全文获取类型
收费全文 | 207篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
林业 | 10篇 |
农学 | 5篇 |
基础科学 | 2篇 |
43篇 | |
综合类 | 26篇 |
农作物 | 11篇 |
水产渔业 | 19篇 |
畜牧兽医 | 93篇 |
园艺 | 4篇 |
植物保护 | 14篇 |
出版年
2023年 | 5篇 |
2021年 | 9篇 |
2020年 | 15篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 11篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1998年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1984年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1948年 | 2篇 |
排序方式: 共有227条查询结果,搜索用时 15 毫秒
81.
82.
83.
Saksida SM Marty GD Jones SR Manchester HA Diamond CL Bidulka J St-Hilaire S 《Journal of fish diseases》2012,35(2):137-151
Juvenile pink salmon, Oncorhynchus gorbuscha (Walbaum), in the Broughton Archipelago region of western Canada were surveyed over 2 years for sea lice (Lepeophtheirus salmonis and Caligus clemensi), gross and microscopic lesions and evidence of infections with viruses and bacteria. The 1071 fish examined had an approximate ocean residence time no longer than 3 months. A high prevalence of degenerative liver lesions, renal myxosporean parasites and a low prevalence of skin lesions and sea lice were observed. No indications of viral or bacterial diseases were detected in either year. The monthly prevalence of sea lice in 2007 (18-51%) was higher than in 2008 (1-26%), and the infestation density exceeded the lethal threshold in only two fish. Degenerative hepatic lesions and renal myxosporean parasites occurred in approximately 40% of the pink salmon examined in June of both years, and the peak monthly prevalence of hepatocellular hydropic degeneration was greater in 2007 (32%, in May) than in 2008 (12%, in June). Logistic regression analysis found skin lesions and hepatocellular hydropic degeneration significantly associated with sea lice. Most parasites and lesions occurred during both years, but the prevalence was often higher in 2007. Fish weight was 35% less in June 2007 than in June 2008, but condition factor was not different. Further research is required to monitor inter-annual variations and aetiology of the liver lesions and to assess their potential role on pink salmon survival. 相似文献
84.
Daniel C Dunn Andre M Boustany Jason J Roberts Eric Brazer Melissa Sanderson Beth Gardner Patrick N Halpin 《Fish and Fisheries》2014,15(3):359-375
Increasingly, fisheries are being managed under catch quotas that are often further allocated to specific permit holders or sectors. At the same time, serious consideration is being given to the effects of discards on the health of target and non‐target species. Some quota systems have incorporated discard reduction as an objective by counting discards (including unmarketable fish) against the overall quota. The potential effect of the introduction of a quota system that includes accountability for discards on the fishing strategies employed by fishermen is enormous. This is particularly true for multispecies fisheries where healthy and depleted stocks co‐exist; resulting in a trip's catch being applied to very large and very small stock quotas simultaneously. Under such a scenario, fishermen have a strong incentive to minimize (i) catch of low‐quota or ‘choke’ stocks, (ii) regulatory discards due to minimum size limits and (iii) catch partially consumed by predators. ‘Move‐on’ rules (i.e. event‐triggered, targeted, temporary closure of part of a fishery when a catch or bycatch threshold is reached) have been employed in a variety of fisheries. However, their efficacy has been limited by a lack of empirical analyses underpinning the rules. Here, we examine the utility of spatiotemporal autocorrelation analyses to inform ‘move‐on’ rules to assist a sector of the New England Multispecies Fishery to reduce discards and maximize profits. We find the use of empirical move‐on rules could reduce catch of juvenile and choke stocks between 27 and 33%, and depredation events between 41 and 54%. 相似文献
85.
Mandi E. Kleman Amara H. Estrada Herbert W. Maisenbacher Robert Prošek Brandon Pogue Andre Shih Joseph A. Paolillo 《Journal of Veterinary Cardiology》2012,14(2):351-361
Subvalvular aortic stenosis (SAS) is one of the most common congenital cardiac malformations in dogs. Unfortunately, the long term success rate and survival data following either open heart surgery or catheter based intervention has been disappointing in dogs with severe subaortic stenosis. Medical therapy is currently the only standard recommended treatment option. A cutting balloon dilation catheter has been used successfully for resistant coronary artery and peripheral pulmonary arterial stenoses in humans. This catheter is unique in that it has the ability to cut, or score, the stenotic region prior to balloon dilatation of the stenosis. The use of cutting balloon valvuloplasty combined with high pressure valvuloplasty for dogs with severe subaortic stenosis has recently been reported to be a safe and feasible alternative therapeutic option. The following report describes this technique, outlines the materials required, and provides some ‘tips’ for successful percutaneous subaortic balloon valvuloplasty. 相似文献
86.
