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   22篇
  免费   0篇
林业   4篇
基础科学   5篇
  2篇
综合类   8篇
农作物   1篇
畜牧兽医   2篇
  2019年   1篇
  2016年   1篇
  2014年   1篇
  2012年   2篇
  2011年   1篇
  2010年   2篇
  2007年   1篇
  2006年   2篇
  2003年   1篇
  2002年   1篇
  2000年   2篇
  1997年   2篇
  1991年   1篇
  1988年   1篇
  1976年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有22条查询结果,搜索用时 343 毫秒
1.
Climatic variation in the natural distribution of Acacia mearnsii in Australia was analysed. Data from sites where the species has been successfully grown in plantations and trials in Africa, Asia and South America were used to determine the species' climatic adaptability. Annual mean temperatures at these plantations and trial sites ranged from 13.9 to 23.9°C, whilst annual mean precipitation ranged from 693 to 2263 mm. The coldest month minimum temperature at these sites was –0.6°C. This information, along with other details of climatic requirements presented in the paper, will assist in selecting sites for future trials at new locations.  相似文献   
2.
3.
Halogen contents similar to those in meteorites are reported in Apollo 11 samples. Concentrations of 0.6 to 13 parts mercury, 0.2 to 0.8 part uranium, 1 to 17 parts lithium, and 1 to 800 parts osmium per million and 0.5 to 1 percent chromium oxide by weight have been measured. In contrast to meteorites and terrestrial rocks a large mercury release below 110 degrees C is observed. Some implications of these results are presented. Fluorapatite, quartz, tridymite, fayalite, and iron-rich, manganese-poor pyroxmangite, previously unreported, have been identified. The small amount of fluorapatite found does not account for the fluorine contents.  相似文献   
4.
Agriculture is a big consumer of fresh water in competition with other sectors of the society. Within the EU-project SAFIR new water-saving irrigation strategies were developed based on pot, semi-field and field experiments with potatoes (Solanum tuberosum L.), fresh tomatoes (Lycopersicon esculentum Mill.) and processing tomatoes as model plants. From the pot and semi-field experiments an ABA production model was developed for potatoes to optimize the ABA signalling; this was obtained by modelling the optimal level of soil drying for ABA production before re-irrigation in a crop growth model. The field irrigation guidelines were developed under temperate (Denmark), Mediterranean (Greece, Italy) and continental (Serbia, China) climatic conditions during summer. The field investigations on processing tomatoes were undertaken only in the Po valley (North Italy) on fine, textured soil. The investigations from several studies showed that gradual soil drying imposed by deficit irrigation (DI) or partial root zone drying irrigation (PRD) induced hydraulic and chemical signals from the root system resulting in partial stomatal closure, an increase in photosynthetic water use efficiency, and a slight reduction in top vegetative growth. Further PRD increased N-mineralization significantly beyond that from DI, causing a stay-green effect late in the growing season. In field potato and tomato experiments the water-saving irrigation strategies DI and PRD were able to save about 20-30% of the water used in fully irrigated plants. PRD increased marketable yield in potatoes significantly by 15% due to improved tuber size distribution. PRD increased antioxidant content significantly by approximately 10% in both potatoes and fresh tomatoes. Under a high temperature regime, full irrigation (FI) should be undertaken, as was clear from field observations in tomatoes. For tomatoes full irrigation should be undertaken for cooling effects when the night/day average temperature >26.5 °C or when air temperature >40 °C to avoid flower-dropping. The temperature threshold for potatoes is not clear. From three-year field drip irrigation experiments we found that under the establishment phase, both potatoes and tomatoes should be fully irrigated; however, during the later phases deficit irrigation might be applied as outlined below without causing significant yield reduction:
Potatoes
°
After the end of tuber initiation, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.
Fresh tomatoes
°
From the moment the 1st truce is developed, DI is applied at 85-80% of FI for two weeks. In the middle period, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.
Processing tomatoes
°
From transplanting to fruit setting at 4th-5th cluster, the PRD and DI threshold for re-irrigation is when the plant-available soil water content (ASWC) equals 0.7 (soil water potential, Ψsoil = −90 kPa). During the late fruit development/ripening stage, 10% of red fruits, the threshold for re-irrigation for DI is when ASWC = 0.5 (Ψsoil = −185 kPa) and for PRD when ASWC (dry side) = 0.4 (Ψsoil, dry side = −270 kPa).
The findings during the SAFIR project might be used as a framework for implementing water-saving deficit irrigation under different local soil and climatic conditions.  相似文献   
5.
6.
小麦F1F2代籽粒醇溶蛋白遗传分析   总被引:2,自引:0,他引:2  
用酸性聚丙烯酰胺凝胶电泳分离、表征4个小麦品种醇溶蛋白组成,并分析其F1,F2代20个醇溶蛋白组分(带)的遗传模式。结果表明,醇溶蛋白呈共显性遗传,在20个组分中,16个组分由1个显性基因支配,2个组分则受控于2个独立基因,其余2个微小组分,由于在电泳谱上难以准确辨认,其遗传模式未能确定。有5对醇溶蛋白组分是共同遗传,表明每组组分由紧密连锁基因控制。另外,7对醇溶蛋白组分或组分群分别由等位位点的不同等位基因支配。  相似文献   
7.
The magnitudes of the mercury anomaly found in unequilibrated meteorites appear to fit a trend. The excesses in the ratios of mercury-202 to mercury-196 are related by simple multiplication factors. This periodicity may be interpreted in terms of the mode of production and ejection of the anomalous isotope from a stellar source.  相似文献   
8.
Lunar samples contain mercury, which may be volatilized at lunar daytime temperatures. Such mercury may constitute part of the tenuous lunar atmosphere. If mercury can escape from the atmosphere by a nonthermal mechanism, an interior reservoir or exterior sources (such as meteorite infall or solar wind, or both) are required to replenish it. Core samples exhibit an increase in surface-related mercury with depth, which suggests that a cold trap exists below the surface. The orientation of rocks on the lunar surface may be inferred by differences in the amounts of surface-related mercury found on exterior and interior samples.  相似文献   
9.
A modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO 3 ? ) and chloride (Cl?) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO 3 ? and Cl? was heterogeneous and the concentration decreased during the monitoring period, with NO 3 ? attenuation (below 10?mg/l) after 650?days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO 3 ? and Cl? concentrations. Cl? was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO 3 ? was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e?3 mg-NO 3 ? /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO 3 ? attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO 3 ? clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain.  相似文献   
10.
Quinoa is an Andean seed crop of many potential uses. In 2009 a field trial was carried out to explore the potential for quinoa growing in climatic conditions of South Eastern Europe. Even under rainfed conditions, without fertilization, a seed yield as high as 1.721 t ha−1 was obtained. Seed quality was remarkably good, with protein content ranging from 15.16 to 17.41 % on a dry weight basis, depending on whether seeds were processed. Amino acid and mineral composition revealed the potential of quinoa seeds as a valuable ingredient in the preparation of highly nutritious foods. Quinoa seeds had higher contents of most essential amino acids, especially lysine, than wheat flour. Dehulled quinoa seeds, devoid of saponins, were included into wheat bread formulations, with up to 20%, which resulted in a positive effect on the rheological characteristics of dough. Furthermore, protein content in bread was increased by around 2%. Sensory characteristics of breads were excellent also at the 20% supplementation level. The study of bread supplemented with quinoa seeds could enable the development of a range of new baking products with enhanced nutritional value.  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