全文获取类型
收费全文 | 861篇 |
免费 | 51篇 |
专业分类
林业 | 80篇 |
农学 | 38篇 |
基础科学 | 3篇 |
242篇 | |
综合类 | 53篇 |
农作物 | 96篇 |
水产渔业 | 76篇 |
畜牧兽医 | 219篇 |
园艺 | 18篇 |
植物保护 | 87篇 |
出版年
2023年 | 12篇 |
2022年 | 26篇 |
2021年 | 46篇 |
2020年 | 48篇 |
2019年 | 30篇 |
2018年 | 31篇 |
2017年 | 32篇 |
2016年 | 41篇 |
2015年 | 35篇 |
2014年 | 36篇 |
2013年 | 44篇 |
2012年 | 62篇 |
2011年 | 73篇 |
2010年 | 46篇 |
2009年 | 40篇 |
2008年 | 46篇 |
2007年 | 63篇 |
2006年 | 37篇 |
2005年 | 38篇 |
2004年 | 26篇 |
2003年 | 32篇 |
2002年 | 22篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有912条查询结果,搜索用时 607 毫秒
221.
Elena L. Peredo M. Ángeles Revilla Barbara M. Reed Branca Javornik Eduardo Cires José Antonio Fernández Prieto Rosa Arroyo-García 《Genetic Resources and Crop Evolution》2010,57(4):575-586
Microsatellite variation at the nuclear and chloroplast genomes was evaluated for wild European and wild American hops, in
order to assess the genetic diversity and origin of cultivated hops. Seven nuclear loci and 32 chloroplast loci were used in the analysis of 182 hop accessions including wild European (68), wild American (48), and cultivars (66). A total
of 116 alleles were identified using 7 nuclear microsatellites showing different averages of polymorphism and distribution
in the wild American and European accessions and cultivars. Two main groups were established as revealed by several statistical
analyses; one including European wild accessions and cultivars and a second group consisting of American wild accessions.
Three polymorphic chloroplast microsatellite loci were detected, six alleles were scored which defined a total of five haplotypes that were exclusive or presented different
distribution between American and European wild accessions. A major influence of the wild European haplotypes was detected
among hop cultivars. To the best of our knowledge, this is the first work reporting the use of chloroplast microsatellites
in hops. 相似文献
222.
Degradation of the herbicides clomazone, paraquat, and glyphosate by thermally activated peroxydisulfate 总被引:1,自引:0,他引:1
Diaz Kirmser EM Mártire DO Gonzalez MC Rosso JA 《Journal of agricultural and food chemistry》2010,58(24):12858-12862
Activated sodium peroxydisulfate has the potential to in situ destruct many organic contaminants because of the generation of the stronger oxidant sulfate radical. From photochemical activation of peroxydisulfate in flash-photolysis experiments, the bimolecular rate constants for the reaction of sulfate radical with glyphosate (1.6 × 10(8) M(-1) s(-1)) and paraquat (1.2 × 10(9) M(-1) s(-1)) at 25 °C were obtained. Thermal activation of peroxydisulfate was shown to degrade the herbicides clomazone, paraquat, and glyphosate. Although the herbicide degradation was observed to take place in less than 1 h, the mineralization of the organic carbon required longer reaction times, because of the formation of stable organic intermediates. For similar initial total organic carbon (TOC) values, TOC profiles were similar for experiments with different substrates (the herbicides, humic acids, and a mixture of glyphosate and humic acids), which indicates that the mineralization of all of the samples is limited by the production of SO(4)(?)?(-) radicals. A linear correlation between the initial amount of SO(4)(?)?(-) needed per mole of C and the average oxidation state was found. 相似文献
223.
Socioeconomic impact of widespread adoption of precision farming and controlled traffic systems in Denmark 总被引:1,自引:0,他引:1
Hans Grinsted Jensen Lars-Bo Jacobsen S?ren Marcus Pedersen Elena Tavella 《Precision Agriculture》2012,13(6):661-677
In this study we assess the economic profitability of implementing various precision farming (PF) technologies and controlled traffic farming (CTF) on 4 main crops in Denmark. The study provides insight into technological requirements, and identifies related costs and benefits to farmers and the Danish society as a whole. At the farm level, the findings from the study indicate that an implementation of CTF systems may have a significant impact on fuel savings due to a reduced overlap with auto guidance systems and easier movement with tractors and tools in the field. The PF site-specific weed management approach may facilitate large savings in the use of herbicides. At the national level, the results clearly show that the benefits to the Danish economy of adopting this new technology is positive with increased income to farmers and a reduction in fuel consumption and pesticides/herbicides use. The obtained results reflect the long term economic effect of implementing new production methods in Denmark where soil fertility increases over time due to reduced traffic increasing yields. Over all, the Danish GDP is estimated to increase by 34?million?? due to the implementation of PF and CTF on larger farms in Denmark. The results also clearly show that adoption of PF and CTF farming systems will benefit the environment. The agricultural sectors input of environmental harmful inputs are reduced in all scenarios presented in this paper. The adoption of PF and CTF systems should thus be of interest to politicians since it clearly facilitates aims of environmental policies currently under implementation by the Danish government. 相似文献
224.
