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121.
The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)–potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF + C + M), a system with manure but without undersowing catch crops (OF ? C + M), and a system without manure and with catch crops (OF + C ? M). A grass-clover green manure was used as N fixing crop in the other organic system with catch crops (OG + C + M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF + C + F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark. 相似文献
122.
123.
Joan Cáliz Genoveva Montserrat Esther Martí Jordi Sierra Ana Paula Chung Paula Vasconcelos Morais Xavier Vila 《Journal of Soils and Sediments》2013,13(2):413-428
Purpose
The effect of pollutants in soil microorganisms is an important issue in order to understand their toxic effects in the environment, as well as for developing adequate bioremediation strategies. In this sense, the main objective of this study was to assess the involvement of the indigenous microbiota of an acidic forest Mediterranean soil by artificial pollution with heavy metals, and to detect and isolate resistant microorganisms that could be useful for bioremediation.Materials and methods
Samples from a previously unpolluted acidic forest soil were amended with Cr(VI), Cd(II) or Pb(II) at total amounts ranging from 0.1 to 5,000 mg?kg?1. These soil microcosms were incubated under controlled laboratory conditions for 28 days. Soluble fractions of metals were determined from aqueous extracts. Both activity and composition of the microbial community were assessed, respectively, by respirometric assays and molecular analysis (polymerase chain reaction denaturing gradient gel electrophoresis). The isolation of metal-resistant microorganisms was attempted by culture plating from microcosms incubated with high concentrations of metals. Isolated strains were tested in cultures with minimal medium to check for their metal resistance and their capacity to reduce the presence of toxic Cr(VI).Results and discussion
A decrease in the soil respirometric activity and changes in the microbial community composition were detected from 10/100 mg?kg?1 Cr and 1,000 mg?kg?1 Cd and Pb. Presumably resistant bacterial and fungal populations developed in most of these polluted microcosms; however, the microbiota was severely impaired at the highest additions of Cr. Even though Cr was the most damaging metal in soil microcosms, if the soluble fractions of metals are considered instead of their total added amounts, the comparison among their toxic effects suggests a similar potential toxicity of Cr and Pb. Isolated multiresistant microorganisms were related mainly to Actinobacteria, Firmicutes and Ascomycota. Some of them showed the capacity to reduce Cr(VI) concentrations between 54 % and 70 % of the initial value. These strains were affiliated to several species of Streptomyces and Bacillus.Conclusions
The combination of respirometric assays with molecular methods has been useful to assess the effect of metals on the soil microbial community, which can greatly be explained by their differential bioavailability. Cultivation-dependent and -independent approaches have proved the presence and development of multiresistant microorganisms in a previously unpolluted soil. Due to their properties, some of the isolated strains are potentially useful for soil bioremediation. 相似文献124.
Frederic Varela Xavier Font Josep E. Valladares Jordi Alberola 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1997,11(5):309-311
A 6–year-old dog was presented for evaluation of recurrent epistaxis. Platelet counts, biochemical tests, and coagulation tests were within the normal range, but a mucosal bleeding time was prolonged; there was hyperproteinemia and a monoclonal gammopathy. Heterogeneity of light chains appeared in urine, however, thus suggesting that the gammopathy was polyclonal. Platelet aggregation tests showed decreased responsiveness to collagen. An Ehrlichia canis indirect fluorescent-antibody titer was positive (1:40). Treatment with tetracycline, melphalan, and prednisone resulted in a rapid clinical improvement that persisted for at least 3 years. 相似文献
125.
Seasonal changes in carbon isotope discrimination (Δ) and gas exchange traits were assessed in four Populus×euramericana clones differing in growth potential. Measurements were made during the second year after establishment in the field under
two watering regimes, which were defined by the time-span between flood irrigations, hence resulting in different dry-down
cycles: high irrigation (conservative schedule currently applied in the Ebro Valley, Spain) and low irrigation (equivalent
to about a one-fourth reduction in water inputs). Net CO2 assimilation rate (A), stomatal conductance (gs), intrinsic water-use efficiency (A/gs) and other related photosynthetic traits (leaf nitrogen concentration, leaf greenness and leaf mass per area) were measured
prior to watering, and Δ was analysed in water-soluble leaf extracts (Δs) and bulk leaves (Δl). Stem growth was monitored over 3 years starting at the year of establishment (1998). Data were subjected to a repeated
measures ANOVA over time for a randomised block split-plot design across watering regimes. Significant differences between
watering regimes were detected using a long-term estimate of photosynthetic performance such as Δl, in agreement with changes in soil water status and evapotranspirative demand. However, the lack of significant genotype×watering
regime interactions for gas exchange traits and Δs suggested that water shortage imposed by low irrigation was not sufficient to reveal physiological adaptations to drought.
