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   1264112篇
  免费   94722篇
  国内免费   1578篇
耳鼻咽喉   16314篇
儿科学   41002篇
妇产科学   34948篇
基础医学   189406篇
口腔科学   34733篇
临床医学   117778篇
内科学   247825篇
皮肤病学   27278篇
神经病学   101919篇
特种医学   46763篇
外国民族医学   265篇
外科学   178606篇
综合类   25749篇
现状与发展   3篇
一般理论   568篇
预防医学   104662篇
眼科学   28047篇
药学   92564篇
  6篇
中国医学   2023篇
肿瘤学   69953篇
  2018年   13530篇
  2017年   10392篇
  2016年   11325篇
  2015年   13081篇
  2014年   18003篇
  2013年   27482篇
  2012年   37584篇
  2011年   39978篇
  2010年   23057篇
  2009年   22252篇
  2008年   37757篇
  2007年   40388篇
  2006年   39973篇
  2005年   39105篇
  2004年   37553篇
  2003年   35960篇
  2002年   34873篇
  2001年   56050篇
  2000年   57061篇
  1999年   48112篇
  1998年   13398篇
  1997年   12227篇
  1996年   12646篇
  1995年   11917篇
  1994年   11110篇
  1993年   10404篇
  1992年   38206篇
  1991年   37677篇
  1990年   36449篇
  1989年   35261篇
  1988年   32693篇
  1987年   32032篇
  1986年   30525篇
  1985年   28788篇
  1984年   21944篇
  1983年   19193篇
  1982年   11364篇
  1981年   10321篇
  1979年   20944篇
  1978年   15393篇
  1977年   12790篇
  1976年   11845篇
  1975年   12810篇
  1974年   15588篇
  1973年   15362篇
  1972年   14512篇
  1971年   13553篇
  1970年   12786篇
  1969年   12065篇
  1968年   11229篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Introduction –  The relative frequencies of different ataxias vary among different ethnic and geographic groups. The aim of this study was to examine patients with cerebellar ataxia and find the occurrence of autosomal dominant and recessive cerebellar ataxias in the population of the southern and eastern parts of Norway and estimate its prevalence.
Materials and methods –  Probands were systematically tested for spinocerebellar ataxia 1, 2, 3, 6 and Friedreich's ataxia. A total of 94 patients with ataxia were assessed.
Results –  We registered 60 patients from 39 unrelated families with hereditary ataxias. One family with SCA2 (two patients), one family with Friedreich's ataxia (two patients), two patients heterozygote for Friedreich's ataxia and one metabolic ataxia were identified.
Conclusions –  We have few Friedreich's ataxia and SCA 1,2,3 and 6 in our population. Prevalence in Oslo County was estimated at 2.2/100,000 for autosomal recessive and 3.0/100,000 for autosomal dominant ataxia, respectively.  相似文献   
993.
994.
995.
Bould  M D; Hunter  D; Haxby  E J 《CEACCP》2007,7(2):66
Contin Educ Anaesth Crit  相似文献   
996.
We have developed a luminol-based assay using intact islets, which allows for quantification of reactive oxygen species (ROS). In addition, an index capable of characterizing metabolic and mitochondrial integrity prior to transplantation was created based on the capacity of islets to respond to high glucose and rotenone (mitochondrial respiratory chain complex I inhibitor) by production of ROS. To validate this assay, lipid peroxidation and antioxidative defense capacity were evaluated by detection of malondialdehyde (MDA) levels and glutathione peroxidase activity (GPx), respectively. Also, flow cytometric analyses of ROS (dihydroethidine), apoptosis (Annexin V, active caspases), necrosis (Topro3), and mitochondrial membrane potential (JC-1) were done in parallel to correlate with changes in luminol-measured ROS. ATP/ADP ratios were quantified by HPLC and the predictive value of ROS measurement on islet functional potency was correlated with capacity to reverse diabetes in a streptozotocin-induced diabetic NOD.scid mouse model as well as in human transplant recipients. Our data demonstrate that levels of ROS in islets correlate with the percentage of apoptotic cells and their functional potency in vivo. The ROS indices following glucose and rotenone exposure are indicative of metabolic potency and mitochondrial integrity and can be used as surrogate markers to evaluate the quality of islets prior to transplantation.  相似文献   
997.
