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   13727篇
  免费   1058篇
  国内免费   30篇
耳鼻咽喉   141篇
儿科学   321篇
妇产科学   310篇
基础医学   2378篇
口腔科学   240篇
临床医学   1543篇
内科学   2814篇
皮肤病学   323篇
神经病学   1362篇
特种医学   666篇
外科学   1637篇
综合类   96篇
一般理论   5篇
预防医学   995篇
眼科学   200篇
药学   849篇
中国医学   18篇
肿瘤学   917篇
  2023年   63篇
  2022年   135篇
  2021年   269篇
  2020年   159篇
  2019年   272篇
  2018年   301篇
  2017年   253篇
  2016年   330篇
  2015年   356篇
  2014年   411篇
  2013年   600篇
  2012年   804篇
  2011年   846篇
  2010年   472篇
  2009年   508篇
  2008年   774篇
  2007年   792篇
  2006年   828篇
  2005年   760篇
  2004年   742篇
  2003年   683篇
  2002年   629篇
  2001年   333篇
  2000年   323篇
  1999年   304篇
  1998年   183篇
  1997年   138篇
  1996年   112篇
  1995年   92篇
  1994年   95篇
  1993年   74篇
  1992年   195篇
  1991年   165篇
  1990年   142篇
  1989年   166篇
  1988年   129篇
  1987年   126篇
  1986年   118篇
  1985年   111篇
  1984年   98篇
  1983年   72篇
  1982年   59篇
  1981年   48篇
  1979年   72篇
  1978年   46篇
  1977年   52篇
  1975年   37篇
  1974年   51篇
  1973年   44篇
  1971年   40篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
3.
4.
Marie Warrer Petersen  Tine Sylvest Meyhoff  Marie Helleberg  Maj-Brit Nørregaard Kjær  Anders Granholm  Carl Johan Steensen Hjortsø  Thomas Steen Jensen  Morten Hylander Møller  Peter Buhl Hjortrup  Mik Wetterslev  Gitte Kingo Vesterlund  Lene Russell  Vibeke Lind Jørgensen  Klaus Tjelle  Thomas Benfield  Charlotte Suppli Ulrik  Anne Sofie Andreasen  Thomas Mohr  Morten H. Bestle  Lone Musaeus Poulsen  Mette Friberg Hitz  Thomas Hildebrandt  Lene Surland Knudsen  Anders Møller  Christoffer Grant Sølling  Anne Craveiro Brøchner  Bodil Steen Rasmussen  Henrik Nielsen  Steffen Christensen  Thomas Strøm  Maria Cronhjort  Rebecka Rubenson Wahlin  Stephan Jakob  Luca Cioccari  Balasubramanian Venkatesh  Naomi Hammond  Vivekanand Jha  Sheila Nainan Myatra  Christian Gluud  Theis Lange  Anders Perner 《Acta anaesthesiologica Scandinavica》2020,64(9):1365-1375

Introduction

Severe acute respiratory syndrome coronavirus-2 has caused a pandemic of coronavirus disease (COVID-19) with many patients developing hypoxic respiratory failure. Corticosteroids reduce the time on mechanical ventilation, length of stay in the intensive care unit and potentially also mortality in similar patient populations. However, corticosteroids have undesirable effects, including longer time to viral clearance. Clinical equipoise on the use of corticosteroids for COVID-19 exists.

Methods

The COVID STEROID trial is an international, randomised, stratified, blinded clinical trial. We will allocate 1000 adult patients with COVID-19 receiving ≥10 L/min of oxygen or on mechanical ventilation to intravenous hydrocortisone 200 mg daily vs placebo (0.9% saline) for 7 days. The primary outcome is days alive without life support (ie mechanical ventilation, circulatory support, and renal replacement therapy) at day 28. Secondary outcomes are serious adverse reactions at day 14; days alive without life support at day 90; days alive and out of hospital at day 90; all-cause mortality at day 28, day 90, and 1 year; and health-related quality of life at 1 year. We will conduct the statistical analyses according to this protocol, including interim analyses for every 250 patients followed for 28 days. The primary outcome will be compared using the Kryger Jensen and Lange test in the intention to treat population and reported as differences in means and medians with 95% confidence intervals.

