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991.
Powdery mildew fungi are parasitized by strains of the genetically distinct Ampelomyces quisqualis. To investigate whether differences in the phylogeny and other cultural, morphological and physiological characteristics
of these different strains are related to differences in their geographic origins or the host species from which they were
isolated, several A. quisqualis strains isolated from different species of Erysiphaceae collected in different countries and possessing different ITS rDNA
sequences were selected and characterized. The results revealed some significant variation among the selected strains, which
provides evidence for the existence of different physiological forms within the A. quisqualis species. Two groups that display differential growth on artificial media were identified. These groups also differ in the
morphology of their mycelium, but not in the morphology of their pycnidia and conidia. Temperature greatly affected the in vitro growth of the A. quisqualis strains and growth rate was closely correlated to colony color. Differences in the conidial germination of distinct strains
were observed during the recognition phase of the parasitic relationship. The germination of each of the investigated strains
was greatly stimulated by all of the examined powdery mildew species and not only by the conidia of their original hosts.
An Italian strain isolated from grapevine in the Trentino Alto-Adige region was identified as the strain that germinates the
most quickly in the presence of powdery mildew conidia. Phylogenetic analysis revealed that these A. quisqualis strains can be classified into five different genetic groups, which generally correlate with the fungal host of origin and
morphological and growth characteristics. 相似文献
992.
The braconid parasitoid Microplitis mediator (Haliday) is a key natural enemy of the cabbage moth, Mamestra brassicae (L.), in Europe. In the context of an Integrated Pest Management approach, the use of selective insecticides is essential
for the conservation of naturally occurring beneficial arthropods. The present laboratory study investigated the side effects
of six insecticides applied at recommended field rates on adults and cocooned pupae of M. mediator. Male and female parasitoids were paired in drum cells contaminated with dry residues of insecticides. Besides lethal effects
after 24 h, parasitization capacity and longevity of the surviving parasitoids was evaluated. Lethal effects on cocooned pupae
were also investigated by assessing adult emergence from treated cocoons. Pirimicarb caused 100% adult mortality after 24 h,
whereas the other tested insecticides caused no direct toxic effects. However, sub-lethal effects in terms of reduced parasitization
activity, percentage of parasitism or female longevity were found for flonicamid, pymetrozine, spinosad and thiacloprid. Spirotetramat
shortened only male longevity. Adult emergence from treated cocoons was reduced only by flonicamid and pymetrozine. 相似文献
993.
Black nightshade (Solanum nigrum L.) is a troublesome weed worldwide, affecting a large number of crops. As weed development is affected by a variety of factors,
advanced knowledge on the plant’s biological and ecological qualities can support favorable management strategies. Seed density
is an ecological factor affecting emergence and early growth of many weed species. For that reason, the current study characterizes
and quantifies the seed density impact on black nightshade seedling-emergence and early growth, and the interaction between
seed density and burial depth on these growth parameters. Greenhouse studies conducted in 2005, 2006 and 2010 examined black
nightshade seed densities of 1, 5, 10, 25 and 50 seeds per pot, buried at, 1, 2, 3, 4 and 5 cm. Impact of seed density on
weed emergence and growth was characterized by number of emerged plants and leaves, followed by biomass measurements. Seed
density had no impact on emergence at the tested burial depths. There was a strong logistic relationship (P < 0.001, and R
2
> 0.97) between time and emergence, and a strong linear relationship (P < 0.002 and R
2
> 0.86) between time and number of leaves produced in all depths and seed densities. A negative relationship was observed
between seed density and plant development and growth rate. Results of this study extend the knowledge on black nightshade
biology and support decision-making concerning rational weed management. 相似文献
994.
Mónica Berbegal Luis Armando Álvarez Ana Pérez-Sierra Josep Armengol 《Phytoparasitica》2012,40(1):1-4
Pythium isolates were recovered from endive plants (Cichorium endivia) showing vascular necrosis collected from commercial fields located in Castellón province (eastern Spain). They were identified
as Pythium tracheiphilum on the basis of their phenotypical and molecular profile. Pathogenicity tests conducted with two P. tracheiphilum isolates, obtained from endive and lettuce (Lactuca sativa), respectively, in this region, confirmed that both isolates were pathogenic to endive, with no significant differences in
virulence between them. This is the first report of vascular necrosis caused by P. tracheiphilum on endive in Spain. 相似文献
995.
