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   784篇
  免费   83篇
  国内免费   60篇
耳鼻咽喉   2篇
儿科学   41篇
妇产科学   7篇
基础医学   123篇
口腔科学   25篇
临床医学   143篇
内科学   179篇
皮肤病学   15篇
神经病学   50篇
特种医学   89篇
外科学   66篇
综合类   20篇
预防医学   49篇
眼科学   5篇
药学   74篇
中国医学   2篇
肿瘤学   37篇
  2021年   5篇
  2019年   10篇
  2018年   11篇
  2017年   5篇
  2016年   13篇
  2015年   14篇
  2014年   25篇
  2013年   29篇
  2012年   17篇
  2011年   15篇
  2010年   35篇
  2009年   32篇
  2008年   40篇
  2007年   67篇
  2006年   32篇
  2005年   33篇
  2004年   31篇
  2003年   22篇
  2002年   22篇
  2001年   18篇
  2000年   15篇
  1999年   21篇
  1998年   35篇
  1997年   38篇
  1996年   25篇
  1995年   24篇
  1994年   32篇
  1993年   21篇
  1992年   13篇
  1991年   14篇
  1990年   6篇
  1989年   22篇
  1988年   20篇
  1987年   13篇
  1986年   8篇
  1985年   15篇
  1984年   10篇
  1983年   8篇
  1982年   13篇
  1981年   12篇
  1980年   9篇
  1978年   7篇
  1977年   8篇
  1976年   11篇
  1975年   9篇
  1973年   7篇
  1972年   4篇
  1971年   3篇
  1970年   8篇
  1969年   4篇
排序方式: 共有927条查询结果,搜索用时 187 毫秒
71.
本文设计合成了丁公藤碱Ⅱ的C_2脱氧和C_8电子等排类似物。药理结果表明,丁公藤碱Ⅱ的C_2羟基是保持其缩瞳活性的关键部分之一;目的物2和4各自分别具有拟和抗胆碱活性;电子等排目的物16和17既无拟也无抗胆碱作用。  相似文献   
72.

Background  

This study aims to contribute to the knowledge of the influence of comorbidity in OA. The objectives of the study were (i) to describe the prevalence of comorbidity and (ii) to describe the relationship between comorbidity (morbidity count, severity and the presence of specific diseases) and limitations in activities and pain in elderly patients with knee or hip OA using a comprehensive inventory of comorbidity.  相似文献   
73.
74.
75.
76.
Streptococcus suis is an economically important pathogen of pigs responsible for a variety of diseases including meningitis, septicemia, arthritis, and pneumonia, although little is known about the mechanisms of pathogenesis or virulence factors associated with this organism. Here, we report on the distribution and genetic diversity of the putative virulence factor suilysin, a member of the thiol-activated toxin family of gram-positive bacteria. On the basis of PCR analysis of over 300 isolates of S. suis, the suilysin-encoding gene, sly, was detected in 69.4% of isolates. However, sly was present in a considerably higher proportion of isolates obtained from cases of meningitis, septicemia, and arthritis (>80%) and isolates obtained from asymptomatic tonsillar carriage (>90%) than lung isolates associated with pneumonia (44%). With the exception of serotypes 1, 14, and 1/14, there was no strong correlation between the presence of suilysin and serotype. Analysis of the genetic diversity of suilysin by restriction fragment length polymorphism and sequence analysis found that the suilysin gene, where present, is highly conserved with a maximum of 1.79% diversity at the nucleotide level seen between sly alleles. Assays of hemolytic activity and hybridization analysis provided no evidence for a second member of the thiol-activated toxin family in S. suis. Inverse PCR was used to characterize regions flanking sly, which in turn allowed the first characterization of the equivalent region in a strain lacking sly. Sequence comparison of these regions from sly-positive (P1/7) and sly-negative (DH5) strains indicated that two alternative arrangements are both flanked by genes with highest similarity to haloacid dehalogenase-like hydrolases (5' end) and putative N-acetylmannosamine-6-phosphate epimerases (3' end). However, sly appears to be completely absent from the alternative arrangement, and a gene of unknown function is located in the equivalent position. Finally, PCR analysis of multiple sly-positive and -negative strains indicated that these two alternative genetic arrangements are conserved among many S. suis isolates.  相似文献   
77.
A modified version of the revised Personality Diagnostic Questionnaire (PDQ-R), based on DSM-III-R personality disorders (PD), was completed by 74 psychiatric patients. A factor analysis of the scores for each of the PD (i.e. of the number of positive DSM-III-R criteria for each of the PD) yielded 3 factors that defined 3 PD clusters. These were similar to the 3 DMS-III-R PD clusters for 7 of the 11 PD categories. The 3-group solution of a cluster analysis of the patients (using their scores of positive criteria for each of the PD) did not reflect these factors; the main discriminating variable between the 3 groups of patients was the total number of positive PD criteria. It is suggested that, for the routine assessment of patients, the most important derivative of the DSM-III-R classification of PD is the total score of positive PD criteria.  相似文献   
78.
79.
目的:分析一遗传性牙釉质发育不全家系的发病情况及病变特征,明确其遗传方式,为进一步基因定位和克隆奠定基础。方法:2003-05在中国山东某市发现一遗传性牙釉质发育不全家系,先证者为1名43岁男性牙釉质发育不全患者。该家系现存活3代,共有36名家庭成员。对先证者及其家族进行口腔检查和全身检查,制备牙齿磨片镜下观察,对该患者及其亲属成员进行家系调查,系谱分析,明确可能的遗传方式。结果:①口腔及全身临床表现:口腔检查可见大量牙石,釉质病变涉及全口牙齿,牙体呈黄褐色,磨耗重,釉质易碎裂剥脱。X射线显示牙釉质密度基本与牙本质相同,髓腔形态未见异常。临床表现符合Witkop1989年分类中的钙化不全型牙釉质发育。全身系统检查排除系统性疾病。无四环素用药史,家族中无近亲结婚者,附近居民无相似病变。②牙齿磨片观察结果:可见釉丛及釉板明显,且数目增多,表明釉质发育较差。③遗传方式:该家系36名成员,3代中均有患者,共检出遗传性牙釉质发育不全患者13人,其中男7例,女6例,传递方式符合常染色体显性遗传的特点。结论:该家系为常染色体显性遗传性钙化不全型牙釉质发育不全家系,为下一步定位该家系致病基因奠定基础。  相似文献   
80.
The Treatment of Septicemia in Pacemaker Patients   总被引:5,自引:0,他引:5  
The authors analyzed the data of seven patients who had undergone open heart surgery because of pacemaker endocarditis in the past 4 years. Repeated surgical interventions on the pacemaker system were found to be the most common predisposing factors. Staphylococcus aureus and Staphylococcus epidermidis were the most common causative organisms. Two-dimensional echocardiography was important in the diagnosis of cases with atypical clinical picture and negative blood cultures. We concluded that: (1) any pacemaker patient with fever should be considered to have a pacemaker endocarditis; (2) all of these patients should be examined by two-dimenensional echocardiography; and (3) the total removal of the infected hardware seems to be the only way to achieve complete recovery.  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