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Till Hornbogen Mirko Glinski Rainer Zocher 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(7):713-718
The cyclic hexadepsipeptide enniatin is known as a phytopathogenic compound from Fusaria causing necrosis and wilt. The molecule consists of three alternating residues each of a branched chain amino acid and D-hydroxyisovaleric acid (D-Hiv). Enniatins are synthesized by a 347kDa multienzyme (enniatin synthetase) via a thiol template mechanism. The corresponding gene esyn1 has an open reading frame of 9393 nucleotides and harbours two modules, one responsible for D-hydroxy acid activation and one for L-amino acid activation with an integrated N-methyltransferase domain. Such methyltransferases build an homologous group among N-methyl peptide synthetases. Enniatins are synthesized by step-wise condensation of dipeptidol building blocks in an iterative manner resembling fatty acid synthesis. A key enzyme in enniatin biosynthesis is the NADPH-dependent D-2-hydroxyisovalerate dehydrogenase, that supplies enniatin synthetase with D-Hiv. Enniatins contribute to the wilt toxic character of Fusaria. Virulence was significantly reduced in F. avenaceum after disruption of the esyn1 gene. 相似文献
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A system dynamic model for epidemics of Blumeria graminis (powdery mildew) on wheat was elaborated, based on the interaction between stages of the disease cycle, weather conditions and host characteristics. The model simulates the progress of disease severity, expressed as a percentage of powdered leaf area, on individual leaves, with a time step of one day, as a result of two processes: the growth of fungal colonies already present on the leaves and the appearance of new colonies. By means of mathematical equations, air temperature, vapour pressure deficit, rainfall and wind are used to calculate incubation, latency and sporulation periods, the growth of pathogen colonies, infection and spore survival. Effects of host susceptibility to infection, and of leaf position within the plant canopy, are also included. Model validation was carried out by comparing model outputs with the dynamics of epidemics observed on winter wheat grown at several locations in northern Italy (1991–98). Simulations were performed using meteorological data measured in standard meteorological stations. As there was good agreement between model outputs and actual disease severity, the model can be considered a satisfactory simulator of the effect of environmental conditions on the progress of powdery mildew epidemics. 相似文献
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A dynamic simulation model for the risk of Fusarium head blight on wheat was elaborated based on systems analysis. The model calculates a daily infection risk based on sporulation, spore dispersal and infection of host tissue of the four main species causing the disease (Gibberella zeae, Fusarium culmorum, Gibberella avenacea, Monographella nivalis). Spore yield and dispersal are calculated as functions of temperature, rainfall and relative humidity, while the main factors affecting the infection rate are temperature, wetness and the host growth stage. The model also calculates a risk for mycotoxin production by G. zeae and F. culmorum in the infected head tissue. First validations against field data, collected in some wheat‐growing areas in northern Italy and not used in model elaboration, produced satisfactory results. 相似文献
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P. Battilani V. Rossi B. Girometta M. Delos J. Rouzet N. Andr S. Esposito 《EPPO Bulletin》2003,33(3):427-431
Diaporthe helianthi is the causal agent of a severe sunflower disease but, in Italy, disease outbreaks are sporadic with no significant losses. The present work investigates the role of meteorological conditions on the potential development of D. helianthi epidemics in Italy, using the French model Asphodel, which simulates the effect of air temperature, relative humidity and rainfall on ascospore maturation and dispersal, infection establishment, disease onset and severity during the period of host susceptibility. Meteorological data measured in eight stations distributed from north to south Italy, over a 5‐year period (1995–99), was used as model input. Results showed that meteorological conditions in Italy are frequently favourable for D. helianthi infections on sunflower, and severe epidemics are possible. Therefore, climatic conditions are not a limiting factor for disease development in the Italian sunflower‐growing areas. The lack of disease epidemics in Italy may be related to differences in the pathogen populations compared with the French ones. 相似文献
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Buckwheat is a pseudocereal that has gained increasing interest of industry and consumers over the past decade. Little, however, is known about its dietary fiber composition and nonstarch polysaccharide structures. Analysis of the monosaccharide composition indicated large amounts of pectic polysaccharides in both insoluble and soluble fiber from buckwheat. Methylation analysis gave further insights into the structures of the polysaccharides. The corresponding partially methylated alditol acetates suggested only low amounts of galactans. Xyloglucans were the main hemicellulosic polysaccharides in the insoluble fiber fraction. Highly branched arabinans, exclusively substituted at position O3, were of higher abundance. These results were confirmed by screening endo‐arabinanase and endo‐galactanase liberated oligosaccharides with high‐performance anion‐exchange chromatography with pulsed amperometric detection and LC‐MS2. Application of this method also demonstrated highly branched arabinan areas within the pectic polysaccharides. Only low amounts of fiber associated hydroxycinnamic acids and diferulic acids were liberated by alkaline treatment, and no evidence was found for their attachment to polysaccharides, suggesting only a minor impact of these structural elements on fiber structures in dehulled buckwheat seeds. 相似文献
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Vignoli M Rossi F Chierici C Terragni R De Lorenzi D Stanga M Olivero D 《Schweizer Archiv für Tierheilkunde》2007,149(7):314-318
This paper reports three clinical cases of needle tract implantation of neoplastic cells on the abdominal and thoracic wall after ultrasound (US) fine needle aspiration biopsy (FNAB). Primary tumors were two transitional cell carcinomas of the urinary bladder (2 dogs) and one pulmonary adenocarcinoma (1 cat). All three masses grew up along the needle tract. To our knowledge, the seeding of pulmonary adenocarcinoma cells after FNAB on the thoracic wall has never been reported in veterinary medicine. 相似文献