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   65篇
  免费   2篇
农学   19篇
  16篇
综合类   1篇
水产渔业   5篇
畜牧兽医   16篇
园艺   4篇
植物保护   6篇
  2021年   1篇
  2020年   1篇
  2018年   1篇
  2017年   1篇
  2015年   3篇
  2013年   1篇
  2012年   5篇
  2011年   8篇
  2010年   2篇
  2009年   4篇
  2008年   6篇
  2007年   7篇
  2006年   5篇
  2005年   1篇
  2004年   2篇
  2003年   4篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1991年   1篇
  1989年   1篇
排序方式: 共有67条查询结果,搜索用时 0 毫秒
21.
The ancient Mexicas, established in the southern and central parts of Mexico at the time of Spanish arrival, used a great variety of minor vegetables, cultivated or collected from the wild. Written sources produced at this time, general reports and pictorial codices that referred to some extent to plants, provide valuable information on the cultivation or collection and use of these minor crops. Some aromatic vegetables were highly esteemed as desserts or condiments. Many of them possess similar properties to other condiments commonly used in the European pharmacopoeia in the 15th–16th Century. These American plants belong to different genera as compared to Eurasian condiments. We have found references to coriander-like condiments (Porophyllum, Cuphea, Arracacia), fennel or anise-like condiments (Piper, Rhodosciadium), cress or water-cress-like condiments (Tropaeolum, Lepidium, Hydrocotyle), horehound-like condiments (Salvia-Hyptis), and some aromatic chenopods. The historic and current utilizations of these plants are presented. Most of them are still collected from the wild, or occasionally cultivated to be used as condiments or for their medicinal properties. Some have the potential to be developed as food or industrial resources.  相似文献   
22.
  1. Historically, the Mediterranean Sea supported a rich shark fauna. Presently, however, populations of most shark species have significantly declined, largely due to intense fishing pressure.
  2. Interviews with crew members of bottom trawlers, drifting longliners and bottom longliners operating off the Costa Brava (Catalonia, NE Spain) were conducted between October 2016 and July 2017 in order to gather information on the current bycatch rate of several shark species.
  3. Interviews covered 41.2% of the fleet and respondents were asked for the bycatch of selected shark species—Alopias vulpinus, Cetorhinus maximus, Galeorhinus galeus, Hexanchus griseus, Isurus oxyrinchus, Mustelus spp., Prionace glauca, and Squalus acanthias—in two distinct time periods.
  4. Bottom trawlers captured the highest diversity of species (eight) followed by bottom longliners (seven), and drifting longliners (three). Most respondents (89.7%) declared having captured at least one shark from 2006 to 2016 but only 56.4% declared having captured at least one shark from 2016 to 2017.
  5. From 2016 to 2017, the whole fleet captured 89 specimens of H. griseus (95% confidence interval (CI) = 145, 34), 14 of G. galeus (95% CI = 30, 0), 3 of A. vulpinus (95% CI = 8, 0), 3 of I. oxyrinchus (95% CI = 8, 0), 3 of C. maximus (95% CI = 6, 0), and no Mustelus spp. The total bycatch of P. glauca and S. acanthias was uncertain due to extremely loose confidence intervals.
  6. A significant decline was perceived by fishermen in the bycatch of C. maximus and S. acanthias, whereas the bycatch of H. griseus was considered to have remained stable.
  7. This study suggests a dramatic reduction in the abundance of most of the medium-sized and large sharks of the Costa Brava and the likely disappearance of Mustelus spp. from the area. Only H. griseus, S. acanthias, and P. glauca are still being bycaught frequently.
  相似文献   
23.
S. Roselló    S. Soler    M. J. Díez    J. L. Rambla    C. Richarte  F. Nuez 《Plant Breeding》1999,118(5):425-429
Mechanical inoculation and transmission by thrips in a growth chamber were used in order to screen Lycopersicon peruvianumand Lycopersicon chilense germplasm for tomato spotted wilt virus (TSWV) resistance. Two highly aggressive Spanish TSWV isolates (HA-931100 and T-941117), having different restrictotypes were used. L. peruvianum accessions PI-126935, PI-126944, CIAPAN 16, PE-18 and CIAPAN 17 showed high resistance to both isolates in mechanical and thrips transmission. Their resistance appears useful in breeding programmes.  相似文献   
24.
