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71.
Pheromones are communication chemicals and regulatory signals used by animals and represent unique tools for organisms to mediate behaviors and make “decisions” to maximize their fitness. Phenotypic plasticity refers to the innate capacity of a species to tolerate a greater breadth of environmental conditions across which it adapts to improve its survival, reproduction, and fitness. The pinewood nematode, Bursaphelenchus xylophilus, an invasive nematode species, was accidentally introduced from North America into Japan, China, and Europe; however, few studies have investigated its pheromones and phenotypic plasticity as a natural model. Here, we demonstrated a novel phenomenon, in which nematodes under the condition of pheromone presence triggered increased reproduction in invasive strains (JP1, JP2, CN1, CN2, EU1, and EU2), while it simultaneously decreased reproduction in native strains (US1 and US2). The bidirectional effect on fecundity, mediated by presence/absence of pheromones, is henceforth termed pheromone-regulative reproductive plasticity (PRRP). We further found that synthetic ascaroside asc-C5 (ascr#9), the major pheromone component, plays a leading role in PRRP and identified 2 candidate receptor genes, Bxydaf-38 and Bxysrd-10, involved in perceiving asc-C5. These results suggest that plasticity of reproductive responses to pheromones in pinewood nematode may increase its fitness in novel environments following introduction. This opens up a new perspective for invasion biology and presents a novel strategy of invasion, suggesting that pheromones, in addition to their traditional roles in chemical signaling, can influence the reproductive phenotype among native and invasive isolates. In addition, this novel mechanism could broadly explain, through comparative studies of native and invasive populations of animals, a potential underlying factor behind of the success of other biological invasions. 相似文献
72.
T. N. Jacob J. P. Pandey K. Raghuveer G. Sreenivasulu A. D. Gupta M. Yoshikuni A. Jagota B. Senthilkumaran 《Fish physiology and biochemistry》2005,31(2-3):271-274
Effect of experimentally induced thyroxine overdose on the testis and seminal vesicles was studied in the air-breathing catfish,
Clarias gariepinus during the preparatory and the pre-spawning phase. The present study revealed a marked reduction in testosterone level in
serum, testis and seminal vesicles (SV). Histological examination showed a considerable reduction in the number of spermatozoa/spermatids
in the seminiferous tubular lumen as well as depletion of fluid in the loculi of SV. SDS-PAGE analysis of SV fluid proteins
demonstrated a significant decrease in the level of a ~27 kDa protein in thyroxine treated fishes. Evidences are presented
here to indicate that thyroid hormone plays a role in regulating testis and SV function in catfish.
T.N. Jacob and J.P. Pandey contributed equally 相似文献
73.
Jacob J. Capelle Gerard Scheiberlich Jeroen W. M. Wijsman Aad C. Smaal 《Aquaculture International》2016,24(5):1459-1472
Mussel losses peak after relaying seed on culture plots. The present paper is an attempt to examine the role of shore crab predation and initial mussel density on mussel losses in mussel bottom culture using an intertidal culture plot as a case study. Because of their small size and loose attachment, mussels are particularly vulnerable to predation at this stage, as well as to handling stress and intraspecific competition. In the experimental field plots (1 × 1 m) in the intertidal Oosterschelde, three different densities (1, 5 and 10 kg m?2) of mussel seed are laid, with half of the experimental plots protected from predation by means of exclosures. Duration of the experiment was 5 weeks (August–September 2012) post-seeding. Protection was the major factor accounting for biomass production, followed by mussel density. Loss rates increased with mussel density, both in the exclosures and in the exposed plots. Losses in the exclosures with the lowest density were still 45 %. There are indications that handling stress prior to the start of the experiment played a major role in these losses. At the higher densities in the exclosures, losses increased to 72.1 % and were not significantly different between 5 and 10 kg m?2. About one-third of the total loss (32.6 %) was attributed to shore crab predation. The number of shore crabs observed on the plots did not differ between treatments. Byssal thread development during the experimental period was followed and was found to be a slow process that was insufficient to protect mussels from crab predation at the sheltered experimental location. 相似文献
74.
75.
Jens Jacob Phil Manson Ralf Barfknecht Timothy Fredricks 《Pest management science》2014,70(6):869-878
Common voles (Microtus arvalis) are common small mammals in some European landscapes. They can be a major rodent pest in European agriculture and they are also a representative generic focal small herbivorous mammal species used in risk assessment for plant protection products. In this paper, common vole population dynamics, habitat and food preferences, pest potential and use of the common vole as a model small wild mammal species in the risk assessment process are reviewed. Common voles are a component of agroecosystems in many parts of Europe, inhabiting agricultural areas (secondary habitats) when the carrying capacity of primary grassland habitats is exceeded. Colonisation of secondary habitats occurs during multiannual outbreaks, when population sizes can exceed 1000 individuals ha?1. In such cases, in‐crop common vole population control management has been practised to avoid significant crop damage. The species' status as a crop pest, high fecundity, resilience to disturbance and intermittent colonisation of crop habitats are important characteristics that should be reflected in risk assessment. Based on the information provided in the scientific literature, it seems justified to modify elements of the current risk assessment scheme for plant protection products, including the use of realistic food intake rates, reduced assessment factors or the use of alternativee focal rodent species in particular European regions. Some of these adjustments are already being applied in some EU member states. Therefore, it seems reasonable consistently to apply such pragmatic and realistic approaches in risk assessments for plant protection products across the EU. © 2013 Society of Chemical Industry 相似文献
76.
