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991.
Karen E. van de Wolfshaar P. Daniël van Denderen Tim Schellekens Tobias van Kooten 《Fish and Fisheries》2020,21(5):962-972
Bottom trawl fisheries have significant effects on benthic habitats and communities, and these effects have been studied intensively in the last decades. Most of these studies have related the changes in benthic community composition to direct effect of trawl gears on benthos, through imposed mortality. This line of argumentation ignores the fact that benthic organisms themselves form a complex food web and that bottom trawling may trigger secondary effects through this food web. We studied the potential consequences of such food web effects using a model of benthic predators, filter feeders, deposit feeders and fish. Our analysis shows how inclusion of ecological interactions complicates the relationship between bottom trawling intensity and the state of the benthic community and causes a non‐linear and non‐monotonic response of the benthic community to trawling. This shows that indirect food web effects can fundamentally alter the response of a benthic ecosystem to bottom trawling, compared to the direct effects of mortality. In light of our results, we argue that indicators of fishing impact on benthos need to account for positive as well as negative effects of bottom trawling, in order to accurately quantify the impact. Our findings highlight that understanding the food web ecology of the benthic ecosystem is crucial for understanding and predicting the effects of trawling on the seafloor. Work that promotes such understanding of the food web ecology seems a more productive research strategy than conducting ever more empirical trawling effect measurements. 相似文献
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An experiment is described that examined mowing with the return of excreta and mowing with the return of clippings as methods of simulating the return of nutrients by grazing animals in experiments where grazing is impracticable. These treatments were applied to a pure grass and to a grass/clover sward. Both methods gave herbage nearer in yield and composition to that resulting from natural grazing than did mowing with no return, but neither was suitable for use on sites outside experimental stations. Although the nitrogen returned in excreta was rather inefficiently used, it appeared to be the major factor in increasing yield on the grass sward and in changing the grass/clover balance on the mixed sward. The return-treatments had a marked effect on the potassium nutrition of both swards and the results suggest that omitting the grazing animal from trials assessing potassium fertilizer requirements may invalidate the results. 相似文献
995.
W. F. Morofsky J. H. Muncie F. J. Stevenson C. M. Voss Floyd Andre Verne C. Beverly H. A. Reilley J. C. Campbell H. J. Evans Walt Jendrzejewski W. C. Barnes John Noonan M. R. Harris R. E. Goodin L. A. Schaal P. A. Ark M. A. Lindsay W. B. Ward H. A. Reiley Verne C. Beverly J. E. Snowden Marx Koehnke J. C. Campbell H. R. Talmage M. E. Gardner E. B. Tussing O. D. Burke Harold L. Bailey Chas D. Gaines 《American Journal of Potato Research》1948,25(10):393-393
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Christie A. Klimas Karen A. Kainer Lúcia H.O. Wadt 《Forest Ecology and Management》2007,250(3):256-265
Carapa guianensis Aublet. is a tropical tree with strong multiple-use characteristics, and is valued for both the high quality oil extracted from its seeds and as a timber resource. This study compares the population structure of this economically important rainforest tree in two contrasting forest types: occasionally inundated and terra firme forests. Main study objectives were (a) to assess the density, spatial distribution, and size class structure of C. guianensis in these two forest types and (b) to use patterns of abundance, distribution and demographic structure to help infer key demographic stages or ecological variables that merit special focus for management. Four 400 m × 400 m plots, two in each forest type, were established to determine distribution and density patterns of C. guianensis ≥10 cm diameter at breast height (dbh) at the landscape level, and 32 10 m × 10 m subplots were randomly nested within each of the larger plots to measure individuals <10 cm dbh. Larger individuals (≥10 cm dbh) were found at higher densities in occasionally inundated forest than in terra firme forest: 25.7 trees ha−1 and 14.6 trees ha−1, respectively. Mean density of C. guianensis individuals <10 cm dbh was also higher in occasionally inundated forests, but variation of regeneration density among the subplots was high. Spatial distribution methods revealed a tendency toward clumping in both forest types, and both had similar size class structures, suggesting that both environments are suitable for C. guianensis. This new finding illustrates the potential for C. guianensis management in terra firme forests. High densities and clumped distributions in both forest types are also indices favorable for sustainable species management. Finally, several ecological variables (tree density and reproductive potential) were sufficiently different between terra firme and occasionally inundated forests to recommend stratification by forest type when conducting further studies on key ecological and management variables of C. guianensis. 相似文献
999.
John E. Bradshaw Glenn J. Bryan Christine A. Hackett Karen McLean Barnaly Pande Helen E. Stewart Robbie Waugh 《Euphytica》2004,137(1):13-18
The theory of linkage and QTL analysis in autotetraploids is summarised. Applications are presented to the analysis of quantitative
disease resistance in the European cultivated potato, Solanum tuberosum subsp. tuberosum. The implications are discussed for practical potato breeding, practical QTL analysis and theory.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.
Gregory S. Mahone Matthias Frisch Eva Bauer Grit Haseneyer Thomas Miedaner Karen Christin Falke 《Plant Breeding》2015,134(4):406-415
Introgression populations are developed to make genetic resources for breeding purposes available. In the case that the number of donor segments exceeds the number of lines, genome‐wide prediction (GWP) methods are suggested as promising for the analysis of such populations. Our objectives were to characterize a rye introgression population with the Rye5K SNP assay and to apply a GWP model with a modification of the restricted maximum likelihood procedure that yields heteroscedastic variances to detect significant donor effects. The introgression lines (ILs) carried on average 4.6 donor segments with a mean length of 27 cM and represented 94% of the donor genome. Two donor effects were detected that significantly increased thousand‐kernel weight. We found four donor effects for protein, total pentosan and starch content that can improve baking quality. Three donor effects for protein content were observed for improving feeding purposes and one donor effect for starch content to improve ethanol production. The effects were localized to small genomic regions. Consequently, these ILs can improve rye breeding by directly employing them in breeding programmes for variety development. 相似文献