Chiou-Chu Su Chung-Jan Chang Wen-Jen Yang Shih-Tien Hsu Kuo-Ching Tzeng Fuh-Jyh Jan Wen-Ling Deng 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(2):203-216
Pear leaf scorch, the only Xylella fastidiosa-induced disease reported from Taiwan, was found in area where the variety Hengshan (Pyrus pyrifolia) was grown. Strains of pear leaf scorch Xyl. fastidiosa (XF-PLS) shared similarities to strains of other host origins in the requirement of complex medium and the exhibition of
rippled cell walls, however, recent serological and molecular biology studies showed difference among them. Five strains of
XF-PLS were compared with 20 other strains originally isolated from almond, oleander, pecan, plum, peach, mulberry, grapes,
citrus, coffee, and sycamore by sequence analyses of the 16S rRNA gene and 16S–23S rRNA internal transcribed spacer region
(ITS). When sequences of 16S rRNA gene based on fragment size of 1,537–1,540 bp were compared, the similarity index among
5 XF-PLS strains was 99.3–99.8%, whereas it was 97.8–98.6% between XF-PLS strains and strains from other hosts. When sequences
of 16S–23S rRNA ITS based on fragment size of 510–540 bp were compared, the similarity index among 5 XF-PLS strains was 99.0–100%,
whereas it was 80.7–82% between XF-PLS strains and strains from other hosts. Multiple sequence alignments led to the identification
of 5 polymorphic nucleotides in the 16S rRNA gene among the 25 Xyl. fastidiosa strains, and there were considerable variations in the nucleotide sequences of 16S–23S rRNA ITS between XF-PLS and the other
20 Xyl. fastidiosa strains. The phylogenetic trees revealed that XF-PLS strains were separated from strains of other hosts. Strains of other
hosts were divided into four subgroups: strains from (1) oleander, (2) grape, almond M23 and mulberry, (3) citrus and coffee,
and (4) pecan, peach, plum, sycamore and almond M12. Results indicate that XF-PLS strains were not closely related to the
above-mentioned strains from other hosts and could possibly belong to a new subspecies of Xyl. fastidiosa. 相似文献
996.
M. I. Tajul Takayuki Motoyama Akikazu Hatanaka M. Sariah Hiroyuki Osada 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):91-100
Four green-odour compounds—trans-2-hexenal, cis-3-hexenol, n-hexanal, and cis-3-hexenal—were applied (0.85 μg ml−1 as vapour) to rice plants in laboratory conditions to observe their biological activity against the phytopathogenic fungus
Maganporthe oryzae, which causes rice blast disease worldwide. Two compounds, trans-2-hexenal and cis-3-hexenal, showed remarkable disease suppression efficacy (99.7% and 100% suppression, respectively), while n-hexanal had moderate (86.5%) and cis-3-hexenol had weak (20.8%) disease-suppressing effects. Pre-application and post-application of trans-2-hexenal or cis-3-hexenal had slight effects on blast incidence, suggesting that these compounds had direct effects to suppress M. oryzae infection. In fact, trans-2-hexenal and cis-3-hexenal exhibited a growth suppression effect on M. oryzae. Interestingly, these two compounds inhibited appressorium formation at lower concentrations than the growth suppression.
Studies on the hypersensitive response (HR)-like reaction and plant β-1,3-glucanase activity in rice plant confirmed that
induced resistance was not the major factor involved in the disease suppression mechanism. Results of this study conclusively
showed that trans-2-hexenal and cis-3-hexenal possess potent inhibitory activities against the growth and the appressorium formation of M. oryzae and could be used as antifungal agents to significantly reduce M. oryzae infections in rice. 相似文献
997.