P. Gómez R. N. Sempere M. A. Aranda S. F. Elena 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(3):445-449
Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops in the Northern hemisphere. After its first identification, the new viral strain PepMV-CH2 has been isolated in several countries worldwide. In order to further understand the evolutionary dynamics of PepMV before and after PepMV-CH2 emergence, we analyzed a collection of PepMV isolates from southeastern Spain, estimating the rate of PepMV molecular evolution and the coalescence process for the effective number of PepMV infections using a Bayesian phylogenetic approach. Our results show that the rate of PepMV molecular evolution was 5.570?×?10?3 substitutions/site/year, a value which is approximately an order of magnitude higher than the rates recently reported for other plant RNA viruses. Moreover, PepMV-CH2 was estimated to have originated in 2000, coincident with the onset of PepMV-CH2 infections in southeastern Spain, its population following now an expansion process. This further illustrates that genetic and ecological interactions among different viral strains can modulate the evolutionary dynamics of PepMV and determine its epidemiological profile. 相似文献
225.
BACKGROUND: The red palm weevil, Rhynchophorus ferrugineus (Olivier), is a phytophagous insect that feeds on soft succulent tissues of most palm species and is considered the main palm pest in the Middle East and the Mediterranean Basin. The aim of this study was to test the efficacy of imidacloprid oil dispersion (OD) as a drench in preventive and curative treatments against R. ferrugineus in Phoenix canariensis, Washingtonia robusta, Washingtonia filifera and Trachycarpus fortunei. RESULTS: Levels of infestation were highest in P. canariensis. There was no infestation in W. filifera. Mean efficacies of 100 and 94% were obtained in preventive and curative treatments respectively. High efficacies in preventive treatments (mean 95.4%) lasted for up to 45 days after application. CONCLUSION: The high efficacies and persistence of imidacloprid OD applied as a drench in young palms show the potential of this product for the management of R. ferrugineus. Copyright © 2011 Society of Chemical Industry 相似文献
226.
Cecchinelli E Aquiloni L Maltagliati G Orioli G Tricarico E Gherardi F 《Pest management science》2012,68(6):839-844
BACKGROUND: The crayfish Procambarus clarkii inflicts severe ecological and economic damages in Europe. To develop an efficient method for its control, four experiments were carried out to assess the impact of natural pyrethrum (i.e. Pyblast) on crayfish: (1) the 24 h LC100 and LC50 were quantified on crayfish; (2) the breakdown time of the 24 h LC100 was assessed using Daphnia magna as a bioindicator; the effects of 24 h LC100 on crayfish were investigated by applying the biocide into burrows (3) and in a drainage channel (4). RESULTS: Pyblast concentrations of 0.05 and 0.02 mg L?1 corresponded to 24 h LC100 and LC50 respectively. The concentration of 0.05 mg L?1 broke down after 72 h, whereas 0.02 mg L?1 did not cause any significant mortality in D. magna after 24 h. However, 0.05 mg L?1 had no effect on crayfish when introduced into the burrows, but led to a mortality of 95% when applied in the water. CONCLUSION: Experimental evidence is provided for the efficacy of Pyblast to control invasive crayfish. Obviously, before its use on a large scale, further studies are needed to find a concentration that will achieve the target 100% mortality with the shortest recovery time of the environment. Copyright © 2012 Society of Chemical Industry 相似文献
227.
228.
Genetic Relationships Among Verticillium dahliae Isolates from Cotton in Greece Based on Vegetative Compatibility 总被引:1,自引:0,他引:1
K. Elena 《European journal of plant pathology / European Foundation for Plant Pathology》1999,105(6):609-616
Vegetative compatibility groups of a collection of 71 Greek Verticillium dahliae isolates obtained from cotton plants were tested. Nit mutants were generated from single spore wild strains by selecting chlorate-resistant sectors on minimal medium amended with potassium chlorate, 25g/l. These mutants were tested against tester strains from the USA and Greece of the previously described VCGs 1, 2, 3 and 4. Forty-six of 71 isolates belonged to VCG2, because they were able to anastomose with the testers of this group, two isolates belonged to VCG4 and one to VCG1, while the 22 remaining strains could not be assigned to any of the identified VCGs. Our data demonstrated that wilt of cotton is caused only by V. dahliae in Greece, and VCG2 is the most commonly detected VCG. Some strains were found to be more virulent to cotton than other strains from the same VCG. This is the first report of VCG1 of Verticillium in Greece. 相似文献
229.
Pocacqua V Provasi E Paltrinieri S Gelain E Comunian C Ceciliani F 《Veterinary immunology and immunopathology》2005,107(1-2):17-26
alpha1-Acid glycoprotein (AGP) is considered one of the major acute phase proteins in cats. In humans, AGP is a heavily glycosylated protein that undergoes several modifications of its glycan moiety during acute and chronic inflammatory pathologies. In this paper we present the feline AGPs (fAGP) glycan moiety modifications in the course of two prevalent feline diseases, the FIV (feline immunodeficiency virus) dependent feline acquired viral immunodeficiency and the feline leukemia virus (FeLV) associated lymphoma. The glycan moiety of fAGP was investigated by means of the binding of its oligosaccharides residues with specific lectins. Four lectins were used: Sambucus nigra agglutinin I and Maackia amurensis agglutinin lectins were used to detect sialic acid residues, Aleuria aurantia lectin was used to detect L-fucose residues and Concanavalin A was used to evaluate the degree of branching. It was found that fAGP undergoes several post-translational modifications of its glycan pattern: in particular the degree of sialylation is increased in FeLV-positive cats diagnosed with lymphoma, while FeLV-positive that did not presented any specific clinical signs cats do not present any increase of expression of sialic acid on the surface. Furthermore, FIV induced a modification of the glycan moiety of fAGP, which however varied widely among individuals. In order to determine the number and the position of oligosaccharide chains, the cDNA sequence of fAGP was also determined. The translation of the mature fAGP coding sequence gave rise to a sequence of 183 residues, with five potential N-glycosylation sites, but also with seven potential phosphorylation sites. 相似文献
230.