全文获取类型
收费全文 | 993篇 |
免费 | 82篇 |
专业分类
林业 | 112篇 |
农学 | 33篇 |
基础科学 | 8篇 |
301篇 | |
综合类 | 37篇 |
农作物 | 49篇 |
水产渔业 | 108篇 |
畜牧兽医 | 327篇 |
园艺 | 23篇 |
植物保护 | 77篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 17篇 |
2018年 | 54篇 |
2017年 | 61篇 |
2016年 | 37篇 |
2015年 | 39篇 |
2014年 | 43篇 |
2013年 | 67篇 |
2012年 | 87篇 |
2011年 | 90篇 |
2010年 | 36篇 |
2009年 | 47篇 |
2008年 | 57篇 |
2007年 | 43篇 |
2006年 | 42篇 |
2005年 | 50篇 |
2004年 | 44篇 |
2003年 | 30篇 |
2002年 | 35篇 |
2001年 | 33篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1945年 | 1篇 |
排序方式: 共有1075条查询结果,搜索用时 15 毫秒
1.
Nutritional Contribution of Biofloc within the Diet of Growout and Broodstock of Litopenaeus vannamei,Determined by Stable Isotopes and Fatty Acids 下载免费PDF全文
Edén Magaña‐Gallegos Rodrigo González‐Zúñiga Gerard Cuzon Miguel Arevalo Eduardo Pacheco Manuel A. J. Valenzuela Gabriela Gaxiola Elisa Chan‐Vivas Korinthia López‐Aguiar Elsa Noreña‐Barroso 《Journal of the World Aquaculture Society》2018,49(5):919-932
The relative contributions of feed sources were determined through the isotopic signal (δ13C and δ15N) and fatty acid profile of feed items, shrimp muscle, and eggs of Litopenaeus vannamei reared in a biofloc system. In the growout phase, the isotope analysis showed the biofloc particle size class ≥250 μm contributed 55–100%; size ≥50 < 250 μm contributed 0–22%; and artificial feed contributed 0–45%. Principal component analysis applied to fatty acid profiles showed that biofloc ≥250 μm and artificial feed were the most important items in shrimp growout. For the egg production, isotope analysis suggested that the most important feed sources according to their relative contributions were polychaetes (0–100%), followed by artemia biomass (0–86%) and semi‐moist feed (0–66%), with lower contributions from squid, mussel, and the muscle of L. vannamei broodstock that had been cultured in biofloc. In terms of fatty acids, the most important items were artemia, polychaetes, and semi‐moist feeds. This work clarified the importance of feed sources for shrimp during culture in biofloc systems and during reproduction. Analysis of stable isotopes and fatty acids can be successfully used to trace the assimilation of nutrients during the nutrition of shrimp. 相似文献
2.
Ana E. González-Santiago Belinda Vargas-Guerrero Pedro M. García-López Alma L. Martínez-Ayala José A. Domínguez-Rosales Carmen M. Gurrola-Díaz 《Plant foods for human nutrition (Dordrecht, Netherlands)》2017,72(2):134-140
Lupinus albus seeds contain conglutin gamma (Cγ) protein, which exerts a hypoglycemic effect and positively modifies proteins involved in glucose homeostasis. Cγ could potentially be used to manage patients with impaired glucose metabolism, but there remains a need to evaluate its effects on hepatic glucose production. The present study aimed to analyze G6pc, Fbp1, and Pck1 gene expressions in two experimental animal models of impaired glucose metabolism. We also evaluated hepatic and renal tissue integrity following Cγ treatment. To generate an insulin resistance model, male Wistar rats were provided 30% sucrose solution ad libitum for 20 weeks. To generate a type 2 diabetes model (STZ), five-day-old rats were intraperitoneally injected with streptozotocin (150 mg/kg). Each animal model was randomized into three subgroups that received the following oral treatments daily for one week: 0.9% w/v NaCl (vehicle; IR-Ctrl and STZ-Ctrl); metformin 300 mg/kg (IR-Met and STZ-Met); and Cγ 150 mg/kg (IR-Cγ and STZ-Cγ). Biochemical parameters were assessed pre- and post-treatment using colorimetric or enzymatic methods. We also performed histological analysis of hepatic and renal tissue. G6pc, Fbp1, and Pck1 gene expressions were quantified using real-time PCR. No histological changes were observed in any group. Post-treatment G6pc gene expression was decreased in the IR-Cγ and STZ-Cγ groups. Post-treatment Fbp1 and Pck1 gene expressions were reduced in the IR-Cγ group but increased in STZ-Cγ animals. Overall, these findings suggest that Cγ is involved in reducing hepatic glucose production, mainly through G6pc inhibition in impaired glucose metabolism disorders. 相似文献
3.
