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41.
The minimum dietary vitamin C requirement for optimal growth and normal development in Atlantic salmon (Salmo salar) fry at the onset of feeding was studied, using Ca ascorbate-2-monophosphate (AP) as dietary source. The requirement was established by means of a feeding study lasting for 23 weeks from the beginning of feeding. The practical diets used were supplemented with AP at levels of 0, 10, 20, 40, 80 and 160 mg ascorbic acid (AA) equivalents/kg. Growth, mortality, hydroxyproline content in skin and backbone, and AA in liver were recorded to evaluate the results. The results suggest that the minimum dietary requirement for optimal growth and normal development is in the range of 10–20 mg AA equivalents/kg dry diet during the period studied.  相似文献   
42.
Soil density fractionation is a common tool to separate organic matter of different function and turnover. But it has not been tested so far how much soil material is necessary to obtain reproducible results. A reduction of chemicals like polytungstate would further save valuable resources. Here, we show that soil weight reduction from 25 to 5 g was not significantly affecting fractionation results. Compared to the commonly used 10–25 g, this corresponds to a saving of resources of up to 80%.  相似文献   
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Journal of Plant Diseases and Protection - Although short-wavelength light and especially UV radiation can induce resistance in plants against herbivorous insects, the optimal wavelengths, light...  相似文献   
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The very wide use of glyphosate to control weeds in agricultural, silvicultural and urban areas throughout the world requires that special attention be paid to its possible transport from terrestrial to aquatic environments. The aim of this review is to present and discuss the state of knowledge on sorption, degradation and leachability of glyphosate in soils. Difficulties of drawing clear and unambiguous conclusions because of strong soil dependency and limited conclusive investigations are pointed out. Nevertheless, the risk of ground and surface water pollution by glyphosate seems limited because of sorption onto variable-charge soil minerals, e.g. aluminium and iron oxides, and because of microbial degradation. Although sorption and degradation are affected by many factors that might be expected to affect glyphosate mobility in soils, glyphosate leaching seems mainly determined by soil structure and rainfall. Limited leaching has been observed in non-structured sandy soils, while subsurface leaching to drainage systems was observed in a structured soil with preferential flow in macropores, but only when high rainfall followed glyphosate application. Glyphosate in drainage water runs into surface waters but not necessarily to groundwater because it may be sorbed and degraded in deeper soil layers before reaching the groundwater. Although the transport of glyphosate from land to water environments seems very limited, knowledge about subsurface leaching and surface runoff of glyphosate as well as the importance of this transport as related to ground and surface water quality is scarce.  相似文献   
46.
The diversity of fungal endophytes in Sorghum bicolor was investigated in samples collected from 10 different geographical regions of Karnataka state, India. A total of 360 endophytes were isolated from leaf, stem, and root tissues and were assigned to 26 fungal species based on morphology and molecular characterization using ITS sequences. All the endophytes belonged to the phylum Ascomycota. The diversity (Shannon H, 2.57; Simpson_1-D, 0.92) and species richness (Margalef's, 4.68; Menhinick, 3.61) were found to be higher for the endophytes isolated from leaf tissues. The species evenness of the endophytic assemblage was strongly influenced by tissue type, followed by geographical location. The biocontrol potential of isolated endophytes was evaluated against economically destructive sorghum grain mould pathogens such as Fusarium thapsinum, Epicoccum sorghinum, Alternaria alternata, and Curvularia lunata using the dual culture method. Biocontrol potential was exhibited by 26 endophytic isolates, of which Trichoderma asperellum recorded broad-spectrum activity against target pathogens, followed by E. nigrum and A. longipes. Most (82%) endophytes showed plant growth-promoting traits. Biosynthesis of indole-3-acetic acid (IAA) was observed in 84% of isolates, and phosphate solubilization, siderophore production, and cellulase activity was observed in 69%, 23%, and 27% of isolates, respectively. Seeds treated with Tasperellum exhibited a significantly higher seed vigour index (2096), germination percentage (94%), and yield under greenhouse and field conditions. The results were substantiated by the confocal microscopy analysis, which clearly demonstrated the colonization of treated endophyte in root tissues. The present study reveals an ecofriendly approach to explore Tasperellum in sorghum disease management.  相似文献   
47.
