全文获取类型
收费全文 | 6095篇 |
免费 | 258篇 |
国内免费 | 338篇 |
专业分类
林业 | 1453篇 |
农学 | 277篇 |
基础科学 | 205篇 |
586篇 | |
综合类 | 2894篇 |
农作物 | 201篇 |
水产渔业 | 295篇 |
畜牧兽医 | 396篇 |
园艺 | 156篇 |
植物保护 | 228篇 |
出版年
2024年 | 28篇 |
2023年 | 86篇 |
2022年 | 142篇 |
2021年 | 149篇 |
2020年 | 130篇 |
2019年 | 169篇 |
2018年 | 61篇 |
2017年 | 161篇 |
2016年 | 186篇 |
2015年 | 189篇 |
2014年 | 280篇 |
2013年 | 289篇 |
2012年 | 440篇 |
2011年 | 455篇 |
2010年 | 392篇 |
2009年 | 391篇 |
2008年 | 452篇 |
2007年 | 561篇 |
2006年 | 437篇 |
2005年 | 355篇 |
2004年 | 262篇 |
2003年 | 205篇 |
2002年 | 154篇 |
2001年 | 140篇 |
2000年 | 85篇 |
1999年 | 83篇 |
1998年 | 62篇 |
1997年 | 63篇 |
1996年 | 43篇 |
1995年 | 38篇 |
1994年 | 29篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有6691条查询结果,搜索用时 15 毫秒
41.
42.
43.
This paper investigates the coordinated operation of the progress planning with the resource planning when carrying out engineering projects and puts forward a method of "RSM" under the resource limit conditions. Then, the "RSM" was improved to avoid complicated calculation. This method not only reduces the calculating work by hand but saves computer's memory as well, making the time-resource optimization work more quick and convenient. 相似文献
44.
Application system generally refers to all kinds of computer information system. It aims at improving the sharing and application of the resource. The resource in application system usually means data resource. For computer management and maintenance, there are not only data resource, but also program resource and network resource. Effective management of this resource is key to ensure proper work of the application system. In this paper, the basic pattern and policy for resource management is put forward and a method to build and realize the resource layer that lies between database layer and application layer is to be found. This management layer, which skillfully connects the application system with resource and establishes good base for application and exploitation of system, is named as resource management system. 相似文献
45.
Urbanization in China is at an essential point in its transformation from the initial stage to accelerating stage. With quick expansion of city scale and large occupation of land for urban construction, the contradiction between land resource shortage and people's living needs becomes more and more prominent. It has great affection on the grand plan of China's sustainable development of economy and society. How to adjust the relations between the development of urban construction and protect the land resource, promote the rational use of urban land, perfect and complete the protection system of land resource for improving the efficiency of urban land use. In order to conserve land resource and find a sustainable way for development of people's living and environment construction, the above mentioned problems are the most important issue for urban construction and important subject of this paper. 相似文献
46.
通过对五大牧区草原区草原资源现状及其分布、草原生产力及载畜能力以及水资源现状及开发利用潜力分析,按照国民经济发展和增加农牧民收入要求,预测2010年五大牧区草原区草业发展对水资源的需求。研究结果表明,2010年五大牧区草原区农牧民人均纯收入为3400元,其中人均畜牧业纯收入2584元,需要养殖牲畜总数16413万羊单位,饲草料需求量1198.2亿kg。牧区产草总量可达1003亿kg,载畜能力13705万羊单位。尚有2708万羊单位,年需要饲料约195亿kg,需要发展灌溉饲草料地来解决,对水资源的需求量将达到 相似文献
47.
The organization of two farmer-managed irrigation systems in the western hills of Nepal is described by examining the ways in which the activities of water allocation, water distribution, maintenance, and resource mobilization are performed. Due to the topography and environment, these two organizations are structured primarily to mobilize the large amount of labor required for maintenance of the intake and canal. Both organizations precisely define each member's water allocation. In one system, water is allocated in proportion to the area of an individual's land holding, while in the other water allocation is by purchased shares. These two cases were used to analyze the importance of the principle of water allocation for expansion of area irrigated and equity of access to irrigation. Evidence from the two systems shows that in this hill environment water allocation by purchased shares provides the individual incentive and an organizational mechanism for efficient development of irrigation resources. Expansion of area irrigated and equity of access to irrigation were found to be greater in the system which allocates water by purchased shares than where water was allocated in proportion to area irrigated. 相似文献
48.
49.
Water and land resource competition and environmental degradation pose difficult questions for resource managers. In particular, the ensuing trade-offs between economic, environmental, and social factors and their spatiotemporal variability must be considered when implementing management policies. This paper describes an integrated modelling toolbox that has been developed for highland catchments – specifically the Mae Chaem catchment in Northern Thailand. This toolbox contains models of crop growth, erosion and rainfall-runoff, as well as household decision and socioeconomic impact models. The approach described advances and complements previous approaches by: considering more complex interactions between land-use decisions and the hydrological cycle; modelling household decisions based on uncertain expectations; and assessing impacts of changes not only on flows and household income, but also on subsistence production and erosion. An example of the types of trade-offs and scenarios that can be assessed using the integrated modelling toolbox is also presented. This demonstrates that for the scenarios presented, the magnitude and direction of impacts simulated by the model is not dependent on climate. Further testing of the model is demonstrated in a companion paper. Overall, the plausibility of the model is shown. 相似文献
50.
波特竞争战略侧重从外部行业环境角度解释企业运营问题,但是实证分析结果证明资源对企业发展影响重大。针对目前尚无具体模式研究企业如何立足现有资源进行发展问题,本文基于资源基础论,将企业资源具体分为物质、信息、资金和知识资源(MICK),提出了MICK-4FI(四流集成)资源运营模式,借助投入产出模型构建MICK-4FI模式分析框架。文中利用聚焦和杠杆作用定性地解释了企业培育或者集成资源,即企业获取资源形成竞争优势的机理。本模式将资源基础论应用到企业实践层次,解决了企业通过集成运营内外部资源以求快速发展的路径依赖问题。资源运营理论从微观资源角度分析企业经营,与波特从宏观行业分析的理论共同构成一套系统的企业运营理论体系。 相似文献