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   2872篇
  免费   312篇
  2021年   37篇
  2019年   42篇
  2018年   28篇
  2016年   44篇
  2015年   67篇
  2014年   77篇
  2013年   89篇
  2012年   124篇
  2011年   151篇
  2010年   72篇
  2009年   85篇
  2008年   105篇
  2007年   124篇
  2006年   116篇
  2005年   93篇
  2004年   84篇
  2003年   85篇
  2002年   74篇
  2001年   83篇
  2000年   74篇
  1999年   60篇
  1998年   35篇
  1997年   33篇
  1996年   29篇
  1995年   27篇
  1994年   30篇
  1993年   29篇
  1992年   48篇
  1991年   40篇
  1990年   56篇
  1989年   45篇
  1988年   55篇
  1987年   56篇
  1986年   43篇
  1985年   58篇
  1984年   36篇
  1983年   44篇
  1982年   39篇
  1981年   28篇
  1980年   34篇
  1979年   48篇
  1978年   32篇
  1977年   39篇
  1976年   33篇
  1975年   44篇
  1974年   33篇
  1973年   43篇
  1972年   45篇
  1971年   43篇
  1970年   35篇
排序方式: 共有3184条查询结果,搜索用时 185 毫秒
1.
2.
3.
Thermal injury triggers a fulminant inflammatory cascade that heralds shock, end-organ failure, and ultimately sepsis and death. Emerging evidence points to a critical role for the innate immune system, and several studies had documented concurrent impairment in neutrophil chemotaxis with these post-burn inflammatory changes. While a few studies suggest that a link between neutrophil motility and patient mortality might exist, so far, cumbersome assays have prohibited exploration of the prognostic and diagnostic significance of chemotaxis after burn injury. To address this need, we developed a microfluidic device that is simple to operate and allows for precise and robust measurements of chemotaxis speed and persistence characteristics at single-cell resolution. Using this assay, we established a reference set of migration speed values for neutrophils from healthy subjects. Comparisons with samples from burn patients revealed impaired directional migration speed starting as early as 24 hours after burn injury, reaching a minimum at 72–120 hours, correlated to the size of the burn injury and potentially serving as an early indicator for concurrent infections. Further characterization of neutrophil chemotaxis using this new assay may have important diagnostic implications not only for burn patients but also for patients afflicted by other diseases that compromise neutrophil functions.  相似文献   
4.
5.
Investigation of two populations of 136 individuals shows several patterns of occlusal wear plane change which are positively correlated with age. For individuals up to the age of 18, there is a characteristic pattern in which the occlusal wear planes of the mandibular teeth are lingually sloped and those of the maxillary dentition buccally sloped, with the exception of the maxillary premolars, which are also lingually sloped. The long axes of the mandibular teeth give them a lingual orientation relative to the maxillary teeth, and the long axes of the maxillary molars, by contrast, are buccally oriented. In the 18-30 age range for all sexes, the mandibular M1 becomes buccally sloped on its occlusal surface while the occlusal wear plane on the maxillary M1 becomes lingually sloped. Later age changes indicate a trend for the mandibular premolars to become buccally sloped, while the wear planes of the maxillary premolars remain lingually sloped. There is a corresponding tendency for the maxillary and mandibular second molars to undergo changes in the initial orientation of the occlusal wear planes.  相似文献   
6.
7.
8.
Lysyl oxidase, the only enzyme involved in collagen crosslinking, is shown to be present in embryos of the sea urchin Strongylocentrotus purpuratus. The enzyme specific activity increases over six-fold during development, showing the greatest rise during gastrulation and prism larva formation. The enzyme is inhibited by the specific inhibitor, beta-aminoproprionitrile (BAPN). Continuous BAPN treatment of S. purpuratus and Lytechinus pictus embryos from late cleavage stages onward increases the amount of noncrosslinked collagen present in prism larvae. When BAPN is added at the 128- or 256-cell stage it causes developmental arrest at the mesenchyme blastula stage. Embryos can be maintained in the arrested state for at least 96 h and will resume normal development and morphogenesis following BAPN removal. If BAPN is added after the mesenchyme blastula stage, it has little adverse effect on development; consequently nonspecific toxic effects of the drug are unlikely. The results suggest that lysyl oxidase and collagen crosslinking play a vital role in primary mesenchyme migration, gastrulation, and morphogenesis during sea urchin development and indicate that BAPN may be very useful in studying the extracellular matrix-cell interactions at the cellular and molecular level.  相似文献   
9.
The host-lysis-inducing functions of phi X174 protein E and MS2 protein L were recently shown to reside on the N-terminal and C-terminal halves of the two respective lysis proteins. In the present study it is shown that the small lysis proteins encoded in various colicinogenic plasmids share local sequence similarities and certain structural characteristics with the essential peptides of their coliphage-coded counterparts. Despite their dissimilar sizes and origins, it is suggested that the colicinogenic lysis proteins are functionally analogous and evolutionarily related to those of icosahedral single- stranded DNA and RNA phages.   相似文献   
10.
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