首页 | 官方网站   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   1590603篇
  免费   133438篇
  国内免费   2567篇
医药卫生   1726608篇
  2018年   14762篇
  2016年   12899篇
  2015年   15025篇
  2014年   20646篇
  2013年   31358篇
  2012年   42548篇
  2011年   44758篇
  2010年   26344篇
  2009年   25310篇
  2008年   43001篇
  2007年   45251篇
  2006年   46052篇
  2005年   44679篇
  2004年   44098篇
  2003年   42118篇
  2002年   41204篇
  2001年   75575篇
  2000年   78136篇
  1999年   65971篇
  1998年   16698篇
  1997年   15336篇
  1996年   15283篇
  1995年   15938篇
  1994年   14986篇
  1993年   14145篇
  1992年   55365篇
  1991年   53767篇
  1990年   52540篇
  1989年   50802篇
  1988年   47187篇
  1987年   46536篇
  1986年   44259篇
  1985年   42826篇
  1984年   31987篇
  1983年   27519篇
  1982年   16085篇
  1981年   14375篇
  1980年   13491篇
  1979年   30414篇
  1978年   21022篇
  1977年   17693篇
  1976年   16649篇
  1975年   17516篇
  1974年   21450篇
  1973年   20643篇
  1972年   18842篇
  1971年   17752篇
  1970年   16270篇
  1969年   15252篇
  1968年   13936篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
The aim of the present study was to evaluate the antimicrobial activity of two synbiotic combinations, Lactobacillus fermentum with short-chain fructooligosaccharides (FOS-LF) and Bifidobacterium longum with isomaltooligosaccharides (IMO-BL), against enterohaemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli O86. Antimicrobial activity was determined (1) by co-culturing the synbiotics and pathogens in batch cultures, and (2) with the three-stage continuous culture system (gut model), inoculated with faecal slurry from an elderly donor. In the co-culture experiments, IMO-BL was significantly inhibitory to both E. coli strains, while FOS-LF was slightly inhibitory or not inhibitory. Factors other than acid production appeared to play a role in the inhibition. In the gut models, both synbiotics effectively inhibited E. coli O157 in the first vessel, but not in vessels 2 and 3. E. coli O86 was not significantly inhibited.  相似文献   
992.
993.
994.
Researchers interested in measuring neighborhood‐level effects should understand how “neighborhood” is defined within nursing sciences and other sciences, and the inherent strengths and weaknesses of current research methodologies. This concept analysis provides clarity around the concept of neighborhood within the context of health, analyzes the current state of development of the neighborhood concept, and proposes areas for future nursing research. Using the Rodger's Method of analysis, the concept of neighborhood within nursing and public health research is described based on existing literature. The concept's attributes, related concepts, antecedents, and consequences are given from the literature. Comparisons of the use of neighborhood are made between nursing, public health, sociology, and other sciences. The evolution of the concept of neighborhood throughout history is described, and important implications for future research are discussed.  相似文献   
995.
996.
997.
Group A Streptococcus (GAS) predominantly exists as a colonizer of the human oropharynx that occasionally breaches epithelial barriers to cause invasive diseases. Despite the frequency of GAS carriage, few investigations into the contributory molecular mechanisms exist. To this end, we identified a naturally occurring polymorphism in the gene encoding the streptococcal collagen-like protein A (SclA) in GAS carrier strains. All previously sequenced invasive serotype M3 GAS possess a premature stop codon in the sclA gene truncating the protein. The carrier polymorphism is predicted to restore SclA function and was infrequently identified by targeted DNA sequencing in invasive strains of the same serotype. We demonstrate that a strain with the carrier sclA allele expressed a full-length SclA protein, while the strain with the invasive sclA allele expressed a truncated variant. An isoallelic mutant invasive strain with the carrier sclA allele exhibited decreased virulence in a mouse model of invasive disease and decreased multiplication in human blood. Further, the isoallelic invasive strain with the carrier sclA allele persisted in the mouse nasopharynx and had increased adherence to cultured epithelial cells. Repair of the premature stop codon in the invasive sclA allele restored the ability to bind the extracellular matrix proteins laminin and cellular fibronectin. These data demonstrate that a mutation in GAS carrier strains increases adherence and decreases virulence and suggest selection against increased adherence in GAS invasive isolates.  相似文献   
998.
Advancement in microelectromechanical system has facilitated the microfabrication of polymeric substrates and the development of the novel class of controlled drug delivery devices. These vehicles have specifically tailored three dimensional physical and chemical features which together, provide the capacity to target cell, stimulate unidirectional controlled release of therapeutics and augment permeation across the barriers. Apart from drug delivery devices microfabrication technology’s offer exciting prospects to generate biomimetic gastrointestinal tract models. BioMEMS are capable of analysing biochemical liquid sample like solution of metabolites, macromolecules, proteins, nucleic acid, cells and viruses. This review summarized multidisciplinary application of biomedical microelectromechanical systems in drug delivery and its potential in analytical procedures.  相似文献   
999.
1000.
Reactive lymphoid infiltrates of the skin composed predominantly of gamma‐delta (γδ) T cells are not well described in the literature. Herein we report a case of an otherwise healthy 4‐year‐old male who presented with a waxing and waning papular rash characterized by small, discrete crusted papules spread across his trunk, face and extremities. Clinical evaluation revealed no evidence of systemic disease. Microscopic examination revealed a dermal, perivascular infiltrate of highly atypical lymphocytes with a γδ T cell phenotype, worrisome for primary cutaneous γδ T cell lymphoma. The clinical course, however, was that of a reactive condition and prompted consideration of a diagnosis of pityriasis lichenoides et varioliformis acuta (PLEVA) and lymphomatoid papulosis (LyP). In many ways, this case defies current classification schemes and seems to expand the spectrum of reactive γδ T cell infiltrates of the skin.  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-23

京公网安备 11010802026262号