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   333篇
  免费   25篇
  国内免费   31篇
儿科学   27篇
妇产科学   2篇
基础医学   19篇
口腔科学   13篇
临床医学   54篇
内科学   78篇
皮肤病学   1篇
神经病学   16篇
特种医学   72篇
外科学   11篇
综合类   19篇
预防医学   18篇
眼科学   4篇
药学   42篇
中国医学   1篇
肿瘤学   12篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2020年   1篇
  2019年   5篇
  2018年   5篇
  2017年   6篇
  2016年   2篇
  2015年   3篇
  2014年   10篇
  2013年   17篇
  2012年   8篇
  2011年   11篇
  2010年   11篇
  2009年   15篇
  2008年   12篇
  2007年   23篇
  2006年   21篇
  2005年   14篇
  2004年   7篇
  2003年   3篇
  2002年   3篇
  2001年   6篇
  2000年   3篇
  1999年   13篇
  1998年   12篇
  1997年   17篇
  1996年   16篇
  1995年   13篇
  1994年   20篇
  1993年   14篇
  1992年   9篇
  1991年   9篇
  1990年   5篇
  1989年   11篇
  1988年   6篇
  1987年   9篇
  1986年   5篇
  1985年   6篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1981年   10篇
  1980年   2篇
  1979年   2篇
  1977年   3篇
  1976年   3篇
  1975年   5篇
排序方式: 共有389条查询结果,搜索用时 15 毫秒
41.
42.
The study investigated whether resistance and aerobic concurrent exercise (CE) with different intensities influenced postexercise hypotension (PEH). 21 healthy men (20.7±0.7?yr) performed 4 sessions: control [CTL 60?min of rest], and CE1, CE2, and CE3 consisting respectively of 2 sets of 6 exercises at 80% 1RM followed by 30?min of cycle ergometer exercise at 50%, 65%, and 80% of peak oxygen consumption (VO2peak). All sessions lasted approximately 60?min and began with resistance prior to aerobic sessions. Systolic (SBP) and diastolic (DBP) blood pressure (BP) were assessed at baseline and every 10?min during 120-min recovery. The magnitude of SBP decrease was similar after all CE sessions [CE1: 4.2±2.5?mmHg; CE2: 4.8±2.7?mmHg; CE3: 6.0±2.0?mmHg; p=0.06], but the PEH lasted approximately 1?h longer following CE2 and CE3 [120?min] compared to CE1 [60-70?min] (P<0.05). The magnitude of DBP decrease was slightly greater after CE3 and CE2 [2?mmHg] than after CE1 [1?mmHg] (P<0.05), being longer following CE3 [60?min] compared to CE2 and CE1 [40?min] (P<0.05). In conclusion, CE sessions combining resistance and aerobic sessions elicited PEH, especially when the intensity of the aerobic exercise was higher than 65% VO2peak.  相似文献   
43.
In the neonatal period, seizures rank among the most common neurological symptoms, often indicating an underlying serious neurological condition. It is remarkable that although new tools have been incorporated into the diagnosis of neonatal seizures, there is no consensus about the therapeutic approach among different doctors and institutions. Hence, although phenobarbital is still considered the initial drug of choice, the protocols reported in the literature show a great variability in the approach to treatment of refractory seizures. We used a questionnaire to gain information regarding the treatment of seizures in the neonatal period in different European institutions. Conclusion: We conclude that phenobarbital is still the initial drug of choice followed by benzodiazepines, except in preterm infants with a birth weight below 1800 g. In refractory seizures, the use of continuous lidocaine infusion is most common. Of note, clinical studies with newer drugs have been mostly performed in the United States but not in Europe.  相似文献   
44.
To investigate structure-function relationships of erythropoietin (Epo), we have obtained cDNA sequences that encode the mature Epo protein of a variety of mammals. A first set of primers, corresponding to conserved nucleotide sequences between mouse and human DNAs, allowed us to amplify by polymerase chain reaction (PCR) intron 1/exon 2 fragments from genomic DNA of the hamster, cat, lion, dog, horse, sheep, dolphin, and pig. Sequencing of these fragments permitted the design of a second generation of species-specific primers. RNA was prepared from anemic kidneys and reverse-transcribed. Using our battery of species-specific 5' primers, we were able to successfully PCR- amplify Epo cDNA from Rhesus monkey, rat, sheep, dog, cat, and pig. Deduced amino acid sequences of mature Epo proteins from these animals, in combination with known sequences for human, Cynomolgus monkey, and mouse, showed a high degree of homology, which explains the biologic and immunological cross-reactivity that has been observed in a number of species. Human Epo is 91% identical to monkey Epo, 85% to cat and dog Epo, and 80% to 82% to pig, sheep, mouse, and rat Epos. There was full conservation of (1) the disulfide bridge linking the NH2 and COOH termini; (2) N-glycosylation sites; and (3) predicted amphipathic alpha- helices. In contrast, the short disulfide bridge (C29/C33 in humans) is not invariant. Cys33 was replaced by a Pro in rodents. Most of the amino acid replacements were conservative. The C-terminal part of the loop between the C and D helices showed the most variation, with several amino acid substitutions, deletions, and/or insertions. Calculations of maximum parsimony for intron 1/exon 2 sequences as well as coding sequences enabled the construction of cladograms that are in good agreement with known phylogenetic relationships.  相似文献   
45.
鼓槌石斛中一新的联苄类化合物——鼓槌石斛素   总被引:6,自引:0,他引:6  
从兰科鼓槌石斛(Dendrobium chrysotoxum)中分得一新的联苄类化合物,经光谱分析(UV,IR,MS,1HNMR,13CNMR和DIFNOE),其结构确定为4-羟基-3,5,3',4'-四甲氧基联苄,命名为鼓槌石斛素。关键词鼓槌石斛;鼓槌石斛素;联苄类化合物。  相似文献   
46.
47.
48.
49.
Thirty-nine preterm infants were studied to compare the predictive value of somatosensory evoked responses (SEPs) following median-nerve and posterior tibial-nerve stimulation with the predictive value of cranial ultrasound. With regard to the SEP, a normal median-nerve response was by no means a guarantee of a normal outcome. A normal posterior tibial-nerve response, however, almost guaranteed a normal outcome, but the test was very time consuming and the number of false positive responses was high (sensitivity. 95.6%, specificity 50%). The presence of parenchymal involvement, either due to a haemorrhage or cystic leukomalacia predicted cerebral palsy with a sensitivity of 95.6% and a specificity of 68.5%. The combination of an abnormal posterior tibial response and the presence of parenchymal brain lesions had the best predictive value with a sensitivity of 91.3% and a specificity of 81.2%. These results show that, although posterior tibial-rferve responses have a better predictive value than median-nerve responses, these values were lower than that of cranial ultrasound. The best prediction was obtained when a combination of posterior-tibial responses and cranial ultrasound was used.  相似文献   
50.
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