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711.
Acid rain sulphate (SO42−) deposition is a known suppressant of methane (CH4) emission from wetlands. However, the hypothesised mechanism responsible for this important biogeochemical interaction, competitive exclusion of methanogens by dissimilatory SO42− reducing bacteria (SRB), lacks supporting evidence. Here, we present data from an acid rain simulation experiment in the Moidach More peat bog of NE Scotland that strengthens this hypothesis. We report a tenfold increase in estimated SO42− reduction during periods when measured CH4 emission rates were suppressed relative to controls receiving only one-tenth the SO42− of treated plots, but no treatment effect on potential methane oxidation. This tenfold increase in estimated SO42− reduction indicates the presence of a more active population of SRB in plots where CH4 emissions were reduced by over 30%. 相似文献
712.
Tyler R. Bonnell Rafael Reyna-Hurtado Colin A. Chapman 《Forest Ecology and Management》2011,261(4):855-864
Uncertainty in recovery times of tropical forests can lead to mismanagement, such as in setting inappropriate harvesting rates or failing to achieving conservation targets. We use long-term plot data (17 y) to estimate recovery times of separate forest compartments, which experienced different levels of timber extraction within Kibale National Park, Uganda. We estimate that structural recovery (basal area) of heavily logged and moderately logged compartments will take respectively 112 and 95 y, when compared to adjacent mature forest. Our data suggests that recovery in terms of species composition will take significantly longer. Our estimates of structural recovery are derived from rates of change of diameter at breast height and basal area measurements which have been used traditionally as indicators of forest growth and productivity. Our results suggest that the severity of the logging has an impact on the rate of recovery, with current recovery rates estimated at 0.32 m2 ha−1 y−1 in a moderately logged compartment and 0.25 m2 ha−1 y−1 in heavily logged areas, highlighting the possible benefits of reduced impact harvesting in increasing long-term yields. We investigate how some representatives of the wildlife community were affected by differential recovery times and find that recovery times of frugivorous primate's forest habitats were 2.5 times slower when compared with folivorous primates. 相似文献
713.
JR Sheats H Antoniadis M Hueschen W Leonard J Miller R Moon D Roitman A Stocking 《Science (New York, N.Y.)》1996,273(5277):884-888
Electroluminescence from organic materials has the potential to enable low-cost, full-color flat-panel displays, as well as other emissive products. Some materials have now demonstrated adequate efficiencies (1 to 15 lumens/watt) and lifetimes (>5000 hours) for practical use; however, the factors that govern lifetime remain poorly understood. This article provides a brief review of device principles and applications requirements and focuses on the understanding of reliability issues. 相似文献
714.
715.
R C Chapman 《Science (New York, N.Y.)》1978,201(4353):365-367
In a pack of ten wolves, one wolf behaved atypically and fought with several packmates. This wolf was shot when it approached the author. Within 4 weeks at least six other members of the pack were dead. Rabies was confirmed in the wolf that was shot and in two others that had not decomposed. Most of the wolves infected with rabies had sought or remained at familiar areas in the core area of their territory, which implies that they were not contacting neighboring packs. This was confirmed with an aerial survey. Arctic foxes, experiencing a regionwide rabies epizootic, were suspected vectors. 相似文献
716.
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718.
A recently published infrared spectrum of Saturn's rings resembles our laboratory spectra of water frosts. Furthermore, there are discrepancies between the ring spectrum and ammonia frost spectra in the 2- to 2.5-micro region. These discrepancies render unlikely a reported ideti tification of ammonia frost in the ring spectrum. 相似文献
719.
Chambers JQ Fisher JI Zeng H Chapman EL Baker DB Hurtt GC 《Science (New York, N.Y.)》2007,318(5853):1107
Hurricane Katrina's impact on U.S. Gulf Coast forests was quantified by linking ecological field studies, Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) image analyses, and empirically based models. Within areas affected by relatively constant wind speed, tree mortality and damage exhibited strong species-controlled gradients. Spatially explicit forest disturbance maps coupled with extrapolation models predicted mortality and severe structural damage to approximately 320 million large trees totaling 105 teragrams of carbon, representing 50 to 140% of the net annual U.S. forest tree carbon sink. Changes in disturbance regimes from increased storm activity expected under a warming climate will reduce forest biomass stocks, increase ecosystem respiration, and may represent an important positive feedback mechanism to elevated atmospheric carbon dioxide. 相似文献
720.
Schipper J Chanson JS Chiozza F Cox NA Hoffmann M Katariya V Lamoreux J Rodrigues AS Stuart SN Temple HJ Baillie J Boitani L Lacher TE Mittermeier RA Smith AT Absolon D Aguiar JM Amori G Bakkour N Baldi R Berridge RJ Bielby J Black PA Blanc JJ Brooks TM Burton JA Butynski TM Catullo G Chapman R Cokeliss Z Collen B Conroy J Cooke JG da Fonseca GA Derocher AE Dublin HT Duckworth JW Emmons L Emslie RH Festa-Bianchet M Foster M Foster S Garshelis DL Gates C Gimenez-Dixon M Gonzalez S 《Science (New York, N.Y.)》2008,322(5899):225-230
Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action. 相似文献