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   447833篇
  免费   28909篇
  国内免费   3366篇
耳鼻咽喉   5872篇
儿科学   10680篇
妇产科学   11840篇
基础医学   61713篇
口腔科学   12599篇
临床医学   40288篇
内科学   90292篇
皮肤病学   9520篇
神经病学   33458篇
特种医学   15425篇
外国民族医学   85篇
外科学   66745篇
综合类   11622篇
现状与发展   1篇
一般理论   173篇
预防医学   25985篇
眼科学   10596篇
药学   35815篇
  15篇
中国医学   2599篇
肿瘤学   34785篇
  2021年   4227篇
  2020年   2746篇
  2019年   4143篇
  2018年   6082篇
  2017年   4716篇
  2016年   4915篇
  2015年   5739篇
  2014年   7927篇
  2013年   10689篇
  2012年   14886篇
  2011年   15450篇
  2010年   9149篇
  2009年   8468篇
  2008年   13961篇
  2007年   15040篇
  2006年   14769篇
  2005年   13976篇
  2004年   13166篇
  2003年   12613篇
  2002年   11928篇
  2001年   29002篇
  2000年   29406篇
  1999年   24384篇
  1998年   5961篇
  1997年   4982篇
  1996年   4454篇
  1995年   4085篇
  1994年   3616篇
  1993年   3243篇
  1992年   16425篇
  1991年   15165篇
  1990年   14461篇
  1989年   14255篇
  1988年   12858篇
  1987年   12309篇
  1986年   11336篇
  1985年   10556篇
  1984年   7151篇
  1983年   5827篇
  1982年   2980篇
  1979年   5622篇
  1978年   3493篇
  1977年   3050篇
  1975年   2703篇
  1974年   3165篇
  1973年   2922篇
  1972年   2876篇
  1971年   2809篇
  1970年   2538篇
  1969年   2561篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.

Objectives

We aimed to evaluate the relationship between baseline renal function and changes in telomere length in Han Chinese.

Methods

The telomere restriction fragment (TRF) length of leukocytes in the peripheral blood was measured in healthy volunteers recruited in 2014. The estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine (Scr) and serum cystatin C (CysC)-eGFRcys and eGFRScr-cys through the Cockcroft-Gault formula (eGFRC-G) or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI / eGFRCKD-EPI) equation. The correlation between telomere length changes over time and renal function was analyzed.

Results

Leukocyte TRF lengths were negatively correlated to age (r = -0.393, p < 0.001) and serum CysC (r = -0.180, p < 0.01), while positively associated with eGFRCKD-EPI, eGFRC-G, eGFRcys, and eGFRScr-cys (r = 0.182, 0.122, 0.290, and 0.254 respectively, p < 0.01). The 3-year change of telomere length was 46 bp/years. When adjusted for age, the associations between telomere length changes and baseline, subsequent TRF lengths, and serum CysC were no longer present. No association was observed between TRF length changes and renal function.

Conclusion

The rate of telomere length changes was affected by age and baseline telomere length. The telomere length changes might be important markers for aging.
  相似文献   
83.
84.
85.
86.
87.
The relationship between volatile fatty acids (VFAs) in pus and infecting bacterial species was examined in order to establish a rapid identification system for anaerobic microorganisms in purulent inflammation in the oro-maxillary region. VFAs were detected by the direct injection of pus into gas-liquid chromatography (GLC). Bacterial examination was carried out by anaerobic culture using blood agar plates. The bacterial identification was carried out mainly according to the VPI manual. Analysis of the direct VFA patterns of each sample resulted in 5 groups. The following bacterial species were the main isolates in each group: Streptococcus intermedius in Group A, Peptostreptococcus micros in Group B, Fusobacterium nucleatum in Group C, Bacteroides gingivalis in Group D, and Peptostreptococcus anaerobius in Group E. The profile of VFAs produced in the PYG culture medium of the above isolated bacteria was compared with the direct VFA patterns. Agreement ratios between direct and PYG VFA patterns were as follows: Group A, 47.1%; Groups B and C, 45.0%; Group D, 87.5%; and Group E, 62.9%. The acetic acid concentration was more than 14 x 10(-4) meq/ml in Group B, the butyric acid concentration was more than 7 x 10(-4) meq/ml in Group C, and the iso-caproic acid concentration was more than 14 x 10(-4) meq/ml in Group E. In these cases, it was found that the agreement ratios between the direct and PYG FVA pattern were high. In Group D, irrespective of the concentration of iso-valeric acid detected, the agreement ratio was very high. The antibiotic susceptibility of the isolates was studied. Efficiency rates of ABPC, PIPC, CCL, CEZ, CMZ, SBT/CPZ, JM, CLDM, MINO and GM were relatively low and resistant rates were high for the gram-negative rods.  相似文献   
88.
Angiolipoma of the tongue: report of a case   总被引:1,自引:0,他引:1  
Angiolipoma is a rare variety of lipoma in the maxillofacial region. Only eight cases have been documented so far. A case in which an angiolipoma occurred within the tongue of a 49-year-old man is described here. The difference from earlier cases occurring in the tongue is noted. Close follow-up has, as yet, revealed no recurrence.  相似文献   
89.
Although hypodontia, or oligodontia, is one of the most common human dental anomalies observed, there have been few studies on the association of other anomalies occurring with it. The present investigation of 1032 patient records found that 65.7% of patients with hypodontia showed ankylosis of primary molars compared to only 1.5% of control children (P less than 0.001). In addition, taurodontism of the mandibular first permanent molar was observed in 34.3% of hypodontia cases compared to 7.1% in the controls (P less than 0.001). Other dental anomalies significantly associated with hypodontia include enamel hypoplasia (11.9%, P less than 0.01) and conical incisors (8.9%, P less than 0.01). In contrast, there were significantly more impacted teeth in control children compared to the hypodontia group. The results indicate that for patients with missing permanent teeth, clinicians should be alert to the possibility of these associated anomalies and their accompanying clinical implications.  相似文献   
90.
The antimicrobial action of natural substances was investigated in vitro against oral bacteria including Streptococcus sp., Actinomyces sp., Actinobacillus sp., Bacteroides sp., Capnocytophaga sp., Eikenella sp., Fusobacterium sp. and Propionibacterium sp. Among the natural substances tested, hinokitiol was the most inhibitory to oral bacteria. Cinnamon bark oil, papua-mace extracts, and clove bud oil in spice extracts were also inhibitory against many oral bacteria. Egg white lysozyme exhibited antimicrobial action against the periodontitis associated bacteria.  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