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51.
The nation‐building process of Timor‐Leste, the newest nation in Asia, faces significant demographic challenges due to its high population growth, which is the fastest in Asia. The major contributor for this unprecedented growth is the extremely high total fertility rate of Timor‐Leste, among the highest in the world. It is of great concern that if the current fertility rate and its implied population growth continue the population of Timor‐Leste will double in 17 years. The analysis in this paper clearly shows that the current extremely high dependency ratio will decline only marginally in the next 10 years and this will put tremendous pressure on the government to constantly keep up with the increasing number of children entering school every year. However, as the intrinsic value of human resource development feeds back into the overall society and economy, an adequate public investment in knowledge‐producing services at the earliest stages of life and throughout that life has the potential to change the demographic concern of Timor‐Leste into a future demographic dividend. 相似文献
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随着经济发展,我国靠传统物质资本投资拉动经济增长的方式需要改变。而此时,人力资本、社会资本作为经济增长的内生变量,其作用受到越来越多学者的关注。本文基于资本投资决策理论,以农民工为对象,利用调查数据,采用有序Logistic模型,对投资影响因子展开深入分析,探讨决定微观个体人力资本、社会资本投资的主要影响因素。结果表明,工资性收入显著影响人力资本、社会资本的投资,工资性收入每增加一个单位,投资则增加0.5个单位。农民工动机内容影响资本投资,越倾向返回农村则投资性越强。人力资本禀赋、性别、生命周期对农民工的人力资本投资有显著影响,对社会资本投资影响不大。研究揭示了农民工在人力资本投资上是理性经济人行为,对投入产出具有理性的权衡;而对社会资本的认知和行为要弱于人力资本。 相似文献
54.
有风险投资与无风险投资组合的研究 总被引:1,自引:0,他引:1
本研究通过引入单位风险的概念,并结合有效边界上的单位风险极小点,给出了各种情况下有风险投资和无风险投资的最优组合方案。 相似文献
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Francisco J. Escobedo David J. Nowak John E. Wagner Carmen Luz De la Maza Manuel Rodríguez Daniel E. Crane Jaime Hernndez 《Urban Forestry & Urban Greening》2006,4(3-4):105-114
Santiago, Chile's semi-arid climate and urbanized environment poses a severe limitation for the establishment and maintenance of urban forests. Municipalities, or comunas, are the main stakeholders in the management of Santiago's public urban forests. A tenable hypothesis would be that as the socioeconomic level of a comuna increases, the better the condition of a comuna's urban forest. Unfortunately, there is little comprehensive information on management, public expenditure, and structure of Santiago's public and private urban forests. To examine this hypothesis, Santiago was divided into socioeconomic strata, then using air photo interpretation and stratified field sampling, urban forest structures were quantified by socioeconomic strata. In addition, interview surveys were used to determine municipal urban forest management and expenditures for different public urban forests based on socioeconomic strata. Urban forests in the high socioeconomic strata had fewer public trees, greater tree cover, tree and leaf area density, and leaf area index than lower socioeconomic strata. The percentage of total municipal budget allocated to public urban forest management was consistent among strata, but the total public urban forest budgets were greater in the high socioeconomic strata. Public urban forest structure is related to the socioeconomic strata of Santiago's different comunas. 相似文献
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Recent studies have emphasized the presence of microclimates in urban settings, but most do not have the high resolution observations necessary to understand the interactions taking place at a neighborhood scale. This study used a network of 10 identical weather stations and high resolution land cover data in Knoxville, Tennessee, to analyze the microclimates of a medium-sized city with a temperate climate. Two stations were installed in each of four urban neighborhoods in locations with varying localized tree cover, and two additional stations were installed in the center of downtown and in a nearby urban nature center. The intra-neighborhood results suggested that there is significant temperature variability within a single neighborhood based on the tree canopy density immediately surrounding a given weather station. However, the inter-neighborhood variability (differences between neighborhoods) was similar in magnitude, which suggests that the overall differences in neighborhood characteristics also have an effect on climate. Land cover at the neighborhood scale (in particular tree canopy percentages at the 500-m radii) had the highest correlation with the minimum daily temperature (Tmin) during the summer season. Maximum daily temperature (Tmax) relied most on the distance of each station from Downtown and the amount of impervious area in the 50 m surrounding each station. Tmax was also most influenced by surrounding land cover during dry conditions (a Dry Moderate air mass). Overall, highly localized impervious land cover percentages and larger-scale forested canopy were important in explaining temperature fluctuation, pointing to the importance of scale in microclimate assessments. Dry air masses enhanced the relationship between land cover and temperature during the day, while moist air masses did the same overnight. These data can be used to better inform planning strategies to build resiliency to extreme heat into urban environments by considering the influence of tree canopy. 相似文献
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There is increasing focus on designing liveable cities that promote walking. However, urban walking routes can expose people to adverse environmental conditions that reduce health, well-being and biodiversity. Our primary objective is to assess how urban form is associated with environmental quality, including biodiversity, for people moving through urban spaces. We assess a range of environmental conditions that influence human health and biodiversity (temperature, noise and particulate pollution) and biodiversity of three taxa (trees, butterflies and birds) along 700 m public walking routes embedded in 500 m x 500 m grid cells across three UK towns. Cells are selected using random stratification across an urbanisation intensity gradient. Walking routes in more built-up areas were noisier and hotter; noise levels further increased in areas with more industrial land-use and large roads. There was no evidence of vegetation mitigating noise or temperature, but there was some evidence that increased vegetation cover mitigated small particulate pollution. Walking routes in more built-up environments had lower butterfly, bird and native tree species richness, and reduced butterfly abundance. Large roads were associated with reduced bird species richness and increased noise was associated with reduced bird abundance. Most specific measures of vegetation in the surrounding matrix (median patch size, structural complexity at 1.5 m resolution) were not detectably associated with biodiversity along walking routes, indicating minimal beneficial spill-over. Increased garden cover in the surrounding matrix was associated with less abundant and less species-rich butterfly communities. Our results highlight considerable heterogeneity in the environmental quality of urban walking routes and pedestrians’ potential to experience biodiversity along these routes, driven by reduced quality in areas with more built cover. A greater focus is needed on mitigating adverse effects of specific features of the built environment (roads, industrial areas, noise) surrounding walking routes to enhance the co-benefits of more biodiversity and healthier conditions for pedestrians. 相似文献
58.
Raimundo Nonato Braga Lobo 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2019,136(5):313-318
The social contribution of goat and sheep industries is very important to many Brazilian families mainly in semi‐arid regions of the country. However, the productive chains of these two species in Brazil are unorganized and ultimately informal. On the other hand, there is potential for growth and development to which an upscaling of breeding programmes will be essential. Historically, many attempts to structure these programmes have been unsuccessful. Inadequate understanding of how to achieve genetic improvement often leading to distributing unsuitable exotic genetics among the producers is one of the reasons for the failure. Another important factor is related to the sources of funding and the priorities for the use of funds. According to the experience and the state of the art in Brazil, the priorities for funding must be in the characterization of the different systems and animal genetic resources, organization of information collection procedures and national databanks, training of technicians and producers and development of system to enable animal evaluation. 相似文献
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