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   99篇
  免费   6篇
林业   13篇
农学   3篇
  21篇
综合类   10篇
农作物   2篇
水产渔业   3篇
畜牧兽医   41篇
园艺   2篇
植物保护   10篇
  2023年   3篇
  2022年   3篇
  2021年   4篇
  2020年   4篇
  2019年   6篇
  2018年   3篇
  2017年   3篇
  2016年   7篇
  2015年   2篇
  2014年   4篇
  2013年   1篇
  2012年   11篇
  2011年   7篇
  2010年   8篇
  2009年   5篇
  2008年   1篇
  2007年   2篇
  2006年   7篇
  2005年   5篇
  2004年   4篇
  2003年   5篇
  2002年   5篇
  2001年   1篇
  1998年   1篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
排序方式: 共有105条查询结果,搜索用时 15 毫秒
81.
82.
A flexible unmanned aerial vehicle for precision agriculture   总被引:1,自引:0,他引:1  
An unmanned aerial vehicle (??VIPtero??) was assembled and tested with the aim of developing a flexible and powerful tool for site-specific vineyard management. The system comprised a six-rotor aerial platform capable of flying autonomously to a predetermined point in space, and of a pitch and roll compensated multi-spectral camera for vegetation canopy reflectance recording. Before the flight campaign, the camera accuracy was evaluated against high resolution ground-based measurements, made with a field spectrometer. Then, ??VIPtero?? performed the flight in an experimental vineyard in Central Italy, acquiring 63 multi-spectral images during 10?min of flight completed almost autonomously. Images were analysed and classified vigour maps were produced based on normalized difference vegetation index. The resulting vigour maps showed clearly crop heterogeneity conditions, in good agreement with ground-based observations. The system provided very promising results that encourage its development as a tool for precision agriculture application in small crops.  相似文献   
83.
Polycyclic aromatic hydrocarbons (PAHs); their derivatives nitro, and methyl-PAHs; n-alkanes; and organic acids were investigated in the aerosol samples collected during two field campaigns conducted at three sampling stations in an industrialized city in southern Italy. The main sources affecting the atmosphere and its toxicity were investigated by means of the diagnostic ratios of: specific particulate-phase PAHs, marker compounds among nitro-PAHs, alkanes, and acids, the dominant wind direction, daily and seasonal abundance of carcinogenic organic substances. The potential importance of the non-regulated pollutants to assess the air quality was confirmed; in fact the carcinogenic organic compounds showed to have scarce correlation with particulate matter (PM) concentration. An exceptionally high variability of toxic compounds at a daily scale was due to meteorological condition causing periods of extremely high pollution levels.  相似文献   
84.
Genetic Resources and Crop Evolution - Northern Italy is an area particularly suitable for the cultivation of different crops. It used to be characterized by a high agrobiodiversity. However, it is...  相似文献   
85.
Introduction of wildlife for game restocking is one major pathway of genetic homogenization. The red-legged partridge (Alectoris rufa, Phasianidae), a small game bird native to south-western Europe, is in high demand by hunters and natural populations are constantly supplemented by commercial stocks of captive-bred individuals. Also, in recent years human-mediated hybridization with congeneric chukar partridges (Alectoris chukar: Greece, Cyprus, from Middle East to East Asia) has been frequently documented in the wild and in captivity. This study attempts to evaluate the genetic consequences of intensive captive breeding and restocking in the A. rufa species. We investigated A. rufa genetic diversity by making comparisons in both a spatial (across the entire species’ range) and a temporal framework. We accomplished this latter by comparing modern vs. ancient partridges resident in museums and collected 1856-1934, well before supplemental stocking became common. Using mtDNA we found significant changes in the haplotype profile of modern vs. ancient A. rufa, and widespread introgression with chukar genes across the entire species range only in modern representatives, with the relevant exception of Corsican populations. However, Random Amplified Polymorphic DNA (RAPD), as opposed to microsatellite DNA markers, showed also modern Corsican populations to harbour many A. rufa × A. chukar hybrids. We conclude that captive breeding programs should make strict use of time-saving and comparatively low cost DNA barcodes to minimize genetic pollution, such as those provided by diagnostic RAPD markers. We also recommend that the active ban on import of exotics and/or hybrids be extended to non-local populations. Altogether this would represent a substantial step forward to preserve A. rufa as well as other game species subjected to similar intensive management.  相似文献   
86.
87.
