全文获取类型
收费全文 | 1467篇 |
免费 | 84篇 |
专业分类
林业 | 102篇 |
农学 | 42篇 |
基础科学 | 18篇 |
451篇 | |
综合类 | 52篇 |
农作物 | 90篇 |
水产渔业 | 175篇 |
畜牧兽医 | 464篇 |
园艺 | 44篇 |
植物保护 | 113篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 35篇 |
2021年 | 68篇 |
2020年 | 55篇 |
2019年 | 74篇 |
2018年 | 46篇 |
2017年 | 51篇 |
2016年 | 59篇 |
2015年 | 46篇 |
2014年 | 59篇 |
2013年 | 93篇 |
2012年 | 118篇 |
2011年 | 103篇 |
2010年 | 70篇 |
2009年 | 59篇 |
2008年 | 92篇 |
2007年 | 94篇 |
2006年 | 79篇 |
2005年 | 88篇 |
2004年 | 73篇 |
2003年 | 59篇 |
2002年 | 40篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1978年 | 1篇 |
1963年 | 1篇 |
1944年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有1551条查询结果,搜索用时 0 毫秒
991.
Rodrigo Neculman Cornelia Rumpel Francisco Matus Roberto Godoy Markus Steffens María de la Luz Mora 《Biology and Fertility of Soils》2013,49(6):681-689
Recent studies with Andisols show that the carbon (C) stabilization capacity evolves with soil age relative to the evolution of the mineral phase. However, it is not clear how soil mineralogical changes during pedogenesis are related to the composition of soil organic matter (SOM) and 14C activity as an indicator for the mean residence time of soil organic matter (SOM). In the present study, we analyzed the contribution of allophane and metal–SOM complexes to soil C stabilization. Soil organic matter was analyzed with solid-state 13C nuclear magnetic resonance spectroscopy. Additionally, the soil was extracted with Na-pyrophosphate (Alp, Fep) and oxalate (Alo, Sio, and Feo). Results supported the hypothesis that allophane plays a key role for SOM stabilization in deep and oldest soil, while SOM stabilization by metal (Al and Fe) complexation is more important in the surface horizons and in younger soils. The metal/Cp ratio (Cp extracted in Na-pyrophosphate), soil pH, and radiocarbon age seemed to be important indicators for formation of SOM–metal complexes or allophane in top- and subsoils of Andisols. Changes in main mineral stabilization agents with soil age do not influence SOM composition. We suggest that the combination of several chemical parameters (Alp, Fep and Cp, metal/Cp ratio, and pH) which change through soil age controls SOM stabilization. 相似文献
992.
Tarradas J Álvarez B Fraile L Rosell R Muñoz M Galindo-Cardiel I Domingo M Dominguez J Ezquerra A Sobrino F Ganges L 《Veterinary immunology and immunopathology》2011,142(3-4):243-251
The objective of this work was to explore whether a plasmid expressing CCL20 chemokine could improve the immune response against CSFV in co-administration with a DNA vaccine expressing the E2 protein. The immunization of pigs with the DNA vaccine formulation, that contains swine CCL20 chemokine, resulted in the homogenous induction of detectable levels of CSFV antibodies at 36 days after the first injection. Remarkably, immunized animals with E2 DNA vaccine in co-administration with the plasmid containing swine CCL20 developed high titers of neutralizing antibodies against homologous and heterologous CSFV strains and were totally protected upon a lethal viral challenge (sterilizing protection). Our results confirm the role of CCL20 to increase antibody-mediated responses. At the same time suggest the ability of CCL20 to enhance the T helper cell response associated with the induction of neutralizing antibodies against CSFV in pigs previously reported. Systemic replication of virulent CSFV in vivo during the acute phase of infection induces type I IFN. Lower average values of IFN alpha were detected in the serum of pigs immunized with pE2 and pCCL20 at 3 days after challenge. The levels of IFN-alpha detected in pigs immunized with pE2 and principally in non-vaccinated challenged animals can be related to viral load in serum at 3 and 7 days post infection and the clinical signs observed. Our results emphasized the capacity of swine CCL20 chemokine to enhance cellular, humoral and anti viral response with an adjuvant effect in the immune response elicited by E2-DNA vaccination against CSFV. To our knowledge, this is the first report demonstrating the adjuvant effect of swine CCL20 to effectively enhance the potential of DNA vaccine in the immune induction and protection against virus challenge in swine infection model. 相似文献
993.
