全文获取类型
收费全文 | 1707篇 |
免费 | 123篇 |
专业分类
林业 | 79篇 |
农学 | 31篇 |
基础科学 | 4篇 |
350篇 | |
综合类 | 165篇 |
农作物 | 87篇 |
水产渔业 | 136篇 |
畜牧兽医 | 804篇 |
园艺 | 60篇 |
植物保护 | 114篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 30篇 |
2021年 | 73篇 |
2020年 | 86篇 |
2019年 | 81篇 |
2018年 | 56篇 |
2017年 | 56篇 |
2016年 | 68篇 |
2015年 | 62篇 |
2014年 | 67篇 |
2013年 | 68篇 |
2012年 | 142篇 |
2011年 | 151篇 |
2010年 | 77篇 |
2009年 | 69篇 |
2008年 | 125篇 |
2007年 | 110篇 |
2006年 | 91篇 |
2005年 | 72篇 |
2004年 | 68篇 |
2003年 | 70篇 |
2002年 | 67篇 |
2001年 | 4篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1830条查询结果,搜索用时 15 毫秒
81.
Pierluigi Carbonara Sbastien Alfonso Francesco Gai Laura Gasco Giovanni Palmegiano Maria Teresa Spedicato Walter Zupa Giuseppe Lembo 《Aquaculture Research》2020,51(7):3007-3016
Welfare in farmed fish got particular attention during the last decades from both governmental and public sides. In aquaculture context, welfare concerns are mainly related to handling procedures, water quality and stoking densities. In Europe, authorities had to clarify the threshold limits of stocking densities to maintain fish good welfare, including for organics aquaculture through the EC regulation 710/2009. However, effects of stocking density on fish welfare are complex and sometimes contradictory. Moreover, there is a lack of knowledge about the impact of density on fish welfare in organic aquaculture. Thus, the aim of the study is to asses welfare state of rainbow trout (Oncorhynchus mykiss) at two initial stocking densities (low density, LD: 12 kg/m3 and high density, HD: 17 kg/m3) fed using organic feed by combining the monitoring of growth performances, behaviour (swimming activity) and physiological indicators (i.e. cortisol, glucose, lactate, hematocrit, red blood cellule count and lysozyme). At the end of experiment, the stocking density reached 21 kg/m3 and 30 kg/m3 for the LD and HD respectively. Overall, growth performances, swimming activity and level of physiological indicators of stress and welfare were similar between HD and LD over the experiment duration. To conclude, we observed no alteration of fish welfare between the two stocking densities monitored. This study suggests that a final stocking density of 30 kg/m3 can be considered for organic aquaculture of rainbow trout respecting welfare. 相似文献
82.
Consumption of fruits and vegetables, which are rich in polyphenols, has been associated with a reduced risk of chronic diseases such as cancer. Dietary polyphenols have antioxidant and antiproliferative properties that might explain their beneficial effect on cancer prevention. The aim of this study was to investigate the effects of different pure polyphenols [quercetin, chlorogenic acid, and (-)-epicatechin] and natural fruit extracts (strawberry and plum) on viability or apoptosis of human hepatoma HepG2 cells. The treatment of cells for 18 h with quercetin and fruit extracts reduced cell viability in a dose-dependent manner; however, chlorogenic acid and (-)-epicatechin had no prominent effects on the cell death rate. Similarly, quercetin and strawberry and plum extracts, rather than chlorogenic acid and (-)-epicatechin, induced apoptosis in HepG2 cells. Moreover, quercetin and fruit extracts arrested the G1 phase in the cell cycle progression prior to apoptosis. Quercetin and strawberry and plum extracts may induce apoptosis and contribute to a reduced cell viability in HepG2 cells. 相似文献
83.
Finnegan Laura Viejou Rebecca MacNearney Doug Pigeon Karine E. Stenhouse Gordon B. 《Landscape Ecology》2021,36(9):2619-2635
Landscape Ecology - Anthropogenic disturbance alters animal movements. Large mammals require vast areas to meet their needs, and they encounter anthropogenic disturbances frequently during daily... 相似文献
84.
