全文获取类型
收费全文 | 782篇 |
免费 | 47篇 |
专业分类
林业 | 92篇 |
农学 | 30篇 |
基础科学 | 4篇 |
182篇 | |
综合类 | 32篇 |
农作物 | 40篇 |
水产渔业 | 133篇 |
畜牧兽医 | 251篇 |
园艺 | 17篇 |
植物保护 | 48篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 35篇 |
2020年 | 24篇 |
2019年 | 36篇 |
2018年 | 31篇 |
2017年 | 30篇 |
2016年 | 29篇 |
2015年 | 21篇 |
2014年 | 47篇 |
2013年 | 47篇 |
2012年 | 75篇 |
2011年 | 84篇 |
2010年 | 37篇 |
2009年 | 42篇 |
2008年 | 52篇 |
2007年 | 46篇 |
2006年 | 38篇 |
2005年 | 31篇 |
2004年 | 28篇 |
2003年 | 23篇 |
2002年 | 27篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有829条查询结果,搜索用时 16 毫秒
821.
Esteller M Fraga MF Paz MF Campo E Colomer D Novo FJ Calasanz MJ Galm O Guo M Benitez J Herman JG 《Science (New York, N.Y.)》2002,297(5588):1807-8; discussion 1807-8
822.
823.
Madrazo J García-Fernández RA García-Iglesias MJ Durán AJ Espinosa J Pérez-Martínez C 《Veterinary journal (London, England : 1997)》2009,180(3):371-376
CD44 is an adhesion molecule implicated in the progression of human breast cancer. The purpose of this study was to describe CD44 antigen expression in canine mammary carcinomas and to evaluate its prognostic significance in relation to other clinico-pathological variables.A reduction in CD44 expression was significantly related to variables such as tumour size and adherence to underlying tissues but was not related to tumour location or to ulceration of the overlying skin. Complex (grade I) and anaplastic (grade III) carcinomas exhibited more intense expression of this antigen than did some tubulopapillary and most solid carcinomas (grade II). Although reduced CD44 expression was associated with infiltrative growth and vascular invasion in solid carcinomas, intense expression was also observed in anaplastic tumours. Although overall these findings suggest a role for this adhesion factor in canine mammary tumour development and progression, the complexity and apparently paradoxical nature of some of the findings currently limit the use of this immunohistochemical marker as a prognostic indicator. 相似文献
824.
Gonzalez-Saiz JM Pizarro C Esteban-Díez I Ramírez O Gonzalez-Navarro CJ Saiz-Abajo MJ Itoiz R 《Journal of agricultural and food chemistry》2007,55(8):2930-2936
The valorization of vegetable byproducts is one of the main objectives of industry today. The project on which this study is based examined the potential usefulness of worthless onions (Allium cepa L. sp.) and overproduction to obtain several functional products with different applications in the food industry. Near-infrared (NIR) spectroscopy, combined with multivariate calibration, has been used to monitor the alcoholic fermentation of onion juice. Good results were obtained, revealing the suitability of NIR spectroscopy for controlling and optimizing this process in real time. 相似文献
825.
Eyad Atalah Carmen María Hernández‐Cruz Eneko Ganuza Tibiabin Benítez‐Santana Rachid Ganga Javier Roo Daniel Montero Marisol Izquierdo 《Aquaculture Research》2011,42(9):1261-1268
Together with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA) is being considered to be an essential fatty acid in marine fish larval diets. The objective of the present study was to determine the importance of dietary ARA levels for larval European sea bass performance, when EPA and DHA are also present in the diet. Eighteen‐day‐old larvae were fed, for 14 days, gelatine‐based microdiets containing the following ARA levels: 0.3%, 0.6% or 1.2%. Elevation of dietary ARA up to 1.2% showed a positive correlation with larval survival and a significant improvement in the specific growth rates, body weight and total length. Arachidonic acid was efficiently incorporated into larval lipids, even at a higher proportion than that in the diets. Increased accumulation of ARA did not affect the incorporation of DHA or EPA from the diet into larval total lipids. A significant positive correlation was found between dietary ARA levels and survival after handling stress, indicating the importance of this fatty acid in sea bass larvae response to acute stressors. The results show the importance of ARA for sea bass larvae, but higher dietary levels should be tested to determine whether there is a negative effect of ARA in sea bass as reported for other species. 相似文献
826.
