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   74篇
  免费   4篇
林业   5篇
农学   6篇
  22篇
综合类   5篇
水产渔业   8篇
畜牧兽医   32篇
  2023年   1篇
  2021年   1篇
  2020年   3篇
  2019年   3篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   4篇
  2012年   3篇
  2011年   10篇
  2010年   3篇
  2009年   9篇
  2008年   1篇
  2007年   3篇
  2006年   8篇
  2005年   7篇
  2004年   3篇
  2002年   1篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1991年   2篇
排序方式: 共有78条查询结果,搜索用时 31 毫秒
1.
Innate and acquired immune responses of Gilthead Seabream Sparus aurata was studied under normal culture and short-term stressful conditions for 18 months in offshore sea cages in Alghero Bay, Italy. Every 45 d, 50 fish were sampled and divided into two groups: fish in the first group (normal culture conditions) were bled after harvesting; fish in the second group were put into a tank under stressful conditions (crowding and confinement) and bled after 2 h. Innate humoral immunity, such as complement-like, hemagglutination, and lysozyme activities, was determined in the sera of both groups. Pathogen challenge was not performed, but the specific humoral immune response was assessed against the most common pathogens affecting cultured fish in Sardinia. Stressed fish, compared with the control, showed a lower lysozyme activity against Vibrio (Listonella) anguillarum, which was not clearly correlated with temperatures. Complement-like activity differed between the first and second half of the study and, at the end of the trial, a slightly higher activity was recorded in the controls than in the stressed fish. Hemagglutination activity was mainly higher in the stressed fish than in control fish. Confinement, crowding, and cold water temperature caused decreased lysozyme activity in short-term stressed Gilthead Seabream compared with those reared normally. The specific humoral immune response, against V. anguillarum, Tenacibaculum mesophilum, Enterococcus Seriolicida, and Aeromonas sobria, fluctuated during the rearing period, particularly during the first year of culture.

Received October 12, 2015; accepted March 24, 2016 Published online August 2, 2016  相似文献   

2.
3.
ABSTRACT:   Seawater fishes are affected by a pathology commonly called 'myxobacteriosis', caused by Tenacibaculum maritimum (formerly Flexibacter maritimus ). The disease is characterized by fin erosion and necrotic ulcers of skin and muscle, and by low but constant mortality in cultured marine fish; in Italy is one of the most important and widely spread diseases affecting sea bass Dicentrarchus labrax , gilthead seabream Sparus aurata , sharp-snouted bream Diplodus puntazzo , white bream Diplodus sargus , and six-tooted bream Dentex dentex . In order to obtain an effective vaccine against the disease, formalin killed cells (FKC), extracellular products (ECPs) and crude lipopolysaccharide (LPS) preparations were obtained from the T. maritimum strain SPVId and injected intraperitoneally twice into the sea bass. The fish immune response to the preparations was studied: agglutinating antibody titer and in vitro phagocytosis were determined after the first and second injection in order to evaluate whether the preparations are immunogenic or not and if the booster effect took place. The results show that FKC and LPS preparations increased the antibody titer after the first injection when compared to the control sea bass. Moreover, all the preparations stimulated a secondary (booster) response. In vitro phagocytosis of the total blood was significantly higher for all the preparations when compared to the controls, but the crude LPS immunized sea bass showed the highest activity.  相似文献   
4.
The objective was to study the effect of future harvesting and handling technologies on the cost and energy efficiency of supply chains for young dense thinnings. The system costs and energy requirements were modeled using type of stands, products delivered, and transport distances as variables. In total, 14 systems were analyzed, of which five represented future systems. The effects of increasing the payloads of off-road and road transportation of whole tree (WT) parts by 10%, 20%, and 30% were also analyzed. If boom-corridor thinning technologies, optimized bundle-harvesters, and load-compression devices are developed, on average, costs are reduced by 12–27% and 11–30% less energy is required when compared with present systems. For example, at an average harvested tree size of 22 dm3, the supply of WT using future technologies would reduce the cost by up to 15% and the energy requirements by 21%. These effects increase with reduced tree sizes and increased transportation distances. The effects of future technologies are especially significant for tree sizes below 30 dm3, representing a significant part of the potential that could be harvested annually in Sweden. Thus, there should be increased research and development of boom-corridor felling technology, bundle-harvesters, and load-compression devices.  相似文献   
5.
F. Pupilli    S. Arcioni  F. Damiani 《Plant Breeding》1991,106(2):122-131
Leaf mesophyll protoplasts of Medicago arborea (2n = 32) were electrofused with cell suspension and/or callus protoplasts of Medicago sativa. Heterokaryons were identified in agarose beds by their dual fluorescein isothiocianate—chlorophyll fluorescence and their coordinates were recorded. Hybrid minicalli were manually picked up and grown first in nurse culture and then in callus induction medium. Hybrid nature of the selected calli was confirmed by isoenzyme analyses. In order to verify whether morphogenesis of somatic hybrid calli was affected by cell incompatibility, mesophyll and cell suspension protoplasts, derived from the same plant of M. sativa with high embryogenic capacity, were fused. Only callus tissues derived from mesophyll protoplasts retained the highly embryogenic character of the M. sativa genotype, while hybrid cell lines were non-morphogenic and showed isoenzyme patterns similar to tissues derived from cell suspension protoplasts. The achievement of somatic hybrid plants in the genus Medicago is discussed.  相似文献   
6.