Theoretical advances in systematic reserve design aim to promote the efficient use of limited conservation resources and to increase the likelihood that reserve networks enhance the persistence of valued species and ecosystems. However, these methods have rarely been applied to species that rely on spatially disjunct habitats. We used the marbled murrelet, a seabird that requires old-growth forest in which to nest and high quality marine habitats in which to forage, as a case study to explore methods of incorporating multiple ecological values into single species spatial reserve design. Specifically, we used the cost function in MARXAN to include the ecological value of marine habitats while identifying spatial solutions for terrestrial nesting habitat reserves. Including marine values influenced terrestrial reserve designs most when terrestrial habitat targets were low and little or none of the target was represented in pre-existing protected areas. Our results suggest that including marine values in the planning process will influence marbled murrelet terrestrial reserve designs most where substantial terrestrial nesting habitat still exists, where new reserves are relatively unconstrained by pre-existing reserves, or when conservation resources only allow the protection of a small fraction of available habitat. This paper presents a novel framework for incorporating multiple measures of ecological value in the spatial reserve design process and should be particularly useful for species that rely on multiple habitats during their life cycle. 相似文献
85.
Monjeau J. Adrian Birney Elmer C. Ghermandi Luciana Sikes Robert S. Margutti Laura Phillips Carleton J. 《Landscape Ecology》1998,13(5):285-306
Assemblages of plants were studied at 14 sites in northern Patagonia corresponding to localities at which we (Monjeau et al. 1997) earlier studied the relationship between small mammal assemblages and landscape classifications. This allowed us to test predictions that both plants and small mammals correspond to the more inclusive hierarchical landscape divisions but that plants track better than small mammals the less inclusive divisions. Species presence or absence of plants at each locality was used in a series of multivariate analyses and compared by correlation analysis with those generated from small mammal species data. Assemblages of both plants and small mammals corresponded to the upper divisions, which are based on climatic and geomorphological features, but small mammal assemblages did not correspond to the lower divisions of the landscape classifications. Three factors are considered as explanations for the observed differences between plants and small mammals: a) small mammal habitat is determined more by plant growth form than by plant species; b) trophic level differences between the two groups; and c) species pool size affects the resolution of microhabitat correspondence. Our data indicate that both plant assemblages and small mammal assemblages respond to climatic and geomorphological features, which is in contrast to the paradigm that mammal assemblages simply follow plant assemblages. We also attempted to reconcile classification systems in Patagonia by proposing a nomenclatural system based on a hierarchical classification. In the system proposed, ecoregion is the lowest division small mammal assemblages can recognize in Patagonia. Finally, we conclude that the hierarchical nature of landscapes based on a holistic view of environments reflects real entities that are not just the perceptions of landscape ecologists. 相似文献
86.
87.
Eckert RE Neuder LE Bell JL Trujillo JC Jones SL 《Veterinary immunology and immunopathology》2007,118(3-4):294-303
The goal of this study was to define the role for p38 mitogen-activated kinase (MAPK) in the signaling mechanism regulating pro-inflammatory cyclooxygenase (COX) gene expression in lipopolysaccharide (LPS)-activated equine leukocytes for the purposes of identifying novel targets for anti-inflammatory therapy in endotoxemic horses. The p38 MAPK has been shown to positively regulate inflammatory gene expression in human leukocytes and can be activated by a variety of stimuli including LPS, TNF-alpha, and IL-1. Activation-associated phosphorylated p38 MAPK has been implicated in the up-regulation of several inflammatory genes, including COX-2 which ultimately results in the production of prostanoids that are responsible for the pathophysiology associated with endotoxemia. Our hypothesis is that activation of p38 MAPK is essential for LPS-induced COX-2 expression in equine peripheral blood leukocytes. We tested our hypothesis by investigating the effects of the specific p38 MAPK inhibitors SB203580 and SB202190 on LPS-induced COX-2 protein expression and PGE(2) production in equine leukocytes. LPS stimulation activated p38 MAPK and increased COX-2 expression in a dose-dependent manner with maximal activation observed after 30min and 4h, respectively, at a concentration of 10 ng/ml LPS. In contrast, LPS stimulation did not affect COX-1 protein expression. Pretreatment with SB203580 or SB202190 significantly inhibited LPS-induced activation-associated p38 MAPK phosphorylation, COX-2 mRNA and protein levels, and PGE(2) production in equine leukocytes. Maximal inhibition of LPS-induced COX-2 protein expression was achieved at a concentration of 10 microM SB203580. We concluded that p38 MAPK is essential for LPS-induced COX-2 expression suggesting that p38 MAPK is a potential target for anti-inflammatory therapy during equine endotoxemia. 相似文献
88.
Maria Holmberg Anu Akujärvi Saku Anttila Lauri Arvola Irina Bergström Kristin Böttcher Xiaoming Feng Martin Forsius Inese Huttunen Markus Huttunen Yki Laine Heikki Lehtonen Jari Liski Laura Mononen Katri Rankinen Anna Repo Vanamo Piirainen Pekka Vanhala Petteri Vihervaara 《Landscape Ecology》2015,30(3):561-577
89.
90.