Javier Asin Brian G. Murphy Monika A. Samol Jose Polanco Janet D. Moore Francisco A. Uzal 《Journal of veterinary diagnostic investigation》2021,33(5):987
Rickets is a metabolic bone disease associated with failure of endochondral ossification and impaired osteoid mineralization in growing animals. As a consequence, affected individuals can develop gross and microscopic bone malformations. The most common causes of rickets in domestic species include vitamin D and phosphorus deficiency. Rickets has been described in multiple species; however, comprehensive postmortem characterizations with confirmatory histopathology in equids have not been published. A 6-mo-old, Thoroughbred-cross foal was diagnosed with rickets based on gross autopsy findings and microscopic examination of the ribs and long bones. Grossly, all costochondral junctions of the ribs were enlarged with a “rachitic rosary” appearance, and there were multiple fracture calluses in the rib bodies. Epiphyses and metaphyses of the long bones appeared widened on sagittal section, and their physes were irregularly thickened. Histologically, there were poorly organized columns of hypertrophic chondrocytes within the physes of affected bones, islands of chondrocytes embedded within the primary and secondary spongiosa, and faintly eosinophilic seams of poorly mineralized osteoid within the bone trabeculae. Areas of focally increased osteoclastic activity were observed in some of the sections, perhaps pointing to a more complex metabolic bone disease in a growing animal. Low serum concentrations of calcium and 25-hydroxyvitamin D were detected in an antemortem sample. The pathogenesis of these imbalances was not definitively established, but lack of sunlight exposure, low concentration of vitamin D precursors in the diet (perhaps secondary to malnutrition), or both, were suspected; a genetic basis cannot be ruled out. 相似文献
994.
de Oliveira Santos Dimas de Araujo Neto Francisco Ribeiro de Abreu Santos Daniel Jordan dos Santos Fabiana Ramos Aspilcueta-Borquis Rusbel Raul de Queiroz Sandra Aidar Tonhati Humberto 《Tropical animal health and production》2020,52(1):243-247
Tropical Animal Health and Production - This study was carried out to estimate genetic parameters for morphology, body weight, and tonic immobility traits in the red-winged tinamou (Rhynchotus... 相似文献
995.
de Sá Francielen Paola Gomes Erik Nunes de Almeida Maggioni Renata Wendling Ivar Helm Cristiane Vieira Sant’Anna-Santos Bruno Francisco Zuffellato-Ribas Katia Christina 《New Forests》2022,53(3):411-430
New Forests - In order to better understand the physiological and technical aspects of yerba mate vegetative propagation, the present study sought to evaluate the rhizogenic capacity of apical and... 相似文献
996.
Santos-Cividanes Terezinha M. Cividanes Francisco J. Garcia Jlio C. Vilela Michelle Moraes Jair C. Barbosa Jos Carlos 《Journal of pest science》2022,95(2):783-795
Journal of Pest Science - The sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae) is a major pest of sugarcane (Saccharum sp.) (Glumiflorae: Poaceae) in Brazil and has been... 相似文献
997.
998.
