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   67篇
  免费   3篇
林业   3篇
农学   1篇
  25篇
综合类   2篇
农作物   1篇
水产渔业   4篇
畜牧兽医   29篇
园艺   1篇
植物保护   4篇
  2023年   3篇
  2022年   1篇
  2021年   2篇
  2020年   1篇
  2019年   3篇
  2018年   2篇
  2017年   1篇
  2016年   4篇
  2015年   5篇
  2014年   9篇
  2013年   7篇
  2012年   3篇
  2011年   5篇
  2010年   3篇
  2009年   4篇
  2008年   4篇
  2007年   3篇
  2006年   1篇
  2005年   3篇
  2004年   2篇
  2003年   1篇
  2002年   3篇
排序方式: 共有70条查询结果,搜索用时 15 毫秒
21.
Landraces (LRs) are crop populations that are locally grown by farmers; they have a strategic role to play in rebuilding healthy and complex agro-ecosystems, but are at risk of extinction. This paper outlines how some LRs were rescued with the support of modern techniques such as molecular markers. Cowpea LRs from Umbria, Italy, were initially characterized for morphological, organoleptic and genetic traits and reintroduced among farmers. These activities led to an expansion of the area under LR based cowpea cultivation and increased farmers’ income. To encourage further LR cultivation a request for the Protected Designation of Origin (PDO) status has been promoted. Investigations were carried out to determine if it is possible to certify that the product actually belongs to the traditional agricultural and cultural context of the cultivation area. The genetic diversity and phylogenetic relationships among local LRs, other LRs, commercial varieties, and other taxa were investigated with five AFLP markers. Although genetic diversity is limited, genetic analysis showed that Umbrian cowpea LRs can be distinguished from commercial varieties, LRs from abroad and other taxa. There is a tight phylogenetic connection among Umbrian LRs. These data confirmed the available historical and sociological data and were included in the PDO specification. AFLP markers can be used to monitor the origin of seed lots that are on the market; this protects the rights of both consumers and farmers. This case study could be a resource for planning activities for the future on-farm conservation of other LRs in different countries.  相似文献   
22.
We describe a rapid, sensitive and reproducible real-time PCR assay for detecting and quantifying canine parvovirus type 2 (CPV-2) DNA in the feces of dogs with diarrhea. An exogenous internal control was added to control the assay performance from extraction to amplification. The method was demonstrated to be highly specific and sensitive, allowing a precise CPV-2 DNA quantitation over a range of eight orders of magnitude (from 10(2) to 10(9) copies of standard DNA). The reproducibility of the CPV-2 real-time PCR assay was assessed by calculating the coefficients of variation (CV) intra-assay and inter-assay for samples containing amounts of CPV-2 DNA spanning the whole range of the real-time PCR standard curve. Then, fecal specimens from diarrheic dogs were analyzed by hemagglutination (HA), conventional PCR and real-time amplification. Comparison between these different techniques revealed that real-time PCR is more sensitive than HA and conventional gel-based PCR, allowing to detect low viral titers of CPV-2 in infected dogs.  相似文献   
23.
The aim of this paper was to investigate pore-size distributions in the nano-diameter range of wood and their alteration due to thermal modification of wood using thermoporosimetry, and to find out what consequences can be derived regarding the biological durability. Thermoporosimetry is a technique that is based on the measurement using differential scanning calorimetry (DSC). The method is based on the fact that frozen water contained within small pores is at elevated pressure and therefore has a depressed melting temperature as a function of the appropriate pore diameter. In addition, the fiber saturation points (FSP) were determined by DSC. The former were performed in an isothermal-step method and the latter using the continuous heating-up method. Native and thermally modified twin samples of Norway spruce (Picea abies (L.) Karst.), Sycamore maple (Acer pseudoplatanus L.) and European ash (Fraxinus excelsior L.) were analyzed. The results clearly show that the pore shares of wood for the measurable diameter range between 4 and 400 nm decrease considerably in all studied wood species due to thermal modification of the wood. Furthermore, thermal modification of wood leads to a decreased FSP for all studied wood species. For evaluation as well as reproducibility of the results of pore-size distribution and FSP, the consideration of sensible heat and specific heat of fusion plays an important role. If this is not done, it can lead to misinterpretations.  相似文献   
24.
25.
26.

Purpose

This study aims to quantify and characterise sediments accumulated in the street gutters in an urban area of Poços de Caldas, Brazil. The main research questions are: What type of urban areas, e.g. those under construction, produce most sediments and what are the main characteristics of such sediments? What differences, e.g. granulometry, can be found in loose and adhered sediments? What trace metals can be found in the sediments?