Developing tomato breeding lines resistant to tomato yellow leaf curl virus   总被引:1,自引:0,他引:1  
Using controlled whitefly-mediated inoculation techniques, seven Lycopersicon chilense accessions, highly resistant to isolates of tomato yellow leaf curl virus(TYLCV) from Southern Europe, TYLCV-Sr, were selected. All exhibited similar levels of partial resistance, being symptomless and with low levels of viral DNA accumulation. However, a differential response to infection was found in interspecific hybrids with tomato and inbred lines derived from different L. chilense accessions, allowing a precise discrimination among them. This selection procedure which considers the expression of the resistance genes in the tomato genetic background led to the selection of two highly resistant F1 hybrids derived from L. chilense LA 1932 and LA 1938. A backcrossing programme was initiated, selecting for horticultural characteristics and TYLCV resistance, in field and controlled inoculation conditions. As a result of this programme, six advanced breeding lines (UPV Ty 1, 3, 6, 9, 17 and 53), exhibiting a high level of resistance to TYLCV-Sr, were obtained. Under high inoculum pressure conditions these lines suffered only 30-40% yield loss relative to non-infected control plants, and compared with 90-95% yield loss in susceptible controls. These lines also have horticultural characteristics appropriate for the fresh market tomato cultivation system in this area, and are a good base material for obtaining commercial hybrids highly resistant to different isolates of TYLCV.  相似文献   
25.
In 2001 a new Pestivirus (Family Flaviviridae) was associated with an outbreak of a previously unreported disease in Pyrenean chamois (Rupicapra pyrenaica) in the Pyrenees (NE Spain). Molecular characterization assigned this virus to the Border Disease Virus (BDV) cluster, BDV-4 genotype. A retrospective study was performed in archived sera and spleen of 74 Pyrenean chamois and in archived sera of 28 mouflon (Ovis ammon), 56 red deer (Cervus elaphus), 43 roe deer (Capreolus capreolus) and 29 fallow deer (Dama dama) from the Pyrenees between the years 1990 and 2000. Thirty six of 74 (48.6%) sera of Pyrenean chamois, one of mouflon and one of red deer were positive by an ELISA antibody test. Comparative virus neutralization tests were performed on 26 seropositive chamois, one mouflon and one red deer, using five pestivirus strains. An ELISA antigen test was performed on 37 seronegative chamois and yielded positive results in one chamois and inconclusive result in two. RT-PCR and virus isolation performed on spleen samples from these three animals gave positive results in the positive and one inconclusive animal. Sequence analysis in the 5' unstranslated region revealed that they were grouped into the BDV-4 genotype. Virological and serological data of the present study indicate that BDV infection has been present in the chamois population since at least 1990, 11 years before the first outbreak of disease. Therefore, the emergence of the disease in 2001 is apparently due to other factors rather than the introduction of a new virus in the chamois population.  相似文献   
26.
    
The Capsicum genus is native to tropical America and consists of 27 species, five of which are used as fresh vegetables and spices: Capsicum annuum L., Capsicum chinense Jacq., Capsicum frutescens L., Capsicum baccatum L. and Capsicum pubescens R. et P. The study of the relationships among species of cultivate Capsicum species will be useful for breeding new cultivars or hybrids. This study is focused on the genetic diversity and relationships of these species that were collected in the Andean region. Ten microsatellites and four AFLP combinations were used to characterize 260 Capsicum accessions. The AFLP tree turned out to be informative regarding relationships among species. The data clearly showed the close relationships between C. chinense and C. frutescens. Moreover, C. cardenasii and C. eximium were indistinguishable as a single, morphologically variable species. Our data showed C. baccatum and C. praetermissum to be distinct species that form a compact group. In the present work, AFLP fingerprinting indicated that C. chacoense was placed in the C. baccatum complex and showed C. tovarii as a separate species. In addition, SSR data indicated that there is intraspecific differentiation in the species C. chinense, C. baccatum and C. pubescens, as the PCoA-based clustering showed a clear geographic division related to country. Even though Bolivia is considered to be the nuclear area for these species, we have found similar variability in Ecuador and Peru for several Capsicum species.  相似文献   
27.
