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231.
Although the role of habitat fragmentation in species declines is well recognised, the effect of habitat quality on species
distributions is often studied using presence–absence models that ignore metapopulation dynamics. We compared three approaches
to model the presence–absence of North Island robins in 400 sites among 74 fragments of native forest in a 15,000-ha agricultural
landscape in New Zealand. The first approach only considered local habitat characteristics, the second approach only considered
metapopulation factors (patch size and isolation), and the third approach combined these two types of factors. The distribution
of North Island robins was best predicted by patch isolation, as their probability of occurrence was negatively correlated
with isolation from neighbouring patches and from the closest major forests, which probably acted as a source of immigrants.
The inclusion of habitat factors gave only a slight increase in predictive power and indicated that robins were more likely
to occur in areas with tall canopy, tall understory and low density of young trees. We modelled the effect of isolation using
an index of functional patch connectivity based on dispersal behaviour of radio-tracked juveniles, and this functional index
greatly improved the models in comparison to classical indices relying on Euclidean distances. This study highlights the need
to incorporate functional indices of isolation in presence–absence models in fragmented landscapes, as species occurrence
can otherwise be a misleading predictor of habitat quality and lead to wrong interpretations and management recommendations. 相似文献
232.
Motoaki Tojo Ken Watanabe Kenichi Kida Yingjie Li Shuhei Numata 《Journal of General Plant Pathology》2007,73(2):121-124
Severe mottle necrosis (Shirogusare-byo in Japanese) was found on mature tubers of sweet potato (Ipomoea batatas) in Ibaraki Prefecture in October 2004. The causal organism was identified as Pythium scleroteichum hitherto unknown in Japan. Sweet potato cultivar Purple Sweet Lord was more susceptible than cultivars Beniazuma, Benimasari,
Koukei-14, and Tamayutaka to the pathogen at 25°C, while this difference in the susceptibility was not clear at 15°C. 相似文献
233.
María Eugenia Salgado Salomón Carolina Barroetaveña Mario Rajchenberg 《New Forests》2011,41(2):191-205
We investigated if Pinus ponderosa plantations in Patagonia are able to produce viable mycorrhizal inocula towards adjacent grasslands, which only harbor endomycorrhizal
vegetation. We hypothesized that these inocula have the potential to contribute to the establishment of naturally disseminated
seedlings. Also, we determined the main fungal taxa involved in this process. Seven plantations in the onset of their reproductive
phase and located in the Patagonian native forest/steppe ecotone (Argentina) were selected. Soil samplings were obtained at
nine points along a 450 m long, W-E transect established in each plantation. Soil bioassays were performed in a greenhouse,
with P. ponderosa seedlings acting as hosts for mycorrhizal inocula present in soil samples, during 12 months. Mycorrhization percentage, morphotype
richness and morphotype composition was determined through morphological evaluation. Viable ecto- and ectendomycorrhizal inocula
were found disseminated outside plantations. The amount of mycorrhizal inoculum followed a decreasing function with distance
to plantation edges. Mycorrhizal fungal genus Rhizopogon and “E-strain” mycorrhizal types appeared as pioneering taxa regarding seedlings colonization, being the most persistent
and frequent symbionts found. Plantations, thus, facilitate the surrounding terrain for newcoming seedlings through the dispersion
of mycorrhizal fungal inocula. 相似文献
234.
Xiangyang Shi Hong Lin 《European journal of plant pathology / European Foundation for Plant Pathology》2018,150(2):351-362
Type IV pili of X. fastidiosa are regulated by pilG, a response regulator protein putatively involved in chemotaxis-like operon sensing stimuli through signal transduction pathways. To elucidate the roles of pilG in pathogenicity of X. fastidiosa, the pilG-deletion mutant XfΔpilG and complemented strain XfΔpilG-C were generated. While all strains had similar growth curves in vitro, XfΔpliG showed significant reduction in cell-matrix adherence and biofilm production compared with wild-type X. fastidiosa and XfΔpilG-C. The genes pilE, pilU, pilT, and pilS were down-regulated in XfΔpliG when compared with its complemented strain and wild-type X. fastidiosa. Finally, no Pierce’s disease symptoms were observed in grapevines inoculated with XfΔpilG, whereas grapevines inoculated with the wild-type X. fastidiosa and complemented strain of XfΔpilG-C developed typical Pierce’s Disease (PD) symptoms. The results indicate that pilG has a role in X. fastidiosa virulence in grapevines. 相似文献
235.
Xiaojie Wang Wenming Zheng Heinrich Buchenauer Jie Zhao Qingmei Han Lili Huang Zhensheng Kang 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(3):241-247
Stripe rust of wheat caused by Puccinia striiformis f. sp. tritici is one of the most important diseases on wheat worldwide, especially in temperate regions with cool moist weather conditions.