Materials and methods

Fieldwork was carried out in a residential area of Poços de Caldas, Brazil. Ten samplings were conducted between May and August 2013 to collect sediments from road gutters. The collected sediments were then divided into ‘loose’ and ‘adhered’, depending on whether they were collected in a first, gentle, sweeping with soft bristled brush or in a subsequent sweeping with a stiff bristled brush. Granulometric curves were drawn for both types of sediments. Fine sediment analyses (≤63 μm) were performed on samples from the last five samplings. Two techniques were used to look for trace elements: energy dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES).

Results and discussion

Larger amounts of sediments were collected after lower intensity rainfall events. Higher intensity events seemed to wash the sediments away. A correlation was found between areas under construction and sediment mass production. A characteristic range of granulometries (medium sand), found in our study is in accordance with studies by other authors. An important presence of heavy metals (Cr, Cd, Pb, Zn, Ni and Cu) was detected and characterised. As and Sn were also detected even though they are not often mentioned in the literature on urban soil pollutants.

Conclusions

Areas under construction were found to produce more sediments than other areas. The trace metals found in highest concentrations were Pb and As. The heavy metal concentration decreases after wet periods, showing that they are carried by runoff. It is expected that this study may serve as an input for establishing diffuse pollution control and mitigation strategies for the accumulation of pollutants in the urban environment.
  相似文献   
27.
Swine influenza monitoring programs have been in place in Italy since the 1990 s and from 2009 testing for the pandemic H1N1/2009 virus (H1N1pdm) was also performed on all the swine samples positive for type A influenza. This paper reports the isolation and genomic characterization of a novel H1N2 swine influenza reassortant strain from pigs in Italy that was derived from the H1N1pdm virus. In May 2010, mild respiratory symptoms were observed in around 10% of the pigs raised on a fattening farm in Italy. Lung homogenate taken from one pig showing respiratory distress was tested for influenza type A and H1N1pdm by two real time RT-PCR assays. Virus isolation was achieved by inoculation of lung homogenate into specific pathogen free chicken embryonated eggs (SPF CEE) and applied onto Caco-2 cells and then the complete genome sequencing and phylogenetic analysis was performed from the CEE isolate. The lung homogenate proved to be positive for both influenza type A (gene M) and H1N1pdm real time RT-PCRs. Virus isolation (A/Sw/It/116114/2010) was obtained from both SPF CEE and Caco-2 cells. Phylogenetic analysis showed that all of the genes of A/Sw/It/116114/2010, with the exception of neuraminidase (NA), belonged to the H1N1pdm cluster. The NA was closely related to two H1N2 double reassortant swine influenza viruses (SIVs), previously isolated in Sweden and Italy. NA sequences for these three strains were clustering with H3N2 SIVs. The emergence of a novel reassortant H1N2 strain derived from H1N1pdm in swine in Italy raises further concerns about whether these viruses will become established in pigs. The new reassortant not only represents a pandemic (zoonotic) threat but also has unknown livestock implications for the European swine industry.  相似文献   
28.

Background and case presentation

A three year old, second lactation Holstein dairy cow presented to the Scottish Centre for Production Animal Health and Food Safety, Glasgow University Veterinary School in November 2014 with a history of post-calving vulval/vaginal bleeding nine days prior to presentation, followed by a sudden reduction in milk yield. Subsequent investigations resulted in a diagnosis of immune-mediated haemolytic anaemia secondary to infection with Mycoplasma wenyonii.

Conclusion

This report of a novel presentation of Mycoplasma wenyonii in a dairy cow illustrates the need to consider M.wenyonii as a potential differential diagnosis when a cow presents with anaemia and will discuss the potential implications of the condition at herd-level.
  相似文献   
29.
30.

Purpose

This paper investigates soils and sediments from the eastern Padanian Plain (northern Italy) in order to delineate the physiographic evolution of the area.

Materials and methods

We present new geochemical, mineralogical and textural analyses of alluvial sediments collected from a 13-m-deep section located a few kilometres south of Ferrara. The chronology of the related depositional events is provided from 14C dating of tree trunks buried at depths of ca. 9 m and organic matter from the underlying horizons.

Results and discussion

The data indicate that (1) the upper part of the sequence (down to depths of 9 m) includes sediments characterized by low nickel–chromium (Ni–Cr) concentrations ascribed to the alluvial deposits of the river Reno, deposited in the last 400 years; (2) buried soils (depths of 9–10.5 m) developed on Ni–Cr-rich sediments related to the river Po; and (3) the deeper facies (depths of 10.5–13 m) are CaCO3-free and characterized by higher amounts of organic carbon, sulphur and arsenic, reflecting episodic lacustrine/marsh environments. These wetlands probably developed in the area during the Iron and Roman ages, persisting up to the Middle Ages.

Conclusions

The data provide a contribution to the understanding of the evolution of the river network during the last 3,000 years and provide insights on the related paleohydrological framework that can be useful for geographical and historical reconstructions of the area. Results highlight the importance of investigating alluvial sediments to elucidate (1) fluctuations of environmental conditions and (2) anthropogenic impacts on the natural landscape.  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