Discussion

The COVID STEROID trial will provide important evidence to guide the use of corticosteroids in COVID-19 and severe hypoxia.
  相似文献   
5.
Radiolabeled octreotide analogs (Oct) and metaiodobenzylguanidine (MIBG) offer 2 different approaches for imaging and targeting metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NET). Despite successful establishment of the revised World Health Organization (WHO) classification, which distinguishes between low- and high-grade malignant GEP-NET, there is a lack of scintigraphic studies comparing uptake behavior on the basis of this categorization. This study aims to define predisposing factors of tracer uptake for both imaging principles implementing the updated tumor criteria of the current WHO classification. METHODS: Fifty-seven consecutive patients with histologically confirmed metastatic GEP-NET evaluated with both 111In-pentetreotide and 123I/131I-MIBG scintigraphy were included in this study. Intensity of tracer uptake was graded according to the different metastatic regions. Patients were classified as overall positive when avid uptake in the clinically relevant tumor lesions was present. Correlation was tested between the proportion of positive patients and tumor origin, function, and malignancy. RESULTS: Overall, 52 patients (91.2%) were Oct positive and 28 patients (49.1%) were MIBG positive. The proportion of tracer-positive patients was significantly higher (P < 0.05) in low-grade malignant tumors for both tracers and in functioning as well as in gastroenteral NET for MIBG. Five patients were negative for both tracers. None of the Oct-negative patients proved to be MIBG positive. CONCLUSION: Oct affinity is observed with high frequency throughout the subgroups of metastatic GEP-NET, whereas corresponding MIBG uptake is overall less prevalent and more group dependent. Tumor differentiation significantly impacts both Oct and MIBG uptake, whereas functionality predisposes only for MIBG accumulation. Though clearly inferior to Oct-based radioimaging in most GEP-NET, MIBG achieves a remarkable rate of radioligand accumulation in functioning midgut enterochromaffin cell metastases (>80% of patients positive). These results may have implications for patient management and potentially for selection and performance of targeted therapy.  相似文献   
6.
Coronary flow reserve (CFR) has been used toassess coronary microcirculation and epicardial coro-nary stenoses[1— 3 ] . CFR is defined as the ratio ofcoronary flow under maximal coronary vasodilatationto coronary flow under resting conditions[4 ] .Whenthe cross- sectional area of epicardial coronary arteriesis constant,coronary flow velocity (CFV) ratios areequal to volume flow ratios.The most common method used clinically formeasuring CFVR is intracoronary Doppler flow(ICD) analysis re…  相似文献   
7.
MR imaging of the labral-capsular complex: normal variations   总被引:3,自引:0,他引:3  
Understanding the normal anatomy of the shoulder and its variations is important for the proper interpretation of MR images. This study was performed to describe variations in the normal labral-capsular complex as seen on MR images. MR images of 52 shoulders in 30 asymptomatic volunteers and 27 shoulders of symptomatic patients who had subsequent arthroscopy and/or reconstructive surgery were obtained with 1.5-T MR. The 52 scans of the asymptomatic group were reviewed by three radiologists in conference, and the assessment of labral shapes and capsular insertions was done by consensus. The 27 MR scans of the shoulders in the symptomatic group were reviewed by one radiologist before and after the asymptomatic cases were interpreted. Differences in these two interpretations were shown on receiver-operating-characteristic curves by using the results of subsequent arthroscopy and surgery as the gold standard. The anterior and posterior parts of the labra, respectively, varied in shape but showed several dominant features: triangular (45%, 73%), round (19%, 12%), cleaved (15%, 0%), notched (8%, 0%), flat (7%, 6%), and absent (6%, 8%). Most capsules inserted anteriorly on the labrum (47%) or glenoid rim (49%). All posterior insertions were on the labrum (100%). Intrinsic labral signal was noted on proton density-weighted images, but never on T2-weighted images. Receiver-operating-characteristic curves from interpretations of the symptomatic and clinical cases made before and after evaluation of the asymptomatic shoulders showed the interpretations improved considerably after scans of asymptomatic volunteers were studied. Our study reveals a wide variability in the MR appearance of the labral-capsular complex in asymptomatic shoulders.  相似文献   
