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281.
Productivity is a poor predictor of plant species richness 总被引:5,自引:0,他引:5
Adler PB Seabloom EW Borer ET Hillebrand H Hautier Y Hector A Harpole WS O'Halloran LR Grace JB Anderson TM Bakker JD Biederman LA Brown CS Buckley YM Calabrese LB Chu CJ Cleland EE Collins SL Cottingham KL Crawley MJ Damschen EI Davies KF DeCrappeo NM Fay PA Firn J Frater P Gasarch EI Gruner DS Hagenah N Hille Ris Lambers J Humphries H Jin VL Kay AD Kirkman KP Klein JA Knops JM La Pierre KJ Lambrinos JG Li W MacDougall AS McCulley RL Melbourne BA Mitchell CE Moore JL Morgan JW Mortensen B 《Science (New York, N.Y.)》2011,333(6050):1750-1753
For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness. 相似文献
282.
Alphey L Beard CB Billingsley P Coetzee M Crisanti A Curtis C Eggleston P Godfray C Hemingway J Jacobs-Lorena M James AA Kafatos FC Mukwaya LG Paton M Powell JR Schneider W Scott TW Sina B Sinden R Sinkins S Spielman A Touré Y Collins FH 《Science (New York, N.Y.)》2002,298(5591):119-121
At a recent workshop, experts discussed the benefits, risks, and research priorities associated with using genetically manipulated insects in the control of vector-borne diseases. 相似文献
283.
R C Collins F Plum F Posner A P Sanders R S Kramer B Woodhall W D Currie 《Science (New York, N.Y.)》1970,170(965):1430-1431
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Thirty soils differing widely in origin, texture and organic carbon content were used to study crust properties and development under laboratory conditions. Crust strength was measured as penetration resistance to an upward moving probe both with and without artificial rain treatment. The patterns of penetration resistance with time of drying under infra-red lamps varied considerably, the time taken to reach maximum and steady values for penetration resistance varying from 4 to 10 days. Maximum penetration resistance values ranged from approximately 50 to 500 kPa with one Iraqi soil recording a value of 800 kPa. The soils separated into 3 fairly distinct groups when penetration resistance was plotted against moisture content: Group I showed a sudden and sharp increase, Group II a gradual increase, whereas Group III did not show a definite relationship. A positive linear relationship was found between maximum penetration-resistance values of soils with and without artificial rain treatment. There was also a high positive correlation between small (2?0.53 mm) water-stable aggregates and penetration resistance and a negative correlation between penetration resistance and percentage water-stable aggregates of > 2 mm in size.In seedling emergence trials with spring barley (Hordeum vulgare L.), maximum emergence (90–98%) was recorded at penetration resistance (no rain treatment) of 75–110 kPa and zero emergence at approximately 300 kPa, with a good negative relationship between these values. There was a positive relationship between seedling emergence and penetration resistance values < 75 kPa, failure to emerge being due to a lack of anchorage and radial support for the shoot. Simulated rain treatment, which led to additional crust strength, reduced seedling emergence further for the limited number of soils tested. 相似文献
288.
James R. Kramer Pierre Brassard Pamela V. Collins 《Water, air, and soil pollution》1989,46(1-4):199-204
A mono-protic multi-site model is developed to obtain a pK(acid) — concentration distribution. Dense and equal interval pH data are required for an accurate characterization. A computer driven titrimetric system is used to obtain the data. The technique is applied to dissolved organic carbon (> 15 mg C L-1) samples from the Kejimkujik region, Nova Scotia. A calculation shows that the acidic (pH=4.6) dystrophic waters can result from mixing 15 mg C L-1 of the organic acids with an initial inorganic system of about 75 peq L-1 alkalinity. 相似文献
289.
Le Gall G Colquhoun IJ Davis AL Collins GJ Verhoeyen ME 《Journal of agricultural and food chemistry》2003,51(9):2447-2456
290.
Young-Ku Choi Wesley O. Johnson Michael T. Collins Ian A. Gardner 《Journal of Agricultural, Biological & Environmental Statistics》2006,11(2):210-229
Sensitivity and specificity are used to characterize the accuracy of a diagnostic test. Receiver operating characteristic
(ROC) analysis can be used more generally to plot the sensitivity versus (1-specificity) over all possible cutoff points.
We develop an ROC analysis that can be applied to diagnostic tests with and without a gold standard. Moreover, the method
can be applied to multiple correlated diagnostic tests that are used on the same individual. Simulation studies were performed
to assess the discrimination ability of the no-gold-standard method compared with the situation where a gold standard exists.
We used the area under the ROC curve (AUC) to quantify the diagnostic accuracy of tests and the difference between AUCs to
compare their accuracies. In particular, we can estimate the prevalence of disease/infection under the no-gold-standard method.
The method we proposed works well in the absence of a gold standard for correlated test data. Correlation affected the width
of posterior probability intervals for these differences. The proposed method was used to analyze ELISA test scores for Johne’s
disease in dairy cattle. 相似文献