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Surface area processing in GIS for different mountain regions 总被引:1,自引:0,他引:1
Surface area is a fundamental parameter derived from terrain analysis in geographical information systems (GIS) for modeling the real world. Therefore, an evaluation of the techniques implemented by GIS models is important in order to obtain reliable area measurements. The study compares two raster-based methods with a TIN-based (triangulated irregular network) method for surface area approximation using a digital elevation model (DEM) with 25 m × 25 m resolution in six mountain regions of Shandong Province, China. Raster-based method Ⅰ calculates surface-area grids from DEMs directly. Eight 3-dimensional triangles connecting the center point of each cell with the center points of the eight surrounding cells are generated and then the areas of the portions of each triangle that lay within the cell boundary are calculated and summed. Raster-based method Ⅱ produces the surface area of each cell directly from the pixel size and the slope value for the pixel. The results demonstrate that the surface areas calculated by raster-based method Ⅰ are equal to those of the TIN-based method. The results of raster-based method Ⅱ are the lowest but the difference in areas between the two raster-based methods decreases with the decrease in terrain complexity. Compared to the method with TINs, raster-based method Ⅱ can do better because it has some advantages, such as neighborhood analysis, more consistent output and faster processing speed. The results also demonstrate that the difference between surface and horizontal areas should be considered if more than 30% of the area of a region has slopes steeper than 18.2 degrees. 相似文献
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中国西部山地旅游资源的基本特征及其开发的限制因素 总被引:3,自引:0,他引:3
山地旅游资源是中国西部地区极为重要的一种自然旅游资源 ,从地理学角度对中国西部地区山地旅游资源的基本特征进行了分析 ,认为西部山地旅游资源具有 6个显著的特点 ,并对西部山地旅游资源开发的限制因素及需注意问题进行了初步探讨 相似文献
106.
Carlos?Wildt Oriol?Gibert José?Luis?CortinaEmail author Giuliana?Coscera 《Journal of Soils and Sediments》2004,4(3):184-191
Goal, Scope and Background The remediation of heavy-metalcontaminated soils and sediments is of significant value to industrial areas around the world.
The spread of such pollutants can result in a potential risk of entering the groundwater system and being transported to potential
receptors. Leaching techniques can be an effective treatment option for the metal removal from soils and sediments. This approach
consists of washing or leaching the contaminated soil with an appropriate reagent and the subsequent treatment of the leaching
in an above-ground installation (on-site treatment) where metals can be removed and concentrated into a smaller volume. Among
the heavy metals, chromium is a commonly identified soil contaminant, particularly in sites with intensive economic activities
including agriculture, industrial, mining and mineral,processing.
Objective The objective of this work was the evaluation and development of a leaching process for the remediation of soils and sediments
polluted with chromium at laboratory scale. Chromium soil pollution was generated after the breakdown of a channel containing
chromium wastes from a tannery plant. The pollution extension has been estimated to be on the order of thousands of tonnes
of soil to be treated, with chromium contents ranging from 500 to 17,000 mg kg-1 soil.
Methods The whole process investigated in this study integrates three stages; a) chromium leaching from a sediment using a diluted
sulphuric acid solution, b) treatment of the leaching effluents with a magnesium oxide/limestone mixture for the precipitation
of chromium hydroxide after acidity neutralisation, and c) polishing step to remove the eventual remaining chromium by adsorption
onto natural zeolite. The amount of contaminated sediment treated ranged from 0.5 to 2 kg with chromium contents of between
2000 and 17,000 mg kg-1.
Results and Discussion The paper describes results on the performance of the process and the optimisation of steps including influence of acid sulphuric
concentration, chromium removal efficiency as well as alkaline reactive mixture proportions. Effluents from the leaching cells
showed a significant decay on the chromium concentration with the increase of leaching runs and a high content of acidity
(pH values close to 0.5). The treatment of these effluents in a second cell containing magnesium oxide/ limestone mixtures
resulted in a high efficiency in neutralisation of acidity (pH values around 7) and chromium removal (concentrations below
5 mg 1-1). The passage through a third compartment containing zeolite as an adsorbent decreased the chromium concentration below 0.5
mg 1-1,
Conclusions From the results obtained on the chromium leaching and immobilisation with magnesium oxide/limestone mixture at a laboratory
scale, it could be pointed out that: (a) diluted sulphuric acid solutions (3%) demonstrated a high efficiency on chromium
removal from sandy polluted soils on the kilogram scale, (b) mixtures of magnesium oxide/limestone demonstrated a high capacity
to neutralise the residual high acidity present on the effluents and to remove chromium by precipitation and (c) between the
limestone and caustic magnesia mixtures, those containing more than 60% of caustic magnesia provide the higher efficiency.
Recommendation and Outlook Future work would be directed to the evaluation of the integrated process of leaching and chromium precipitation on column
at a scale of 100 to 1000 kg. 相似文献
107.
坚持治理开发山乡面貌大变柴学松(四川省铜梁县水土保持办公室,632560)铜梁县双山乡位于涪江支流平滩河的上游,北、西、南三面为坪块低山环绕,中部由七沟八梁的中低丘陵与宽谷构成,在总面积为33.83km2的范围内,水土流失面积达13.64km2,森林... 相似文献
108.
Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies. 相似文献
109.
为了解长江三峡库区森林土壤的物理性质,运用分形原理,研究重庆缙云山4种典型林分林地土壤分形特征,建立土壤结构分维与土壤性质预测模型,运用弹性分析与边际分析,探讨土壤结构分形变化与土壤性质变化的关系。研究表明:土壤机械组成分维、微团聚体组成分维和孔隙组成分维可作为评价土壤结构的指标。不同林分林地土壤颗粒机械组成分维值为2.7~2.9,土壤微团聚体组成分维为2.5~2.8,土壤孔隙组成分维为2.3~2.8。从质地、微团聚体组成和孔隙组成来看,常绿阔叶灌丛土壤结构要明显优于其他林地土壤,而楠竹林最差。不同林分及农地土壤的微团聚体组成、机械颗粒组成和孔隙组成分维与土壤性质存在较明显相关关系,相关系数都在0.5以上。由弹性系数和边际量可以看出,机械分维的影响要大于微团聚体分维和孔隙组分维。这对进一步探讨分形学在土壤结构与土壤性质的应用方面有重要的意义。 相似文献
110.