In this regard, the reduction in water inputs brought about by low irrigation did not reduce tree growth for any of the clones,
suggesting that the current irrigation scheme employed in the region is superfluous to the water consumption needs of poplars.
Genotypic variation was detected in gas exchange traits, Δs, Δl and stem growth under both watering treatments. Significant correlations with stem volume for Δs (r = −0.60, p<0.05) and A (r = + 0.61, p<0.05) suggested that growth was improved by higher water-use efficiency (the ratio of carbon fixed to water lost, as inferred
by Δs) due to variation in A rather than in gs. This observation corroborated the expectation derived from current theories that a lower Δ is related to higher stem volume,
as a result of changes in net CO2 assimilation rates. 相似文献
126.
Enrique L Michelotti José I Borrell Renee Roemmele Josep L Matallana Jordi Teixidó Lois M Bryman 《Journal of agricultural and food chemistry》2002,50(3):495-498
The preparation in multigram scale of two metabolites 3-(3,5-dichloro-4-methyl-benzoylamino)-2-hydroxy-3-methyl-pentanoic acid and 3-(3,5-dichloro-benzoylamino)-3-methyl-2-oxo-butyric acid isolated from soil treated with either Zoxium fungicide or Kerb herbicide was efficiently accomplished using a common 5-step synthetic process starting from easily available raw materials. 相似文献
127.
We investigated morphological evidence that might allow wild Pyrus spp. to be distinguished from cultivated material (Pyrus communis L.) in the North-eastern Iberian Peninsula. 134 pear trees were identified in the wild and characterized by 13 quantitative
and 13 qualitative leaf–shoot and fruit traits. The trees were visually classified into two preliminary groups of wild and
cultivated material and discriminant functions, based on a reference collection for allocating individuals to one of the groups,
were constructed. Both classifications were compared with a near-optimal numerical classification (the two-stage Ward-MLM
strategy) using two criteria. The visual assignment of trees allocated 60% of trees to the wild group and 40% to the cultivated
group. The overall discrepancy rate between the field classification and the discriminant analysis was low (17.4%). In general,
wild individuals had smaller leaves, shorter petioles and more rounded and smaller fruits than their cultivated counterparts.
They also had small-to-intermediate petiole widths, thorns on their shoots and straight or convex fruit profiles. However,
the Ward-MLM strategy always formed better groups, in terms of the two criteria used, in all the continuous and categorical
variables, for both leaf–shoot and fruit traits. Likewise, the agreement between classifications (discriminant analysis and
Ward-MLM strategy) was only partial, with some Ward-MLM groups composed of both wild and cultivated material in similar proportions.
This result suggests a limited success in identifying genuine wild individuals based on morphometric data, which can be ascribed
either to poor phenotypic diversity and lack of distinguishing traits among species or to widespread crossability and subsequent
development of hybrid/introgressant populations between wild and cultivated specimens. 相似文献
128.
129.
The stability of the cyclopropane ring and the fatty acid composition of microbial cells were determined using chlorotrimethylsilane as reagent with three different conditions 80 degrees C for 1 h, 60 degrees C for 1 h, and 60 degrees C for 2 h. Chlorotrimethylsilane permits a simultaneous extraction and derivatization of fatty acids. A basic method was used as reference. The bacteria, Escherichia coli, Burkholderia cepacia, and Lactobacillus brevis, and fungi Aspergillus niger and Gibberella fujikuroi were used. The stability of the cyclopropane ring on acidic conditions was tested using the cyclopropanecarboxylic acid and a commercial mixture of bacteria fatty acid methyl esters (BAME). Fisher's least significant difference test showed significant differences among the methods. The method using chlorotrimethylsilane and 1-pentanol for 1 h at 80 degrees C gave the best results in cyclopropane, hydroxyl, and total fatty acid recoveries. This procedure allows the fast and easy one-step direct extraction derivatization. 相似文献
130.
Javier Rodríguez-Bocanegra Núria Roca Anna Febrero Jordi Bort 《Journal of Soils and Sediments》2018,18(6):2305-2317