Francimary da Silva Carneiro Bernd Degen Milton Kanashiro Andre Eduardo Biscaia de Lacerda Alexandre Magno Sebbenn 《Forest Ecology and Management》2009,258(7):1260-1266
In this study, six highly polymorphic microsatellite loci and a categorical paternity analysis approach were used to investigate the contemporary pollen gene flow in the neotropical tree species Symphonia globulifera. Data for this study were taken from a 500 ha experimental plot in a dense terra firme forest in the Eastern Brazilian Amazon and included the mapping and genotyping of 161 reproductive trees, representing more than 90% of all adult trees, and the collection of 748 open-pollinated seeds from 56 seed-trees over two field seasons (2002 and 2003). High levels of pollen immigration from outside of the study plot were detected in both sampled seed-years (≥49%) suggesting long distance pollen gene flow. Low levels of self-fertilization were also detected (≤2%). The analysis showed long distance pollen dispersal occurred within the study area in both 2002 (δ = 907 ± 652 m SD) and 2003 (δ = 963 ± 542 m SD). Patterns of pollen dispersal distance within the plot were also found to be shorter than the distances between potential male parents and seed-trees. This result indicates that the distance between trees does not explain the identified pollen dispersal pattern. Our results support the hypothesis that animal pollinated species occurring in low-density populations can disperse pollen in long distances, despite the very dense nature of the forest. 相似文献
87.
88.
Lompe T Ottenstein TB Serwane F Wenz AN Zürn G Jochim S 《Science (New York, N.Y.)》2010,330(6006):940-944
The quantum mechanical three-body problem is one of the fundamental challenges of few-body physics. When the two-body interactions become resonant, an infinite series of universal three-body bound states is predicted to occur, whose properties are determined by the strength of the two-body interactions. We used radio-frequency fields to associate Efimov trimers consisting of three distinguishable fermions. The measurements of their binding energy are consistent with theoretical predictions that include nonuniversal corrections. 相似文献
89.
Adoption potential of selected organic resources for improving soil fertility in the central highlands of Kenya 总被引:1,自引:0,他引:1
Jayne Mugwe Monicah Mucheru-Muna Daniel Mugendi James Kung’u Andre Bationo Franklin Mairura 《Agroforestry Systems》2009,76(2):467-485
Soil fertility decline is the major cause of declining crop yields in the central highlands of Kenya and elsewhere within
the African continent. This paper reports a study conducted to assess adoption potential of two leguminous trees, two herbaceous
legumes, cattle manure, and Tithonia diversifolia either solely applied or combined with inorganic fertilizer, for replenishing soil fertility in the central highlands of
Kenya. The study examined biophysical performance, profitability, feasibility and acceptability, and farmers experiences in
managing and testing the inputs. The study was based on a series of studies incorporating both sociological and experimental
approaches for two and a half years. Results of on farm trials showed that manure + fertilizer and tithonia + fertilizer treatments
increased yields by more than 100% above the control. These treatments were the most profitable having highest net benefits
and benefit cost ratios. They were also the most commonly preferred by farmers who used them on larger plots compared to the
other inputs. In conclusion, cattle manure and tithonia were found to be the organic materials with the highest adoption potential
for soil fertility improvement in this area. Calliandra calothyrsus and Leucaena trichandra, on the other hand, have potential for use as animal fodder. The herbaceous legumes had the least adoption potential due
to poor performance recorded on the farms that possibly led to low preference by the farmers. However, issues of sustainable
seed production could have played a role. This study recommends some policy issues for enhancing adoption and research issues
focusing on exploring strategies for increasing biomass production and use efficiency on farms.
Andre Bationo was formerly working for Tropical Soil Biology and Fertility Institute of CIAT (TSBF-CIAT) as the African network
Coordinator. 相似文献
90.