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   2495篇
  免费   144篇
  国内免费   6篇
耳鼻咽喉   9篇
儿科学   72篇
妇产科学   24篇
基础医学   380篇
口腔科学   89篇
临床医学   332篇
内科学   519篇
皮肤病学   70篇
神经病学   293篇
特种医学   81篇
外科学   301篇
综合类   6篇
一般理论   3篇
预防医学   216篇
眼科学   25篇
药学   121篇
中国医学   1篇
肿瘤学   103篇
  2023年   18篇
  2022年   24篇
  2021年   45篇
  2020年   35篇
  2019年   41篇
  2018年   33篇
  2017年   46篇
  2016年   74篇
  2015年   49篇
  2014年   74篇
  2013年   165篇
  2012年   172篇
  2011年   165篇
  2010年   110篇
  2009年   129篇
  2008年   169篇
  2007年   166篇
  2006年   155篇
  2005年   181篇
  2004年   152篇
  2003年   141篇
  2002年   132篇
  2001年   26篇
  2000年   14篇
  1999年   30篇
  1998年   27篇
  1997年   21篇
  1996年   19篇
  1995年   24篇
  1994年   15篇
  1993年   10篇
  1992年   20篇
  1991年   8篇
  1990年   7篇
  1988年   10篇
  1987年   8篇
  1986年   7篇
  1985年   10篇
  1984年   6篇
  1983年   8篇
  1982年   8篇
  1981年   9篇
  1979年   6篇
  1978年   12篇
  1977年   5篇
  1976年   4篇
  1975年   4篇
  1972年   4篇
  1970年   6篇
  1966年   6篇
排序方式: 共有2645条查询结果,搜索用时 15 毫秒
81.
82.
Abstract

Objectives. Chest pain is a common complaint in the emergency department (ED), and it is a challenge to identify low-risk chest pain patients eligible for early discharge. We aimed to develop a simple objective decision rule to exclude 30-day major adverse cardiac events (MACE) in ED chest pain patients.

Design. We analyzed prospectively included patients presenting with chest pain. Low risk patients were identified with the clinical objective rule-out evaluation (CORE). CORE was based on high sensitivity cardiac troponin T (hs-cTnT) tests at ED presentation (0?h) and 2?h later together with a simplified risk score consisting of four objective variables: age ≥65 years and a history of arterial disease, hypertension or diabetes. For the patient to be classified as low risk in the CORE rule, hs-cTnT had to be ≤14?ng/L both at 0 and 2?h, and the sum of the risk score had to be 0. The primary outcome was MACE within 30 days.

Results. Among the 751 patients in the final analysis, 90 (11.9%) had a MACE. CORE identified 248 (33%) of patients as low risk with a sensitivity of 98.9% (CI 93.1–99.9) and a negative predictive value of 99.6% (95% CI 97.4–100) for 30-day MACE. Adding the ED physician’s interpretation of the ECG to CORE did not improve diagnostic performance.

Conclusion. A simple objective decision rule (CORE) identified one-third of all patients as having a very low 30-day risk of MACE. These patients may potentially be discharged without additional investigations for acute coronary syndrome.  相似文献   
83.
Objectives. To assess how ethanol in potential lethal serum concentrations affects features of the ECG that may be associated with cardiac arrhythmias. Design. We included 84 patients, who were hospitalised with assumed acute ethanol intoxication. In the emergency room resting ECG was recorded and blood was collected for serum osmolality measurement used as a proxy for ethanol level. Thirty-two also had ECG recorded at discharge. Twenty-seven hospitalised patients without known alcohol ingestion served as controls. ECG segment durations were compared with controls and related to intoxication level. Results. In subjects with moderately elevated to high serum osmolality, the P wave and QTc intervals were prolonged compared with sober subjects. P wave, PR, QRS and QTc intervals were longer when the subjects had high blood ethanol levels (at admission) than at discharge (p-values: 0.0001, 0.0002, 0.010 and < 0.0001 for P wave, PR, QRS and QTc intervals. n = 32). Conclusions. Ethanol at high to very high blood concentration causes several changes in the ECG that might be associated with increased risk of arrhythmias.  相似文献   
84.
Objective—Evaluation of the centrifugal pump vs roller pump concerning effects upon platelet function, hemolysis and clinical outcome in elective coronary artery bypass surgery.

Design—Thirty‐four patients were randomized to centrifugal or roller pump. Platelet activation was studied by flow cytometry before, during and up to 3 days after bypass.

