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1.
2.
The colored patterns on arbitrary cut plane is an important method in 3D data-field visualization of finite element.By using the technology of the Object-Oriented Programming and the method of scan-line,the colored patterns on arbitrary cut plane are given.The example by the OPENGL of Visual C++ R6 can support the theory satisfactorily. 相似文献
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《Land Degradation \u0026amp; Development》2017,28(5):1704-1716
Phosphorus (P) loss from arable sloping land due to water erosion causes off‐site environment pollution in the Three Gorges area in China. This study aims to estimate the effects of agricultural practices on the reduction of P losses during water erosion processes under natural precipitation conditions: contour culturing with organic matter addition (CT + OM), contour culturing with wheat straw mulching (CT + SM), contour culturing with straw mulching and organic matter addition (CT + OM + SM) and conventional downslope culturing framework as a control (CK). Results demonstrated that CT + OM + SM could viably diminish runoff, sediment yields and P losses from arable sloping land. Compared with CK, CT + OM, CT + SM and CT + OM + SM lessened the surface runoff depths by 19%, 34% and 50%, respectively. A high curve number value induced a notable runoff potential from the plot. The surface‐runoff‐related total P (TP) loads for CK with yearly measures of 1·56 kg ha−1 were significantly higher than those for CT + OM, CT + SM and CT + OM + SM at 1·07, 0·77 and 0·51 kg ha−1 (p < 0·05), respectively. With all things considered, the particulate P losses represented a significant division of TP losses, adding up to almost 80% in 2014 and 79% in 2015. The outcomes demonstrated that surface protection and organic matter addition are two of the greatest agricultural protection practices that lessen P losses in the surface runoff from sloping farmland by water erosion. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
5.
Martina M. Backes 《Agroforestry Systems》2001,50(2):119-132
In order to precisely assess the role of agroforestry for the conservation of (agro-)biological diversity there is a need
to adjust sampling methods used in plant sociology. This study is on the contribution of agroforestry land use to the in-situ conservation of indigenous trees within a typical East-African smallholder farming system in Western Kenya. A modified approach
to measuring species richness and abundance is presented. The selection of tree-rich structures was done according to management
patterns rather than considering syntaxonomic classifications from the vegetation science point of view. This approach, which
is better suited to the strongly human-influenced vegetation of agroecosystems, employs between-management unit diversity
measures to help evaluate abundance and constancy of species in particular management units.
The predominant off-farm vegetation patterns are riverine forests, rocky hillsides, hedgerows, wooded grassland relicts, woodlands or colline forest
relicts and tree groves whereas the noticeable tree-rich on-farm management units are homegardens, homesteads, life fences, coffee- and banana-groves and annual cropping fields. 98% out
of all indigenous tree species known from Bungoma, occur in off-farm lands. 53% of the indigenous tree species occur in tree rich on-farm management units while 47% of the indigenous trees are dependent on the maintenance of off-farm lands. Hedgerows embody the most promising secondary vegetation structure that shows ample potential to accommodate a wide
range of indigenous perennial species outside the natural vegetation formations. The pattern of distribution of various vegetation
structures, and the mixture with diverse tree-based on-farm plots are interesting features in regard to floristic and eco-diversity on a landscape level. In this respect, three areas
that show different population densities and distinct agro-historical conditions were compared. In regions of particular high
population density the degree of association of various functional land use forms and woodland structures – each characterised
by its own floristic make-up – is comparatively high. In contrast, in regions with less population but that were settled at
a later date, one encounters fewer stands of woody plants with lower numbers of species.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
E. T. Craswell A. Sajjapongse D. J. B. Howlett A. J. Dowling 《Agroforestry Systems》1997,38(1-3):121-137
Steeply sloping lands are widespread in the tropics. An estimated 500 million people practice subsistence agriculture in these
marginal areas. Continued population growth has led to the intensified cultivation of large areas of the sloping lands, exacerbating
the problem of soil erosion. Although research shows that alley cropping and other contour agroforestry systems can stabilize
the sloping lands, these systems have not been widely adopted by farmers.
The Framework for Evaluating Sustainable Land Management (FESLM) has been tested in sloping land areas in the Philippines.
Sustainable land management must be productive, stable, viable, and acceptable to farmers, while protecting soil and water
resources. Farms on which contour hedgerow intercropping has been adopted meet the multifaceted requirements of FESLM, whereas
the farmers' current practice does not. Appropriate land management measures for particular locations depend on a complex
suite of social, economic, and biophysical factors, and need to be developed in participation with farmers.
The role of agroforestry in sustainable management of sloping lands is the subject of networks coordinated by the International
Board for Soil Research and Management (IBSRAM) in seven countries in Asia (ASIALAND) and four countries in the Pacific (PACIFICLAND).
