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   290篇
  免费   41篇
林业   9篇
农学   2篇
基础科学   1篇
  37篇
综合类   28篇
农作物   32篇
水产渔业   21篇
畜牧兽医   171篇
园艺   11篇
植物保护   19篇
  2023年   7篇
  2022年   9篇
  2021年   17篇
  2020年   19篇
  2019年   18篇
  2018年   16篇
  2017年   13篇
  2016年   9篇
  2015年   12篇
  2014年   7篇
  2013年   11篇
  2012年   14篇
  2011年   18篇
  2010年   5篇
  2009年   13篇
  2008年   13篇
  2007年   13篇
  2006年   15篇
  2005年   10篇
  2004年   10篇
  2003年   9篇
  2002年   7篇
  2001年   3篇
  2000年   4篇
  1998年   4篇
  1992年   3篇
  1989年   3篇
  1988年   4篇
  1983年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1966年   1篇
  1948年   1篇
  1947年   1篇
  1946年   5篇
  1945年   2篇
  1944年   2篇
  1943年   4篇
  1940年   2篇
  1939年   1篇
  1937年   3篇
  1936年   1篇
  1935年   4篇
  1934年   1篇
  1932年   1篇
  1928年   1篇
  1881年   1篇
排序方式: 共有331条查询结果,搜索用时 15 毫秒
321.
PrP(c) (cellular prion protein, CD230) expression by subpopulations of lymphoid cells has been widely investigated in a variety of species, possibly because of the possible link between transmissible spongiform encephalopathies (TSE) transmission and blood transfusion. However, the role of the immune cells in the transmission of the disease is still unclear. Here we describe the optimisation and standardisation of a three-colour staining procedure to detect PrP in association with phenotypic and activation markers in ovine immune cells. We demonstrate a reproducible, flexible and sensitive method and that the combination of isotype-specific antibodies and Fab fragments is feasible. To our knowledge, this is the first report of such labelling of ovine cells. Using this method, we were able to detect differences in levels of PrP expression between blood and lymph node cells of the same animal, and considerable variability between animals. Moreover, we were able to explore possible associations between PrP expression and cellular activation and to identify cell subsets with different labelling patterns. We are currently employing this approach to evaluate variations in immunological parameters during experimental infection in sheep.  相似文献   
322.
We conducted a global systematic literature review of climate change adaptation in fisheries. We addressed three specific questions: (i) What are fisheries adapting to? (ii) How are fisheries adapting? and (iii) What research gaps need to be addressed? We identified, characterized and examined case studies published between 1990 and 2019 that lie at the intersection of the domains of climate change, adaptation and fisheries. We characterized the documented climate change effects in fisheries that are being adapted to multiple stressors, general climate impacts, extreme events, ocean conditions, marine system shifts, climate variability, fishery dynamics, species distribution and atmospheric warming. Three categories of adaptive responses came to light: coping mechanisms (e.g. changing fishing location, use of traditional knowledge); adaptive strategies (e.g. livelihood diversification, incorporation of technology); and management responses (e.g. adaptive management, adaptation planning). We identified key potential areas for future research, including studies on the limits and barriers for adaptation, studies using specific conceptual and methodological approaches, and studies focussing on the top-producing countries such as China, Indonesia, Peru and Russia. This analysis gives broader insights to the fisheries industry and to climate change adaptation research to proceed in the face of new global challenges.  相似文献   
323.
324.
Given the widespread degradation of freshwater habitats, assessing the distributions of species that may be negatively or positively impacted should be of general interest. However, determining distributions of freshwater organisms that are small and patchily distributed and attached or sedentary is particularly problematic, as it is time consuming, inaccurate, and nearly impossible when the focal species is rare. Here we illustrate the use of indirect sampling approaches to survey the distribution of the rare freshwater bryozoan Lophopus crystallinus, a priority species in the UK Biodiversity Action Plan [Anonymous, 1999. UK Biodiversity Group Tranche 2 Action Plans. Invertebrates, vol. 4. Environment Agency, Peterborough, pp. 437-439.]. By utilising two complementary methods for sampling bryozoan propagules (statoblasts), namely the collection of debris samples and sediment cores, we achieved an efficient and integrative sampling of habitats across spatial and temporal scales. Analysis of 154 debris samples, encompassing 62 rivers and lakes, identified at least 16 new populations while analysis of 26 sediment cores provided evidence of current or very recent (in the last 10-20 years) occurrence in a further six localities. These results represent a more than 10-fold increase in the current recorded distribution of the species in the UK. Logistic regression analysis provided evidence that L. crystallinus is generally found in lowland sites and is tolerant of eutrophication. Our study exemplifies how integrative and indirect sampling approaches can greatly aid in assessing the conservation status of rare aquatic species and reveals, in this case, that the focal species is less rare than previously appreciated.  相似文献   
325.
326.
327.
328.
Assistance of microbial glycolipid antigen processing by CD1e   总被引:1,自引:0,他引:1  
Complexes between CD1 molecules and self or microbial glycolipids represent important immunogenic ligands for specific subsets of T cells. However, the function of one of the CD1 family members, CD1e, has yet to be determined. Here, we show that the mycobacterial antigens hexamannosylated phosphatidyl-myo-inositols (PIM6) stimulate CD1b-restricted T cells only after partial digestion of the oligomannose moiety by lysosomal alpha-mannosidase and that soluble CD1e is required for this processing. Furthermore, recombinant CD1e was able to bind glycolipids and assist in the digestion of PIM6. We propose that, through this form of glycolipid editing, CD1e helps expand the repertoire of glycolipidic T cell antigens to optimize antimicrobial immune responses.  相似文献   
329.
Kessler et al. (Reports, 21 January 2011, p. 312) reported that methane released from the 2010 Deepwater Horizon blowout, approximately 40% of the total hydrocarbon discharge, was consumed quantitatively by methanotrophic bacteria in Gulf of Mexico deep waters over a 4-month period. We find the evidence explicitly linking observed oxygen anomalies to methane consumption ambiguous and extension of these observations to hydrate-derived methane climate forcing premature.  相似文献   
330.
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