998.
Mesenchymal stem cells (MSC), easily culture-expanded from bone marrow, can significantly enhance bone defect healing. Several proteins, such as the bone morphogenetic proteins (BMPs) and in particular BMP-7, are involved in bone formation in vitro and in vivo. In this preclinical study, we evaluated if the association of human MSC (hMSC) with BMP-7 had synergic action on bone healing. Rat femoral defects (n=12) were treated with: autoclaved bone and mononucleated cells (MNC) as control group G1; bone and hMSC, group G2; bone with BMP-7, group G3; bone and hMSC plus BMP-7, group G4. Defect regeneration was evaluated with plain radiographs after 2, 4, 8 and 12 weeks and with histological analysis. We observed organized trabeculae bridging between the osteotomic ends of the host bone in rats treated with the association of hMSC and rhBMP-7. These trabeculae, formed by a core of devitalized tissue surrounded by osteoblasts, osteocytes and osteoclasts, were continuous with a cortical-like structure of bony tissue. Such new bone formation of the group treated with the association of hMSC and rhBMP-7 (G4) was clearly superior compared to rats treated with rhBMP-7 (G2) or hMSC (G3) alone, as shown by radiographic analysis and histological study. The present study suggests that the association of hMSC and BMP-7 is more effective than hMSC or BMP-7 alone in the healing of femoral defects in rats. Further studies with larger samples are required to confirm these results and to evaluate the best dosage.  相似文献   
999.
The objective of this study was to investigate the effect of fluoridated elastomeric ligatures on the microbiology of local dental plaque in vivo. This randomized, prospective, longitudinal, clinical trial had a split-mouth crossover design. The subjects were 30 patients at the beginning of their treatment with fixed orthodontic appliances in the orthodontic departments of the Liverpool and the Sheffield dental hospitals in the United Kingdom. The study consisted of 2 experimental periods of 6 weeks with a washout period between. Fluoridated elastomers were randomly allocated at the first visit to be placed around brackets on tooth numbers 12, 11, 33 or 22, 21, 43. Nonfluoridated elastomers were placed on the contralateral teeth. Standard nonantibacterial fluoridated toothpaste and mouthwash were supplied. After 6 weeks (visit 2), the elastomers were removed, placed in transport media, and plated on agar within 2 hours. Nonfluoridated elastomers were placed on all brackets for 1 visit to allow for a washout period. At visit 3, fluoridated elastomers were placed on the teeth contralateral to those that received them at visit 1. At visit 4, the procedures at visit 2 were repeated. Samples were collected on visits 2 and 4. A logistic regression was performed, with the presence or absence of streptococcal or anaerobic growth as the dependent variable. A mixed-effects analysis of variance was carried out with the percentage of streptococcal or anaerobic bacterial count as the dependent variable. The only significant independent variables were the subject variable (P =<.001) for the percentage of streptococcal and anaerobic bacterial count and the visit variable for the percentage of streptococcal count (P =<.001). The use of fluoridated or nonfluoridated elastomers was not significant for percentage of either streptococcal (P =.288) or anaerobic count (P =.230). Fluoridated elastomers are not effective at reducing local streptococcal or anaerobic bacterial growth after a clinically relevant time in the mouth.  相似文献   
1000.
The authors have studied hepatoprotective actions of new derivatives of 3-hydroxipyridine on an experimental model of toxic hepatitis (140 white mice). Mexidol and berlithion are choosed as the preparations of comparison. The method of light microscopy is used for the exploration of morphological changes. The cytolytic contents activity, catalase activity and the level of MDA have been determined in blood serum. The antitoxic effect is valued by the survival of the animals. It is found that all examined bonds is corrected morphological changes in toxic hepatitis and increased the index of animals survival, which is more expressed than the preparations of comparison.  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