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991.
Spatial sensitivity of species habitat patterns to scenarios of land use change (Switzerland) 总被引:3,自引:2,他引:3
Long-term societal trends which include decreasing population in structurally poorer regions and changes in agricultural policies
have been leading to land abandonment in various regions of Europe. One of the consequences of this development includes spontaneous
forest regeneration of formerly open-land habitats with likely significant effects on plant and animal diversity. We assess
potential effects of agricultural decline in Switzerland (41,000 km2) and potential impacts on the spatial distribution of seven open-land species (insects, reptile, birds) under land-use change
scenarios: (1) a business-as-usual scenario that extrapolates trends observed during the last 15 years into the future, (2)
a liberalisation scenario with limited regulation, and (3) a lowered agricultural production scenario fostering conservation.
All scenarios were developed in collaboration with socio-economists. Results show that spontaneous reforestation is potentially
minor in the lowlands since combinations of socio-economic (better accessibility), topographic (less steep slopes), and climatic
factors (longer growing seasons) favour agricultural use and make land abandonment less likely. Land abandonment, spontaneous
reforestation, and subsequent loss of open-land, however, are potentially pronounced in mountainous areas except where tourism
is a major source of income. Here, socio-economic and natural conditions for cultivation are more difficult, leading to higher
abandonment and thus reforestation likelihood. Evaluations for open-land species core habitats indicate pronounced spatial
segregation of expected landscape change. Habitat losses (up to 59%) are observed throughout the country, particularly at
high elevation sites in the Northern Alps. Habitat gains under the lowered agricultural production scenario range between
12 and 41% and are primarily observed for the Plateau and the Northern Alps. 相似文献
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994.
【目的】用已有的采集标本分布记录,模拟三叶海棠的地理分布。【方法】从中国4个标本馆获取三叶海棠的291个分布数据,从WorldClim网站下载1950-2000年生物气候数据,用最大熵模型(MaxEnt)模拟其地理分布。【结果】①三叶海棠的潜在分布地区有:巴基斯坦东北部;不丹中部、东北部;印度东北部;中国西藏东南部、河北省东北部和北京西部山区。②依据模拟分布值0.5~0.7标定的三叶海棠分布区域,排除其潜在分布区域,再结合这些区域的地理间隔性,从宏观景观上将三叶海棠的地理分布格局划分为4个区块:中国四川、甘肃、陕西三省交界地区;中国重庆大部分地区,贵州大部分地区,湖北西南部,湖南大部分地区,广西与贵州、湖南交界地区,江西,广东与湖南、江西交界地区,福建东北部,浙江大部分地区,安徽南部;韩国南部沿海地区;日本岛大部分地区。③刀切法检测表明,温暖季节平均降雨量对三叶海棠的分布增益贡献最大,三叶海棠喜生于温暖季节平均降雨量在450~800mm的地区。【结论】用MaxEnt模拟三叶海棠的地理分布有一定的准确性,反映出了三叶海棠基本的地理分布格局和潜在分布区域,并阐明了主导其地理分布的生物气候因子。 相似文献
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Nearly 60 per cent of the geographical area of Haryana state in Indian Union is underlain by saline ground water. The intra-basin transfer of surface water in the early sixties for irrigation has disturbed the hydrodynamic equilibrium resulting in waterlogging and salinization in large parts of the state. The existing inland drainage basin conditions did not permit the disposal of drainage effluent. The reuse system was therefore, integrated with the drainage system. A model RESBAL was coupled with the calibrated and validated on-farm water management model FAIDS and run for eight years to optimally design a series of connected reservoirs for the disposal of drainage effluent from an area provided with a subsurface drainage system. The possibility of the reuse of the disposed water for irrigation, aqua culture and salt harvesting was also studied comprehensively in order to maintain proper salt balance in the root zone. 相似文献
997.
Summary The use of crop simulation models to predict yield, associated with decision support systems such as Decision Support System
for Agrotechnology Transfer (DSSAT), are useful tools to test different management strategies.
The potato growth model included in DSSAT is SUBSTOR-potato. To evaluate its performance in Argentina it was calibrated and
validated using experimental results from different sites and years. Cultivar-specific coefficients were obtained during calibration.
Validation based on several independent sets of field data, including cvs Huinkul, Kennebec, Mailén and Spunta showed good
agreement (R2=0.915; n=24) between observed and simulated values in normal ranges of tuber yields. However, when the input parameter maturity
date was not taken into account, tuber yields were overvalued due to an overestimation of LAI values during maturation. To
solve this problem, a genetic coefficient for the duration of tuber filling needs to be included in the model. 相似文献
998.
Two laboratory studies compared the effect of fish density and number of infectious fish on characteristics of survival of rainbow trout fry during controlled epidemics of infectious pancreatic necrosis (IPN). Analyses of hazard functions and survivor functions were used to determine whether peak death rate, time at which the peak death rate occurred and probability of survival to the end of the experiment were associated with fish density and number of infectious fish added (i.e. pathogen concentration). When number of infectious fish was low and fish density increased, the peak death rate increased, time of the peak death rate decreased and the probability of survival to the end of the experiment decreased. When number of infectious fish was high, the effect of density diminished. Loglogistic regression of survival data revealed that fish density, number of infectious fish and interaction between these two variables significantly affected time to death from IPN (P < 0.01). 相似文献
999.
Clifford L.K. Robinson Beatrice Proudfoot Christopher N. Rooper Douglas F. Bertram 《水产资源保护:海洋与淡水生态系统》2021,31(10):2855-2869
- The Pacific sand lance (Ammodytes personatus) is a key forage species for many commercially important fish (e.g. salmon and groundfish), marine birds, and whales found in nearshore coastal waters of British Columbia, Canada.
- Sand lance lack a swim bladder and have a requirement for low-silt, medium-coarse sandy sea-bed habitat for burying. Little information is available describing the distribution of burying habitat, partly because there are no commercial fisheries for A. personatus in British Columbia.
- This information is required by habitat and wildlife managers to identify and protect uncommon patches of burying habitats from detrimental activities, including dredging, infilling, and oil spills.
- In this study, habitat distribution results from five suitability modelling algorithms were evaluated: maximum entropy, generalized linear model, generalized additive model, random forest, and an ensemble model of the latter three.
- The maximum entropy model had the highest performance score (area under the receiver operator characteristic curve was 0.78) and was selected as the model that most accurately identified the presence of suitable A. personatus burying habitat.
- Model results indicate that suitable burying habitat is primarily influenced by derived sea-bed substrate, distance to estuary, distance to sand-gravel beaches, and bottom sea temperature.
- Overall, the spatial modelling identified only 105 km2 of highly suitable sand lance burying habitat, or 2.6% of the study area (0–150 m), primarily in Haro Strait, along the east coast of Vancouver Island, and in northern regions of the strait near Cortes, Savary, and Harwood islands.
- Identification of this uncommon and patchy burying habitat will contribute to the ongoing conservation of an important coastal prey species.
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