全文获取类型
收费全文 | 415篇 |
免费 | 17篇 |
专业分类
林业 | 38篇 |
农学 | 9篇 |
基础科学 | 4篇 |
74篇 | |
综合类 | 14篇 |
农作物 | 24篇 |
水产渔业 | 36篇 |
畜牧兽医 | 205篇 |
园艺 | 4篇 |
植物保护 | 24篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 29篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 23篇 |
2012年 | 31篇 |
2011年 | 41篇 |
2010年 | 25篇 |
2009年 | 28篇 |
2008年 | 19篇 |
2007年 | 27篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有432条查询结果,搜索用时 15 毫秒
51.
Per McCord Vanessa Gordon Gopesh Saha Jacqueline Hellinga George Vandemark Richard Larsen Mark Smith David Miller 《Euphytica》2014,200(2):269-279
Alfalfa (Medicago sativa L.) is an internationally significant forage crop. Forage yield, lodging resistance and spring vigor are important agronomic traits conditioned by quantitative genetic and environmental effects. The objective of this study was to identify quantitative trait loci (QTL) and molecular markers associated with increased forage yield, resistance to lodging, and spring vigor. A backcross population composed of 128 progeny was developed by crossing the breeding parents DW000577 (lodging susceptible) and NL002724 (lodging-resistant) and back-crossing an individual F1 plant to the maternal parent (i.e. DW000577). A linkage map of NL002724 was developed based upon the segregation of 236 AFLP, SRAP, and SSR markers among the backcross progeny. The markers were distributed among 14 linkage groups, covering an estimated recombination distance of 1497.6 centiMorgans (cM). Replicated clones of both parents and backcross progeny were evaluated in the field for estimated forage yield, lodging, and spring vigor in Washington and Wisconsin during 2007 and 2008. Significant QTL were found for all three traits. In particular, two QTL for lodging resistance were identified that explained ≥14 % of trait variation, and were significant in all years and locations. Major QTL explaining over 25 % of trait variation for forage yield were detected in multiple environments at two separate locations on chromosome III. Several QTL for spring vigor were located in the same or similar positions as QTL for forage yield, possibly explaining the significant correlation between these traits. Molecular markers associated with the aforementioned QTL were also identified. 相似文献
52.
Restoration of salt-affected soils is a global concern. In the western United States, restoration of salinized land, particularly in river valleys, often involves control of Tamarix, an introduced species with high salinity tolerance. Revegetation of hydrologically disconnected floodplains and terraces after Tamarix removal is often difficult because of limited knowledge regarding the salinity tolerance of candidate native species for revegetation. Additionally, Tamarix appears to be non-mycorrhizal. Extended occupation of Tamarix may deplete arbuscular mycorrhizal fungi in the soil, further decreasing the success of revegetation efforts. To address these issues, we screened 42 species, races, or ecotypes native to southwestern U.S. for salinity tolerance and mycorrhizal responsiveness. As expected, the taxa tested showed a wide range of responses to salinity and mycorrhizal fungi. This variation also occurred between ecotypes or races of the same species, indicating that seed collected from high-salinity reference systems is likely better adapted to harsh conditions than seed originating from less saline environments. All species tested had a positive or neutral response to mycorrhizal inoculation. We found no clear evidence that mycorrhizae increased salinity tolerance, but some species were so dependent on mycorrhizal fungi that they grew poorly at all salinity levels in pasteurized soil. 相似文献
53.
54.
Until recently, pyothorax in the cat has been generally considered to have a poor prognosis. However, it has become clear that most cats that survive the first 48 h following presentation can be successfully treated with aggressive medical management. In this second part of a two-part review, logical guidelines for the management of the disease are discussed, with particular emphasis on antimicrobial selection. Patient stabilisation and supportive care, techniques for pleural space drainage and lavage and indications for surgery are reviewed. 相似文献
55.
