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991.
A recent survey of insecticide resistance in two of the most problematic pests in UK glasshouses revealed some new developments. At least some individuals in all UK samples of Trialeurodes vaporariorum that were tested resisted the insect growth regulator (IGR) buprofezin. The most strongly resistant strains were unaffected by the field application rate of this compound, and even samples from populations that had never been exposed to buprofezin contained individuals that survived the highest concentration applied (10,000 mg litre-1). The field rate of buprofezin was shown to select for resistance through vapour action alone. The benzophenylurea teflubenzuron, an unrelated IGR, was cross-resisted by buprofezin-resistant individuals. There was no evidence of resistance to imidacloprid, but all T vaporariorum strains tested, regardless of origin, exhibited a high innate tolerance to nicotine, when compared with another whitefly species, Bemisia tabaci. Marked resistance to fenbutatin oxide and tebufenpyrad was found in single glasshouse populations of Tetranychus urticae, but these compounds and abamectin appeared to remain highly effective against all other strains collected. 相似文献
992.
A.N. Markoglou B.N. Ziogas 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(1):21-30
Mutants of Ustilago maydis resistant to the piperidine fungicide piperalin were isolated in a mutation frequency of 2.4 × 10–5 after UV-irradiation and selection on media containing 50gml–1 piperalin. Genetic analysis with 15 such mutant isolates resulted in the identifications of two unlinked chromosomal loci, the U/ppl-1 locus with two allelic genes (U/ppl-1A and U/ppl-1B) and the U/ppl-2 locus. The U/ppl-2 and U/ppl-1A mutations are responsible for two levels of moderate and high resistance to piperalin (resistance factor, Rf: 54 and 135, respectively, based on effective concentration causing a 50% reduction in the growth rate, EC50), while the U/ppl-1B mutation gives only a small reduction (approximately 8-fold) in piperalin sensitivity. Cross-resistance studies with other SBIs shows that the major gene (U/ppl-2 and U/ppl-1A) mutants are resistant to fenpropidin (Rf: 43 and 68), fenpropimorph (Rf: 261 and 283) and tridemorph (Rf: 9 and 10), but not to the inhibitors of C-14 demethylase (DMIs) and squalene epoxidase. The minor gene mutation U/ppl-1B codes a low-level of resistance (approximately 5—12-fold) to the above morpholine-type fungicides, but in contrast with the major gene mutations it increases 2–10 times the sensitivity to triazoles: triadimefon, triadimenol, propiconazole and flusilazole. Crosses between mutants carrying the U/ppl-genes with compatible isolates carrying the U/fpd, U/fpm or U/tdm mutations, which have been identified in previous genetic works for resistance to morpholine-type fungicides, yielded, with the exception of U/ppl-2 ×U/fpm-2 cross, a large number of recombinants with wild-type sensitivity, indicating that the mutant genes involved in these crosses, were not allelic. An additive gene effect was observed only between nonallelic minor genes U/ppl-1B and U/fpm-1B or U/tdm-1,2. Studies of the fitness of piperalin-resistant isolates showed that the reduced sensitivity of major gene mutants was not associated with changes on the phytopathogenic fitness determining characteristics, such as growth in liquid culture and pathogenicity on young corn plants. Conversely, the minor gene mutation U/ppl-1B appeared to be pleiotropic, having significantly adverse effects on the phytopathogenic fitness. 相似文献
993.
A.M.Q. Lopez J.A. Lucas 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(5):409-420
The plant defence activators acibenzolar-S-methyl (Benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester, ASM), 2,6-dichloro-isonicotinic acid (DCINA), salicylic acid (SA), and dibasic potassium phosphate (K2HPO4) were tested for their ability to protect cashew (Anacardium occidentale) seeds and leaves from anthracnose disease caused by Colletotrichum gloeosporioides. No inhibition of the early stages of pathogen development was caused by concentrations equal to or lower than 1.1mM a.i. ASM, 1.2mM a.i. DCINA, 5mM SA and 50mM K2HPO4. Maximum reduction of the disease in detached leaves, without phytotoxic effects, was obtained with 0.07mM a.i. ASM and DCINA, 5mM SA, and 50mM K2HPO4, with a time interval of at least 72h between application of the activator and inoculation with the pathogen. On attached leaves, foliar sprays were slightly more efficient than soil drench treatments, with 5mM SA being the most effective treatment, while 50mM SA as well as 0.3mM a.i. ASM and DCINA caused phytotoxic effects. In field-grown plants, protection was conferred by a soil drench of concentrations as low as 12.6M a.i. ASM and DCINA and 2.6mM SA. These concentrations were not phytotoxic suggesting that plant defence activators have potential for control of anthracnose disease in the field. 相似文献
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997.
多杀菌素的作用机理及其抗药性的研究进展 总被引:2,自引:0,他引:2
多杀菌素是一类新的杀虫剂,具有高效、低毒、选择性强、对环境安全的特点。其作用机制是通过激活烟碱型乙酰胆碱受体(nAChR),使正常昆虫神经细胞去极化,也可通过抑制γ-氨基丁酸受体(GABAR)使神经细胞超极化。本文综述了多杀菌素作用机理及其抗药性的研究进展。 相似文献
998.
随着近年分子生物学技术的发展与应用,植物霜霉病抗性的研究有了长足的进展。本文就拟南芥抗霜霉病基因的克隆与结构分析,抗病信号传导,防卫反应和系统获得抗性,以及寄主一寄生菌共进化冲突方面进行了综述,并就今后的研究进行了展望。 相似文献
999.
Cavity spot is a major disease of carrots, causing cavities on the surface of the root. Available commercial varieties show a range of susceptibility but no significant resistance. Seed progeny from 46 tissue culture-derived carrot ( Daucus carota ) somaclones were screened for viability, then 19 selected somaclone families were sown under glasshouse conditions, along with commercial cultivars (Bertan, Nandor, Bolero and Vita Longa) as controls. Mature roots were exposed to Pythium violae in a cavity spot bioassay to determine their response as measured by disease incidence and severity. Some somaclones formed fewer lesions than the least susceptible control cultivar, Vita Longa. Seven somaclonal families that showed a range of susceptibility were sown under field conditions and the assessment was repeated. Although there was little relationship between glasshouse and field-trial results, under field conditions one of the somaclones had a mean incidence of disease, as estimated by transformed data, of 1·9 compared with 37·9 for the most susceptible somaclone and 3·5 for Bolero, the most resistant commercial cultivar. The results indicated that significant genetic variation in susceptibility to cavity spot disease was present in the somaclones. 相似文献
1000.
The wheat cultivar Kariega expresses complete adult plant resistance against stripe rust, whereas cv. Avocet S is susceptible. Using confocal laser scanning microscopy, initial fungal penetration into flag leaves was identical in both cultivars, with directional germ-tube growth towards stomata that were penetrated without the formation of an appressorium, followed by differentiation of a substomatal vesicle, infection hyphae, haustorial mother cells and haustoria. During the following 4 days, further fungal development occurred more quickly in the resistant than in the susceptible cultivar. However, by 7 days postinoculation (dpi) the situation changed, with exponential growth of the pathogen occurring only in the susceptible line. Induced cellular lignification, a typical defence reaction of cereals, was observed at 4 dpi in the resistant cultivar, and 2 days later lignified tissue completely surrounded the fungal colonies. In the susceptible cultivar, isolated lignified host cells occurred at 6 dpi, and long, unbranched fungal hyphae outgrowing the resistance reaction were observed. 相似文献