8.
The aim of this study was to evaluate a case-mix system to classify inpatients with mental disorders in Germany by means of self-report and expert-rated instruments. The use of case-mix systems enhances the transparency of performance and cost structure and can thus improve the quality of mental health care. We analysed a consecutive sample of 1677 inpatients with mental disorders from 11 hospitals using regression tree analysis. The model assigns patients to 17 groups, accounting for 17% of the variance for duration of stay. Patients with eating disorders had a longer duration of stay than patients with anxiety disorder, duration of mental illness of less than 3–5 years, lower levels of interpersonal problems and higher occupational position. The results showed that besides diagnosis, variables such as duration of illness and interpersonal problems are important for classifying inpatients with mental disorders. The results of the study should be critically reviewed regarding the empirical results of other studies and the appropriateness of case group concepts for inpatients with mental disorders.  相似文献   
9.
PURPOSE: To study the effect of treatment time prolongation following initial dose acceleration on the response of subcutaneously growing R1H tumor. MATERIAL AND METHODS: Continuous standard fractionation (30 fractions/40 days) was compared to initially accelerated treatment (30 fractions/21 days) followed by five to two fractions per week yielding total treatment times from 40 to 72 days. Local tumor control was assessed as endpoint. RESULTS: Radiation dose to control 50% of the tumors (TCD50%) decreased statistically significant from 83.5 Gy (95% confidence interval [CI]: 78.6 .. 88.4) for standard fractionation to 74.1 Gy (95% CI: 72.7 .. 75.5) determined for all accelerated treatment arms (p = 0.003). Prolongation of treatment time after initial acceleration from 40 to 72 days led to a small but statistically not significant increase in TCD50% from 72.0 Gy (95% CI: 71.0 .. 72.9) to 76.2 Gy (95% CI: 69.9 .. 82.4) corresponding to a repopulated dose of 0.9 Gy per week. This time factor is considerably smaller than for conventional radiation treatment as determined in previous experiments. CONCLUSION: The results indicate that initially accelerated irradiation not only improves local tumor control but also minimizes the negative effect of treatment time prolongation. This might be due to changes in tumor cell repopulation kinetics.  相似文献   
10.
The purpose of the study was to compare skin blood flow by laser Doppler flowmetry (LDF) and the 133-Xenon washout technique in UVB-inflamed human skin. Six healthy subjects participated in the study. Forearm skin blood flow was measured prior to irradiation and then 8, 24, 48 and 72 h after the exposure to twice the minimal erythema dose of UVB. Baseline blood flow as measured by the 133-Xenon washout method was 5.2 (range 3.0 to 10.4) ml/100g/min and LDF flux was 3.1 (range 2.7 to 5.7) arbitrary units. Following irradiation, maximum blood flow increase as evaluated by the 133-Xenon washout was 10.8 (95% confidence interval 3.7 to 11.3) times baseline blood flow, corresponding to an absolute blood flow of 47.5 (range 33.8 to 56.3) ml/100g/min. Maximum increase after induction of inflammation as assessed by LDF was 34.6 (95% confidence interval 24.6 to 56.5) times baseline flux. The two methods showed comparable time courses in all subjects. A significant correlation between the two methods was found, Spearman's rho = 0.54, p = 0.006. The relative LDF blood flow increase was 4.2-fold (95% confidence interval 2.7 to 5.0) greater than the increase measured by the 133-Xenon washout method. These results are at variance with previous comparative studies of the two methods. Some explanations are discussed.  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