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   903篇
  免费   0篇
化学工业   7篇
建筑科学   1篇
轻工业   1篇
石油天然气   1篇
无线电   9篇
冶金工业   879篇
自动化技术   5篇
  2014年   1篇
  2013年   3篇
  2012年   1篇
  2004年   6篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  1999年   36篇
  1998年   289篇
  1997年   167篇
  1996年   116篇
  1995年   64篇
  1994年   58篇
  1993年   40篇
  1992年   8篇
  1991年   12篇
  1990年   8篇
  1989年   18篇
  1988年   13篇
  1987年   10篇
  1986年   4篇
  1985年   2篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   5篇
  1978年   1篇
  1977年   8篇
  1976年   14篇
  1975年   2篇
排序方式: 共有903条查询结果,搜索用时 0 毫秒
811.
812.
Investigating the levels of lipid peroxidase (LPO) and superoxide dismutase (SOD) in serum, bronchoalveolar lavage fluid (BALF) and alveolar macrophage (AM) were determined in 40 chronic bronchitis patients with Pulmonary Qi Deficiency (PQD) Syndrome and 36 normal subjects. Results showed: (1) No significant differences were found between PQD syndrome and normal subjects on serum SOD or LPO levels. (2) Patients with PQD Syndrome. LPO level in BALF was significantly higher, and SOD significantly lower, when compared with normal subjects. (3) Through correlation analysis, it was found in BALF that SOD level was markedly correlated with AM, while LPO was significantly correlated with neutrophil. In short, SOD and LPO in BALF play an important role in the development of the PQD Syndrome, and are good indications in evaluating the PQD Syndrome.  相似文献   
813.
814.
Previous studies have shown an association between cancer survival and socioeconomic status. In the United States Armed Forces, military rank is a measure of socioeconomic status. To determine whether an association exists between socioeconomic status (as measured by military rank) and prostate cancer, we carried out a retrospective review of the clinical data from 237 patients entered into the Tumor Registry. There was no statistically significant association between rank and the stage of disease at diagnosis or actual 5-year survival. In the military, health care is provided free of charge, independent of rank, and this study showed that when there is equal access to health care, socieconomic status does not correlate with prostate cancer outcome. Future studies comparing outcomes of prostate cancer should control for accessibility to health care.  相似文献   
815.
BACKGROUND AND PURPOSE: Increasing evidence that oxidative stress contributes to delayed neuronal death after global cerebral ischemia has led to reconsideration of the prolonged use of 100% ventilatory O2 following resuscitation from cardiac arrest. This study determined the temporal course of oxidation of brain fatty acyl groups in a clinically relevant canine model of cardiac arrest and resuscitation and tested the hypothesis that postischemic ventilation with 21% inspired O2, rather than 100% O2, results in reduced levels of oxidized brain lipids and decreased neurological impairment. METHODS: Neurological deficit scoring and high performance liquid chromatography measurement of fatty acyl lipid oxidation were used in an established canine model using 10 minutes of cardiac arrest followed by resuscitation with different ventilatory oxygenation protocols and restoration of spontaneous circulation for 30 minutes to 24 hours. RESULTS: Significant increases in frontal cortex lipid oxidation occurred after 10 minutes of cardiac arrest alone with no reperfusion and after reperfusion for 30 minutes, 2 hours, and 24 hours (relative total 235-nm absorbing peak areas=7.1+/-0.7 SE, 17.3+/-2.7, 14.2+/-3.2, 16.1+/-1.0, and 14.0+/-0.8, respectively; n=4, P<0.05). The predominant oxidized lipids were identified by gas chromatography/mass spectrometry as 13- and 9-hydroxyoctadecadienoic acids (13- and 9-HODE). Animals ventilated on 21% to 30% O2 versus 100% O2 for the first hour after resuscitation exhibited significantly lower levels of total and specific oxidized lipids in the frontal cortex (1.7+/-0.1 versus 3.12+/-0.78 microg 13-HODE/g wet wt cortex., n=4 to 6, P<0.05) and lower neurological deficit scores (45.1+/-3.6 versus 58.3+/-3.8, n=9, P<0.05). CONCLUSIONS: With a clinically relevant canine model of 10 minutes of cardiac arrest, resuscitation with 21% versus 100% inspired O2 resulted in lower levels of oxidized brain lipids and improved neurological outcome measured after 24 hours of reperfusion. This study casts further doubt on the appropriateness of present guidelines that recommend the indiscriminate use of 100% ventilatory O2 for undefined periods during and after resuscitation from cardiac arrest.  相似文献   
816.
BACKGROUND: The relationship between psychiatric disorders and alopecia areata has not been well studied. Although previous reports have been unable to correlate psychiatric illness with hair loss, a recent study determined that 74% of patients with alopecia areata (AA) under evaluation had one or more lifetime psychiatric diagnoses. METHODS: Two hundred and ninety-four community-based patients with alopecia areata responded to a detailed questionnaire distributed by Help Alopecia International Research, Inc. The prevalence of psychiatric disorders was determined using diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IIIR). RESULTS: Major depression, generalized anxiety disorder, social phobia, and paranoid disorder were all present in patients with alopecia areata at rates significantly higher than in the general population. CONCLUSIONS: Alopecia areata patients are at a higher risk of developing psychiatric comorbidity during their clinical course.  相似文献   
817.
818.
819.
820.
The factors involved in atrial vulnerability are the presence of intra-atrial conduction disorders and abnormalities of refractory periods which are short, dispersed and poorly adapted to heart rate. All these factors are arrthythmogenic. The main value of the study of atrial vulnerability consists of investigation of unexplained ischaemic cerebrovascular accidents in young subjects. In practice, atrial vulnerability can be measured in the context of a classical endocavitary electrophysiological investigation. The stimulation and recording parameters must be standardized. Latent atrial vulnerability can be considered to be present when at least one of the following elements are found: significant inducibility, very short and poorly adapted effective refractory periods, decreased latent atrial vulnerability index.  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