全文获取类型
收费全文 | 348篇 |
免费 | 16篇 |
专业分类
林业 | 17篇 |
农学 | 13篇 |
82篇 | |
综合类 | 14篇 |
农作物 | 15篇 |
水产渔业 | 17篇 |
畜牧兽医 | 153篇 |
园艺 | 7篇 |
植物保护 | 46篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 16篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 34篇 |
2007年 | 29篇 |
2006年 | 24篇 |
2005年 | 19篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1926年 | 1篇 |
排序方式: 共有364条查询结果,搜索用时 15 毫秒
101.
102.
C. Monterroso F. Macías A. Gil Bueno C. Val Caballero 《Land Degradation \u0026amp; Development》1998,9(5):441-451
The reclamation and monitoring methodologies implemented at the mining waste dump at the As Pontes Lignite Mine in Galicia (NW Spain) are briefly described. In addition the factors affecting achievement of reclamation objectives and an evaluation of the factors limiting plant growth on the constructed soils are outlined. The most serious limitations were found in the oldest mine soils constructed from sulphide-bearing spoils; high acidity, toxicity, nutrient deficiency, seasonal waterlogging due to their impermeability, and compaction. The youngest soils were constructed using sulphide-free spoils as topsoil substitutes and had fewer limitations for plant development. The results show that proper handling of spoils, and paying special attention to selective placement of sulphide bearing materials, are the most important factors in providing a suitable medium for plant growth. © 1998 John Wiley & Sons, Ltd. 相似文献
103.
Background
Fluorescent hybridization techniques are widely used to study the functional organization of different compartments within the mammalian nucleus. However, few examples of such studies are known in the plant kingdom. Indeed, preservation of nuclei 3D structure, which is required for nuclear organization studies, is difficult to fulfill. 相似文献104.
Merchant SS Prochnik SE Vallon O Harris EH Karpowicz SJ Witman GB Terry A Salamov A Fritz-Laylin LK Maréchal-Drouard L Marshall WF Qu LH Nelson DR Sanderfoot AA Spalding MH Kapitonov VV Ren Q Ferris P Lindquist E Shapiro H Lucas SM Grimwood J Schmutz J Cardol P Cerutti H Chanfreau G Chen CL Cognat V Croft MT Dent R Dutcher S Fernández E Fukuzawa H González-Ballester D González-Halphen D Hallmann A Hanikenne M Hippler M Inwood W Jabbari K Kalanon M Kuras R Lefebvre PA Lemaire SD Lobanov AV 《Science (New York, N.Y.)》2007,318(5848):245-250
Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the approximately 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella. 相似文献
105.
106.
Rabbit haemorrhagic disease: an investigation of some properties of the virus and evaluation of an inactivated vaccine. 总被引:1,自引:0,他引:1
An inactivated vaccine against rabbit haemorrhagic disease (RHD), developed and tested in our laboratory, is produced commercially by Bioveta, Ivanovice, Czechoslovakia. Rabbits developed full protection against infection 3 weeks after the administration of a single dose. Antibodies were detectable from day 5 after vaccination. Naturally acquired antibodies were demonstrated in some rabbits kept on commercial farms. The virus survived at least 225 days in an organ suspension kept at 4 degrees C, at least 105 days in the dried state on cloth at room temperature (around 20 degrees C), and at least 2 days at 60 degrees C, both in organ suspension and in the dry state. Experimental infection of rabbits younger than 2 months was successful in some animals. Hares, guinea pigs, white mice, golden and Chinese hamsters, chinchillas and hysterectomy-derived, colostrum-deprived piglets were resistant to infection. 相似文献
107.
