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181.
黑鲷的营养需要及配合饲料研究 总被引:9,自引:0,他引:9
本文论述了黑鲷饲料中最适蛋白质含量及动,植物蛋白比例的有关研究,黑鲷对于饲料中磷的需要量及钙磷化,黑鲷饲料中必需氨基酸添加的必要性,在此基础上,制成黑鲷配合饲料并与冰冻玉筋鱼进行了比较养殖试验,取得较好的结果。 相似文献
182.
183.
Sodium (Na+) in poor quality irrigation water participate in ion-exchange processes results in the displacement of base cations into
solution and a raised concentration in groundwater. Knowledge of the rate of decrease of nutrients from soils resulting from
poor water quality application is essential for long-term planning of crop production while minimizing the impact on groundwater
quality. In this study, we examined the effect of sodium adsorption ratio (SAR) of irrigation water on nutrients leaching
and groundwater quality in columns of sandy soil. Three types of irrigation waters at three NaCl–CaCl2 solutions with the following levels of SAR (5, 15, and 30) were synthesized in laboratory. With the application of solutions,
exchange occurred between solution Na+ and exchangeable cations (Ca2+, Mg2+, and K+), resulting in the displacement of these cations and anions into solution. Increasing the level of SAR from 5 to 15 and 30
resulted in increase in the average exchangeable sodium percentage (ESP) of the soil from 10.4 to 20.3, and 32.5, respectively.
Adverse effect of high Na+ concentration in the solutions on raising ESP was less pronounced in solution having low SAR. Leaching of Ca2+, Mg2+, K+, and P from soil with the application of solutions represents a significant loss of valuable nutrients. This sandy soil showed
the high risk for nutrients transfer into groundwater in concentrations exceeding the groundwater quality standard. Irrigation
with poor quality water, which is generally more sodic and saline than regional groundwater, increases the rate of sodification
and salinization of shallow groundwater. 相似文献
184.
基于 Markov 理论的加权非等距GM(1,1)预测优化模型 总被引:1,自引:0,他引:1
背景值的构造方法是影响加权非等距GM(1,1)预测模型的精度和适应性的关键因素。文中通过等分函数法构造新的背景值对传统的加权非等距GM(1,1)模型进行优化,优化后的模型使其同时适应于高增长指数序列和低增长指数序列,提高传统模型的预测精度和适应性能力。但是优化后的模型依然易受建模数据随机扰动影响。马尔科夫(Markov)模型具有削弱建模数据的随机扰动性的优势。基于此,将优化的加权非等距GM(1,1)模型和Markov理论有机结合,构建优化的加权非等距Markov-GM(1,1)预测模型。最后,结合秀山湖二期工程的变形实测数据,运用新陈代谢的计算模式进行预测验证。结果表明:优化的加权非等距Markov-GM(1,1)预测模型的拟合和预测精度都优于传统的加权非等距GM(1,1)预测模型,新的预测模型的适用性更强,具有实际的参考价值。 相似文献
185.
喀斯特地区土壤侵蚀及养分流失定位试验研究——以贵阳市修文县久长镇为例 总被引:10,自引:4,他引:6
2001- 2003年对黔中喀斯特地区(久长镇) 20°坡耕地(黄壤土)不同种植处理条件下的土壤侵蚀与养分流失进行为期3年的观测。结果表明: 种植牧草(三叶草与黑麦草播)截流效果最佳,所产生径流量最小,为63. 47mm,仅占3年总量平均值的20% ,防治土壤侵蚀和阻止养分流失效果最好—— 土壤侵蚀模数仅为225t /km2· a ,养分(全钾)流失( 3年平均)仅为32. 76 kg /hm2; 其次是条带种植处理,侵蚀模数591 t /km2· a ,养分流失(全钾) 26. 65 kg /hm2。此外,条带种植还可以获得高产,比习惯种植增产746 kg /h m2。因此,在喀斯特地区20°坡度区发展条带种植势在必行。 相似文献
186.
