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   489篇
  免费   26篇
  国内免费   1篇
耳鼻咽喉   11篇
儿科学   4篇
妇产科学   19篇
基础医学   71篇
口腔科学   3篇
临床医学   19篇
内科学   139篇
皮肤病学   1篇
神经病学   31篇
特种医学   25篇
外科学   53篇
预防医学   9篇
眼科学   13篇
药学   60篇
中国医学   1篇
肿瘤学   57篇
  2023年   2篇
  2022年   2篇
  2021年   32篇
  2020年   15篇
  2019年   7篇
  2018年   13篇
  2017年   8篇
  2016年   17篇
  2015年   18篇
  2014年   21篇
  2013年   26篇
  2012年   38篇
  2011年   39篇
  2010年   31篇
  2009年   13篇
  2008年   43篇
  2007年   31篇
  2006年   37篇
  2005年   42篇
  2004年   23篇
  2003年   32篇
  2002年   20篇
  2001年   1篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1991年   1篇
排序方式: 共有516条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
The aim of this study was to investigate somatic properties and physiological capacity, and analyze kinematic parameters in the 200 m breaststroke swimming race. Twenty-seven male swimmers participated in the study. They were 15.7±1.98 years old. Their average height was 1.80 ± 0.02 m and lean body mass (LBM) was 62.45 ± 8.29 kg. Physiological exercise capacity was measured in two separate 90 sec. all-out tests, one for the arms and second for legs. During the tests total work of arm cranking (TWAR) and cycling (TWLG) as well as peak of VO2 for arm (VO2peakAR) and leg (VO2peakLG) were measured. The underwater swimmers body movements were recorded during the all-out swimming 200m breaststroke speed test using an underwater camera installed on a portable trolley. The swimming kinematic parameters and propulsive or non-propulsive movement phases of the arms and legs as well as average speed (V200), surface speed (V200surface) and swimming speed in turn zones (V200turns) were extracted. V200surface was significantly related to the percentage of leg propulsion and was shown to have large effect on VO2peakLG in the Cohen analysis. V200turns depended significantly on the indicators of physiological performance and body structure: TWAR, VO2peak LG and LBM, LBM, which in turn strongly determined the measured results of TWAR, TWLG, VO2peakAR and VO2peakLG. The V200turns and V200surface were strongly associated with V200, 0.92, p < 0.001 and 0.91, p < 0.001 respectively. In each lap of the 200m swimming there was an increased percentage of propulsion of limb movement observed simultaneously with a reduction in the gliding phase in the breaststroke cycles.

Key points

  • This study investigated the influence of the selected indicators of somatic properties and physiological capacity as well kinematic and coordination parameters on breaststroke swimming.
  • In this observations the body’s functional capacity have an important impact on achieving good breaststroke swimming results, the V200 was moderately associated on VO2peakLG, moreover, separate V200turns depended with VO2peakLG and on LBM and TWAR.
  • The speed of surface breaststroke swimming - V200surface similarly as V200turns had a very strong influence on the end result of V200 , 0.91, p<0.001 and 0.92, p<0.001 respectively.
  • The ability to swim fast on the surface (V200surface) was positively and significantly associated with the percentage time of propulsion generation -LP in the breaststroke cycle.
Key words: Breaststroke swimming, physiological indices, lean body mass, kinematic indices  相似文献   
5.
So far, a reliable spectrum of mitochondrial DNA mutations in colorectal cancer cells is still unknown, and neither is their significance in carcinogenesis. Indeed, it remains debatable whether mtDNA mutations are “drivers” or “passengers” of colorectal carcinogenesis. Thus, we analyzed 200 mitogenomes from normal and cancer tissues of 100 colorectal cancer patients. Minority variant mutations were detected at the 1% level. We showed that somatic mutations frequently occur in colorectal cancer cells (75%) and are randomly distributed across the mitochondrial genome. Mutational signatures of somatic mitogenome mutations suggest that they might arise through nucleotide deamination due to oxidative stress. The majority of somatic mutations localized within the coding region (in positions not known from the human phylogeny) and was potentially pathogenic to cell metabolism. Further analysis suggested that the relaxation of negative selection in the mitogenomes of colorectal cancer cells may allow accumulation of somatic mutations. Thus, a shift in glucose metabolism from oxidative phosphorylation to glycolysis may create advantageous conditions for accumulation of mtDNA mutations. Considering the fact that the presence of somatic mtDNA mutations was not associated with any clinicopathological features, we suggested that mtDNA somatic mutations are “passengers” rather than the cause of colorectal carcinogenesis.  相似文献   
6.

Objectives

The aim of the study was to investigate the prevalence of selected organ-specific autoantibodies in rheumatoid arthritis (RA) and primary Sjögren''s syndrome (pSS) patients, and discuss their clinical significance.

Material and methods

The study included 121 RA and 30 pSS patients. Sera were tested for the presence of autoantibodies to thyroid peroxidase (anti-TPO), thyroglobulin (anti-TG), TSH receptor (TRAbs), mitochondrial antigen M2 (AMA-M2-3E) and gliadin-analogous fusion peptides (anti-GAF(3X)) using the ELISA method. Non-organ-specific antibodies were determined: rheumatoid factor in IgM class, anti-citrullinated peptide antibodies and antinuclear antibodies. The occurrence of antibodies was also examined with regards to RA activity.

Results

The following autoantibodies were detected in RA patients: anti-TPO – 13 (10.7%), anti-TG – 6 (5%), AMA-M2-3E – 3 (2.5%), anti-GAF(3X) – 5 (4.1%). The respective levels of these autoantibodies in pSS patients were 3 (10%), 2 (6.7%), 4 (13.3%) and 2 (6.7%). Polyautoimmunity was confirmed in 34 RA patients (including 20 cases of autoimmune thyroid disease [AITD]) and in 6 pSS patients (6 cases of AITD). When RA patients were divided into anti-TPO positive and anti-TPO negative groups, we found a statistically significant relationship between groups regarding age and hemoglobin concentration. In pSS patients the anti-TPO positive group was less likely to use immunosuppressive drugs as compared with the anti-TPO negative group. Anti-TPO was significantly more frequently detected in RA + AITD vs. RA, RA + SS + AITD vs. RA and in pSS + AITD vs. pSS patients.

Conclusions

Organ-specific autoantibodies are relatively frequently observed in patients with RA and pSS. Their presence is connected with the clinical picture of the diseases.  相似文献   
7.
8.
9.
Phenolic lipids were isolated from rye grains, cashew nutshell liquid (CNSL) from Anacardium occidentale, and fruit bodies of Merrulius tremellosus, and their effects on the electric eel acetylcholinesterase activity and conformation were studied. The observed effect distinctly depended on the chemical structure of the phenolic lipids that were available for interaction with the enzyme. All of the tested compounds reduced the activity of acetylcholinesterase. The degree of inhibition varied, showing a correlation with changes in the conformation of the enzyme tested by the intrinsic fluorescence of the Trp residues of the protein.  相似文献   
10.
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