Jean-Paul Laclau Jacques Ranger José Leonardo de Moraes Gonçalves Valérie Maquère Alex V. Krusche Armel Thongo M’Bou Yann Nouvellon Laurent Saint-André Jean-Pierre Bouillet Marisa de Cassia Piccolo Philippe Deleporte 《Forest Ecology and Management》2010,259(9):1771-1785
The sustainability of fast-growing tropical Eucalyptus plantations is of concern in a context of rising fertilizer costs, since large amounts of nutrients are removed with biomass every 6–7 years from highly weathered soils. A better understanding of the dynamics of tree requirements is required to match fertilization regimes to the availability of each nutrient in the soil. The nutrition of Eucalyptus plantations has been intensively investigated and many studies have focused on specific fluxes in the biogeochemical cycles of nutrients. However, studies dealing with complete cycles are scarce for the Tropics. The objective of this paper was to compare these cycles for Eucalyptus plantations in Congo and Brazil, with contrasting climates, soil properties, and management practices.The main features were similar in the two situations. Most nutrient fluxes were driven by crown establishment the two first years after planting and total biomass production thereafter. These forests were characterized by huge nutrient requirements: 155, 10, 52, 55 and 23 kg ha?1 of N, P, K, Ca and Mg the first year after planting at the Brazilian study site, respectively. High growth rates the first months after planting were essential to take advantage of the large amounts of nutrients released into the soil solutions by organic matter mineralization after harvesting. This study highlighted the predominant role of biological and biochemical cycles over the geochemical cycle of nutrients in tropical Eucalyptus plantations and indicated the prime importance of carefully managing organic matter in these soils. Limited nutrient losses through deep drainage after clear-cutting in the sandy soils of the two study sites showed the remarkable efficiency of Eucalyptus trees in keeping limited nutrient pools within the ecosystem, even after major disturbances. Nutrient input–output budgets suggested that Eucalyptus plantations take advantage of soil fertility inherited from previous land uses and that long-term sustainability will require an increase in the inputs of certain nutrients. 相似文献
108.
Pablo C. Gontijo Valéria F. Moscardini J. P. Michaud Geraldo A. Carvalho 《Journal of pest science》2014,87(4):711-719
The use of systemic insecticides as seed treatments has raised concern about the possible impacts of these products on natural enemies. This study assessed the effects of sunflower seed treatments with chlorantraniliprole and thiamethoxam on Chrysoperla carnea by exposing larvae and adults to sunflower stem segments grown from treated seeds and the nectar secreted by their extrafloral nectaries. Confinement of larvae with stem segments for their entire developmental period had no effect on their survival or any life history parameter, except that the sex ratio of resulting adults was lower in the thiamethoxam treatment than in chlorantraniliprole. However, when adult pairs of C. carnea were exposed to treated stem segments during their maturation period, their subsequent survival and fecundity was significantly reduced by both materials, with thiamethoxam reducing median survival (LT50) and fecundity to a greater degree than chlorantraniliprole. Insufficient offspring were obtained from adults exposed to thiamethoxam to permit assessment of their fitness, but the offspring in the chlorantraniliprole-exposed adults had reduced larval survival relative to controls. The greater impact of seed treatments on adult lacewings may be partly attributable to their greater consumption of extra-floral nectar. Our results indicate that seed treatment with systemic insecticides can cause negative effects on beneficial insects, potentially disrupting their population dynamics, and should not be assumed compatible with biological control and IPM simply because this mode of application limits direct exposure. 相似文献
109.
Morgan V Delmotte M van Ommen T Jouzel J Chappellaz J Woon S Masson-Delmotte V Raynaud D 《Science (New York, N.Y.)》2002,297(5588):1862-1864
The last deglaciation was marked by large, hemispheric, millennial-scale climate variations: the B?lling-Aller?d and Younger Dryas periods in the north, and the Antarctic Cold Reversal in the south. A chronology from the high-accumulation Law Dome East Antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the Antarctic Cold Reversal did not follow the abrupt warming during the northern B?lling transition around 14,500 years ago. This result suggests that southern changes are not a direct response to abrupt changes in North Atlantic thermohaline circulation, as is assumed in the conventional picture of a hemispheric temperature seesaw. 相似文献
110.
T. V. Denisova K. Sh. Kazeev S. I. Kolesnikov V. F. Val’kov 《Eurasian Soil Science》2007,40(9):978-985
The dynamics of changes in the number of microorganisms and biochemical properties of an ordinary chernozem were studied in model experiments 3, 30, and 90 days after the soil was subjected to gamma radiation at doses of 0.12–2.0 Mrad. The microscopic fungi are the most radiosensitive soil microorganisms. In 90 days of incubation after the gamma radiation, the number of microorganisms remained lower than that in the control variant by 31–96% in accordance with the dose. The enzyme activity of the ordinary chernozem, as compared to that of the microorganisms, was more resistant to the gamma radiation. The integral index of the soil biological state (ISBSI) decreased by 20–63% upon the radiation depending on the dose applied. After 90 days, the ISBSI value was close to the control variant (doses of 0.1–0.5 Mrad), whereas, in the variants with high doses of radiation (1.0 and 2.0 Mrad), its values were 46 and 59% lower, respectively, than in the control. The rate of restoring of the biological properties was related to the dose of radiation: the less the dose, the quicker the rate of restoration of the biological properties of the ordinary chernozem. However, at the high levels of gamma radiation, some biological properties were not restored even after 90 days. 相似文献