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21.
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
22.
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
23.
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
24.
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
25.
Alley cropping of sorghum with Leucaena during the post-rainy season on Vertisols in semi-arid India
A field experiment was conducted for two years (1989– 1991) on a Vertisol in Bijapur, India in a split-plot design, replicated
four times, to evaluate the potential of alley cropping post-rainy season sorghum between Leucaena hedgerows. Leucaena produced
on average 2.74 t per ha of prunings and 1.57 t per ha of wood annually. Alley cropping decreased sorghum yields by 28 to
45% when all Leucaena prunings were removed from the system and by 21 to 24%, when on average 1.92 t per ha prunings were
applied to the soil annually. The reduction of sorghum yield increased as higher rates of N were applied to sorghum. Although
alley cropping increased organic carbon by 21% and available N by 19% at the time of crop sowing, it did not result in increased
crop yields because of competition for water between hedgerows and crops. Calculation of land equivalent ratios based on total
Leucaena biomass indicated that alley cropping was more productive than sole cropping of sorghum only in one year, and that,
too, when no N was applied to sorghum. Therefore, alley cropping of Vertisols with post-rainy season sorghum is not likely
to have any advantage in the short term.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
26.
Field studies carried out in a forest transition site on a tropical Alfisol in southwestern Nigeria, show that shading by
gliricidia (Gliricidia sepium (Jacq.) Steud) and leucaena (Leucaena leucocephala (Lam.) de Wit) hedgerow species reduced density of speargrass (Imperata cylindrica (L.) Raeuschel) by 67% and 51%, respectively. Shoot biomass of speargrass decreased by 81% and 78% in gliricidia and leucaena
hedgerows, respectively. Reduction in speargrass rhizome biomass in gliricidia plots was 96% while rhizome reduction in the
leucaena plots was nearly 90%. Rhizome mortality was significantly higher in gliricidia plots than in leucaena and control
plots. The bulk of rhizomes was found between 10 cm and 20 cm of soil depth but rhizome did not penetrate further than 30
cm depth in the Alfisol in which this study was carried out. Gliricidia was better than leucaena hedgerow species in suppressing
speargrass. 相似文献
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30.
计算机视觉在玉米果穗中的应用主要是对外观质量进行评定,本文利用MATLAB对采集系统传来的玉米果穗图像进行转换、灰度化、滤波降噪、区域增强等一系列处理后,选用Log算子提取出玉米果穗轮廓,效果良好,为后续的考种数据测量做准备。 相似文献