首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   144篇
  免费   11篇
林业   7篇
农学   18篇
基础科学   1篇
  38篇
综合类   9篇
农作物   12篇
水产渔业   3篇
畜牧兽医   52篇
园艺   4篇
植物保护   11篇
  2023年   1篇
  2022年   2篇
  2021年   5篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2017年   3篇
  2016年   9篇
  2015年   5篇
  2014年   4篇
  2013年   11篇
  2012年   5篇
  2011年   17篇
  2010年   11篇
  2009年   10篇
  2008年   10篇
  2007年   3篇
  2006年   7篇
  2005年   9篇
  2004年   2篇
  2003年   12篇
  2002年   3篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1995年   2篇
  1990年   1篇
  1989年   2篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1983年   3篇
  1981年   1篇
  1978年   1篇
  1969年   1篇
  1955年   1篇
排序方式: 共有155条查询结果,搜索用时 15 毫秒
61.
62.
Phenolic acid intake through the consumption of whole-wheat foods provides important health benefits associated with reduced risks of cardiovascular diseases and colon cancer. The genetic variation for phenolic acids was extensively studied in common wheat, but a comprehensive survey in tetraploid wheat is lacking. In this study we evaluated the genetic variability for individual and total phenolic acids concentration existing in a large collection of tetraploid wheat (Triticum turgidum L.). A 2-year evaluation was undertaken on the whole-meal flour of 111 genotypes belonging to seven T. turgidum subspecies including cultivars, landraces and wild accessions. Durum cultivars [T. turgidum subsp. durum (Desf.) MacKey], had the highest average concentration of total phenolic acids (828.7 μg g?1 dm in 2012; 834.5 μg g?1 dm in 2013) with amounts varying from 550.9 μg g?1 dm to 1701.2 μg g?1 dm, indicating a variation of greater than threefold fold. The lowest concentration of phenolic acids was found in T. turgidum subsp. dicoccum (Schrank ex Schübler) Thell. Rivet wheat (T. turgidum L. subsp. turgidum) had phenolic acid concentrations similar to those in durum, but less variation was noted among the accessions. On the other hand, the accessions of the four remaining subspecies showed lower phenolic acid concentrations and variation among the accessions as compared to durum. A total of six phenolic acids were identified across the wheat genotypes. The effects of genotype, year and year × genotype were estimated by ANOVA and resulted significant for all phenolic acids. The ratio of genotypic variance to total variance suggested the possibility of improving phenolic acid content in elite wheat germplasm through appropriate breeding programs. Moreover, significant correlations between phenolic acids and other quality characteristics of the grain were detected.  相似文献   
63.
Two experiments were designed to determine if melatonin concentrations differ between jugular veins. In a first experiment, blood was collected continuously every 30 min from each jugular during 12-h from 6 ewes. In a second experiment, 100 ewes were sampled twice at night simultaneously from the two jugular veins. In both experiments, mean melatonin concentrations were similar between right and left jugulars. However, within individuals, large differences were observed between the two sides (p < 0.001). This difference was stable over time and the higher side varies among individuals. The concentrations of prolactin and oxytocin, measured in the same samples did not show such differences. This observation raises the question of the origin of this phenomenon. Moreover, it has important implications for studies in which melatonin concentrations need to be assessed accurately. Indeed, a reliable quantitative assessment of melatonin production by the pineal gland requires sampling from both jugular veins.  相似文献   
64.
In order to provide values of key parameters in aquaculture waste degradation modelling specifically for the Mediterranean, sampling campaigns were carried out in 2006. Accurate measurements of particulate carbon input and benthic respiration rates were performed using sediment traps and intact core incubations. The in situ measurements, compared with data from Atlantic salmon production, showed lower carbon flux and oxygen consumption, while a greater degradation capability was observed. Moreover, a temperature dependence of the benthic parameters was highlighted. Successively, the model Finite Organic Accumulation Module was used for an accurate comparison between different parameterizations. Finite Organic Accumulation Module simulates the organic carbon degradation and the net carbon accumulation on the sediment, yielding a benthic state index. In comparison with previous results, there was a decrease in benthic impacts due to minor inputs of carbon and higher mineralization rates. Moreover, a seasonal variation could be observed in the organic carbon concentration. Nevertheless, the new results remain consistent with the old ones on two points: (a) the negligible benthic impact of faeces with respect to uneaten feed and (b) the dependence of that impact on the different feed release conditions.  相似文献   
65.
66.
67.