Mascha Jacob Christian Platner Christoph Leuschner 《Soil biology & biochemistry》2009,41(10):2122-119
In the litter of six deciduous tree species (Fagus sylvatica, Tilia spp., Fraxinus excelsior, Carpinus betulus, Acer pseudoplatanus and Acer platanoides) and in stand-specific litter mixtures, we compared mass loss and nutrient release across diversity levels along a gradient of decreasing proportion of Fagus in stands with similar environmental and physical soil conditions. The litterbag studies ran over 22 months. The decomposition rate constants (k) of the temperate forest species ranged from k = 0.5 for Fagus to k = 1.5-2 for all other tree species. In Fagus, k was closely negatively correlated with the thickness of the litter layer and positively correlated with soil pH and isopod abundance. k was significantly higher in the mixed species stands (except for Carpinus and Fraxinus) and was positively correlated with earthworm abundance. Over the whole incubation time, nutrient amount and release rates of N, P, K, Ca and Mg as well as C-related ratios showed significant differences between tree species but no consistent differences among the diversity levels. Initial C-related nutrient ratios of the leaf litter and abundance of mesofauna and macrofauna were correlated with the length of time lag before nutrient release. We conclude that the mere number of tree species is not the main driver of nutrient release and decomposition processes, but that key groups of the decomposer fauna as well as the characteristic traits of the individual tree species are decisive. 相似文献
77.
78.
Rodents are mostly controlled by using anticoagulant rodenticides to minimise adverse effects along the food production chain. Genetic resistance to anticoagulant compounds occurs in populations of Norway rats (Rattus norvergicus) and other rodents throughout the world. This can be problematic for control operations and put predators and scavengers at risk because resistant prey individuals carry high anticoagulant loads. Single nucleotide polymorphisms (SNPs) in the vitamin K reductase complex subunit 1 (VKORC1) gene that are associated with rodenticide resistance are related to several pleiotropic effects including increased vitamin K requirement. The uptake of dietary vitamin K available from food sources present on farms including corn silage and garden herbs may mitigate such effects. We tested the preference for food rich in vitamin K1/3 in Norway rats susceptible or resistant to bromadiolone due to the homozygous amino acid variant Tyr139Cys. We also studied the effect of vitamin K consumption from several food sources on blood clotting in bromadiolone resistant and susceptible Norway rats. There was no general preference of rats for food sources rich in vitamin K. Surprisingly, there was no effect of vitamin K uptake on blood clotting times. However, the consumption of 4 of 5 corn silages prevented the rise in blood clotting times that otherwise occurred in vitamin K deficient bromadiolone resistant rats. This seemed to be due to substances with vitamin K activity present in silage and may contribute to the sustaining and spreading SNPs that are related to rodenticide resistance. As corn silage is becoming increasingly available to rats due to the expansion in generating bio-energy from corn silage, there may be a future increase in the occurrence of anticoagulant resistant Norway rats and associated problems in agro-ecosystems. 相似文献
79.
C. Bindu Roy Zoe-Joy Newby Jacob Mathew David Ian Guest 《European journal of plant pathology / European Foundation for Plant Pathology》2017,147(1):129-139
In 2010, symptoms of cobweb disease were observed on cultivated Pleurotus eryngii crops in Spain. Based on morphological and genetic analyses, the causal agent of cobweb was identified as Cladobotryum mycophilum. Pathogenicity tests on fruit bodies were performed using conidial suspensions of three C. mycophilum isolates. The causal agent was re-isolated in 80–85 % of the fruit bodies inoculated internally and 15–40 % of those fruit bodies inoculated on the cap surface. The results pointed to a certain resistance of the P. eryngii cap surface to the mycelium of C. mycophilum. Two cropping trials inoculated with C. mycophilum were set up to evaluate the pathogenicity of the causal agent of cobweb in two casings. At the end of the growth cycle, 50–60 % of the inoculated blocks cased with mineral soil, and 20–33 % of the inoculated blocks cased with black peat showed cobweb symptoms. This difference in the appearance of the disease and its aggressiveness may be partly explained by different electrical conductivity values of the casing materials used. In vitro sensitivity of the C. mycophilum isolates and P. eryngii strains against four fungicides (chlorothalonil, prochloraz-Mn, thiabendazole and thiophanate-methyl) was assessed in radial growth experiments on fungicide-amended media. The most effective fungicides for inhibiting the in vitro growth of C. mycophilum were prochloraz-Mn and chlorothalonil, while prochloraz-Mn was also the most selective fungicide between P. eryngii and C. mycophilum, and chlorothalonil was the most toxic fungicide against the P. eryngii mycelium. 相似文献
80.
Vianey Leos-Barajas Eric J. Gangloff Timo Adam Roland Langrock Floris M. van Beest Jacob Nabe-Nielsen Juan M. Morales 《Journal of Agricultural, Biological & Environmental Statistics》2017,22(3):232-248
Hidden Markov models (HMMs) are commonly used to model animal movement data and infer aspects of animal behavior. An HMM assumes that each data point from a time series of observations stems from one of N possible states. The states are loosely connected to behavioral modes that manifest themselves at the temporal resolution at which observations are made. Due to advances in tag technology and tracking with digital video recordings, data can be collected at increasingly fine temporal resolutions. Yet, inferences at time scales cruder than those at which data are collected and, which correspond to larger-scale behavioral processes, are not yet answered via HMMs. We include additional hierarchical structures to the basic HMM framework, incorporating multiple Markov chains at various time scales. The hierarchically structured HMMs allow for behavioral inferences at multiple time scales and can also serve as a means to avoid coarsening data. Our proposed framework is one of the first that models animal behavior simultaneously at multiple time scales, opening new possibilities in the area of animal movement and behavior modeling. We illustrate the application of hierarchically structured HMMs in two real-data examples: (i) vertical movements of harbor porpoises observed in the field, and (ii) garter snake movement data collected as part of an experimental design. Supplementary materials accompanying this paper appear online. 相似文献