全文获取类型
收费全文 | 459篇 |
免费 | 27篇 |
专业分类
林业 | 35篇 |
农学 | 27篇 |
84篇 | |
综合类 | 41篇 |
农作物 | 24篇 |
水产渔业 | 74篇 |
畜牧兽医 | 177篇 |
园艺 | 9篇 |
植物保护 | 15篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 3篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 19篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 35篇 |
2012年 | 36篇 |
2011年 | 26篇 |
2010年 | 22篇 |
2009年 | 8篇 |
2008年 | 20篇 |
2007年 | 20篇 |
2006年 | 25篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 23篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1966年 | 3篇 |
1958年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有486条查询结果,搜索用时 15 毫秒
481.
Eva Blixt Åke Olson Björn Lindahl Annika Djurle Jonathan Yuen 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(3):373-386
The fungal communities on wheat leaves showing symptoms similar to stagonospora nodorum blotch were analysed using terminal
restriction fragment length polymorphism (T-RFLP). Collection of diseased leaves was carried out in eleven winter wheat fields
located in three regions of Sweden during mid-July in 2003–2005. Fourteen different fungal species were found on the leaves
out of which thirteen were identified to the species level and one to the genus level. The majority of the samples had between
one and four species present of which at least one was a pathogen. Among the analysed leaves three major leaf pathogens were
found: Phaeosphaeria nodorum was common during 2003 and 2004, Mycosphaerella graminicola dominated during 2005. Pyrenophora tritici-repentis was present in all fields, but sometimes in just a few samples. Phaeosphaeria nodorum and P. tritici-repentis often co-occurred on the same leaf. In addition, seven species of yeast and three saprophytes frequently occurred on the
leaves every year. The variation in fungal community was largest between the different years while the region of Uppland diverged
from the other two regions in species composition. No significant differences in fungal communities were found within a single
field, indicating a uniform community at the lowest spatial level. 相似文献
482.
Trond Bjørndal Amalie Tusvik 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):449-475
AbstractLand-based farming of salmon is emerging for a number of reasons. The demand for salmon is increasing in many parts of the world. In recent years there has been limited growth in production due to binding government regulations and environmental challenges in sea-based salmon aquaculture. This is true both for Norway (sea lice, salmon escapes) and Chile (sea lice, disease problems), the two largest producers of salmon. Growing demand and limited expansion in production have made for a very profitable industry. At the same time, there have been technological developments when it comes to land-based farming (a technology used for smolt production and species such as sole and turbot), and cost of production has changed. Currently, land-based salmon farming is in operation or in development in several countries including the USA, Denmark, and Norway. In this paper, the economics of land-based salmon farming in a Norwegian context is presented, with an emphasis on the relative competitiveness of this vis-à-vis sea-based farming. If successful, land-based farming could potentially have an important impact on the dynamics of the salmon market. 相似文献
483.
Trond Bjørndal 《Aquaculture Economics & Management (Blackwell Science)》2013,17(1-2):97-116
Abstract Commercial salmon and trout farming has emerged as a major industry in Chile during the 1990s. Salmon is not a native species to Chile, still excellent climatic conditions are provided for farming. Since 1992 Chile has been the second largest producer of farmed salmon and trout in the world after Norway. This report reviews the development of the Chilean salmonid industry from its early stages until today with respect to production patterns, legislation and main markets. A cost comparison between Chilean and Norwegian farmed salmon is also provided. Finally, the international competitiveness and future challenges of the Chilean salmonid farming industry are analysed. 相似文献
484.
Injuries and deformities in fish: their potential impacts upon aquacultural production and welfare 总被引:1,自引:0,他引:1
Noble C Jones HA Damsgård B Flood MJ Midling KØ Roque A Sæther BS Cottee SY 《Fish physiology and biochemistry》2012,38(1):61-83
Fish can be the recipients of numerous injuries that are potentially deleterious to aquacultural production performance and
welfare. This review will employ a systematic approach that classifies injuries in relation to specific anatomical areas of
the fish and will evaluate the effects of injury upon production and welfare. The selected areas include the (1) mouth, (2)
eye, (3) epidermis and (4) fins. These areas cover a large number of external anatomical features that can be injured during
aquacultural procedures and husbandry practices. In particular, these injuries can be diagnosed on live fish, in a farm environment.
For each anatomical feature, this review addresses (a) its structure and function and (b) defines key injuries that can affect
the fish from a production and a welfare perspective. Particular attention is then given to (c) defining known and potential
aquacultural risk factors before (d) identifying and outlining potential short- and long-term farming practices and mitigation
strategies to reduce the incidence and prevalence of these injuries. The review then concludes with an analysis of potential
synergies between risk factors the type of injury, in addition to identifying potential synergies in mitigation strategies.
The paper covers both aquaculture and capture-based aquaculture. 相似文献
485.
Sten Ivar Siikavuopio Rune Knudsen Per Arne Amundsen Bjørn Steinar Sæther Philip James 《Aquaculture Research》2012,44(1):8-12
The effect of three different temperatures on growth in a first progeny generation, hatchery reared, subarctic population of European whitefish (Coregonus lavaretus L.) were investigated. The whitefish (start weight 444 g, ±SD 125 g) were reared for 60 days at three constant temperatures; 15, 18 and 21°C and under ambient light regimes for 70°N latitude. The results showed that temperature had a significant influence on the growth of the fish with the highest increase in weight increment occurring at 18°C (mean final weight 656 g ± SD 151 g) compared with the growth of fish held at 15°C (mean final weight 591 g ± SD 143 g) and 21°C (mean final weight 505 g ± SD 121 g). The cumulative per cent mortality of the fish during the experimental period increased with increasing temperature, from 10% at 15°C to 30% at 21°C. The present study indicates that the optimal temperature for farming of European whitefish is somewhere between 15 and 18°C rather than between 18 and 21°C. 相似文献
486.
Petra Griekspoor Eva Olsson Engvall Björn Olsen Jonas Waldenström 《Veterinary microbiology》2010,140(1-2):180-185
Campylobacter jejuni isolates from a national Swedish Campylobacter monitoring in broilers were characterized by multilocus sequencing typing (MLST) in order to study the genetic diversity of this bacterial population. Isolates were initially characterized by pulsed-field gel electrophoresis (PFGE). One hundred were chosen for MLST genotyping. PFGE identified 69 distinct types compared to 44 different sequence types (STs) identified with MLST. Eighteen STs had not been described previously, while the remaining 26 STs were assigned to previously known clonal complexes. The majority of isolates were of genotypes noted in broilers and in humans in earlier studies. However, three clonal complexes, ST-206 complex, ST-677 complex and ST-1034 complex, previously associated with wild bird and environmental samples, were among the genotypes found. This study shows that most of the Swedish broiler isolates were of genotypes noted as common in broilers. However, it also highlights the potential influence of environmental sources on the broiler C. jejuni genotypes. 相似文献