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   189篇
  免费   27篇
林业   10篇
农学   6篇
基础科学   2篇
  83篇
综合类   8篇
农作物   16篇
水产渔业   17篇
畜牧兽医   42篇
园艺   5篇
植物保护   27篇
  2023年   3篇
  2022年   2篇
  2021年   3篇
  2020年   2篇
  2019年   4篇
  2018年   11篇
  2017年   8篇
  2016年   12篇
  2015年   13篇
  2014年   7篇
  2013年   8篇
  2012年   8篇
  2011年   17篇
  2010年   10篇
  2009年   8篇
  2008年   6篇
  2007年   10篇
  2006年   14篇
  2005年   7篇
  2004年   11篇
  2003年   5篇
  2002年   11篇
  2001年   4篇
  2000年   7篇
  1999年   6篇
  1998年   1篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1974年   1篇
  1963年   1篇
排序方式: 共有216条查询结果,搜索用时 343 毫秒
31.
Pot experiments were carried out to characterize the response of two Cucumis metuliferus accessions (BGV11135 and BGV10762) against Mi1.2 gene (a)virulent Meloidogyne arenaria, M. incognita and M. javanica isolates and to determine the compatibility and the effect on physicochemical properties of fruit melons. In addition, histopathological studies were conducted. One week after transplanting, plants were inoculated with one J2 cm?3 of sterilized sand (200 cm3 pots) and maintained in a growth chamber at 25 °C for 40 days. The susceptible cucumber cv. Dasher II or melon cv. Paloma were included for comparison. The number of egg masses and number of eggs per plant were assessed, and the reproduction index (RI) was calculated as the percentage of eggs produced on the C. metuliferus accessions compared to those produced on the susceptible cultivars. The compatibility and fruit quality were assessed by grafting three scions, two of Charentais type and one of type piel de sapo, under commercial greenhouse conditions. The resistance level of both C. metuliferus accessions ranged from highly resistant (RI < 1%) to resistant (1% ≤ RI ≤ 10%) irrespective of Meloidogyne isolates. Melon plants grafted onto C. metuliferus accession BGV11135 grew as self‐grafted plants without negatively impacting fruit quality traits. Giant cells induced by Meloidogyne spp. on C. metuliferus were in general poorly developed compared to those on cucumber. Furthermore, necrotic areas surrounding the nematode were observed. Cucumis metuliferus accession BGV11135 could be a promising melon rootstock to manage Meloidogyne spp., irrespective of their Mi1.2 (a)virulence, without melon fruit quality reduction.  相似文献   
32.
Based on their composition, marine algae, and namely red seaweeds, are good potential functional foods. Intestinal mucosal barrier function refers to the capacity of the intestine to provide adequate containment of luminal microorganisms and molecules. Here, we will first outline the component of seaweeds and will summarize the effects of these on the regulation of mucosal barrier function. Special attention will be paid to unique components of red seaweeds: proteins and derived peptides (e.g., phycobiliproteins, glycoproteins that contain “cellulose binding domains”, phycolectins and the related mycosporine-like amino acids) together with polysaccharides (e.g., floridean starch and sulfated galactans, such as carrageenans, agarans and “dl-hybrid”) and minerals. These compounds have been shown to exert prebiotic effects, to regulate intestinal epithelial cell, macrophage and lymphocyte proliferation and differentiation and to modulate the immune response. Molecular mechanisms of action of peptides and polysaccharides are starting to be elucidated, and evidence indicating the involvement of epidermal growth factor receptor (EGFR), insulin-like growth factor receptor (IGFR), Toll-like receptors (TLR) and signal transduction pathways mediated by protein kinase B (PKB or AKT), nuclear factor-κB (NF-κB) and mitogen activated protein kinases (MAPK) will also be summarized. The need for further research is clear, but in vivo experiments point to an overall antiinflammatory effect of these algae, indicating that they can reinforce membrane barrier function.  相似文献   
33.
34.