María Gabriela Pizarro Inostroza Vincenzo Landi Francisco Javier Navas González José Manuel León Jurado María del Amparo Martínez Martínez Javier Fernández Álvarez Juan Vicente Delgado Bermejo 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2020,137(4):407-422
Goat milk casein proteins (αS1, αS2, β and κ) are encoded by four loci (CSN1S1, CSN1S2, CSN2 and CSN3, respectively) clustered within 250 kb in chromosome 6. In this study, 159 Murciano-Granadina goats were genotyped for 48 SNPs within the entire casein region. Phenotypes on milk yield and components were obtained from 2,594 dairy registries. Additive and dominance effects on milk composition and quality were studied using non-parametric tests and principal component analysis to prevent SNPs multicollinearity. Two deletions in exon 4 (CSN1S1 and CSN3), one in exon 7 (CSN2) and one in exon 15 (CSN1S2) have been found at frequencies ranging from 0.12 to 0.50. Bonferroni-corrected significant SNP additive and dominance effects were found for milk yield, fat, protein, dry matter and lactose, and somatic cells. Exons 15 and 7 were significantly associated with milk yield and components except for lactose and somatic cells, while exon 4 was significantly associated with milk yield and components except for protein and dry matter. SNPs' associations with somatic cells were less frequent and weaker than those with milk yield and components. As caseins increase, somatic cells decrease, reducing milk enzymatic activity and consumption suitability. Hence, including molecular information in breeding schemes may promote production efficiency, as selecting against undesirable alleles could prevent the compromises derived from their dominance effects. 相似文献
999.
Esther Sebastián-González José Antonio Sánchez-Zapata Francisco Botella Jordi Figuerola Fernando Hiraldo Brendan A. Wintle 《Biological conservation》2011,(9):2354-2361
Prioritizing management actions for wildlife conservation is a difficult task due to the large number of problems relative to available conservation resources and uncertainty about the benefits arising from numerous potential management actions. In this study we use a cost-efficiency protocol to evaluate and prioritize eight different management actions for waterbird community in wetlands throughout southeastern Spain. The protocol generated an action priority ranking based on the costs and predicted benefits of the actions in terms of waterbird carrying capacity. Action prioritization outcomes were also evaluated using population viability analysis models for two of the study species. Removal of dead bird carcasses to prevent disease outbreaks was identified as the most cost efficient action. Removing lead pellets from the sediment was the least efficient strategy. Our approach highlights the role of detailed risk assessment as a form of quality control on the simpler prioritization protocols. We recommend a two-step prioritization protocol based on (i) a rapid, usually simpler prioritization approach for the bulk of species or values being managed, and (ii) a more sophisticated risk assessment for a subset of the species of interest for which detailed risk assessments are tractable. This process strikes a balance between sophistication and practicality. 相似文献
1000.
Pérez-Trujillo JP Hernández Z López-Bellido FJ Hermosín-Gutiérrez I 《Journal of agricultural and food chemistry》2011,59(11):6150-6164
The detailed phenolic composition of five single-cultivar (Baboso Negro, Listán Negro, Negramoll, Tintilla, and Vijariego Negro) young and aged (vintages 2005-2009) red wines of the Canary Islands has been determined by HPLC-DAD-ESI-MS(n). Despite the total monomeric anthocyanin content decreasing for older wines in each set of single-cultivar wines, the corresponding anthocyanin profiles remained almost unchanged. Although all wine anthocyanin profiles were dominated by malvidin 3-glucoside, their differentiation by grape cultivar was possible, with the exception of Listán Negro. In contrast, the total content of non-anthocyanin phenolics did not appreciably change within vintages but polymerization, hydrolysis, and isomerization reactions greatly modified the phenolic profiles. Aglycone-type flavonol profiles offered the best results for differentiation of the wines according to grape cultivar (Listán Negro and Negramoll; Baboso Negro and Vijariego Negro; and Tintilla). Within flavan-3-ols, the B-ring trihydroxylated monomers ((-)-epigallocatechin and (-)-gallocatechin) and also (-)-epicatechin provided additional cultivar differentiation. Hydroxycinnamic acid derivatives and stilbene profiles were very heterogeneous with regard to both grape cultivar and vintage and did not significantly contribute to wine differentiation, even when structure-type profiles were obtained, with the exception of Tintilla, which always appeared as the most different single-cultivar wines. Finally, most Canary Islands wines showed characteristic high contents of stilbenes, especially trans-resveratrol. 相似文献