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1.

Background

Developmental biology has made great strides in recent years towards the quantification of cellular properties during development. This requires tissues to be imaged and segmented to generate computerised versions that can be easily analysed. In this context, one of the principal technical challenges remains the faithful detection of cellular contours, principally due to variations in image intensity throughout the tissue. Watershed segmentation methods are especially vulnerable to these variations, generating multiple errors due notably to the incorrect detection of the outer surface of the tissue.

Results

We use the level set method (LSM) to improve the accuracy of the watershed segmentation in different ways. First, we detect the outer surface of the tissue, reducing the impact of low and variable contrast at the surface during imaging. Second, we demonstrate a new edge function for a level set, based on second order derivatives of the image, to segment individual cells. Finally, we also show that the LSM can be used to segment nuclei within the tissue.

Conclusion

The watershed segmentation of the outer cell layer is demonstrably improved when coupled with the LSM-based surface detection step. The tool can also be used to improve watershed segmentation at cell-scale, as well as to segment nuclei within a tissue. The improved segmentation increases the quality of analysis, and the surface detected by our algorithm may be used to calculate local curvature or adapted for other uses, such as mathematical simulations.
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The growth and survival of kalbasu, Labeo calbasu, was evaluated at stocking densities of 5, 10 and 15 million spawn ha−1 in nursery rearing in concrete tanks of 50 m2, each for a period of 25 days. Survival of fry was density dependent and significantly higher (54.5%) at 5 million ha−1 than those at 10 million ha−1 (50.1%) and 15 million ha−1 (46.9%). Similarly, growth and specific growth rate were inversely related to the stocking density and varied significantly among the three densities.  相似文献   
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Several Bartonella spp. associated with fleas can induce a variety of clinical syndromes in both dogs and humans. However, few studies have investigated the prevalence of Bartonella in the blood of dogs and their fleas. The objectives of this study were to determine the genera of fleas infesting shelter dogs in Florida, the prevalence of Bartonella spp. within the fleas, and the prevalence of Bartonella spp. within the blood of healthy dogs from which the fleas were collected. Fleas, serum, and EDTA-anti-coagulated whole blood were collected from 80 healthy dogs, and total DNA was extracted for PCR amplification of Bartonella spp. The genera of fleas infesting 43 of the dogs were determined phenotypically. PCR amplicons from blood and flea pools were sequenced to confirm the Bartonella species. Amplicons for which sequencing revealed homology to Bartonella vinsonii subsp. berkhoffii (Bvb) underwent specific genotyping by targeting the 16S–23S intergenic spacer region.A total of 220 fleas were collected from 80 dogs and pooled by genus (43 dogs) and flea species. Bartonella spp. DNA was amplified from 14 of 80 dog blood samples (17.5%) and from 9 of 80 pooled fleas (11.3%). B. vinsonii subsp. berkhoffii DNA was amplified from nine dogs and five of the flea pools. Bartonella rochalimae (Br) DNA was amplified from six dogs and two flea pools. One of 14 dogs was co-infected with Bvb and Br. The dog was infested with Pulex spp. fleas containing Br DNA and a single Ctenocephalides felis flea. Of the Bvb bacteremic dogs, five and four were infected with genotypes II and I, respectively. Of the Bvb PCR positive flea pools, three were Bvb genotype II and two were Bvb genotype I.Amplification of Bvb DNA from Pulex spp. collected from domestic dogs, suggests that Pulex fleas may be a vector for dogs and a source for zoonotic transfer of this pathogen from dogs to people. The findings of this study provide evidence to support the hypothesis that flea-infested dogs may be a reservoir host for Bvb and Br and that ectoparasite control is an important component of shelter intake protocols.  相似文献   
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Algal bioassay studies on the effect of F concentrations on diatoms Nitzschia palea (freshwater) and Amphora coffeaeformis (brackishwater) were conducted in the laboratory. Significant enhancement of growth occurred in N. palea at F concentrations between 10 and 110 mg L?1. In A. coffeaeformis statistically significant stimulation occurred at 70 mg L?1 F and above 90 mg L?1 F the growth declined. The results indicate that the diatom N. palea and A. coffeaeformis can tolerate high F concentration.  相似文献   