Jeroen G. J. Boerrigter Hans W. van de Vis Ruud van den Bos Wout Abbink Tom Spanings Jan Zethof Laura Louzao Martinez Wouter F. M. van Andel Javier Lopez-Luna Gert Flik 《Fish physiology and biochemistry》2014,40(4):1201-1212
Aquaculture practices bring several stressful events to fish. Stressors not only activate the hypothalamus–pituitary–interrenal-axis, but also evoke cellular stress responses. Up-regulation of heat shock proteins (HSPs) is among the best studied mechanisms of the cellular stress response. An extract of the prickly pear cactus (Opuntia ficus indica), Pro-Tex, a soluble variant of TEX-OE®, may induce expression of HSPs and reduce negative effects of cellular stress. Pro-Tex therefore is used to ameliorate conditions during stressful aquaculture-related practices. We tested Pro-Tex in zebrafish (Danio rerio), common carp (Cyprinus carpio L.) and yellowtail kingfish (Seriola lalandi) exposed to aquaculture-relevant stressors (thermal stress, net confinement, transport) and assessed its effects on stress physiology. Heat shock produced a mild increase in hsp70 mRNA expression in 5-day-old zebrafish larvae. Pro-Tex increased basal hsp70 mRNA expression, but decreased heat-shock-induced expression of hsp70 mRNA. In carp, Pro-Tex increased plasma cortisol and glucose levels, while it did not affect the mild stress response (increased plasma cortisol and glucose) to net confinement. In gills, and proximal and distal intestine, stress increased hsp70 mRNA expression; in the distal intestine, an additive enhancement of hsp70 mRNA expression by Pro-Tex was seen under stress. In yellowtail kingfish, Pro-Tex reduced the negative physiological effects of transport more efficiently than when fish were sedated with AQUI-S®. Overall, our data indicate that Pro-Tex has protective effects under high levels of stress only. As Pro-Tex has potential for use in aquaculture, its functioning and impact on health and welfare of fish should be further studied. 相似文献
827.
Sonia Mediavilla Montserrat Martínez-Ortega Santiago Andrés Javier Bobo Alfonso Escudero 《林业研究》2022,33(1):39-50
Implications of the differences in leaf life span are still subject to debate in the field of ecophysiology. Since leaf traits associated with these differences may be decisive for determining the distribution of tree species, this topic is particularly relevant in the context of climate change. This study analyzes the effects of the differences in leaf life span on premature losses of leaf area owing to insect herbivory and to abiotic stress. Loss of leaf area may be an important determinant of... 相似文献
828.
Luciano Lazzarini Wolff Edson Fontes de Oliveira Javier Lobón-Cerviá 《Ecology of Freshwater Fish》2023,32(1):195-208
Fish ecomorphological analyses often deal with several traits simultaneously, making it challenging to interpret general patterns, and have not addressed the longitudinal component of streams in morphology-habitat relationships. We identified ecomorphotypes of fishes and correlated their morphological variation with food, structural/hydrological variables, and abundances to detect their links with diet and local-scale habitat categories. Eighteen morphometric traits were obtained from specimens collected by electrofishing in a coastal Atlantic stream in Brazil. To test for morphology-habitat associations, headwaters, middle, and mouth reaches were divided into shorter sampling sites, with the middle reach being classified into riffle, run, and pool mesohabitats. Multivariate analyses highlighted the morphological variations and associated the form categories of 18 fish species with food and habitat categories. It resulted in four combined trophic and habitat ecomorphotypes: (1) benthic AB/lithophilic, composed of smaller to longer loricariids, detritivores, of fast-water, and pebbly habitats; (2) benthic C/lithophilic of very fast-waters, algal and detritus scrapers, with longer intestines than the other benthic species, wider suctorial mouths, inhabitants of headwaters, and riffles habitats; (3) nektobenthic/lithophilic with streamlined bodies, invertebrate feeders, and dwellers of faster-water, cobbly habitats; and (4) nektonic/limnophilic composed mainly by characins, which had strong correlations with terrestrial insect consumption, and lentic/pool, sandy habitats. The morphology–environment correlations linked these ecomorphotypes to the broad habitat gradient arrayed in longitudinal and local scales. These results permit inferring the larger form patterns expected for local fish assemblages and emphasise the fish trait categorisation as a possible surrogate to reveal broader ecomorphological associations. 相似文献
829.
Tortilla chips were slow dried after baking and then fried in fresh soybean oil. Control chips were not dried before frying. Final oil content of sun-dried tortilla chips was significantly (P < 0.05) lower than those receiving the control treatment. As a result of drying, the structure of the tortilla chips was tighter before frying but expanded significantly during frying. An attempt was made to produce tortilla chips with the same characteristics of the sun-dried chips using impinging hot-air drying techniques. Results indicated that tortilla chips drying rate was mostly affected by air temperature; texture was crispier at higher air temperatures; shrinkage of the piece was higher at lower convective heat transfer coefficient; and microstructure looked smoother at higher air temperature. 相似文献