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   242篇
  免费   13篇
  国内免费   3篇
儿科学   1篇
妇产科学   1篇
基础医学   31篇
口腔科学   9篇
临床医学   28篇
内科学   81篇
神经病学   16篇
特种医学   11篇
外科学   24篇
综合类   20篇
预防医学   10篇
眼科学   3篇
药学   18篇
中国医学   1篇
肿瘤学   4篇
  2023年   4篇
  2022年   5篇
  2021年   16篇
  2020年   10篇
  2019年   5篇
  2018年   15篇
  2017年   7篇
  2016年   10篇
  2015年   6篇
  2014年   10篇
  2013年   12篇
  2012年   18篇
  2011年   30篇
  2010年   9篇
  2009年   11篇
  2008年   12篇
  2007年   13篇
  2006年   15篇
  2005年   12篇
  2004年   8篇
  2003年   4篇
  2002年   8篇
  2001年   4篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
  1983年   1篇
  1975年   1篇
  1973年   1篇
  1972年   2篇
  1967年   1篇
排序方式: 共有258条查询结果,搜索用时 15 毫秒
191.
192.
The marine endophytic fungus Coniothyrium cereale produces the structurally unusual polyketide-type alkaloids (-)-cereolactam (1) and (-)-cereoaldomine (3), incorporating a lactam and an imine functionality, respectively, as well as the related metabolite (-)-trypethelone (2). Compounds 1 and 3 showed selective inhibition of human leukocyte elastase with IC50 values of 9.28 and 3.01 μM, respectively. Compound 2 was found to be inhibitory toward Mycobacterium phlei, Staphylococcus aureus, and Escherichia coli and also cytotoxic against mouse fibroblast cells (IC50=7.5 μM).  相似文献   
193.
Hepatitis B virus (HBV) genotypes and subtypes have been identified worldwide. As HBV genotypes/subtypes, the HBV subgenotypes seem to be associated with their geographical distribution and ethnic origin. A previous study showed the novel HBV subgenotype C6 based on the complete genome sequences of isolates in Papua, Indonesia. In the present study, further characterization of HBV in Jayapura (capital of Papua Province), particularly from native people of Papua originating from the highland (highland Papuans) and those from the lowland (lowland Papuans) were examined. Of 32 HBV isolates from both highland and lowland Papuan blood donors with HBsAg positive, part of the S gene and the core gene sequences were analyzed. Analyses of some isolates from highland Papuans were confirmed by the complete genome sequences. Most HBV isolates were classified into genotype C (78.1%), followed by genotype B (18.8%), and genotype D (3.1%). The subtype adr was predominant (71.9%), followed by adw2 (25.1%), and ayw2 (3.1%). As with previous findings, phylogenetic analyses revealed that most HBV isolates from Papuans, C/adr, belonged to subgenotype C6. Interestingly, some C/adr isolates from highland Papuans formed a distinct cluster from all reported subgenotypes of HBV/C, and they differed from HBV/C1-C10 by 4.2-7.2% over the complete genome. SimPlot analysis showed no evidence of recombination with HBV/C1-C10. The isolated life and closed social systems of highland Papuans, even though some have been moving to Jayapura, likely contribute to the formation of this unique cluster of infection with a novel subgenotype of HBV, named C11.  相似文献   
194.

Purpose

To compare the short-term hemodynamic effects of levosimendan and dobutamine in chronic obstructive pulmonary disease (COPD) patients experiencing weaning difficulties in relation with increased left ventricular filling pressure.

Materials and Methods

This prospective, sequential, pilot study included 10 COPD patients experiencing weaning difficulties in relation with increased left ventricular filling pressure ascertained by an increase >10 mm Hg of pulmonary artery occlusion pressure (PAOP) at the shift from mechanical to spontaneous breathing (SB). Patients received 1 h infusion of 7 μg/kg per minute of dobutamine, followed by 24-hour infusion of 0.2 μg/kg per minute levosimendan. Hemodynamic variables were measured under MV and 15 to 30 minutes after SB at baseline, at the end of dobutamine infusion, at a washout period, and after levosimendan infusion.

Results

At baseline, the shift from mechanical ventilation to spontaneous ventilation was associated with a significant increase in PAOP from a median of 15 (interquartile range [IQR], 6) to 29 (9) mm Hg. Both drugs reduced significantly the level of PAOP increase at SB, but levosimendan had a greater effect than dobutamine [median PAOP increase (IQR): 5 (2) vs 9 (4) mm Hg, respectively; P < .01].

Conclusions

Both drugs reduced the magnitude of PAOP increase at SB in difficult-to-wean COPD patients. PAOP increase was reduced to a greater extent by levosimendan.  相似文献   
195.

Introduction  

In patients with acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS), recent randomised controlled trials (RCTs) showed a consistent trend of mortality reduction with prone ventilation. We updated a meta-analysis on this topic.  相似文献   
196.
197.

Introduction

Head movement during CT brain perfusion (CTP) acquisition can deteriorate the accuracy of CTP analysis. Most CTP software packages can only correct in-plane movement and are limited to small ranges. The purpose of this study is to validate a novel 3D correction method for head movement during CTP acquisition.

Methods

Thirty-five CTP datasets that were classified as defective due to head movement were included in this study. All CTP time frames were registered with non-contrast CT data using a 3D rigid registration method. Location and appearance of ischemic area in summary maps derived from original and registered CTP datasets were qualitative compared with follow-up non-contrast CT. A quality score (QS) of 0 to 3 was used to express the degree of agreement. Furthermore, experts compared the quality of both summary maps and assigned the improvement score (IS) of the CTP analysis, ranging from ?2 (much worse) to 2 (much better).

Results

Summary maps generated from corrected CTP significantly agreed better with appearance of infarct on follow-up CT with mean QS 2.3 versus mean QS 1.8 for summary maps from original CTP (P?=?0.024). In comparison to original CTP data, correction resulted in a quality improvement with average IS 0.8: 17 % worsened (IS?=??2, ?1), 20 % remained unchanged (IS?=?0), and 63 % improved (IS?=?+1, +2).

Conclusion

The proposed 3D movement correction improves the summary map quality for CTP datasets with severe head movement.  相似文献   
198.

Objective

Computed Tomography Perfusion (CTP) is a promising tool to support treatment decision for acute ischemic stroke patients. However, head movement during acquisition may limit its applicability. Information of the extent of head motion is currently lacking. Our purpose is to qualitatively and quantitatively assess the extent of head movement during acquisition.

Methods

From 103 consecutive patients admitted with suspicion of acute ischemic stroke, head movement in 220 CTP datasets was qualitatively categorized by experts as none, minimal, moderate, or severe. The movement was quantified using 3D registration of CTP volume data with non-contrast CT of the same patient; yielding 6 movement parameters for each time frame. The movement categorization was correlated with National Institutes of Health Stroke Scale (NIHSS) score and baseline characteristic using multinomial logistic regression and student's t-test respectively.

Results

Moderate and severe head movement occurred in almost 25% (25/103) of all patients with acute ischemic stroke. The registration technique quantified head movement with mean rotation angle up to 3.6° and 14°, and mean translation up to 9.1 mm and 22.6 mm for datasets classified as moderate and severe respectively. The rotation was predominantly in the axial plane (yaw) and the main translation was in the scan direction. There was no statistically significant association between movement classification and NIHSS score and baseline characteristics.

Conclusions

Moderate or severe head movement during CTP acquisition of acute stroke patients is quite common. The presented registration technique can be used to automatically quantify the movement during acquisition, which can assist identification of CTP datasets with excessive head movement.  相似文献   
199.
200.
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