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41.
The incidence and severity of citrus variegated chlorosis (CVC) caused by Xylella fastidiosa are higher in the northern region of Sao Paulo, Brazil than in the southern region. This phenomenon is partly due to differences in the climate, especially rainfall, as the northern region tends to be drier than the southern region. The progress of CVC under three levels of irrigation was assessed in a grove located in the northern region of Sao Paulo. Trees (10-year-old Natal sweet orange) were arranged in a randomized complete block in a 3 × 2 factorial scheme with three levels of irrigation and two methods of infection with X. fastidiosa. The disease incidence in branches and the number of symptomatic fruits per tree were evaluated for three years. A monomolecular model was used to describe the progress of CVC incidence for all treatments. Irrigation reduced CVC symptoms in trees, especially the number of symptomatic fruits per tree. Based on this significant reduction, citrus irrigation can be used to reduce the main negative effect of CVC: reduced fruit size. Our results also explain the higher incidence of CVC in the northern region of Sao Paulo, where a dry season occurs. 相似文献
42.
Md. Rezaul Karim Sheikh A. Nayeem Farouqui Rosiyah Yahya Aziz Hassan 《Fibers and Polymers》2011,12(5):642-647
In this paper, Rajshahi silk fabric was modified by acetic acid, tannic acid and their mixture. After acid modification, the
silk fabric was dyed with three dyes classes namely: Reactive Orange 14, Direct Yellow 29 and Mordant Blue 9. Results revealed
that the fabric modified with acid mixture of 30 % acetic acid and 20 % tannic acid improved the colorfastness of the dyed
fabric after 7 days exposure on simulated sunlight and washing with hot soap solution. Also, the acid modification could improve
the dyed fabrics’ colorfastness properties to acids and alkalis. Optimum dyeing condition was observed at 1.5, 2.0, and 2.0
% dyes for Reactive Orange 14, Direct Yellow 29 and Mordant Blue 9 respectively. The optimum dyeing time was observed 50,
60, and 50 min; and temperature was 90, 100 and 80 °C respectively. Modification of silk fabrics with acids improves the dyeability
and colorfastness of Rajshahi silk fabrics. However, the acid modification could reduce the loss in tenacity of silk fabric
upon exposure to sunlight. 相似文献
43.
M. J. Hill J. Biggs I. Thornhill R. A. Briers M. Ledger D. G. Gledhill P. J. Wood C. Hassall 《Landscape Ecology》2018,33(3):389-405
Purpose
Urbanisation is a leading cause of biotic homogenisation in urban ecosystems. However, there has been little research examining the effect of urbanisation and biotic homogenisation on aquatic communities, and few studies have compared findings across different urban landscapes. We assessed the processes that structure aquatic macroinvertebrate diversity within five UK cities and characterise the heterogeneity of pond macroinvertebrate communities within and among urban areas.Methods
A total of 132 ponds were sampled for invertebrates to characterise biological communities of ponds across five UK cities. Variation among sites within cities, and variation among urban settlements, was partitioned into components of beta diversity relating to turnover and nestedness.Results
We recorded 337 macroinvertebrate taxa, and species turnover almost entirely accounted for the high beta-diversity recorded within each urban area and when all ponds were considered. A total of 40% of all macroinvertebrates recorded were unique to a particular urban settlement. In contrast to the homogenisation of terrestrial and lotic communities in urban landscapes reported in the literature, ponds support highly heterogeneous communities within and among urban settlements.Conclusions
The high species turnover (species replacement) recorded in this study demonstrates that urban pond biodiversity conservation would be most efficient at a landscape-scale, rather than at the individual ponds scale. Pond conservation practices need to consider the spatial organization of ecological communities (landscape-scale) to ensure that the maximum possible biodiversity can be protected.44.