Postprandial hyperlipemia is a well-defined risk factor for atherosclerosis. A reasonable contributing mechanism could involve the postprandial increase of plasma lipid hydroperoxides (LPO) affecting the oxidant/antioxidant balance and increasing the susceptibility of LDL to oxidation. Wine has been shown to prevent both these events. The present study was designed to investigate the effect of supplementing a meal with grape seed proanthocyanidins (the main phenolic antioxidant of red wine) on plasma postprandial oxidative stress. In two different sessions, 8 healthy volunteers consumed the same test meal rich in oxidized and oxidizable lipids without (control) or with 300 mg of a proanthocyanidin-rich grape seeds extract (GSE). Lipid hydroperoxide concentration, antioxidant status, and LDL resistance to oxidative modification were measured in postprandial plasma. The content of LPO in chylomicrons was 1.5-fold higher after the control meal than after the GSE-supplemented meal. Plasma LPO increased only after consumption of the control meal. The plasma antioxidant capacity increased in the postprandial phase only following the GSE supplemented meal. LDL isolated 3 h after the control meal tended to be more susceptible to oxidative modification (but the difference did not reach statistical significance). An opposite trend was observed following the GSE supplemented meal. In conclusion, the supplementation of a meal with GSE minimizes the postprandial oxidative stress by decreasing the oxidants and increasing the antioxidant levels in plasma, and, as a consequence, enhancing the resistance to oxidative modification of LDL.  相似文献   
7.
Quantitation of polyphenols in different apple varieties   总被引:1,自引:0,他引:1  
Forty-one apple samples, representing eight of the most widely cultivated varieties in western Europe, were collected in Trentino, Italy. Samples were extracted from fresh fruit with a mixture of acetone/water to achieve a good extraction of polyphenols, including proanthocyanidin oligomers which were analyzed by normal-phase HPLC. Up to 20 compounds including catechin, epicatechin, B2 procyanidin, hydroxycinnamates, flavonols, anthocyanins, and dihydrochalcones were analyzed by reversed-phase HPLC and LC-MS. Total polyphenol content was independently measured with an optimized Folin-Ciocalteu assay. The mean content of total polyphenols lay between 66.2 and 211.9 mg/100 g of FW depending on the variety. With chromatographic analysis, it was possible to explain the whole amount of total polyphenols measured by the FC assay. Flavanols (catechin and proanthocyanidins) are the major class of apple polyphenols (71-90%), followed by hydroxycinnamates (4-18%), flavonols (1-11%), dihydrochalcones (2-6%), and in red apples anthocyanins (1-3%).  相似文献   
8.
Sequencing of 81 entire human mitochondrial DNAs (mtDNAs) belonging to haplogroups M1 and U6 reveals that these predominantly North African clades arose in southwestern Asia and moved together to Africa about 40,000 to 45,000 years ago. Their arrival temporally overlaps with the event(s) that led to the peopling of Europe by modern humans and was most likely the result of the same change in climate conditions that allowed humans to enter the Levant, opening the way to the colonization of both Europe and North Africa. Thus, the early Upper Palaeolithic population(s) carrying M1 and U6 did not return to Africa along the southern coastal route of the "out of Africa" exit, but from the Mediterranean area; and the North African Dabban and European Aurignacian industries derived from a common Levantine source.  相似文献   
9.
The effect of transportation on peripheral blood lymphocyte subsets in 24 calves was investigated by flow cytometry. Blood was collected before departure, on arrival, at 24h and 1 week after arrival. Highest leucocyte and neutrophil counts, associated with increased concentrations of cortisol and catecholamines, indicated that stress was maximal upon arrival. At this time, a decrease in the percentages of all T lymphocyte subsets was evident, while they did not decrease as absolute counts. The proportion of CD21(+) cells did not change, indicating that the relative reduction of T lymphocyte subsets was not related to an increase in B lymphocytes. These variations may be due to the increase of a natural killer (NK) cell subset. NK cell expansion, together with increasing lymphocyte count and increasing major histocompatibility complex class II expression, may indicate stress-induced stimulation of the immune system.  相似文献   
10.
The chromosomes of sexual diploid plants of Paspalum simplex were colchicine-doubled and the plant obtained were crossed with their aposporous natural tetraploid counterparts to generate a F1 population segregating for apomixis. Analysis of the DNA content during megagametogenesis indicated that although the nuclei of nucellus and developing embryo sacs were in both the G1 and G2 phases, polar nuclei and egg cells of mature embryo sacs tended to remain in the G1 phase. Because both meiotic and aposporous mature embryo sacs are of the 8-nucleated-type in P. simplex and are barely distinguishable, nuclear DNA content of polar nuclei was used to distinguish apomictic and sexual phenotypes and confirmation obtained by progeny testing. This revised version was published online in August 2006 with corrections to the Cover Date.  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