A rapid and reliable detection of the pathogen in latent infected wheat leaves during overwintering of the fungus in the dormant
stage will contribute to determine the initial inoculum potential and thus to predict early outbreak and to improve effective
management of the disease. To achieve this aim, a PCR-based method was developed for specific and sensitive detection of P. striiformis. Specific primers were designed according to a genome-specific sequence of P. striiformis. To evaluate the specificity of the primers, seven different isolates and races of P. striiformis as well as six other pathogens of wheat were tested. All isolates of P. striiformis yielded a distinct band of a fragment of 470 bp, while using DNA of the other wheat pathogens as a template no amplification
product was detected. The sensitivity of the primers was tested using serial dilutions of total DNA from P. striiformis; the limit of detection was 10 pg of DNA. Using extracts from P. striiformis-infected wheat leaves, the fungus could be determined in the leaves before symptoms appeared. The stripe rust could also
be detected in the dormant stage by the PCR assay in samples of wheat leaves taken during the winter season. The application
of the PCR assay may be useful for rapid and reliable detection of P. striiformis in latent infected leaves of overwintering wheat plants. 相似文献
236.
237.
238.
An introductory study was conducted to investigate the pyrethroid resistance ofHelicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) strains in Turkey, collected from cotton fields in the Adana and Antalya provinces, through
two different synthetic pyrethroid insecticides: lambda-cyhalothrin and esfenvalerate. In addition, the roles of glutathioneS-transferases (GSTs) in this resistance mechanism were analyzed. It was found that whereas resistance ratios for lambda-cyhalothrin
(LD50 levels) were 3- and 98-fold increased in the Adana and Antalya strains, respectively, esfenvalerate ratios were 3.3- and
92.3-fold increased in the Adana and Antalya strains, respectively, with respect to the susceptible strain. Furthermore, Adana
and Antalya strains showed 2.4- and 2.9-fold higher GST activities than the susceptible strain, respectively. In the Antalya
field strain, the minor increase in GST activity compared with the resistance levels implies that GSTs may be not greatly
involved in this resistance. It also provides evidence that they could not be the only metabolic mechanism responsible for
resistance to lambda-cyhalothrin and esfenvalerate inH. armigera from Turkey.
http://www.phytoparasitica.org posting Nov. 16, 2006. 相似文献
239.
Are hedgerows effective corridors between fragments of woodland habitat? An evidence-based approach 总被引:1,自引:1,他引:1
Anthropogenic modification of the countryside has resulted in much of the landscape consisting of fragments of once continuous
habitat. Increasing habitat connectivity at the landscape-scale has a vital role to play in the conservation of species restricted
to such remnant patches, especially as species may attempt to track zones of habitat that satisfy their niche requirements
as the climate changes. Conservation policies and management strategies frequently advocate corridor creation as one approach
to restore connectivity and to facilitate species movements through the landscape. Here we examine the utility of hedgerows
as corridors between woodland habitat patches using rigorous systematic review methodology. Systematic searching yielded 26
studies which satisfied the review inclusion criteria. The empirical evidence currently available is insufficient to evaluate
the effectiveness of hedgerow corridors as a conservation tool to promote the population viability of woodland fauna. However,
the studies did provide anecdotal evidence of positive local population effects and indicated that some species use hedgerows
as movement conduits. More replicated and controlled field investigations or long-term monitoring are required in order to
allow practitioners and policy makers to make better informed decisions about hedgerow corridor creation and preservation.
The benefits of such corridors in regard to increasing habitat connectivity remain equivocal, and the role of corridors in
mitigating the effects of climate change at the landscape-scale is even less well understood. 相似文献
240.
Identification of functional corridors with movement characteristics of brown bears on the Kenai Peninsula,Alaska 总被引:2,自引:1,他引:2
Tabitha A. Graves Sean Farley Michael I. Goldstein Christopher Servheen 《Landscape Ecology》2007,22(5):765-772
We identified primary habitat and functional corridors across a landscape using Global Positioning System (GPS) collar locations
of brown bears (Ursus arctos). After deriving density, speed, and angular deviation of movement, we classified landscape function for a group of animals
with a cluster analysis. We described areas with high amounts of sinuous movement as primary habitat patches and areas with
high amounts of very directional, fast movement as highly functional bear corridors. The time between bear locations and scale
of analysis influenced the number and size of corridors identified. Bear locations should be collected at intervals ≤6 h to
correctly identify travel corridors. Our corridor identification technique will help managers move beyond the theoretical
discussion of corridors and linkage zones to active management of landscape features that will preserve connectivity. 相似文献