Recent plant diversity changes on Europe's mountain summits   总被引:2,自引:0,他引:2  
In mountainous regions, climate warming is expected to shift species' ranges to higher altitudes. Evidence for such shifts is still mostly from revisitations of historical sites. We present recent (2001 to 2008) changes in vascular plant species richness observed in a standardized monitoring network across Europe's major mountain ranges. Species have moved upslope on average. However, these shifts had opposite effects on the summit floras' species richness in boreal-temperate mountain regions (+3.9 species on average) and Mediterranean mountain regions (-1.4 species), probably because recent climatic trends have decreased the availability of water in the European south. Because Mediterranean mountains are particularly rich in endemic species, a continuation of these trends might shrink the European mountain flora, despite an average increase in summit species richness across the region.  相似文献   
68.
Pre-harvest multiple treatments of grapevine (cv. Merlot) with the plant activator benzothiadiazole (BTH, 0.3 mM) enhanced trans-resveratrol content in berries by about 40%. An even more striking effect was observed on anthocyanin synthesis, particularly on malvidine 3-glucoside, malvidine 3-(6-O-acetyl)glucoside and malvidine 3-(6-O-p-coumaroyl)glucoside, whose amounts were more than doubled. These data were obtained with a novel and time-saving HPLC method, set up for the simultaneous detection of stilbenes and anthocyanins, using an RF-10Axl fluorimetric detector instrument, with excitation at 330 nm and emission at 374 nm, and a SPD-Avp UV detector with absorption at 520 nm. Furthermore, BTH treatments induced systemic acquired resistance in grapevine, as assessed by inoculating clusters from treated and untreated plants with Botrytis cinerea. Disease severity, estimated according to the percentage of infected berries per cluster, was significantly reduced in grapes from BTH-treated plants. These results indicate that BTH treatments, besides improving the content of two important classes of nutraceuticals, with their well-known antioxidant, antitumoral, and phytoestrogenic activities, could be exploited in vineyard to protect grape against gray mould infection, thereby limiting an excessive use of fungicides  相似文献   
69.
Results are reported for a collaborative study of a method for the extraction of light filth from spirulina (a blue-green alga) powder and tablets. A 50 g portion of either powder or tablets is dispersed in water, and then boiled with dilute HCI solution. Hairs and insect fragments are isolated by wet sieving on a No. 230 sieve, flotation with mineral oil, and washings of the mineral oil in a percolator. Average recoveries by 12 collaborators for tablets and powders were 70.6 and 70.2%, respectively, for 10 rat hair spikes and 68.3 and 84.4%, respectively, for 20 insect fragment spikes. The method has been approved interim official first action.  相似文献   
70.
The effects of ozone on bean plants pretreated with the SAR activator benzothiadiazole (BTH) have been investigated after fumigations with an acute dose of the pollutant (200 nL x L(-1) for 4 h), carried out at different times from BTH application. BTH pretreatment induced opposite effects on bean susceptibility to O(3), depending on the time elapsed before fumigation. When this time was only 1-2 days, bean plants were more susceptible to O(3) than untreated controls, showing rapid and extensive cell death in both palisade and spongy mesophyll. These damages appeared to be closely correlated with the amount and localization of H(2)O(2) in the leaf tissues. In BTH-pretreated, but not fumigated, plants, H(2)O(2) accumulation occurred in the cell walls and no dead cells were detected, whereas O(3) fumigation of untreated plants produced H(2)O(2) accumulation also inside some palisade mesophyll cells, causing their death. When BTH pretreatments were carried out 5-7 days before fumigation, plants appeared to be more tolerant to O(3) compared to untreated controls. Under these conditions, no visible symptoms of phytotoxicity were observed for at least 2 weeks after fumigation and no H(2)O(2) accumulation was detected. Biochemical assays showed a significant increase in the ascorbate (AA) level, taking place from the fifth to the seventh day after BTH treatment and unaffected by O(3) when given at these times. Ascorbate peroxidase (APX) activity appeared to decrease during the first 2 days after BTH treatment, and the decrease was somewhat enhanced by fumigation. On the contrary, guaiacol peroxidase (GuPX) activity was found to steadily increase up to the fifth day after BTH treatment but showed a bimodal trend upon fumigation. These results suggest that, during the first 1-2 days after BTH application, the H(2)O(2) level is enhanced by O(3) over a critical threshold for cell viability. However, in the absence of the pollutant, H(2)O(2) decreases in the following days under the effect of AA accumulation and increased GuPX activity. As GuPX is known to promote cell wall lignification and protein cross-linking, these effects would protect plasmalemma from O(3) irreversible damage, provided the priming by BTH has been fully developed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号