Michel Almaguer Teresa Irene Rojas Francisco Javier Rodríguez-Rajo María Jesús Aira 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(2):473-482
This study characterised the airborne mycobiota of a rice plantation in Bauta (Havana, Cuba), with a view to improving crop
quality. Culturable airborne fungi were sampled between March 2007 and February 2008 using a volumetric method (SAS Super
100) with potato dextrose agar as culture medium. The total fungal count was 51,425 cfu/m3. The 39 filamentous genera identified included several major rice pathogens (Bipolaris, Curvularia, Alternaria, Pyricularia, Cercospora and Fusarium) as well as potentially mycotoxigenic species of Fusarium, Penicillium and Aspergillus. Analysis of the influence of weather-related factors on spore counts revealed that total counts and Penicillium counts correlated positively with daily relative humidity, mean temperature and dew point. 相似文献
998.
Jan Wunderle Andreas Leclerque Ulrich Schaffrath Alan Slusarenko Eckhard Koch 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(4):865-875
Loose smut fungi of barley and wheat (Ustilago nuda and U. tritici, respectively) colonize the plant without causing obvious disease symptoms before heading. The availability of diagnostic methods to detect and follow the growth of these pathogens in the plant would therefore be highly advantageous for both resistance breeding and the development of effective seed treatments. Using seed lots of barley and wheat highly infected with loose smut, we studied the early establishment of the loose smut pathogens in the plant by fluorescence microscopy. In hand-cut sections stained with the fluorochrome Blankophor?, fungal hyphae were observed to invade the shoot apical meristem and leaf primordia during the first days after the onset of germination. At the first node stage the ear and leaf primordia were generally extensively colonized. Hyphae of U. nuda were also regularly observed in high density in the nodes. A protocol was developed for the specific amplification of U. nuda and U. tritici DNA extracted from infected plant tissue. PCR screening of U nuda in seedlings from infected and healthy seed lots was compared to ELISA, microscopy and ultimately head infection of mature plants derived from tillers of the tested seedlings. The results indicated that a prediction of loose smut infection by real-time PCR is possible at the second leaf stage, and that the assay is equally suited for use with spring and winter varieties of barley and wheat. 相似文献
999.
Nalini Mallikarjuna Deepak R. Jadhav Kanaka Reddy Fatema Husain Kumkum Das 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):17-21
Cultivated groundnut is susceptible to late leaf spot (LLS) caused by Phaeoisariopsis personata [(Berk. & M.A. Curtis) Aex] and resistance is low to moderate in the primary gene pool of groundnut. Closely related wild
species in the secondary gene pool are highly resistant to the disease. All the closely related Arachis species are diploid and cultivated groundnut is a tetraploid. Utilization of diploid Arachis species to transfer LLS resistance is time consuming and cumbersome. New sources of Arachis hypogaea (also called synthetic groundnut) were developed at ICRISAT. These are tetraploids and the present investigation has shown
that they are resistant to LLS. 相似文献
1000.
Sameh Boukef Bruce A. McDonald Amor Yahyaoui Salah Rezgui Patrick C. Brunner 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):111-122
The occurrence of fungicide resistance in Mycosphaerella graminicola populations from Tunisia was investigated by examining mutations known to be associated with strobilurin and azole resistance.
Few mutations associated with fungicide resistance were detected. No evidence for strobilurin resistance was found among 357
Tunisian isolates and only two among 80 sequenced isolates carried mutations associated with azole resistance. A network analysis
suggested that these mutations emerged independently from mutations found in previously described European populations. The
population genetic structure of M. graminicola in Tunisia was analyzed using variation at 11 microsatellite loci. Populations in Tunisia were characterized by high gene
and genotype diversity. All populations were in gametic equilibrium and mating type proportions did not deviate from the 1:1
ratio expected under random mating, consistent with regular cycles of sexual reproduction. In combination with a high degree
of gene flow among sampling sites, M. graminicola must be considered a pathogens with high evolutionary potential. Thus, control strategies against Septoria blotch in Tunisia
should be optimized to reduce the emergence and spread of resistant isolates. 相似文献