First identification and characterization of Tenacibaculum dicentrarchi isolated from Chilean red conger eel (Genypterus chilensis,Guichenot 1848) 下载免费PDF全文
4.
Barrera-Reyes Paloma K de Lara Josué Cortés-Fernández González-Soto Melissa Tejero M Elizabeth 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(1):1-11
Plant Foods for Human Nutrition - The effects of cocoa-derived polyphenols on cognitive functions have been analyzed through numerous studies using different interventions (doses, vehicles, time... 相似文献
5.
Wild olive (Olea europaea subsp. europaea var. sylvestris) is an important component of Mediterranean forests and a key genetic source for olive improvement programmes. Since 2009, a severe decline caused by Phytophthora cryptogea and P. megasperma has been detected in a protected wild olive forest of high ecological value (Dehesa de Abajo, Seville, Spain). In this natural forest, sampling of roots and soil was carried out on 25 wild olives with symptoms in 2014 and 2015. Apart from the already known P. cryptogea A1 and P. megasperma, a third Phytophthora species was consistently isolated from wild olive rootlets with symptoms. These isolates conformed morphologically with the newly described species P. oleae and were confirmed by analysis of their ITS regions and cox1 sequences. Temperature–growth relationships showed a maximum growth at 19.9 °C on carrot agar medium, making it the lowest temperature Phytophthora species infecting wild olive roots. Pathogenicity was confirmed on 1-year-old healthy wild olive seedlings and was similar to the previously known pathogenic phytophthoras. As temperature requirements are quite different, the three Phytophthora species may be active against wild olive roots in different seasons. However, the prevalence of P. oleae infecting wild olives in recent years could be due to its introduction as a new invasive pathogen. The probable invasive nature of P. oleae, together with increasing rain episodes concentrated in short periods frequent in southern Spain, would allow the outbreak of infections in wild olive forests, and also put cultivated olive orchards at risk. 相似文献
6.
7.
Summary The observed kinetics of Pinus pinaster bark with acetic acid after alkali treatment, with or without intervening acid prehydrolysis, are satisfactorily explained by a model involving both solubilization and condensation reactions.This study was subsidised by the Xunta de Galicia. J. González is grateful to DGICYT for a research grant 相似文献
8.
José Ramón González Antoni Trasobares Marc Palahí Timo Pukkala 《Annals of Forest Science》2007,64(7):733-742
The study developed models for predicting the post-fire tree survival in Catalonia. The models are appropriate for forest planning purposes. Two types of models were developed: a stand-level model to predict the degree of damage caused by a forest fire, and tree-level models to predict the probability of a tree to survive a forest fire. The models were based on forest inventory and fire data. The inventory data on forest stands were obtained from the second (1989–1990) and third (2000–2001) Spanish national forest inventories, and the fire data consisted of the perimeters of forest fires larger than 20 ha that occurred in Catalonia between the 2nd and 3rd measurement of the inventory plots. The models were based on easily measurable forest characteristics, and they permit the forest manager to predict the effect of stand structure and species composition on the expected damage. According to the stand level fire damage model, the relative damage decreases when the stand basal area or mean tree diameter increases. Conversely, the relative stand damage increases when there is a large variation in tree size, when the stand is located on a steep slope, and when it is dominated by pine. According to the tree level survival models, trees in stands with a high basal area, a large mean tree size and a small variability in tree diameters have a high survival probability. Large trees in dominant positions have the highest probability of surviving a fire. Another result of the study is the exceptionally good post-fire survival ability of Pinus pinea and Quercus suber. 相似文献
9.
10.
The biological activities of ethanol and petroleum ether extracts from leaves and fruits of Schinus molle against adults of Blattella germanica were examined by repellence test and topical application. All extracts produced significant repellent effect and mortality. 相似文献