全文获取类型
收费全文 | 333篇 |
免费 | 16篇 |
专业分类
林业 | 35篇 |
农学 | 16篇 |
86篇 | |
综合类 | 16篇 |
农作物 | 19篇 |
水产渔业 | 43篇 |
畜牧兽医 | 71篇 |
园艺 | 17篇 |
植物保护 | 46篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 25篇 |
2011年 | 27篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有349条查询结果,搜索用时 31 毫秒
11.
Sofia Trattner Jana Pickova Jacques Rinchard 《Aquaculture (Amsterdam, Netherlands)》2007,273(1):158-164
The effects of dietary α-lipoic acid (LA) and vitamin C on the fatty acid (FA) composition in the brain and muscle and vitamins E and C levels in the brain were studied in the fish Piaractus mesopotamicus. A two-factorial design, where diets were devoid or supplemented with ascorbate (500 mg AA kg− 1) and/or lipoic acid (1000 mg kg− 1), was used. The levels of eicosapentaenoic acid (20:5n − 3, EPA) increased (P < 0.01) in muscle polar lipids (PL) in LA groups (6.93% ± 0.43 vs. 5.83% ± 0.40 and 6.68% ± 0.53 vs. 6.00% ± 0.39), and the same trend was also seen in the brain, however not significant. These changes are suggested to be caused by a change in lipid metabolism rather than being a direct effect of protection by LA against lipid peroxidation. No interaction of vitamin C and LA neither effects of LA on vitamin E (15.1-19.2 mg α-tocopherol g− 1 tissue) or vitamin C (total AA, 41.7-89.8 μg g− 1 tissue) in brain was detected. 相似文献
12.
Influence of sediment phosphorus on utilization efficiency of phosphate fertilizer: a mesocosm study
Influence of initial sediment phosphorus content of the pond sediment on P dose efficiency was examined in a laboratory experiment using four types of sediments collected from ponds located along a nutrient gradient in a sewage‐fed fish farm. Each sediment type (500 g) was dispensed in a glass jar with water and treated with single super phosphate (SSP) treatment at 1.25, 2.5, 5.0 and 10.0 mg L?1 in triplicate. Determination of orthophosphate (OP) and soluble reactive phosphorus (SRP) in water and available and total P in sediment showed increased response in relation to dose and time. At a given dose, the rate of increase for all species of phosphate in sediment or water was maximum in the case of local pond (LP) soil followed by stocking pond (SP), facultative pond (FP) and anaerobic pond (AP) soil, suggesting that utililization of phosphate fertilizer was much better under oligotrophic conditions than under eutrophic states. The SSP‐induced OP peak at 10 mg L?1 in LP sediment was similar to that of 5.0 mg L?1 in AP sediment containing 59% enhanced initial phosphate, implying that fertilizer application can be profitably reduced by 18% in the former without limiting the OP level in the water phase. It is concluded that dosage selection of phosphorus fertilizer in aquaculture ponds should be based on an evaluation of the initial P status of the system. 相似文献
13.
Juraj Lieskovský Pavol Kenderessy Jana Špulerová Tibor Lieskovský Peter Koleda Felix Kienast Urs Gimmi 《Landscape Ecology》2014,29(5):867-877
Collectivization of agriculture (1950s–1970s) was one of the most important periods in landscape development in Slovakia. Traditionally managed agricultural landscapes, that covered more than half of the Slovak territory, were transformed into large-scale fields and only fragments of traditional agricultural landscapes survived. We mapped the remaining traditional agricultural landscapes using aerial photos and historical maps. We then statistically analyzed the various geographical factors and their influence on the transformation process of traditional and collectivized fields, i.e., slope steepness, soil fertility, distance from settlements and isolation from regional capital cities. The comparison was performed using classification tree analysis. We constructed a set of decision rules that explain why fields were managed traditionally or collectivized. Our findings show that traditional agricultural fields were more likely to persist on steep terrain, less fertile soils, and on locations that were closer to the settlements, but more isolated from the regional capital cities. Steepness played the most important role: small-scale fields located on steep areas were not accessible to heavy machinery and therefore, frequently survived the collectivization. We show that the selected geographical factors are good explanatory variables for the collectivization of arable fields and orchards. For vineyards and grasslands, however, the explanatory power of the selected geographical factors is lower, and we suspect that other factors, not depicted in the analysis play an important role. 相似文献
14.
Physicochemical changes in the water were monitored at different hours of embryonic and larval development of Indian carp (Cirrhinus mrigala) eggs in a Chinese hatchery system with 75–85% hatching success. At a water temperature of 29.3°C, mass hatching of the embryos started at about 11–12 h after fertilization and was completed within 4 h. The amount of dissolved oxygen and chemical oxygen demand ranged between 4.8 and 9.63 mg l?1 and 16.5 and 185.0 mg l?1, respectively. A marked rise in the concentration of bicarbonate and total hardness of the water after egg transfer into hatching tanks was perhaps due to liberation of Ca2+ and Mg2+ from the egg mass. A sharp decline in phosphate content during hatching was associated with the building of bones, while the ammonia level was greatly increased due to a high rate of nitrogenous excretion during hatching. 相似文献
15.