Bovine gammaherpesvirus 4 (BoHV4) is a member of the family Herpesviridae. In Argentina, BoHV4 was isolated and characterized in 2007 from samples of aborted cows. Argentinean isolates are highly divergent and are classified as: Genotype 1(Movar-like), Genotype 2 (DN599-like) and Genotype 3 (a novel group). The aim of this study was to comparatively evaluate the biological characteristics of six Argentinean BoHV4 field isolates in cell lines from different origins. All strains induced productive infection in the cell lines used, with different degrees of permissiveness. A direct relationship among the times of appearance of cytopathic effect, the growth kinetics, the size of the lysis plaques and the virulent-like behaviour in vitro could not be established. However, although slight, there are differences in the biological behaviour of the BoHV4 fields isolates analyzed. This variability is independent of their genetic classification but would be conditioned by the nature of the infected cells. 相似文献
45.
T-SNAREs are a family of conserved proteins involved in intracellular transport of membrane-coated cargo among subcellular compartments. In this study, we identified a putative t-SNARE gene, MoTLG2, in Magnaporthe oryzae via insertion mutagenesis. Deletion of MoTLG2 resulted in slower vegetative growth and less conidiation relative to the wild-type strain, but the ΔMotlg2 null mutant was as virulent as the wild-type strain. MoTlg2 has 30% overall amino acid identity with Saccharomyces cerevisiae Tlg2, and rescued the defect of monensin de-sensitivity in the yeast strain where TLG2 had been deleted. More importantly, apical regions of the hyphae of the ΔMotlg2 null mutant were only weakly stained by FM4-64, which was reported as an excellent vesicle tracer, suggesting that the Spitzenkörper was not well formed in the ΔMotlg2 null mutant. In addition, more uneven lateral deposition of chitin was observed in the cell wall of vegetative hyphae of the ΔMotlg2 null mutant. Taken together, this study shows that the t-SNARE Tlg2 is important for both vegetative hyphal growth and conidiation, but dispensable for plant infection in filamentous fungi, and suggests that Tlg2 is important for formation of the Spitzenkörper and polar distribution of chitin. 相似文献
46.
Soil magnetic characteristics are correlated with soil p H and organic matter content. Analyzing soil magnetic characteristics, organic matter content and p H can indirectly evaluate soil pollution caused by human activities. This study analyzed the soil magnetic characteristics, organic matter content and p H in surface soil samples from different land use types in Shihezi city, a newly and rapidly developing oasis city in Xinjiang of China. The aims of this study were to explore the possible relationships among the soil magnetic parameters and thereby improve the understanding of influence of urbanization on soil properties. Eighty surface soil samples at the depth of 0–10 cm were collected from 29 July to 4 August 2013. The results showed that the magnetic minerals in surface soil were dominated by ferromagnetic minerals. Spatially, the magnetic susceptibility(χLF), anhysteretic remanent magnetization susceptibility(χARM), saturation isothermal remanent magnetization(SIRM) and "soft" isothermal remanent magnetization(SOFT) were found to be most dominant in the new northern urban area B(N-B), followed by built-up areas(U), suburban agricultural land(F), and then the new northern urban area A(N-A). The values of χLF, χARM, SIRM and SOFT were higher in the areas with high intensities of human activities and around the main roads. Meanwhile, the property "hard" isothermal remanent magnetization(HIRM) followed the order of UN-BFN-A. Built-up areas had an average p H value of 7.93, which was much higher than that in the new northern urban areas as well as in suburban agricultural land, due to the increased urban pollutant emissions. The average value of soil organic matter content in the whole study area was 34.69 g/kg, and the values in the new northern urban areas were much higher than those in the suburban agricultural land and built-up areas. For suburban agricultural land, soil organic matter content was significantly negatively correlated with χLF, and had no correlation with other magnetic parameters, since the soil was frequently ploughed. In the new northern urban areas(N-A and N-B), there were significant positive correlations of soil organic matter contents with χARM, SIRM, SOFT and HIRM, because natural grasslands were not frequently turned over. For the built-up areas, soil organic matter contents were significantly positively correlated with χLF, χARM, SIRM and SOFT, but not significantly correlated with frequency-dependent susceptibility(χFD, expressed as a percentage) and HIRM, because the soil was not frequently turned over or influenced by human activities. The results showed that soil magnetic characteristics are related to the soil turnover time. 相似文献
47.