Results—Duration of bypass, ischemic period, peripheral anastomoses, hospital stay and mortality did not differ. In roller pump patients, platelet aggregates increased by 250% between end of bypass and 3?h postoperatively (p?<?0.001). A secondary, fivefold increase in number of platelet aggregates was found on the 3rd postoperative day (p?<?0.001). In the centrifugal pump group, these changes were not significant. Hemolysis increased (20%) at end of bypass and 3?h postoperatively (p?<?0.005), and decreased to preoperative levels the next day without group difference.

Conclusion—Platelet aggregation was significantly increased in roller compared with centrifugal pump patients, indicating higher susceptibility to postoperative thrombotic complications with the roller pump. Otherwise, there was no clinical evidence for superiority of the centrifugal pump.  相似文献   
85.
86.
The paper presents a constraint transformation approach for nonlinear model predictive control (MPC) subject to a class of state and control constraints. The approach uses a two‐stage transformation technique to incorporate the constraints into a new unconstrained MPC formulation with new variables. As part of the stability analysis, the relationship of the new unconstrained MPC scheme to an interior penalty formulation in the original variables is discussed. The approach is combined with an unconstrained gradient method that allows for computing the single MPC iterations in a real‐time manner. The applicability of the approach, for example, to fast mechatronic systems, is demonstrated by numerical as well as experimental results. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
87.
88.
Although chronic wounds have a high socio‐economic impact, data on comparative effectiveness of treatments are rare. UrgoStart® is a hydroactive dressing containing a nano‐oligosaccharide factor (NOSF). This study aimed at evaluating the cost‐effectiveness of this NOSF‐containing wound dressing in vascular leg ulcers compared with a similar neutral foam dressing (UrgoCell® Contact) without NOSF. Cost‐effectiveness analysis from the perspective of the German statutory health care system was performed using a decision tree model for a period of 8 weeks. Cost and outcome data were derived from the clinical study ‘Challenge’ suggesting a response rate (≥40% wound size reduction) of UrgoStart® of 65·6% versus 39·4% for the comparator. In the treatment model, effect‐adjusted costs of €849·86 were generated after 8 weeks for treatment with UrgoStart® versus €1335·51 for the comparator resulting in an effect‐adjusted cost advantage of €485·64 for UrgoStart®. In linear sensitivity analyses, the outcomes were stable for varying assumptions on prices and response rates. In an 8‐week period of treatment for vascular leg ulcers, UrgoStart® shows superior cost‐effectiveness when compared with the similar neutral foam dressing without any active component (NOSF). As demonstrated within a randomised, double‐blind clinical trial, UrgoStart® is also more effective in wound area reduction than the neutral foam dressing. Wound healing was not addressed in this clinical trial. Follow‐up data of 12 months to allow for reulceration assessment were not generated.  相似文献   
89.
90.
Expression of the transforming growth factor-beta (TGF-beta) protein family in the peripheral nervous system is well established, but the role of their cognate receptors TGF-beta receptor type 1 (R1) and type 2 (R2) has been less well studied. TGF-beta plays an essential role in Schwann cell proliferation and differentiation, and is involved in neurotrophic effects of several neurotrophic substances. TGF-beta is also expressed in benign peripheral nervous system tumors such as vestibular schwannomas. In the present study, we aimed to detect TGF-beta R1 and R2 in a total of 40 sporadic vestibular schwannomas using immunohistochemistry, and correlated the findings to essential clinicopathologic data. TGF-beta, TGF-beta R1, and TGF-beta R2 mRNA was further analyzed by RT-PCR in six vestibular schwannomas. TGF-beta R1 immunoexpression was found in about 95% of the tumors. TGF-beta R1 was equally present in Antoni A and Antoni B areas of the tumors. TGF-beta R2 was found immunohistochemically in 77%. In addition, all tumors showed strong expression of TGF-beta. No correlation between TGF-beta R1 or R2 expression and clinicopathologic parameters such as age, sex, clinical symptoms, growth pattern, and proliferation acitivity as measured by Ki-67 (MIB-1) staining was found. Moreover, all schwannomas studied contained TGF-beta, TGF-beta R1, and TGF-beta R2 mRNA. Therefore, the TGF-beta/TGF-beta R1 and -R2 system is present in human schwannomas, but its biologic role for tumor development and growth remains unclear.  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