The spatial variability in the mineralisation rate of linuron [N-(3,4-dichlorophenyl)-N'-methoxy-N'-methylurea] was studied within a previously treated Danish agricultural field by sampling soils from eleven different plots randomly distributed across an area of 20 x 20 m. The soils were characterised with respect to different abiotic and biotic properties including moisture content, organic matter content, pH, nutrient content, bacterial biomass, potential for mineralisation of MCPA [(4-chloro-2-methylphenoxy)acetic acid] and linuron. Five soils had a potential for mineralisation of linuron, with 5-15% of the added [ring-U-14C]linuron metabolised to 14CO2 within 60 days at 10 degrees C, while no extensive mineralisation of linuron was observed in the six remaining soils within this period. A TLC analysis of the methanol-extractable residues showed no development of 14C-labelled metabolites from linuron in any of the samples. Multivariate analysis was conducted to elucidate relationships between the intrinsic properties of single soil samples and initial rate of linuron mineralisation. The analysis indicated that important soil parameters in determining the spatial heterogeneity included the C(total)/N(total) ratio, pH and the water-extractable potassium contents, with the first of these highly negatively correlated and the last two highly positively correlated to the initial linuron mineralisation rate. This study shows that enhanced biodegradation of linuron may develop with successive field treatments, but that considerable in-field spatial heterogeneity in the degradation rate still exists. Combined with a parallel enrichment study focused on the underlying microbial processes, the present results suggest that intrinsic soil properties affect the linuron-metabolising bacterial population and thereby determine the spatial variability in the linuron mineralisation activity.  相似文献   
48.
The current study compared two approaches for estimating change of aboveground biomass (AGB) in montane forests in Norway using field- and remotely sensed data from airborne laser scanning (ALS) from two points in time (four-year interval). The first was an indirect method that involved modeling and prediction of AGB at two points in time using ALS metrics as predictors, estimating the change from differences between AGB predictions. The second was a direct method, where change was modeled and predicted directly using differences between corresponding ALS metrics derived at the two measurement occasions as predictors, and the estimate was based on the predicted differences. Both methods were applied over a 1500?km long and 250?m wide transect from south to north in Norway comprising 250?m2 grid cells. The results showed that the indirect method was more precise than the direct method. The indirect method estimated 0.65?Mg?ha?1 change in AGB over the observation period, with a corresponding 95% confidence interval of ±0.27?Mg?ha?1. The corresponding figures for the direct method was 0.54 and ±0.51?Mg?ha?1. The direct method has been recommended previously. We conclude that the indirect method is both more precise and versatile.  相似文献   
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50.
While nitrogen and carbon stable isotope values can reflect ecological segregation, prey choice and spatial distribution in seabirds, the interpretation of bulk stable isotope values is frequently hampered by a lack of isotopic baseline data. In this study, we used compound-specific isotope analyses of amino acids (CSIA-AA) to overcome this constraint and to study interspecific differences, seasonal and historical changes in trophic positions of five seabird species, three penguins and two petrels, from a sub-Antarctic seabird community. CSIA-AA allowed comparing trophic positions of seabirds with temperate and polar distributions. Gentoo and Magellanic penguins had the highest trophic positions during the breeding season (3.7 and 3.9), but decreased these (2.9 and 3.3) during the feed-up for moult. Intra-specific differences were also detected in Thin-billed prions, where carbon isotope values clearly separated individuals with polar and temperate distributions, both in the breeding and interbreeding periods. Thin-billed prions that foraged in polar waters had lower trophic positions (3.2) than conspecifics foraging in temperate waters (3.8). We further investigated historical changes by comparing museum samples with samples collected recently. Our pilot study suggests that Rockhopper penguins, Magellanic penguins and Thin-billed prions with temperate non-breeding distributions had retained their trophic levels over a 90–100 year period, while Gentoo penguins and Thin-billed prions with polar non-breeding distributions had decreased trophic levels compared to historical samples. In contrast, Wilson’s storm-petrels had slightly increased trophic levels compared to samples taken in 1924–1930. We applied compound-specific stable isotope analyses across a range of contexts, from intra-specific comparisons between stages of the breeding cycle to inter-specific seabird community analysis that would not have been possible using bulk stable isotope analyses alone due to differences in isotopic baselines.  相似文献   
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