全文获取类型
收费全文 | 218篇 |
免费 | 11篇 |
专业分类
林业 | 9篇 |
农学 | 5篇 |
基础科学 | 2篇 |
37篇 | |
综合类 | 18篇 |
农作物 | 4篇 |
水产渔业 | 38篇 |
畜牧兽医 | 96篇 |
园艺 | 7篇 |
植物保护 | 13篇 |
出版年
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
排序方式: 共有229条查询结果,搜索用时 15 毫秒
1.
2.
Mads Christoffersen Jon C. Svendsen Jane W. Behrens Niels Jepsen Mikael van Deurs 《Fisheries Management and Ecology》2019,26(2):172-182
In just two decades, round goby Neogobius melanostomus (Pallas) has dispersed throughout most of the Baltic and the North American Great Lakes. It thrives in shallow sheltered areas, where it is impacting native fauna. In Denmark, researchers, governmental institutions and fishers have joined in an effort to establish a sustainable round goby fishery. To do so, basic information about the movement of round goby is essential, so the movements of 50 round gobies were tracked using acoustic telemetry. The results revealed that activity took place mainly at night and seasonal migrations were common. The most frequent migration behaviour observed was a seaward return migration during winter, which was further confirmed by a snorkel survey. Tracking data also revealed riverine upstream dispersal. The results demonstrate that the round goby can be mapped using telemetry, and it is suggested that fishing for round goby may improve efficiency by targeting seasonal migration corridors. 相似文献
3.
Sigríur Gumundsdttir Niccol Vendramin Argelia Cuenca Heia Sigurardttir Arni Kristmundsson Tine Moesgaard Iburg Niels Jrgen Olesen 《Journal of fish diseases》2019,42(1):47-62
A novel viral haemorrhagic septicaemia virus (VHSV) of genotype IV was isolated from wild lumpfish (Cyclopterus lumpus), brought to a land‐based farm in Iceland, to serve as broodfish. Two groups of lumpfish juveniles, kept in tanks in the same facility, got infected. The virus isolated was identified as VHSV by ELISA and real‐time RT‐PCR. Phylogenetic analysis, based on the glycoprotein (G) gene sequences, may indicate a novel subgroup of VHSV genotype IV. In controlled laboratory exposure studies with this new isolate, there was 3% survival in the I.P. injection challenged group while there was 90% survival in the immersion group. VHSV was not re‐isolated from fish challenged by immersion. In a cohabitation trial, lumpfish infected I.P. (shedders) were placed in tanks with naïve lumpfish as well as naïve Atlantic salmon (Salmo salar L.). 10% of the lumpfish shedders and 43%–50% of the cohabiting lumpfish survived after 4 weeks. 80%–92% of the Atlantic salmon survived, but no viral RNA was detected by real‐time RT‐PCR nor VHSV was isolated from Atlantic salmon. This is the first isolation of a notifiable virus in Iceland and the first report of VHSV of genotype IV in European waters. 相似文献
4.
Niccol Vendramin Argelia Cuenca Juliane Srensen Anna L. F. Alencar Debes H. Christiansen Jan A. Jacobsen Charlotte Axen Franois Lieffrig Neil M. Ruane Patrick Martin Timothy Sheehan Tine M. Iburg Espen Rimstad Niels J. Olesen 《Journal of fish diseases》2019,42(8):1107-1118
Piscine orthoreovirus genotype 1 (PRV‐1) is widespread in farmed Atlantic salmon (Salmo salar L.) populations in northern Europe, Canada and Chile. PRV‐1 occurs in wild fish in Norway and Canada; however, little information of its geographical distribution in wild populations is currently available, and the effect of PRV‐1 infection in wild populations is currently unknown. In this study, we present the findings of a survey conducted on 1,130 wild salmonids sampled in Denmark, Sweden, Ireland, Faroe Islands, France, Belgium and Greenland between 2008 and 2017. PRV‐1 is reported for the first time in wild salmonids in Denmark, Sweden, Faroe Island and Ireland. The annual PRV‐1 prevalence ranged from 0% in France, Belgium and Greenland to 43% in Faroe Islands. In total, 66 samples tested positive for PRV‐1, including Atlantic salmon broodfish returning to spawn and Atlantic salmon collected at the feeding ground north of Faroe Islands. The phylogenetic analysis of S1 sequences of the PRV‐1 isolates obtained in this survey did not show systematic geographical distribution. This study sheds light on the spread and genetic diversity of the virus identified in populations of free‐living fish and provides rationale for screening wild broodfish used in restocking programmes. 相似文献
5.
A method for mapping potentially acid sulfate soils in Jutland, Denmark is described. First the wetlands were outlined, using already existing topographic maps. Then 7900 profiles, evenly distributed over the wetland areas, were examined to point out areas with potentially acid sulfate soils. The method used to identify potentially acid sulfate material was, for carbonate-free samples, a pH-measuring at the sampling time and after the samples were inoculated with soil water extract from an acid sulfate soil and 2, 8 or 16 weeks of incubation. For carbonate-containing samples the pyrite content was compared to the acid-neutralizing capacity. A map was constructed showing the ratio of profiles containing potentially acid sulfate soil samples to total number of profiles examined within natural geographical wetland regions.The investigation showed that 35% of the wetlands in Jutland have a high frequency of potentially acid sulfate soils. 相似文献
6.