《Geoderma》2007,137(3-4):394-400
The field tension infiltrometer (TI) and the laboratory unit hydraulic gradient (UHG) methods are widely applied to determine the near-saturated soil hydraulic conductivity, K. Comparison between the two methods is relevant given that they differ in the explored soil volume (undetached or detached) and in the flow process (unconfined or confined). The objective of this investigation was to compare unconfined and confined measurements of unsaturated hydraulic conductivity. Twenty TI experiments were conducted in a relatively coarse-textured soil having an appreciable hysteretic behavior by using two different dry-to-wet-to-dry (DTWTD) sequences of pressure head, h0, values that differed by the highest h0 value imposed within the sequence (i.e. h0 = − 150, − 75, − 30, + 5, − 30, − 75, − 150 in site A or h0 = − 150, − 75, − 30, − 10, − 30, − 75, − 150 in site B). The same pressure head sequences were applied on twenty undisturbed soil cores, collected at the exact location of the TI measurements, to perform the laboratory UHG measurements. Regardless of the type of experiment (i.e. unconfined or confined) and the applied pressure head sequence (i.e. site A or B), higher K0 values were obtained with a drying sequence of h0 values (K0,d) than with a wetting one (K0,w)and the discrepancies between K0,w and K0,d decreased as the imposed h0 value increased, as it was expected due to hysteresis. A tendency of the UHG method to overestimate the K0 values was detected (ratios of mean K0,1D to mean K0,3D values ranging from 0.93 to 4.35), but the statistical significance of the observed differences varied with the considered sequence of pressure head values. It was concluded that both the TI and the UHG methods were effective in detecting hysteresis effects on K0, but the laboratory method resulted in K0 values that were higher and more variable probably as a consequence of a more substantial effect of macropore flow on the measured flow rates. 相似文献
48.
《Applied soil ecology》2011,47(3):464-469
Bacteria with the ability to solubilize phosphorus (P) and to improve plant health were selected and tested for growth and survival in P-rich animal bone charcoal (ABC). ABC is suggested to be suitable as a carrier for biocontrol agents, offering them a protected niche as well as delivering phosphate to plants, meanwhile re-using P from waste of the food chain. Ninety-seven bacterial isolates from different soils were tested for their potential to dissolve P from ABC. Of these isolates, 60% showed positive scores; they belonged to the genera Arthrobacter, Bacillus, Burkholderia, Collimonas, Paenibacillus, Pseudomonas, Serratia, and Streptomyces. Twelve isolates from different taxonomic groups were selected for further research on growth ability and survival in ABC, and on their potential to control plant pathogens. The highest concentrations of P were dissolved by Pseudomonas chlororaphis and Bacillus pumilus, followed by Paenibacillus polymyxa, Burkholderia pyrrocinia and three Streptomyces isolates. P. chlororaphis and P. polymyxa showed strongest growth inhibition of plant pathogenic Pythium and Fusarium sp., followed by the Streptomyces spp. isolates. 相似文献
49.
Emblica officinalis G. dried fruit tannin was extracted and applied as a natural mordant alone and in combination with metal mordant namely copper
sulphate for dyeing on cotton and silk fabrics using natural dyes. The color strength, color-coordinates, wash and light fastness
were also evaluated for cotton and silk fabrics with and without mordanting. The pre-mordanted cotton and silk fabrics on
dyeing gave better color strength, wash and light fastness than those dyeing obtained without mordanting. The total phenolic
content of the extract was calculated. Cotton and silk fabrics resulted in good antibacterial activity using the Emblica officinalis G. mordant. When mordant was used along with 0.5 and 1 % copper sulphate mordant and the activity enhanced and was active up
to 20 washes. 相似文献
50.
李彦东 《云南农业大学学报(自然科学版)》2010,4(1):41-45
现代报业史上,《晨报》是与《申报》、《大公报》并立的著名报纸。晨报社开创的文化空间肇端自清末民众启蒙的理念,它充分展示了现代文化在媒介形式里的表现。《晨报》副刊展示了新文化运动从同人期刊到更为大众的传播时所产生的变化和转折。在这样一个特殊的转型时代,《晨报》所开辟的文化空间里,关乎民众的通俗教育与现代艺术实践并行不悖,而启蒙的话语也散落在报刊、戏剧等多种媒介当中。 相似文献