The increasing presence of aquaculture in coastal waters calls for a better understanding of its environmental effects. Currently little information is available on the impact of shellfish farms on cetaceans. Here we compare long-term ranging patterns of adult female bottlenose dolphins (Tursiops sp. in Shark Bay, Western Australia) before and during full-scale pearl oyster farming operations, to determine if they were displaced. When the exact location of the oyster farm was determined, the dolphins decreased their use of that area after the farm was in place. Tracks of adult female dolphin movement near the oyster farm were compared to tracks of dolphin movement near an ecologically similar area where no oyster farm existed. Tracks near the oyster farm were less likely to enter the oyster farm itself than tracks near an ecologically similar location. This suggests that shellfish aquaculture could have a large impact on small cetaceans. The analytical techniques discussed apply broadly to aquatic and terrestrial animals. 相似文献
16.
17.
Gelfand MJ Raver JL Nishii L Leslie LM Lun J Lim BC Duan L Almaliach A Ang S Arnadottir J Aycan Z Boehnke K Boski P Cabecinhas R Chan D Chhokar J D'Amato A Ferrer M Fischlmayr IC Fischer R Fülöp M Georgas J Kashima ES Kashima Y Kim K Lempereur A Marquez P Othman R Overlaet B Panagiotopoulou P Peltzer K Perez-Florizno LR Ponomarenko L Realo A Schei V Schmitt M Smith PB Soomro N Szabo E Taveesin N Toyama M Van de Vliert E Vohra N Ward C Yamaguchi S 《Science (New York, N.Y.)》2011,332(6033):1100-1104
With data from 33 nations, we illustrate the differences between cultures that are tight (have many strong norms and a low tolerance of deviant behavior) versus loose (have weak social norms and a high tolerance of deviant behavior). Tightness-looseness is part of a complex, loosely integrated multilevel system that comprises distal ecological and historical threats (e.g., high population density, resource scarcity, a history of territorial conflict, and disease and environmental threats), broad versus narrow socialization in societal institutions (e.g., autocracy, media regulations), the strength of everyday recurring situations, and micro-level psychological affordances (e.g., prevention self-guides, high regulatory strength, need for structure). This research advances knowledge that can foster cross-cultural understanding in a world of increasing global interdependence and has implications for modeling cultural change. 相似文献
18.
Richter Jana Baltruschat Helmut Kabrodt Kathrin Schellenberg Ingo 《植物病害和植物保护杂志》2011,118(3-4):109-118
Journal of Plant Diseases and Protection - The importance of herbal plants is evident in the prevalent use as flavoring ingredients in food. However, meeting the growing demand for organic grown... 相似文献
19.
G. V. Subbarao C. Johansen J. V. D. K. Kumar Rao M. K. Jana 《Biology and Fertility of Soils》1990,9(1):49-53
Summary There were significant differences among pigeonpea [Cajanus cajan (L.) Millsp] Rhizobium sp. strains (IC 3506, IC 3484, IC 3195, and IC 3087) in their ability to nodulate and fix N2 under saline conditions. Pigeonpea plants inoculated with IC 3087 and IC 3506 were less affected in growth by salinity levels of 6 and 8 dS m-1 than plants inoculated with the other strains. For IC 3506, IC 3484, and IC 3195, there was a decrease in the number of nodules with increasing salinity, while the average nodule dry weight and the specific nitrogenase activity remained unaffected. However, in IC 3087, the number of nodules increased slightly with increasing salinity. Leaf-P concentrations increased with salinity in the inoculated plants irrespective of the Rhizobium sp. strain, and leaf-N concentrations decreased with increasing salinity in IC 3484 and IC 3195 only. Shoot-Na and-Cl levels were further increased in these salt-sensitive strains only at 8 dS m-1. Therefore there may be scope for selecting pigeonpea Rhizobium sp. symbioses better adapted to saline conditions. The Rhizobium sp. strains best able to form effective symbioses at high salinity levels are not necessarily derived from saline soils.Submitted as JA No. 919 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) 相似文献
20.
The effects of Hg, As, Pb, Cu, Cd, and Cr (1, 2, and 5 mg L?1 each) on Azolla pinnata R. Br. were analyzed. The treatments (2 and 5 mg L?1) of the heavy metal pollutants decreased Hill activity, chlorophyll, protein and dry wt, and increased tissue permeability over control values. The effects were most pronounced with the treatment of 5 mg L?1. The harmful effects of the metals were, in general, found by the treatments in the order: Cd 〉 Hg 〉 Cu 〉 As 〉 Pb 〉 Cr. There was no significant change in these parameters at 1 mg L?1 of the metals over control. Thus Azolla pinnata shows tolerance to the heavy metals tested up to 1 mg L?1 each. 相似文献