全文获取类型
收费全文 | 248篇 |
免费 | 6篇 |
专业分类
林业 | 29篇 |
农学 | 3篇 |
基础科学 | 1篇 |
52篇 | |
综合类 | 28篇 |
农作物 | 10篇 |
水产渔业 | 25篇 |
畜牧兽医 | 83篇 |
园艺 | 11篇 |
植物保护 | 12篇 |
出版年
2022年 | 2篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 16篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 11篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有254条查询结果,搜索用时 15 毫秒
91.
92.
Terje van der Meeren Svein Wilhelmsen Jarle Klungsosyr Per Gunnar Kvenseth 《Journal of the World Aquaculture Society》1993,24(2):167-185
Three different groups of cod larvae Gadus morhua L ., feeding on natural plankton in two large enclosures, were analyzed for fatty acid composition through development. Unfed control groups and different size-fractions of plankton were also analyzed. Consistency in changes of fatty acid composition suggests three developmental periods during early larval development. The periods corresponded with dietary shifts in the larvae, but a metabolic origin for changes in certain fatty acids was also evident. In the first period, relative amounts of n-9 monounsaturates decreased, while n-3 polyunsaturates together with certain fatty acids abundant in the small-sized phytoplankton fraction increased. In the second and third periods, relative amounts of the longer n-3 PUFA decreased, while fatty acids of calanoid copepod origin occurred in one group. The consistency in changes of larval fatty acid profiles in cod suggests development in both lipid absorption and lipid metabolism during ontogenesis. 相似文献
93.
94.
The concentrations of copper, molybdenum and zinc were measured in the liver of normal grazing sheep and lambs from Eastern Norway, and in sheep dead of chronic copper poisoning. The following mean values were found: Normal sheep: 173 ± 130 μg Gu/g wet weight, 1.0 ±0.3 μg Mo/g, and 49 ± 10 μg Zn/g; lambs: 129 ± 59 μg Gu/g, 0.9 ± 0.3 μg Mo/g, and 46 ±9 μg Zn/g; sheep dead of copper poisoning: 429 ± 249 μg Gu/g, 0.4 ± 0.1 μg Mo/g, and 43 ± 2d μg Zn/g. Sheep with low liver copper (Gu < 10 μg/g) were also analyzed for molybdenum and zinc, with the following results: 1.0 ± 0.2 μg Mo/g, and 45 ± 8 μg Zn/g wet weight. The differences in liver copper between all the groups, and the differences in molybdenum concentrations between the normal sheep and the lambs and between the normal sheep and the poisoned sheep were significant (P < 0.001). No significant correlations between liver copper/liver molybdenum or liver copper/liver zinc were detected. 相似文献
95.
96.
ABSTRACT In spring 2002, an unusual disease outburst was recorded on Norway spruce seedlings in southeast Norway. Extensive damage was recorded on 1- and 2-year-old Norway spruce seedlings that either had wintered in nursery cold storage or had been planted out in autumn 2001. The damage was characterized by leader shoot dieback and stem necroses on the upper or lower part of the shoot from 2001. Gremmeniella abietina and a Phomopsis sp. frequently were isolated from the diseased seedlings. Internal transcribed spacer (ITS) ribosomal (r)DNA sequence analysis and random amplified microsatellites profiling indicated that the G. abietina strains associated with diseased nursery seedlings belonged to the large-tree type (LTT) ecotype of the European race of G. abietina var. abietina, and inoculation tests confirmed their pathogenicity on Norway spruce. Based on ITS rDNA sequence analysis, the Phomopsis strains associated with diseased seedlings did not represent any characterized Phomopsis spp. associated with conifers. The Phomopsis sp. was not pathogenic in inoculation tests, indicating that it may be a secondary colonizer. ITS-based real-time polymerase chain reaction assays were developed in order to detect and quantify G. abietina and Phomopsis in the nursery stock. We describe here the G. abietina-associated shoot dieback symptoms on Norway spruce seedlings and conclude that the unusual disease outburst likely was related to the G. abietina var. abietina epidemic caused by the LTT on large Scots pines in 2001. 相似文献
97.
98.