The effect of land use (forest and grassland) on the deposition and mobility of Pb and Cd has been studied by extraction with 1M HCl, 1M NH4Ac/HAc and 1M NH4Ac. The soils were described pedologically and the main physical and chemical parameters were determined. The Pb concentration in the A horizon is higher in the profile under forest than in the profile under grassland. We assign this difference to the filter action of the forest. The Cd concentration is highest in the grassland profile because the forest soil is more degraded and Cd is leached to a higher degree in this soil. Both metals are more mobile (easier to extract) in the forest because the forest soil is most acidic, and because a greater part is bound to organic compounds (humic and fulvic acids) which are more abundant in the forest than in the grassland. The concentrations of Pb and Cd in the A horizons are 26 ppm and 0.1 ppm under the forest and 9 ppm and 0.2 ppm under grassland, respectively. 相似文献
7.
Poulsen KA Young JF Theil P Kolko M Oksbjerg N Lambert IH 《Journal of agricultural and food chemistry》2007,55(5):1970-1976
The role of phospholipase A2 in the induction of drip loss from pig muscle has been investigated. In samples from porcine M. longissimus dorsi, total PLA2 activity as well as mRNA and protein levels of the group VIA iPLA2 (iPLA2-VIA) increased during the initial 4 h post-mortem period. Morphological studies of porcine muscle showed that at 4 h post-mortem, gaps had formed between muscle fibers and that the sarcolemma membrane borders appeared blurred. At the same time iPLA2-VIA protein levels were increased inside muscle fibers and at the sarcolemma. iPLA2-VIA mRNA abundance in samples from different breeds of pigs with variations in drip loss revealed no clear correlation between drip loss level and iPLA2-VIA expression. Together, these data indicate that during the post-mortem period, iPLA2-VIA expression and activity is increased at the muscle fiber membranes. PLA2 activity may affect membrane permeability and consequently the progression of drip formation in porcine muscle. 相似文献
8.
Hanne Christine Bertram Niels Bastian Kristensen Mogens Vestergaard Søren Krogh Jensen Jakob Sehested Niels Christian Nielsen Anders Malmendal 《Livestock Science》2009,120(1-2):127-134
The metabolic profile of calf rumen epithelial tissue was for the first time characterized by 1H NMR spectroscopy of chloroform/methanol extracts. The metabolite profiles comprised a number of amino acids, creatine, taurine, short-chain fatty acids and triglycerides. The effects of two dietary interventions; i) four levels of milk allowance with a concomitant different uptake of starter concentrate, and ii) two diets with varying content of starch and fibre in the concentrate, were elucidated. Partial least square regression analysis revealed that the intensity of NMR signals assigned to leucine, isoleucine and valine (0.90 ppm), propionate (1.06 and 2.18 ppm), lactate (1.32 ppm), butyrate (1.56 ppm), acetate (1.93 ppm), glutamine/glutamate (2.18, 2.35 and 3.75 ppm), creatine (3.04 and 3.94 ppm) and glycine (3.55 ppm) decreased with increasing milk allowance. In addition, the analysis revealed that the main difference between the two diets was the content of propionate in the epithelia tissue extracts. Previous morphological analyses of the same rumen epithelia were not able to detect any significant effects of either milk allowance or dietary starch content. Accordingly, the present study demonstrated that 1H NMR spectroscopy applied on extracts is a useful tool for metabolite profiling of epithelial tissue and for following the development of epithelia tissue in young calves, and that the technique may be more sensitive to dietary effects than morphological studies. 相似文献
9.
Petersen MA Hyldig G Strobel BW Henriksen NH Jørgensen NO 《Journal of agricultural and food chemistry》2011,59(23):12561-12568
Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs. 相似文献
10.
For control and enforcement purposes, all fishing vessels operating in European waters are equipped with satellite-based Vessel Monitoring by Satellite systems (VMS) recording their position at regular time intervals. VMS data are increasingly used by scientists to study spatial and temporal patterns of fishing activity and thus fishing impact (e.g. surface of sea bed trawled during a fishing trip). However, due to their low resolution (2 h basis), these data may provide a biased perception of fishing impact. We present here a method aiming at interpolating vessel trajectories from VMS data points to obtain higher-resolution data on vessel trajectories which in turn should provide improved estimates of the spatial and temporal patterns of fishing activity and hence fishing impact. This method is based on a spline interpolation technique, the cubic Hermite spline (cHs), using position, heading and speed to interpolate the trawl track of a vessel between two succeeding VMS data points. To take uncertainty of the interpolated track into account, the method also determines a confidence interval, which represents the spatial distribution of vessel presence probability between two successive VMS positions. The cHs method was compared to the straight line interpolation technique using a reference data set with intervals of 6 min which was assumed to represent the real trawl tracks. The results showed that the cHs method approximates the real trawl track markedly better than a straight line interpolation. The cHs method should therefore be preferred to the conventional straight line approach to interpolate vessel tracks in studies aiming at estimating fishing impact from VMS data. 相似文献