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   191篇
  免费   7篇
林业   18篇
农学   12篇
基础科学   5篇
  38篇
综合类   12篇
农作物   12篇
水产渔业   10篇
畜牧兽医   56篇
园艺   10篇
植物保护   25篇
  2022年   5篇
  2021年   13篇
  2020年   8篇
  2019年   15篇
  2018年   9篇
  2017年   14篇
  2016年   9篇
  2015年   6篇
  2014年   3篇
  2013年   8篇
  2012年   15篇
  2011年   17篇
  2010年   15篇
  2009年   7篇
  2008年   10篇
  2007年   7篇
  2006年   6篇
  2005年   10篇
  2004年   9篇
  2003年   7篇
  2001年   3篇
  1998年   1篇
  1991年   1篇
排序方式: 共有198条查询结果,搜索用时 125 毫秒
51.
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   
52.
Journal of Soils and Sediments - Loess in Northern Italy has been usually considered deposited during the MIS 4-2 period, which corresponds to the last Pleistocene glacial cycle. In particular, no...  相似文献   
53.
Sucrose is the economic product from sugar beet. Disease resistance is often available in low-sucrose genotypes and, prior to the deployment of such novel genes as available into the cultivated spectrum, selection for increased sucrose content is required during introgression. The objective of this work was to evaluate a relatively rapid and inexpensive enzymatic-fluorometric microtiter plate assay for sucrose quantification in sugar beet root dry matter, both for progeny testing in the greenhouse and for evaluation of field-grown mother roots. As determined using HPLC, sucrose content in diverse populations of sugar and table beet assayed over various developmental stages ranged from 0.213 to 2.416 mmol g(-1) of dry matter, and these values were used as references for both refractometry and enzymatic-fluorometric assay. As expected, refractometric analysis generally overestimated sucrose content. Enzymatic-fluorometric analyses were reasonably well correlated with HPLC results for young greenhouse-grown root tissues (R2 = 0.976), and less so with older field-grown roots (R2 = 0.605), for unknown reasons. Enzymatic-fluorometric assays may be best deployed for progeny testing of young seedlings.  相似文献   
54.
Seven sediment cores were collected along a transect about20 km off from the mouth of the Po River, in the northernAdriatic Sea (Italy). Cores were characterised by differentdepositional sequences associated with late Pleistocene-Holocene lowstand (LST), transgressive (TST) and highstand (HST) system tracts. Sediment samples were analysed for mercury, copper, nickel, chromium, manganese and iron, aswell as for total organic matter. Metal distributiongenerally showed vertical and spatial variability ascribed tograin size effects with no significant anthropogenicperturbation. Conversely, mercury showed vertical profilescharacterised by surface enrichment, with concentrations inthe upper layer (50–230 ng g-1) exceeding 3–11 times the background value of 20 ng g-1 determined in bottomcores. Surface maxima were attributed to anthropogenic mercurydelivered mainly by the Po River.  相似文献   
55.
In 2011, Trypanosoma equiperdum reemerged in Italy, almost 10 years after its last appearance. A total of eight infected horses have been observed to date. Six horses were affected by natural outbreaks of the disease, whereas two were infected experimentally. The aim of this study was to offer a recent perspective on clinical cases of dourine in Europe. Investigation of the clinical aspects confirmed the three stages reported in the literature: stage 1 (genital lesions), stage 2 (cutaneous signs), and stage 3 (nervous signs). The most common signs in the horses under study were notable weight loss, edematous skin eruptions and oedemas of the abdomen, mammary glands and hind legs. Three animals presented neurological signs (lip ptosis of lower lip and ataxia). Infections were paucisymptomatic or asymptomatic in some animals. Hyperthermia was not reported in infected animals and considerable anemia was observed. High antibody titers did not always correspond to clinical signs. Positive polymerase chain reaction test results of blood or tissue (skin, eye swab) often correspond to an advanced stage of the disease. Dourine is a variable disease; owing to its low prevalence and chronic manifestation, it can be difficult to make a quick diagnosis when facing a Dourine-positive horse.  相似文献   
56.
Forests near the Mediterranean coast have been shaped by millennia of human disturbance. Consequently, ecological studies relying on modern observations or historical records may have difficulty assessing natural vegetation dynamics under current and future climate. We combined a sedimentary pollen record from Lago di Massacciucoli, Tuscany, Italy with simulations from the LandClim dynamic vegetation model to determine what vegetation preceded intense human disturbance, how past changes in vegetation relate to fire and browsing, and the potential of an extinct vegetation type under present climate. We simulated vegetation dynamics near Lago di Massaciucoli for the last 7,000 years using a local chironomid-inferred temperature reconstruction with combinations of three fire regimes (small infrequent, large infrequent, small frequent) and three browsing intensities (no browsing, light browsing, and moderate browsing), and compared model output to pollen data. Simulations with low disturbance support pollen-inferred evidence for a mixed forest dominated by Quercus ilex (a Mediterranean species) and Abies alba (a montane species). Whereas pollen data record the collapse of A. alba after 6000 cal yr bp, simulated populations expanded with declining summer temperatures during the late Holocene. Simulations with increased fire and browsing are consistent with evidence for expansion by deciduous species after A. alba collapsed. According to our combined paleo-environmental and modeling evidence, mixed Q. ilex and A. alba forests remain possible with current climate and limited disturbance, and provide a viable management objective for ecosystems near the Mediterranean coast and in regions that are expected to experience a mediterranean-type climate in the future.  相似文献   
57.
Nitrate contamination of groundwater represents a threat to human health. Many researchers have studied zerovalent iron as a mean to remediate nitrate contamination. However, the application of such method is limited by ammonium production. This work investigates the use of microscale iron particles in association with zeolitite, a natural material containing zeolite, to remove nitrate and ammonium from groundwater. The association of the two materials is shown to lower the nitrate concentration in both deionized water and groundwater under the limit suggested by the European Union and to significantly reduce the ammonium concentration. The method is potentially applicable in water filtration.  相似文献   
58.
59.
Bioassay-guided fractionation of the EtOAc crude extract from Sicilian almond hulls, a waste material from Prunus dulcis crop, allowed identification of 10 constituents, isolated as pure compounds (1-5, 7, and 10) or unseparable mixtures (5 + 6 and 8 + 9). All compounds were subjected to spectroscopic analysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide bioassay on MCF-7 human breast cancer cells. In addition to the main components oleanolic (1), ursolic (2), and betulinic (3) acids, the 2-hydroxy analogues alphitolic (4), corosolic (5), and maslinic (6) acids, as well as the related aldehydes, namely, betulinic (7), oleanolic (8), and ursolic (9), were identified. From a more polar fraction, the beta-sitosterol 3-O-glucoside (10) was also identified. A sample of commercially available betulin (11) was also included in bioassays as further support to a structure-activity relationship study. Betulinic acid showed antiproliferative activity toward MCF-7 cells (GI50 = 0.27 microM), higher than the anticancer drug 5-fluorouracil.  相似文献   
60.
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