Gerhard Langenberger Vanessa Prigge Konrad Martin Beatriz Belonias Joachim Sauerborn 《Agroforestry Systems》2009,76(1):173-194
Complex agroforestry systems that mimic local forest structure, so-called ‘analogs’, are assumed to be of specific value to
rural people as well as the environment. The objective of this study was to document and evaluate the utilization of plant
resources by Philippine lowland farmers to identify native species suitable for integration in such a system. The interviewed
farmers maintain a comprehensive ethnobotanical knowledge. They reported using 122 plant species for 77 purposes. Eighty species
have medicinal value, 35 provide food, and 32 serve other uses. About 64% of the identified species are Philippine natives.
The life form composition of these species is dominated by trees but also includes herbs, lianas, and graminoids, thus providing
the structural elements required in analog systems. Nevertheless, only a few of the species seem to be promising for cultivation.
Many of them are ubiquitous in the vicinity of villages. Some species are also not much appreciated but act as staple food
only during food shortage. Even though several of the species have proven market value, such as rattan (e.g. Calamus
merrillii), or are reputed medicines, such as ‘Philippine ginseng’ (Sarcandra glabra), no cultivation could be observed. This shows that usefulness in itself cannot be the only criterion to promote species
but that it requires a careful analysis of the marketability of the respective species. In this context we suggest the following
three species that are of proven medicinal value for in-depth study: the liana Tinospora crispa (Menispermaceae), the tree Picrasma javanica (Simaroubaceae), and the herb Sarcandra glabra (Chloranthaceae). They represent three different life form strategies and would thus fit well in vertically structured agroforestry
systems. 相似文献
56.
María Vanessa Lencinas Guillermo Martínez Pastur Emilce Gallo Juan Manuel Cellini 《Forest Ecology and Management》2009
Alternative silvicultural approaches to timber management, such as regeneration treatments with different degrees of stand retention, may mitigate negative effects of clear-cutting or shelterwood cuts in forested ecosystems, including changes in old-growth forest bird communities. The aims of this work were: (a) to compare bird species richness and densities among different silvicultural designs with variable retention (dispersed and/or aggregated) and unmanaged primary forests, and (b) to assess temporal changes at community and species levels before and after treatments. A baseline avian survey was conducted prior to harvesting to evaluate canopy gap presence and forest stand site quality influences. Subsequent to harvesting, data on bird species richness and density were collected by point-count sampling during the summer season for 5 consecutive years (4 treatments × 5 years × 6 sampling points × 5 counts). Bird species richness and density (15 species and 9.2 individuals ha−1) did not change significantly with forest site quality of the stands and canopy gap presence in unmanaged forests. However, both variables were significantly modified in managed forests, increasing over time to 18 species and reaching to 39 individuals ha−1. Inside the aggregated retention, bird communities were more similar to unmanaged primary forests than those observed within the dispersed retention or in clear-cuts. Opting for a regeneration method with dispersed and aggregated retention has great potential for managing birds in Nothofagus pumilio forests. This method retained enough vegetation structure in a stand to permit the establishment of early successional birds (at least in dispersed retention), and to maintain the bird species of old-growth forests which could persisted in the retention aggregates. 相似文献
57.
Vanessa Dias Capriles Eveline Lopes Almeida Reinaldo Eduardo Ferreira Jos Alfredo Gomes Arêas Caroline Joy Steel Yoon Kil Chang 《Cereal Chemistry》2008,85(5):614-618
The sum of wheat flour and corn starch was replaced by 10, 20, or 30% whole amaranth flour in both conventional (C) and reduced fat (RF) pound cakes, and the effects on physical and sensory properties of the cakes were investigated. RF presented 33% fat reduction. The increasing amaranth levels darkened crust and crumb of cakes, which decreased color acceptability. Fresh amaranth‐containing cakes had similar texture characteristics to the controls, evaluated both instrumentally and sensorially. Sensory evaluation revealed that replacement by 30% amaranth flour decreased C cakes overall acceptability scores, due to its lower specific volume and darker color. Amaranth flour levels had no significant effect on overall acceptability of RF cakes. Hence, the sum of wheat flour and corn starch could be successfully replaced by up to 20% amaranth flour in C and up to 30% in RF pound cakes without negatively affecting sensory quality in fresh cakes. Moisture losses for all the cakes were similar, ≈1% per day during storage. After six days of storage, both C and RF amaranth‐containing cakes had higher hardness and chewiness values than control cakes. Further experiments involving sensory evaluation during storage are necessary to determine the exact limit of amaranth flour replacement. 相似文献
58.
