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   2081篇
  免费   171篇
  2023年   16篇
  2022年   18篇
  2021年   79篇
  2020年   41篇
  2019年   46篇
  2018年   48篇
  2017年   47篇
  2016年   82篇
  2015年   119篇
  2014年   122篇
  2013年   161篇
  2012年   190篇
  2011年   166篇
  2010年   105篇
  2009年   94篇
  2008年   110篇
  2007年   115篇
  2006年   124篇
  2005年   92篇
  2004年   87篇
  2003年   61篇
  2002年   59篇
  2001年   18篇
  2000年   13篇
  1999年   14篇
  1998年   17篇
  1997年   11篇
  1996年   14篇
  1995年   11篇
  1994年   11篇
  1993年   12篇
  1992年   6篇
  1991年   9篇
  1990年   6篇
  1989年   3篇
  1988年   4篇
  1986年   10篇
  1985年   5篇
  1982年   6篇
  1981年   5篇
  1980年   6篇
  1979年   8篇
  1978年   7篇
  1975年   3篇
  1974年   4篇
  1973年   5篇
  1971年   9篇
  1969年   7篇
  1968年   4篇
  1963年   3篇
排序方式: 共有2252条查询结果,搜索用时 15 毫秒
1.
Multiple sclerosis, the most common cause of neurological disability in young population after trauma, represents a significant public health burden. Current challenges associated with management of multiple sclerosis (MS) patients stem from the lack of biomarkers that might enable stratification of the different clinical forms of MS and thus prompt treatment for those patients with progressive MS, for whom there is currently no therapy available. In the present work we analyzed a set of thirty different plasma cytokines, chemokines and growth factors present in circulation of 129 MS patients with different clinical forms (relapsing remitting, secondary progressive and primary progressive MS) and 53 healthy controls, across two independent cohorts. The set of plasma analytes was quantified with Luminex xMAP technology and their predictive power regarding clinical outcome was evaluated both individually using ROC curves and in combination using logistic regression analysis. Our results from two independent cohorts of MS patients demonstrate that the divergent clinical and histology-based MS forms are associated with distinct profiles of circulating plasma protein biomarkers, with distinct signatures being composed of chemokines and growth/angiogenic factors. With this work, we propose that an evaluation of a set of 4 circulating biomarkers (HGF, Eotaxin/CCL11, EGF and MIP-1β/CCL4) in MS patients might serve as an effective tool in the diagnosis and more personalized therapeutic targeting of MS patients.  相似文献   
2.
A Cu,Zn superoxide dismutase was purified for the first time from an elasmobranch species (Prionace glauca) and showed the following differences with respect to other animal superoxide dismutases. The enzyme displays a low isoelectric point. The enzyme activity is unusually independent of ionic strength. The isolated enzyme has 30% of its copper in the reduced state.  相似文献   
3.
4.
International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body...  相似文献   
5.
l-Prolyl-l-leucyl-glycinamide is rapidly hydrolyzed by hypothalamic, hypophyseal and cortical homogenates from male or female rats. The peptidase activity is higher in the pituitary followed in decreasing order by the hypothalamus and the cerebral cortex. It is mostly localized in the supernatant fraction of a 100,000 g centrifugation and is inhibited by bacitracin.Tissues from female rats are half as active as those from male rats and show variations during the estrous cycle, with very low PLG metabolism at diestrus 1 in pituitary and hypothalamus. In contrast, the cerebral cortex at proestrus and estrus has significant lower hydrolyzing activity than at diestrus. No change of the peptidase activity is observed in tissues from ovariectomized animals after treatment with estrogen or progesterone.The results obtained suggest the existence of a correlation between peptidasic activity and melanotropin secretion.  相似文献   
6.
Cobalamin (B12) is an essential cofactor that is exclusively synthesized by some prokaryotes while many prokaryotes and eukaryotes require an external supply of B12. The spatial and temporal availability of B12 is poorly understood in marine ecosystems. Field measurements of B12 along with a large set of ancillary biotic and abiotic factors were obtained during three oceanographic cruises in the NW Iberian Peninsula, covering different spatial and temporal scales. B12 concentrations were remarkably low (<1.5 pM) in all samples, being significantly higher at the subsurface Eastern North Atlantic Central Water than at shallower depths, suggesting that B12 supply in this water mass is greater than demand. Multiple regression models excluded B12 concentration as predictive variable for phytoplankton biomass or production, regardless of the presence of B12-requiring algae. Prokaryote production was the best predictor for primary production, and eukaryote community composition was better correlated with prokaryote community composition than with nutritional resources, suggesting that biotic interactions play a significant role in regulating microbial communities. Interestingly, co-occurrence network analyses based on 16S and 18S rRNA sequences allowed the identification of significant associations between potential B12 producers and consumers (e.g. Thaumarchaeota and Dynophyceae, or Amylibacter and Ostreococcus respectively), which can now be investigated using model systems in the laboratory.  相似文献   
7.
8.
9.
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