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Imbalanced and inadequate use of chemical fertilizers is responsible for low rice- (Oryza sativa L.) wheat (Triticum aestivum L.) productivity in many resource-poor farmers' fields. Wheat yields in post-rice soils are also constrained due to soil conditions created by puddling in rice, especially in fine to medium textured soils. Organic amendments are known to improve soil productivity under rice-wheat cropping by way of improving physical conditions and nutrient status of the soil, but their availability is restricted. There is a need to identify locally available and cost-effective organic materials, which have minimal alternate uses as fodder and fuel. We evaluated lantana (Lantana spp. L.) residues, a fast-growing weed in nearby wastelands, as a potential soil organic amendment. Yield trends, and soil and crop nutrient status in a 12-year rice-wheat experiment at Palampur, India, involving four levels (0, 10, 20, and 30 Mg ha-1 year-1 fresh mass) of lantana addition were investigated. Chopped lantana was incorporated into soil 10–15 days before puddling. Lantana additions at 10, 20 and 30 Mg ha-1 increased rice yields on average by 18%, 23% and 30%, wheat yields by 11%, 14% and 20%, and total system productivity (rice + wheat) by 15%, 20% and 26% over controls, respectively, and at the same time saved NPK fertilizer. Linear regression analyses over 12 years did not show any change in yield trends of rice and wheat at P =0.05. Continuous cultivation of rice-wheat significantly increased total C, labile C, and other C indices of soils. Total N, Olsen's P, and NH4OAc-extractable K in the lantana-amended plots were higher than in the controls. Nutrient concentrations in crop biomass, however, remained generally unaffected by lantana treatments. Results suggest that lantana residues, which improved the nutrient status of soil and system yield, have the potential for resource conservation and sustaining rice-wheat productivity.  相似文献   
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We investigated C management index (CMI; an indicator of sustainability of a management system and is based on total and labile C) and soil aggregation in medium-textured soils (silt loam and silty clay loam) under different cropping systems as follows: maize-wheat (M-W), rice-wheat (R-W), soybean-wheat (S-W), Guinea grass, and Setaria grass. Field experiments were 6–32 years long and were located in the wet-temperate zone of northwest Himalayas. The plant nutrients were applied through chemical fertilizers (urea, superphosphate, and muriate of potash) with or without organic materials (FYM, wheat straw, and Lantana spp.). The content of total C (CT), labile C (CL), CMI, mean weight diameter (MWD), and aggregate porosity varied significantly under different cropping systems. The range was 1.59 (R-W)–4.29% (Setaria) for CT, 1.23 (R-W)–3.89 mg/kg (Guinea grass) for CL, 52.09 (R-W)–129.77 (Guinea grass) for CMI, 0.90 (R-W)–5.09 (Guinea grass) for MWD, and 41.5 (R-W)–56.8% (S-W) for aggregate porosity. Aggregate porosity was highest (56.8%) under S-W, followed by grasses (50.1–51.2%), and M/R-W (41.5–50.0%). As per these data, (a) continuous use of N alone as urea lowered soil sustainability over control (no fertilizers); (b) use of NPK at recommended rates improved soil productivity over control; (c) the NPK + organic amendments further improved soil sustainability; and (d) the sustainability under different cropping systems followed the order: perennial grasses > soybean-wheat > maize-wheat > rice-wheat.  相似文献   
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A ciliate protozoan, Tetrahymenapyriformis was exposed to three insecticides, dieldrin, dimethoate, and permethrin for 12 hr to study the uptake and bioconcentration potential. Ciliates concentrated 922, 3547, and 1056 gg g?1 dry wt. over an initial concentration of 1 gg mL?1 of dieldrin, dimethoate, and permethrin, respectively. The highest bioconcentration factor for three insecticides was 2095, 3547, and 1110, respectively. It is suggested that if levels in the environment reach 1 gg mL?1 the chief effects would be reduction of cell population, and accumulation of the toxicants by ciliates. Accumulation of insecticides by ciliates would permit the toxicants to enter aquatic food chains. Thus the compounds could exert toxic effects at higher trophic levels.  相似文献   
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