The greatest extent of genetic variation and outcrossing for Lycopersicon pimpinellifolium occurs in northern Peru. This is also the area most affected by EI Niño Southern Oscillation (ENSO). Using morphological and the molecular markers SSRs and AFLPs, we studied the genetic structure of L. pimpinellifolium populations collected after the ENSO event of 1997–1998. This was the most intense in the last century and caused a vast increase in the size of L. pimpinellifolium populations. Populations in the area surveyed were not regionally differentiated. We did not find any cline or eco-geographic association for genetic diversity, and positive correlations between genetic and geographic distances were found only at very short distances. Flooding and water streams caused by ENSO might have facilitated a periodical seed migration from distant areas. Gene flow between populations could then occur, facilitated by the increase in the population sizes of plants and pollinators and by the high levels of stigmatic exsertion. Results revealed a significant lack of heterozygotes in comparison with those expected in a panmictic population without consanguinity. A high degree of endogamy was found in all populations. In this context, endogamy can be explained by the occurrence of crosses between relatives rather than by autogamy. In an area intensely disturbed by ENSO, we found a population that had not been reported by earlier collectors in this region. This yellow-fruited population remained morphologically and molecularly differentiated from all L. pimpinellifolium and L. esculentum populations analyzed.  相似文献   
28.
    
Chamois have been translocated for more than 100 years but their stress response to transport remains to be elucidated. In this study, 21 free-ranging Southern chamois were captured, physically restrained and then transported. The animals were randomly injected intramuscularly with acepromazine (nine adult males, one adult female and one yearling male) or saline (five adult males, two adult females and three yearling males). Heart rate and body temperature were monitored with telemetric devices, and blood samples were obtained at capture, immediately before and immediately after transport to determine haematological and serum biochemical parameters. Heart rate and blood parameters (erythrocytes, haemoglobin, packed cell volume, leukocytes, monocytes, band neutrophils, lactate, muscular enzymes and creatinine) indicated that transport was more stressful than previous physical restraint. Acepromazine reduced the adverse consequences of transport stress, as demonstrated by heart rate, body temperature, cortisol, creatinine, muscular enzymes, urea, sodium and potassium.  相似文献   
29.
    
The aim of this study was to identify ultrasound accessible blood vessels in the loggerhead sea turtle (Caretta caretta) and describe their Doppler waveform patterns, peak systolic velocity, mean velocity, systolic/diastolic ratio as well as pulsatility and resistive indices. B-mode, colour and pulsed-wave Doppler examinations were performed on 10 turtles. Flow measurements were recorded for the left and right aorta, epigastric and internal iliac arteries, and right hepatic vein. Additionally, the large blood vessels of three dead turtles were injected with latex and dissected for anatomical support. A parabolic flow velocity profile was observed in all arteries. The waveforms of the right and left aortic arteries showed an unusual pattern when compared with mammals. The hepatic vein flow velocity waveform of the loggerhead sea turtle was found to be similar to that in the dog, although the flow velocity in the C-wave was higher than that in the A-wave. The low resistance flow pattern observed suggests that the loggerhead sea turtle's organs require a continuous blood supply.  相似文献   
30.
Following consumer complaints about the quality of modern varieties of tomato, landraces have strengthened their quality markets. In Spain, two tomato landraces, ‘Montserrat’ and ‘Pera Girona’, are grown in contiguous areas and have different market niches. We used amplified fragment length polymorphism (AFLP) to characterize 13 accessions of Montserrat, 14 accessions of Pera Girona, and 4 control varieties. We found a narrow genetic base for ‘Montserrat’ and ‘Pera Girona’ (8.5% of polymorphic loci) and no differences between the landraces. We studied agronomical and sensory traits to determine why the two landraces continue to have separate market niches. We found high variability among accessions within each landrace and overlapping among accessions of both landraces for all traits except fruit morphology. Consumers probably came to associate the organoleptic quality of these landraces with their external traits, but due to spontaneous crossings and introgressions these relations have been lost. Selection within landraces will be necessary to reestablish the link between morphology and sensory value and to consolidate these quality markets.  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