Highly pathogenic avian influenza (HPAI) viruses of the H5 and H7 subtype pose a major public health threat due to their capacity to cross the species barrier and infect mammals, for example dogs, cats and humans. In the present study we tested the capacity of selected H7 and H5 HPAI viruses to infect and to be transmitted from infected BALB/c mice to contact sentinels. Previous experiments have shown that viruses belonging to both H5 and H7 subtypes replicate in the respiratory tract and central nervous system of experimentally infected mice. In this study we show that selected H7N1 and H5N1 HPAI viruses can be transmitted from mouse-to-mouse by direct contact, and that in experimentally infected animals they exhibit a different pattern of replication and transmission. Our results can be considered as a starting point for transmission experiments involving other influenza A viruses with α 2-3 receptor affinity in order to better understand the viral factors influencing transmissibility of these viruses in selected mammalian species.  相似文献   
88.
The antimicrobial activity of leaf and callus extracts of Melia azedarach was tested on in vitro shoot cultures of the peach rootstoch ‘MRS 2/5’ (Prunus cerasifera × Prunus spinosa) that were heavily contaminated with Sphingomonas paucimobilis (Sp) and Bacillus circulans (Bc). The extracts were filter-sterilised and added at 0%, 1%, 5%, 10% and 20% to a modified Murashige and Skoog proliferation medium previously autoclave-sterilised. Up to about 17% shoots died with 10–20% extract, except for Sp-contaminated shoots, whose survival was reduced to 50% after treatment with 20% extract. No shoots died with 1% to 5% supplement. The undiluted leaf extract showed bactericidal activity on plated Sp and Bc isolates. The homogenates of shoots randomly collected from treated cultures were processed for bacterial colony counting. Thus the 10% supplement was the best treatment for ridding Bc-contaminated cultures of bacteria (although 5% had a similar bactericidal effect), and allowing shoot growth and proliferation comparable to controls at the fifth subculture on a standard medium, while 20% extract was needed to eliminate Sp, and could induce higher growth and proliferation rates in surviving shoots than in untreated cultures. Callus extract was ineffective. The bactericidal activity of the leaf extract seemed attributable to a synergistic effect of azadirachtin with other unidentified compounds present in the extract.  相似文献   
89.
ABSTRACT Contamination of apples (Malus domestica) and derived juices with fungicide residues and patulin produced by Penicillium expansum are major issues of food safety. Biocontrol agents represent an alternative or supplement to chemicals for disease control. Our data show that these microbes could also contribute to actively decreasing patulin accumulation in apples. Three biocontrol agents, Rhodotorula glutinis LS11, Cryptococcus laurentii LS28, and Aureobasidium pullulans LS30, were examined for their in vitro growth in the presence of patulin and for their capability to decrease mycotoxin recovery from the medium. Strain LS11 yielded the highest growth rates and the greatest decrease of toxin recoveries. Further, it caused the appearance of two major spots on thin-layer chromatography (TLC) plates, suggesting possible metabolization of the mycotoxin. In vivo, i.e., in the low percentage of LS11-pretreated apples infected by P. expansum, patulin accumulation was significantly lower than in nontreated infected fruits. Yeast cells survived and increased in infected apples and, in a model system emulating decaying apple, resulted in accelerated breakdown of patulin and the production of the same TLC spots as those detected in vitro. These data suggest that biocontrol yeast cells surviving in decaying apples could metabolize patulin and/or negatively affect its accumulation or synthesis. To our knowledge, this is the first report describing the effect of a biocontrol agent on patulin accumulation in vivo.  相似文献   
90.
Isolation and identification of mycobacteria from captive reptiles   总被引:1,自引:0,他引:1  
The occurrence of Mycobacterium species in clinically healthy pet reptiles was studied in Italy during the period 2004-2006. The feces samples of 223 animals were examined bacteriologically. Thirty-seven strains were isolated, in particular from 13/18 (72.2%) ophidians, 13/134 (9.7%) saurians and 11/71 (15.5%) chelonians. The isolates were classified, after HPLC analysis of bromophenacyl esters of cell wall mycolic acids, as Mycobacterium fortuitum (14 strains, 37.8%), Mycobacterium fortuitum-like (17, 45.9%), Mycobacterium peregrinum (4, 10.8%), and Mycobacterium chelonae (1, 2.7%). M. fortuitum was isolated from seven pythons, five saurians and two turtles; M. fortuitum-like from six saurians, six pythons and five turtles; M. peregrinum from four turtles; M. chelonae from one lizard. One isolate from an Iguana iguana could not be identified by HPLC analysis showing a previously unreported profile. Comparative 16S rDNA sequencing showed a low similarity with Mycobacterium triviale (97.2%) and Mycobacterium confluentis (97.1%). On the basis of such data the unidentified bacterium turned out to belong to a not yet described Mycobacterium species.  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