Salicylic acid (SA) is an inducer of systemic acquired resistance (SAR) and could be a potential candidate in the control of plant virus diseases. In this study we assayed under controlled conditions the potential effect of three doses of exogenous SA treatment on tomato plants infected with Potato virus X (PVX) and measured their effects on: different physiological parameters (gas exchange, stable isotopes, chlorophyll content), the activation of secondary metabolism, viral accumulation and induction of the expression of pathogenesis-related proteins (PRs) such as ß-1, 3-glucanase (PR2) and chitinase (PR3). SA treatment increased the expression of PR2, the activity of phenylalanine ammonia lyase (PAL) and the concentration of antioxidant compounds at 7 days post-treatment. Earlier expression of PR3 compared to PR2 was observed. SA treatment delayed the detection of PVX by ELISA in uninoculated leaves of mechanically infected tomato plants. Although the effect of PVX infection on physiological parameters was weak, moderate SA treatments showed enhanced photosynthesis, particularly for infected plants. The results obtained confirm that SA promotes major changes in the induction of resistance in tomato plants and suggest that treatment with exogenous SA could be considered to reduce the infections caused by PVX.  相似文献   
35.
Acrosin is an acrosomal protease synthesized as an inactive precursor, proacrosin, which is processed via autoproteolysis into active forms alpha- and beta-acrosin. In this paper, a comparative study on the immunoreactivity of acrosin during in vitro capacitation of frozen and fresh (control) canine sperm using Western blot analysis is reported. Semen samples were obtained by digital stimulation and ejaculates processed as fresh and frozen samples and then capacitated for 0, 30, 60 and 90 min. At each time period, samples were analyzed with monoclonal antibody C5F10 by Western blot. The antibody specifically recognized, in fresh and frozen/thawed spermatozoa, a 40-, 32- and 27-kDa bands corresponding to proacrosin, alpha- and beta-acrosin, respectively, during capacitation. Western immunoblots showed that the beta-acrosin reactivity in fresh sperm was directly proportional to the time of capacitation, whereas a decreased reactivity of active form of acrosin was observed with frozen-thawed sperm (p   < 0.05). These results suggest that proacrosin is activated to beta-acrosin earlier in frozen/thawed dog spermatozoa than in fresh dog spermatozoa.  相似文献   
36.
In the contemporary Amazon, ‘discourse’ is increasingly a new means of exercising power, influencing local society and the ways in which natural resources are managed. As society becomes ever more complex, direct means of exercising power no longer enjoy the same legitimacy and efficacy. Discourses are instead now assuming a dominant role in defining governance regimes; the sense of what is correct and socially acceptable, and what is not. This is particularly relevant for the rapidly advancing development frontiers in the Amazon region, where local communities are coming into contact with external players highly interested in their forest resources. This study focuses on understanding how external discourses can restrict the Amazonian communities' options for using their forests, but also how communities can harness these discourses to achieve their own claims and objectives. Empirical evidence from four study areas in the Bolivian, Brazilian and Peruvian Amazon regions is used to show how discourses on sustainable forest management are moulding forestry governance. The conclusion shows that while the discourses used by loggers and development organisations are strongly influencing the way communities manage their forests, some communities are also successfully using these discourses in alliances with environmental organisations to achieve acknowledgment of their demands.  相似文献   
37.
This report describes a suspect case of West Nile virus (WNV) encephalomyelitis, reported for the first time in a horse in the UK. The affected gelding had been imported from the Republic of Cyprus and travelled through several WNV endemic areas in Europe before arriving at the premises in Lincolnshire. Clinical signs included muscle fasciculations, weakness of the hindlimbs and transient lip twitching that quickly progressed to depression and recumbency. West Nile virus specific antibodies were detected by serological tests in the absence of a previous history of vaccination. The horse improved clinically 10 days after the onset of disease and fully recovered in 12 weeks. Follow‐ups at 12 and 20 months post event did not reveal any sequela and the horse was performing adequately at novice level. This article refers to the same horse mentioned by Fooks et al. (2014) and it is an extension of the previous published work.  相似文献   
38.
39.
Soil suppressiveness against Fusarium was tested using solarized and non-solarized soils combined with composts of three maturation levels, and a non-amended control. The soils were sampled on three dates: after previous year solarization but before current year solarization (0 weeks), at the end of the solarization period of the current year (4 weeks), and 4 weeks later (recovery time). Melon seedlings were inoculated with Fusarium spores and disease severity was assessed. The study showed a reduction of soil suppressiveness capacity against Fusarium oxysporum f. sp. melonis after 1 year of solarization (0 weeks). Fusarium disease severity in artificially inoculated melon plants, expressed by area under the disease progress curve, was higher in solarized soil than in non-solarized soil. Compost addition lowered the disease severity, both in the solarized and in the non-solarized soils. However, suppression was not obtained at the end of the solarization period, whereas compost beneficial effect was found at this time.  相似文献   
40.
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