全文获取类型
收费全文 | 115篇 |
免费 | 4篇 |
专业分类
林业 | 10篇 |
农学 | 1篇 |
基础科学 | 2篇 |
20篇 | |
综合类 | 4篇 |
农作物 | 14篇 |
水产渔业 | 25篇 |
畜牧兽医 | 30篇 |
园艺 | 2篇 |
植物保护 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有119条查询结果,搜索用时 31 毫秒
1.
Andreia I. G. Raposo Susana M. F. Ferreira Rodolfo Ramos Pedro M. Santos Catarina Anjos Teresa Baptista Carla Tecelo Jos L. Costa Ana Pombo 《Aquaculture Research》2019,50(8):2023-2038
In this study, the effects of three diets were investigated to enhance Paracentrotus lividus production for commercial purposes. P. lividus were fed ad libitum for 80 days with: diet A—fresh Codium tomentosum Stackhouse, 1797; diet B—formulated using a jellified mix of macroalgae and vegetables, including C. tomentosum (20%), Coralina sp. Linnaeus, 1758 (17%), cabbage Brassica oleracea var. capitata Linnaeus, 1753 (30%), carrot Daucus carota Linnaeus, 1753 (30%) and agar (3%) as a gelling agent. Diet C consisted of maize Zea mays Linnaeus, 1753 (56%) and New Zealand spinach Tetragonia tetragonoides (Pallas, 1781) Kuntze, 1891 (44%). Their effects on the gonadal and somatic growths, gonadosomatic index (GI) and gametogenesis were evaluated, as well as on the total lipid content and fatty acid composition of sea urchin's gonads. Diet A provided high values of eicosapentaenoic acid (EPA). Gonads of sea urchins fed with diet A were found mostly in growth and maturation stages of gametogenesis and showed the lowest lipid content. Sea urchins fed with diet B presented their gonads in the reabsorption stage and had the highest values of omega‐3 polyunsaturated fatty acids (PUFAs). Sea urchins fed with diet C were in the early stages of gametogenesis and had the highest values of lipid content, plus omega‐6 PUFAs. Once as an ingredient in a balanced mix with vegetables, C. tomentosum can be a key factor to the development of new promising high‐quality and low‐cost feed for P. lividus roe enhancement. 相似文献
2.
3.
4.
The spectral data of a new Δ7,22 sterol, 24S-ethyl-5α-cholesta-7,22E-dien-3α-ol β-galactopyranoside, isolated from the bulbs of Autonoë madeirensis, are reported. 相似文献
5.
Understanding the major causes of growth variation is crucial for the success of fish farming since its reduction contributes to maximize production efficiency, reduce food waste and improve water quality. The growth variation observed in aquaculture has been associated with the establishment of social hierarchies. However, some studies suggest that this variation may not be mainly a consequence of social hierarchies but mainly a result of inherent (genetic) differences. This study investigates the magnitude of individual responses, independently of group effects (fish housed individually), in growth efficiency and feeding behaviour of African catfish Clarias gariepinus (Burchell 1822). Despite the low variation in initial body weight (6.5%) and cumulative feed consumption (7.5%) over the experimental period, catfish exhibited high variation in final body weight (18.1%), specific growth rate (17.2%) and feed conversion ratio (27.9%), suggesting that individual variation in growth efficiency is important in determining growth rate. This individual variation may be related with individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated with individual differences in growth efficiency. Fast eaters were the fast growers. We suggest that the growth variation observed in African catfish may be inherent and that the use of grading to increase uniformity should be further investigated. 相似文献
6.
Maria Jo?o Rodrigues Katkam N. Gangadhar Catarina Vizetto-Duarte Sileshi G. Wubshet Nils T. Nyberg Luísa Barreira Jo?o Varela Luísa Custódio 《Marine drugs》2014,12(4):2228-2244
Extracts of five halophytes from southern Portugal (Arthrocnemum macrostachyum, Mesembryanthemum edule, Juncus acutus, Plantago coronopus and Halimione portulacoides), were studied for antioxidant, anti-inflammatory and in vitro antitumor properties. The most active extracts towards the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical were the methanol extracts of M. edule (IC50 = 0.1 mg/mL) and J. acutus (IC50 = 0.4 mg/mL), and the ether extracts of J. acutus (IC50 = 0.2 mg/mL) and A. macrostachyum (IC50 = 0.3 mg/mL). The highest radical scavenging activity (RSA) against the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical was obtained in the ether extract of J. acutus (IC50 = 0.4 mg/mL) and H. portulacoides (IC50 = 0.9 mg/mL). The maximum total phenolic content (TPC) was found in the methanol extract of M. edule (147 mg gallic acid equivalents (GAE)/g) and in the ether extract of J. acutus (94 mg GAE/g). Significant decreases in nitric oxide (NO) production were observed after incubation of macrophages with lipopolysaccharide (LPS) and the chloroform extract of H. portulacoides (IC50 = 109 µg/mL) and the hexane extract of P. coronopus (IC50 = 98.0 µg/mL). High in vitro cytotoxic activity and selectivity was obtained with the ether extract of J. acutus. Juncunol was identified as the active compound and for the first time was shown to display selective in vitro cytotoxicity towards various human cancer cells. 相似文献
7.
Carolina Parada Billy Ernst Sebastián Cornejo-Guzmán Francisco Santa Cruz Marco Sandoval Belmar Pablo Rivara Braulio Tapia Stéphane Gauthier Josefa Pino-Aguilera Ruben Escribano Carmen E. Morales 《水产资源保护:海洋与淡水生态系统》2021,31(2):253-272
- The Juan Fernandez Ridge, a vulnerable marine ecosystem located far off the coast of central Chile and formed by several seamounts, guyots and three islands (Robinson Crusoe, Santa Clara and Alejandro Selkirk), has recently been declared a Coastal Marine Protected Area of Multiple Uses with several National Parks embedded in it.