Vanessa Ap R O Vieira Alexandre W S Hilsdorf Renata Guimarães Moreira 《Aquaculture Research》2012,43(4):565-576
Protein and lipid content as well as the fatty acid (FA) composition of storage tissues were analysed in two varieties of Oreochromis niloticus (Red‐Stirling and Chitralada) and their hybrid. The animals were maintained in cages for 11 months. The samples were taken when the animals weighed 10, 50, 100, 250 and 500 g. The results showed that changes in the metabolic processes occur during an increase in body mass in both varieties of tilapia and also their hybrid, but that these differences are not found in animals collected at the commercial weight. The protein content of the fillet and liver decreased with growth and the same protein content associated with growth was found for fillet lipid content. The genetic variety did not influence the FA profile of the fillet, but different genotypes had different hepatic FA compositions. Even with the same lipid content, the hepatocytes of Chitralada accumulated higher levels of polyunsaturated fatty acids (PUFA) n6 in triglycerides and increased C22:6n3 in the hepatocyte membranes. The higher n6PUFA content was compensated by a lower fraction of saturated FA in the hepatocyte triglycerides. The skin of Chitralada also had higher n6PUFA and C22:6n3 contents, suggesting a higher ability to deposit PUFA in the skin due to alterations in the liver synthetic pathway. 相似文献
59.
Danielle Wisniewski Zelinski Tâmisa Pires Machado dos Santos Thiago Atsushi Takashina Vanessa Leifeld Luciana Igarashi-Mafra 《Water, air, and soil pollution》2018,229(6):207
Artificial sweeteners are food additives widely used, mainly in reduced sugar or sugar-free foods and beverages. Acesulfame potassium (ACE-K) and sodium saccharin (SAC) are among the most widely consumed sweeteners worldwide. These compounds when ingested are not metabolized by the body, being excreted unchanged. They arrive at treatment plants, where they are partially degraded and consequently released directly into water bodies. For this reason, artificial sweeteners have been detected in the most diverse aquatic environments, being recognized as emerging contaminants. In this work, aqueous solutions of ACE-K and SAC, submitted to heterogeneous photocatalysis (TiO2/UV-A) for 60 min, showed degradations of more than 99% and maximum mineralization of 57% for ACE-K and 49% for SAC. The effects of certain variables were evaluated, with pH having a greater influence on the degradation of acesulfame and the mass of semiconductor on that of saccharin. The degradation of ACE-K and SAC followed a pseudo-first-order kinetic model according to the Langmuir–Hinshelwood model. Assays using Artemia salina as the test organism demonstrated the low toxicity of the photocatalyzed solutions of ACE-K and SAC. The contribution of different reactive species to the photocatalysis was investigated using specific radical inhibitors; the results indicate that singlet oxygen (1O2) has a fundamental role in the photocatalytic degradation of ACE-K and SAC. 相似文献
60.
de Oliveira Silva Alan Savi Daiani Cristina Raiser Paulo Henrique Schueda Gonçalves Fabrício Packer Kava Vanessa Galli-Terasawa Lygia Vitória Glienke Chirlei 《植物病害和植物保护杂志》2017,124(1):73-80
Journal of Plant Diseases and Protection - Citrus black spot (CBS) is a disease caused by the fungus Phyllosticta citricarpa that is associated with significant yield losses. The pathogen forms... 相似文献