A universal nutrient application strategy for the bioremediation of oil-polluted beaches 总被引:2,自引:0,他引:2
Biostimulation by nutrient application is a viable technology for restoring oil-contaminated beaches. Maximizing the nutrient residence time is key for achieving a rapid cost-effective cleanup. We considered the nutrient injection strategy through a perforated pipe at the high tide line and we simulated numerically beach hydraulics, which allowed us to estimate the optimal injection flow rate of nutrient solution. Our results indicate that the optimal application is one that starts following the falling high tide and lasts for half tidal cycle. The saturated wet-front of the nutrient solution on the beach surface would move seaward with the same speed of the falling tide keeping a constant distance with the tide line. The numerical results were generalized to beaches of wide ranges of hydraulic and tidal properties using a novel dimensionless formulation for water flow and solute transport in porous media. Nomographs were presented to provide the flow rate based on four parameters: The beach slope and hydraulic conductivity, and tidal amplitude and period. 相似文献
187.
188.
Robert Pascal Laurent Boiteau Patrick Forterre Muriel Gargaud Antonio Lazcano Purificación Lopez-Garcia Marie-Christine Maurel David Moreira Juli Pereto Daniel Prieur Jacques Reisse 《Earth, Moon, and Planets》2006,98(1-4):153-203
This chapter is devoted to a discussion about the difficulties and even the impossibility to date the events that occurred during the transition from non-living matter to the first living cells. Nevertheless, the attempts to devise plausible scenarios accounting for the emergence of the main molecular devices and processes found in biology are presented including the role of nucleotides at early stages (RNA world). On the other hand, hypotheses on the development of early metabolisms, compartments and genetic encoding are also discussed in relation with their role in extant living organisms. The nature of the Last Common Ancestor is also presented as well as hypotheses on the evolution of viruses. The following sections constitute a collection of independent articles providing a general overview of these aspects. 相似文献
189.
Accurate and detailed accounting of energy-induced carbon dioxide(CO2) emissions is crucial to the evaluation of pressures on natural resources and the environment, as well as to the assignment of responsibility for emission reductions. However, previous emission inventories were usually production- or consumption-based accounting, and few studies have comprehensively documented the linkages among socio-economic activities and external transaction in urban areas. Therefore, we address this gap in proposing an analytical framework and accounting system with three dimensions of boundaries to comprehensively assess urban energy use and related CO2 emissions. The analytical framework depicted the input, transformation, transfer and discharge process of the carbon-based(fossil) energy flows through the complex urban ecosystems, and defined the accounting scopes and boundaries on the strength of ‘carbon footprint' and ‘urban metabolism'. The accounting system highlighted the assessment for the transfer and discharge of socio-economic subsystems with different spatial boundaries. Three kinds methods applied to Beijing City explicitly exhibited the accounting characteristics. Our research firstly suggests that urban carbon-based energy metabolism can be used to analyze the process and structure of urban energy consumption and CO2 emissions. Secondly, three kinds of accounting methods use different benchmarks to estimate urban energy use and CO2 emissions with their distinct strength and weakness. Thirdly, the empirical analysis in Beijing City demonstrate that the three kinds of methods are complementary and give different insights to discuss urban energy-induced CO2 emissions reduction. We deduce a conclusion that carbon reductions responsibility can be assigned in the light of production, consumption and shared responsibility based principles. Overall, from perspective of the industrial and energy restructuring and the residential lifestyle changes, our results shed new light on the analysis on the evolutionary mechanism and pattern of urban energy-induced CO2 emissions with the combination of three kinds of methods. And the spatial structure adjustment and technical progress provides further elements for consideration about the scenarios of change in urban energy use and CO2 emissions. 相似文献
190.
Ying Ge Chongbang Zhang Yueping Jiang Chunlei Yue Qinsu Jiang Hang Min Haitian Fan Qiang Zeng Jie Chang 《洁净——土壤、空气、水》2011,39(3):206-211
Rhizosphere microorganism is an important bio‐component for wastewater treatment in constructed wetlands (CWs). Microbial abundance and enzyme activities in the rhizospheres of nine plant species were investigated in an integrated vertical‐flow CW. The abundance of denitrifiers, as well as urease, acid, and alkaline phosphatase activities were positively correlated to plant root biomass. The abundance of bacteria, fungi, actinomycetes, ammonifiers, denitrifiers, and phosphorus decomposers, related to nutrient removal efficiencies in CWs, greatly varied among rhizospheres of different plant species (p < 0.05). Significant differences in rhizosphere enzyme activity among plant species were also observed (p < 0.05), with the exception of catalase activity. The principal component analysis using the data of microbial abundance and enzyme activity showed that Miscanthus floridulus, Acorus calamus, and Reineckia carnea were candidates to be used in CWs to effectively remove nitrogen and phosphorus from wastewater. 相似文献