- Recent studies have highlighted the influence of remote and local oceanographic structures on the hydrographic dynamics of this ridge. However, there is still a gap in understanding how they affect the structure and dynamics of the surrounding insular planktonic communities.
- A hydroacoustic and oceanographic survey was conducted during the austral spring (October 2016), including hydrographic and zooplankton sampling around Robinson Crusoe Island. Oceanographic features were identified and tracked using satellite data (chlorophyll-a (Chl-a) and sea surface temperature) and modelling results.
- Two events of Chl-a increase relative to a threshold (>0.45 mg m−3) were forced by different physical processes, both affecting the western side of Robinson Crusoe Island. In event A during the cruise period, Chl-a subsurface maxima were associated with the arrival of a coastal meander originating on the continental shelf off Chile (remote process); the zooplankton was dominated by copepods and salps, with an evident coastal–oceanic gradient. In event B, Chl-a maxima were linked to a local upwelling forced by the intensification of a localized SSW wind. No influence of remote eddies or local Von Kármán vortices on Chl-a distribution was observed.
- These findings highlight the influence of remote and local physical processes on the structure of planktonic communities around Robinson Crusoe Island. Understanding the variability of these mechanisms and their effects at the base of the pelagic food web is critical in adopting an ecosystem-level approach.
8.
Luís?Borda-de-águaEmail author Laetitia?Navarro Catarina?Gavinhos Henrique?M.?Pereira 《Landscape Ecology》2011,26(2):253-265
Roads can have drastic impacts on wildlife populations. Although there is wide recognition of the negative impacts caused
by roads and a wealth of practical studies, there is a lack of theoretical work that can be used to predict the impact of
road networks or to implement mitigation measures. Here, using Skellam’s diffusion model, we develop analytic and numerical
approaches to analyze the impact of road networks on the survival of populations. Our models show that the viability of a
population is determined not only by road density but also by the size and shape of patches. Accordingly, we studied the minimum
size of a patch to sustain a population with given diffusion and growth parameters. We provide simple formulas to estimate
the minimum patch size, and illustrate the importance of shape with square and rectangular patches. Our models also allow
the estimation of time to extinction after road construction for a population in a patch smaller than that of the minimum
size. Finally, using numerical computations we illustrate how the spatial arrangement of fences strongly affects both the
equilibrium density and the spatial distribution of populations, and that not all fence layouts are equally effective. We
anticipate that our methods provide a tool to assess the impact of geometrical features of road networks on wildlife and that
they can be used to design mitigation measures to prevent the decline and extinction of populations in an anthropogenically
disturbed landscape. 相似文献
9.
Guillemette?Garry Alberto?Salas Gregory?A.?ForbesEmail author Wilmer?Perez Magnolia?Santa?Cruz Rebecca?J.?Nelson 《European journal of plant pathology / European Foundation for Plant Pathology》2005,113(1):71-81
To determine whether populations of Phytophthora infestans attacking wild and cultivated potatoes in the highlands of Peru are specialized on their hosts of origin, we characterized
isolates using several neutral markers, metalaxyl resistance and for aggressiveness in a detached leaf assay. One hundred
and fifty-three isolates were collected from the northern and central highlands of Peru from different potato cultivars (both
modern and native cultivars) and from different species of wild, tuber-bearing potatoes. All the isolates analyzed belonged
to one of four clonal lineages that had been described previously in Peru: EC-1, US-1, PE-3 and PE-7. The EC-1 lineage (n = 133) was dominant and present in similar frequencies on wild and cultivated potatoes. PE-3 (n = 14) was found primarily on cultivated potatoes, with only one isolate coming from a wild host. US-1 (n = 2) and PE-7 (n = 4) were rare; all but one (PE-7) occurred on wild potatoes. Isolates from the EC-1 lineage from modern cultivars were compared
in three separate detached leaf inoculation assays with EC-1 isolates from the wild potato species S. sogarandinum, S. bill-hookerii or S. huancabambense, respectively. No significant interactions between isolate type (from wild or cultivated potato) and host type (wild or cultivated)
were measured for any assay. It appears that the pathogen genotypes in the EC-1 lineage indiscriminately attack both wild
and cultivated tuber-bearing solanaceous hosts in Peru, and breeders should be able to select for resistance using the common
EC-1 lineage. 相似文献
10.
Germline mutations in genes within the MAPK pathway cause cardio-facio-cutaneous syndrome 总被引:1,自引:0,他引:1
Rodriguez-Viciana P Tetsu O Tidyman WE Estep AL Conger BA Cruz MS McCormick F Rauen KA 《Science (New York, N.Y.)》2006,311(5765):1287-1290
Cardio-facio-cutaneous (CFC) syndrome is a sporadic developmental disorder involving characteristic craniofacial features, cardiac defects, ectodermal abnormalities, and developmental delay. We demonstrate that heterogeneous de novo missense mutations in three genes within the mitogen-activated protein kinase (MAPK) pathway cause CFC syndrome. The majority of cases (18 out of 23) are caused by mutations in BRAF, a gene frequently mutated in cancer. Of the 11 mutations identified, two result in amino acid substitutions that occur in tumors, but most are unique and suggest previously unknown mechanisms of B-Raf activation. Furthermore, three of five individuals without BRAF mutations had missense mutations in either MEK1 or MEK2, downstream effectors of B-Raf. Our findings highlight the involvement of the MAPK pathway in human development and will provide a molecular diagnosis of CFC syndrome. 相似文献