We review selected outcomes from a wealth of network data. From these results the following conclusions about the sustainability
of various agroforestry systems for sloping lands can be drawn:
• In the Pacific, soil loss from sloping lands due to water erosion under farmers' current practices is episodic, unpredictable,
and possibly not severe;
• Agroforestry systems that utilize legume shrubs, fruit trees, coffee (Coffea spp.) or rubber (Hevea brasiliensis) provide
useful economic returns, but are not an essential component in terms of soil protection because grass or pineapple (Ananas
comosus) planted on the contour are equally effective in reducing erosion;
• Agricultural intensification will lead to nutrient mining, reduction of aboveground biomass, declining yields, and less
soil protection unless external sources of nutrients are used;
• nitrogen can be effectively supplied using legumes;
• Cash derived from hedgerow trees and/or shrubs may providean incentive for their adoption by farmers, as well as funds to
purchase external inputs such as fertilizers;
• Labor may be a major constraint to the adoption of complex agroforestry systems.
We also discuss the information management systems required to effectively manage and utilize the extensive sets of experimental
and indigenous data being accumulated. We believe such information systems can facilitate technology transfer across and between
regions, and improve the efficiency of research into agroforestry and other land-management approaches.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Although alley cropping has been shown elsewhere to permit continuous cropping, it has not been widely tested in the highlands of east and central Africa where it has the additional potential of controlling soil erosion. The effect of four rates (0, 30, 60 and 90 kg N ha–1) of inorganic N on the performance of alley cropping using Leucaena diversifolia as the hedgerow species was studied in the central highlands of Burundi. Significant increase in maize yield (average of 26%) due to alley cropping was only first realised in 1992, three years after the commencement of the trial. In 1993, the average yield advantage of the alley cropping plots was 21%. The prunings augmented the response of maize yield to inorganic N in 1992 and 1993. Compared with the control, economic benefits over the five-year period for all the treatments were negative. 相似文献
8.
In the Philippines, smallholder farmers have become major timber producers. But the systems of timber production practiced
have several limitations. In intercropping systems, the practice of severe branch and/or root pruning reduces tree-crop competition
and increases annual crop yields, but is detrimental to tree growth and incompatible with commercial timber production. In
even-aged woodlots, lack of regular income and poor tree growth, resulting from farmers’ reluctance to thin their plantations,
are major constraints to adoption and profitable tree farming. In the municipality of Claveria, Misamis Oriental, the recent
practice of planting trees on widely spaced (6–8 m) contour grass strips established for soil conservation suggests ways to
improve the adoptability (i.e., profitability, feasibility and acceptability) of timber-based agroforestry systems. Assuming
that financial benefits are the main objective of timber tree farmers, we develop a simple linear programming (LP) model for
the optimal allocation of land to monocropping and tree intercropping that maximizes the net present value of an infinite
number of rotations and satisfies farmers’ resource constraints and regular income requirements. The application of the LP
model to an average farmer in Claveria showed that cumulative additions of widely spaced tree hedgerows provides higher returns
to land, and reduce the risk of agroforestry adoption by spreading over the years labour and capital investment costs and
the economic benefits accruing to farmers from trees. Therefore, incremental planting of widely spaced tree hedgerows can
make farm forestry more adoptable and thus benefit a larger number of resource-constrained farmers in their evolution towards
more diverse and productive agroforestry systems. 相似文献
9.
Previously published hypothesis concerning the potential impact of alley farming on maize yields are re-examined relative
to the humid regions of West Africa. When more realistic assumptions regarding the availability of organic nitrogen are used,
it is concluded that alley farming may have potential in a wider range of maize yield environments in West Africa than previously
proposed. A pragmatic approach to alley farming research is proposed, and the importance of on-farm research in the development
of ‘farmer friendly’ alley farming is stressed.
(Former Agronomist, International Livestock Centre for Africa, P.M.B. 5320, Ibadan, Nigeria) 相似文献
10.
A hedgerow intercropping study was conducted for 7 years in West Sumatra, Indonesia on an acid and highly Al-saturated soil to determine growth and yield responses of tree hedgerows and upland rice and cowpea intercrops. Three tree species,Paraserianthes falcataria, Calliandra calothyrsus, andGliricidia sepium and a no-tree control were planted at three lime rates with low annual fertilizer inputs of 20 kg P and 50 kg K ha–1.Paraserianthes andCalliandra grew vigorously, whileGliricidia grew poorly and was replaced after four years withFlemingia macrophylla. After four years,Paraserianthes yields declined due to tree mortality, probably due to intensive pruning.Calliandra andFlemingia were well adapted to intensive pruning (4 to 6 times per year).
Gliricidia growth was especially limited by low soil Ca availability and high soil acid saturation.Calliandra andFlemingia yields increased with liming only in the last several years of the study whileParaserianthes did not respond to lime. The species can be tentatively ranked in response to lime as:Gliricidia > Calliandra > Flemingia > Paraserianthes. 相似文献