Sidsel Fiskaa Hagen Grethe Iren A. Borge Knut Asbjørn Solhaug Gunnar B. Bengtsson 《Postharvest Biology and Technology》2009,51(1):36-42
In this study, curly kale stored at 1 °C for 3 and 6 weeks was compared with plants remaining in the field regarding several properties related to human health and sensory quality. Cold storage had no effect on the antioxidant capacity (ORAC assay), total phenols (Folin-Ciocalteu assay) or flavonol content, but reduced the content of vitamin C and soluble sugars. The ratio ascorbic:dehydroascorbic acid decreased from about 3 to 0.5 upon storage. The largest changes in the content of bioactive compounds were found in plants that remained in the field for 6 additional weeks, including many frost days. In these plants, the levels of flavonols, total phenols and antioxidant capacity were reduced by 25–35% and the vitamin C content by more than 50%, whereas soluble sugars and dry matter increased by roughly 20% and 30%, respectively. Among all the curly kale samples, the antioxidant capacity was positively correlated with the level of total phenols (r = 0.73, P < 0.001) and total flavonols (r = 0.70, P < 0.001). Values obtained with a non-destructive method based on chlorophyll fluorescence (ChlF) were well correlated with the flavonol content in the leaves, with the highest correlation found for quercetin (r = 0.76, P < 0.001). Using the ChlF method, the kinetics of the flavonol content during the experiment was recorded. The same method also showed gradients of flavonol content within the plant, with the highest values in the upper leaves and in the tip of the leaves. ChlF measurement, therefore, proved to be a quick and cost-effective alternative to chemical analyses of the flavonol content in curly kale. 相似文献
99.
K. Alvåsen M. Jansson Mörk I.R. Dohoo C. Hallén Sandgren P.T. Thomsen U. Emanuelson 《Preventive veterinary medicine》2014
Dairy cow mortality (unassisted death and euthanasia) has increased, worldwide and in Sweden. On-farm mortality indicates suboptimal herd health or welfare and causes financial loss for the dairy producer. The objective of this study was to identify cow-level risk factors associated with on-farm cow mortality. Cows with at least one calving between 1 July 2008 and 30 June 2009 from herds enrolled in the Swedish official milk recording scheme with >40 cow-years were included. Each cow was followed from the day of calving until she calved again or left the herd (died, slaughtered or sold). The effects of potential risk factors on on-farm cow mortality were analysed using a Weibull proportional hazard model with a gamma distributed frailty effect common to cows within herd. The event of interest (failure) was euthanasia or unassisted death. An observation was right censored if the cow was slaughtered, sold, calved again or had an on-going lactation at 500 days after calving. The lactations were split into seasons (January to April, May to August and September to December) and at 30 and 100 days in milk in order to evaluate seasonal effects and the effect of disease in different lactation stages. Primiparous and multiparous cows were analysed separately. The highest hazards for both primiparous and multiparous cows were found for traumatic events and diseases, both in the lactation stage in which the cow died and in the preceding stage. The hazard was higher in early lactation and lower in 2nd parity compared to higher parities. Increased age at first calving (for primiparous cows), calving between January and April, dystocia and stillbirth also increased the mortality hazard. Differences were also found between breeds, between milk production parameters at first test milking and between management types. The results from this study show the importance of good management and preventive health actions, especially around calving, to avoid mortality in dairy cows. 相似文献
100.
The purpose of this study was to investigate the influence of soil geochemistry on the concentrations of Ca, K, Mg, P, Co, Ni, Zn, Mn, Cu, and Fe in cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate (AS) soils in Western Finland. A total of 11 topsoil (0–20 cm) and corresponding cabbage samples and three whole‐soil profiles (≈ 0–260 cm) were collected on three agricultural fields. The concentrations of Co and Zn in cabbage were correlated with the NH4Ac‐extractable (easily available) concentrations in the topsoil, indicating that the uptake of these elements in cabbage is largely governed by soil geochemistry. Yet, the concentrations of Co and Zn in cabbage were not in general elevated relative to that of Finnish average values, although some AS soils showed enriched concentrations of these metals in the soil and cabbage. Significant geochemical differences (e.g., oxidation depth, organic‐matter and S content, pH) were observed among the studied AS soils, while, on the other hand, the concentrations of Ca, K, Mg, P, Ni, Mn, Cu, and Fe in cabbage were relatively similar. The hydroxylamine‐extractable concentrations of these elements in the topsoil were not correlated to those in cabbage, suggesting that uptake is not governed by the oxide‐bound fraction of these elements in the soil. Similarly, the easily available concentrations of Ca, P, Ni, Mn, Cu, and Fe in the topsoil were not correlated to those in cabbage, indicating that uptake is independent of the easily available concentrations in the soil. Hence, it is suggested that cabbage can regulate and thus optimize its concentrations of Ca, P, Ni, Mn, Cu, and Fe. Oxidation depth affected neither the easily available concentrations of Co, Ni, Zn, and Mn in the topsoil nor the concentrations in cabbage. However, the subsoil with a lower oxidation depth, which is to a smaller extent affected by leaching, may partly be enriched in these metals. Nevertheless, these showed no increased concentrations in cabbage. Based on these findings, it is suggested that the large amounts of metals mobilized in AS soils are easily lost to drains, subsequently contaminating nearby waterways and estuaries whereas they are only partly enriched in cabbage and other previously studied crops (oat). 相似文献