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   371篇
  免费   19篇
  2019年   1篇
  2018年   6篇
  2017年   2篇
  2016年   6篇
  2015年   16篇
  2014年   17篇
  2013年   23篇
  2012年   14篇
  2011年   16篇
  2010年   29篇
  2009年   26篇
  2008年   15篇
  2007年   13篇
  2006年   15篇
  2005年   15篇
  2004年   16篇
  2003年   4篇
  2002年   7篇
  2001年   7篇
  2000年   6篇
  1999年   5篇
  1998年   10篇
  1997年   11篇
  1996年   5篇
  1995年   6篇
  1994年   3篇
  1993年   7篇
  1992年   2篇
  1991年   8篇
  1990年   1篇
  1989年   3篇
  1988年   8篇
  1986年   2篇
  1985年   4篇
  1984年   4篇
  1983年   3篇
  1982年   17篇
  1981年   5篇
  1980年   1篇
  1979年   5篇
  1978年   2篇
  1977年   6篇
  1976年   3篇
  1975年   3篇
  1974年   1篇
  1972年   2篇
  1971年   4篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
排序方式: 共有390条查询结果,搜索用时 593 毫秒
301.
302.
303.
The effect of six phosphorus levels (0, 40, 80, 120, 160 and 200 kg/ha) on the duration of cumulative leaf area, biomass and agronomic yield was determined in the maize cultivars: Amarillo Almoloya, Cacahuacintle and Condor in 2010 and 2011. Such cultivars were sown in the Cerrillo Piedras Blancas Mexico. A completely randomized complete block design with factorial arrangement was utilized. High phosphorus levels (120, 160 and 200 kg/ha) positively affected the duration of cumulative leaf area; greatest values were obtained in Cacahuacintle. A greater duration of accumulated leaf area contributes to determine high values of biomass accumulation and grain yield in this cultivar. Leaf area duration appeared to be a useful tool for evaluating different genotypes in a given environment.  相似文献   
304.
The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.  相似文献   
305.
306.
307.
308.

Introduction  

The glucocorticoid receptor (GR) plays an important regulatory role in the immune system. Four polymorphisms in the GR gene are associated with differences in glucocorticoid (GC) sensitivity; the minor alleles of the polymorphisms N363 S and BclI are associated with relative hypersensitivity to GCs, while those of the polymorphisms ER22/23EK and 9β are associated with relative GC resistance. Because differences in GC sensitivity may influence immune effector functions, we examined whether these polymorphisms are associated with the susceptibility to develop Rheumatoid Arthritis (RA) and RA disease severity.  相似文献   
309.

Introduction  

Chondrocytes experience a hypertonic environment compared with plasma (280 mOsm) due to the high fixed negative charge density of cartilage. Standard isolation of chondrocytes removes their hypertonic matrix, exposing them to nonphysiological conditions. During in vitro expansion, chondrocytes quickly lose their specialized phenotype, making them inappropriate for cell-based regenerative strategies. We aimed to elucidate the effects of tonicity during isolation and in vitro expansion on chondrocyte phenotype.  相似文献   
310.

Background  

Tilt series are commonly used in electron tomography as a means of collecting three-dimensional information from two-dimensional projections. A common problem encountered is the projection alignment prior to 3D reconstruction. Current alignment techniques usually employ gold particles or image derived markers to correctly align the images. When these markers are not present, correlation between adjacent views is used to align them. However, sequential pairwise correlation is prone to bias and the resulting alignment is not always optimal.  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