n?=?40). The intervention group received both MBAT and regular treatment for 8 weeks while the control group received regular treatment. Both groups were assessed with the GDS, Beck Anxiety Inventory (BAI), and Oxford Happiness Questionnaire (OHQ) at baseline, immediately post-intervention, and at 3 months post-intervention.

Results: There were a total of 73 participants that completed the intervention. The scores of GDS and BAI decreased significantly, but the scores of OHQ increased significantly in the intervention group after 8 sessions of MBAT (P?<?.01). The reduction in depression symptoms after the intervention was maintained at the 3-month follow-up. Significant differences in GDS, BAI, and OHQ scores were observed between the intervention group and the control group (P?<?.01).

Conclusion: MBAT produced a significantly greater reduction in depressive symptoms than regular care in rural left-behind elderly.

Clinical or methodological significance of this article: A modified behavioral activation (BA) psychotherapy can significantly reduce the recurrence and seriousness of depression symptoms in the left-behind elderly with mild to moderate depression. This study also suggests that further study of the MBAT as an intervention will provide a direction for the management of mental health in rural left-behind elders.  相似文献   

9.
Medical education fellowship programs (MEFPs) are a form of faculty development contributing to an organization’s educational mission and participants’ career development. Building an MEFP requires a systematic design, implementation, and evaluation approach which aligns institutional and individual faculty goals. Implementing an MEFP requires a team of committed individuals who provide expertise, guidance, and mentoring. Qualified MEFP directors should utilize instructional methods that promote individual and institutional short and long term growth. Directors must balance the use of traditional design, implementation, and evaluation methodologies with advancing trends that may support or threaten the acceptability and sustainability of the program. Drawing on the expertise of 28 MEFP directors, we provide twelve tips as a guide to those implementing, sustaining, and/or growing a successful MEFP whose value is demonstrated by its impacts on participants, learners, patients, teaching faculty, institutions, the greater medical education community, and the population’s health.  相似文献   
10.
儿童心脏移植是治疗年龄18岁终末期心力衰竭患者的有效手段。1967年美国Adrian Katrowitz实施第一例儿童心脏移植,近五年全球80家单位每年开展500例左右。中国儿童心脏移植起步晚、发展慢。自1995年开展第一例儿童心脏移植以来,目前国内已登记病例超过130例。中华医学会器官移植学分会组织心脏移植专家,总结国内外相关研究最新进展,结合国际指南和临床实践,针对儿童心脏移植受者选择及常用术式的操作要点、程序和方法,以及各类复杂先天性心脏病心脏移植的特殊操作,制订《中国儿童心脏移植适操作规范(2019版)》。  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-23

京公网安备 11010802026262号