全文获取类型
收费全文 | 1149篇 |
免费 | 45篇 |
国内免费 | 90篇 |
专业分类
安全科学 | 182篇 |
废物处理 | 13篇 |
环保管理 | 424篇 |
综合类 | 205篇 |
基础理论 | 190篇 |
环境理论 | 4篇 |
污染及防治 | 88篇 |
评价与监测 | 54篇 |
社会与环境 | 66篇 |
灾害及防治 | 58篇 |
出版年
2023年 | 16篇 |
2022年 | 23篇 |
2021年 | 31篇 |
2020年 | 35篇 |
2019年 | 32篇 |
2018年 | 29篇 |
2017年 | 33篇 |
2016年 | 57篇 |
2015年 | 45篇 |
2014年 | 47篇 |
2013年 | 98篇 |
2012年 | 37篇 |
2011年 | 68篇 |
2010年 | 33篇 |
2009年 | 60篇 |
2008年 | 47篇 |
2007年 | 64篇 |
2006年 | 50篇 |
2005年 | 41篇 |
2004年 | 39篇 |
2003年 | 47篇 |
2002年 | 31篇 |
2001年 | 28篇 |
2000年 | 34篇 |
1999年 | 27篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有1284条查询结果,搜索用时 15 毫秒
81.
Incident reporting systems are playing an increasingly important role in the development and maintenance of safety-critical applications. The perceived success of the FAA's Aviation Safety Reporting System (ASRS) and the FDA's MedWatch has led to the establishment of similar national and international schemes. These enable individuals and groups to report their safety concerns in a confidential or anonymous manner. Unfortunately, many of these systems are becoming victims of their own success. The ASRS and MedWatch have both now received over 500,000 submissions. In consequence, the administrators of incident reporting systems increasingly rely upon software tools to support the administration of their systems. In the past, these systems have relied upon ad hoc applications of conventional database technology. However, there are several reasons why this technology is inadequate for many large-scale reporting schemes. In particular, the problems of query formation often result in poor precision and recall. This, in turn, has profound implications for safety-critical applications. Users may fail to identify similar incidents within national or international collections. These ad hoc approaches also neglect the opportunities provided by recent developments in computer assisted interviewing and in the monitoring of retrieval activities to build models of user behavior. These techniques offer a number of potential benefits. For instance, it is possible to automatically detect potential biases in the way that investigators analyze particular incidents. 相似文献
82.
ABSTRACT. The non-power requirements of a large hydro-power system of multiple-purpose projects often conflict with the best power peaking operation. In order to schedule an optimum multiple-purpose operation, advanced procedures that necessitate the use of computers are required. Special techniques are used in a computer program developed in the Reservoir Control Center, North Pacific Division of the Corps of Engineers that provide the ability to define operating constraints in order of priority. These techniques are easily adapted to practical reservoir regulation problems so that the program is useful in daily reservoir regulation scheduling. 相似文献
83.
Randall E. Brummett 《Environment, Development and Sustainability》1999,1(3-4):315-321
An incremental, farmer participatory approach to the development of sustainable aquaculture in integrated farming systems has been tested in Malawi. Average fish production rose from 900 to approximately 1500 kg ha-1 as farms achieved increasing levels of integration. Integrated farms produce almost six times the cash generated by the typical Malawian smallholder. The integrated pond-vegetable garden generates almost three times the annual net income from the staple maize crop and the homestead combined. The ecological footprint of integrated aquaculture is approximately 4 m2 per kg of fish produced compared to 170 m2 for more intensive systems. The incremental approach offers the possibility of fostering substantial improvement in rural livelihoods among African smallholding farmers. 相似文献
84.
Y Tachikawa M. Shiiba T Takasao 《Journal of the American Water Resources Association》1994,30(1):9-17
ABSTRACT: To make a distributed rainfall-runoff model, it is very important to build a model of topographic surface of a basin which takes account of the direction of water flow. In this paper, a geographic information system in hydrologic modeling, the BGIS (Basin Geomorphic Information Systems) are presented for modeling a river basin using a TIN-DEM (Triangulated Irregular Network - Digital Elevation Model) data structure. The BGIS have two core systems, which are the TIN-DEM generating system and the topographic analysis system. In the TIN-DEM generating system, landscapes are modeled as a set of contiguous non-overlapping terangular facets whose vertices are made up of points on a regular grid DEM and on river segments. These triangular facets are subdivided, if needed, so that each of them has only one side through which water flows out. The TIN-DEM generating system is made up of four modules, (1) a module for generating triangles from a grid DEM, (2) a module for getting rid of pits, (3) a module for joining discontinuous valley segments to a channel network, (4) a module for subdividing triangular facets. In the topographic analysis system, using datasets processed with the TIN-DEM generating system, a watershed source area for any segments in a stream network are delineated automatically, and topographic attributes of slopes, aspects, flow path lengths and upslope contributing areas are computed. 相似文献
85.
The Information Cycle as a Framework for Defining Information Goals for Water-Quality Monitoring 总被引:2,自引:0,他引:2
/ The necessity to tailor information becomes increasingly urgent as the information revolution continues to generate ever-increasing flows of data and so-called information. From European experiences, a new approach for monitoring system design is suggested in this paper. In this approach, careful and detailed specification of information needs is a major contributing factor to the effectiveness of information products. To develop better specifications for information products, the process of collecting and transforming data into useful information requires careful thought and guidance. A dialogue between information users on one hand and information producers on the other is essential. This dialogue can be based on the information cycle, describing the continuous process from specifying information needs for water management and a strategy to collect information through data collection and data analysis up to utilization of information by water management. By following the respective steps in the information cycle, the process of information gathering can be completed. The cyclic character provides a quantitative means of connecting monitoring system design and operations with the information expectations and/or products required by management. 相似文献
86.
Integrated Resource Management: Moving from Rhetoric to Practice in Australian Agriculture 总被引:1,自引:0,他引:1
/ Implementing the concept of sustainability through integrated approaches to natural resource management poses enormous challenges for both the rural communities and government agencies concerned. This paper reviews the underlying rhetoric of sustainable agricultural systems and the integrated resource management paradigm and identifies some of the challenges being experienced in translating this rhetoric into practice. A relatively recently implemented community-based integrated catchment management (ICM) process in a rural community in northeast Australia is examined in terms of some of the lessons learned that may be relevant to other similar integrated resource management (IRM) processes. It reveals a pragmatic, opportunistic, and evolving implementation process based on adaptive learning rather than a more traditional "rational" planning approach. Some essential characteristics of a community-based IRM process are identified, including fostering communication; providing a structure that fosters cooperation and facilities coordination among community, industry, and government agencies; the integration of IRM principles into local government planning schemes; and an emergent strategic approach to IRM program implementation. We conclude by identifying some essential characteristics of an IRM process that can assist a community to adapt to, and manage change for, sustainable resource use. 相似文献
87.
88.
Peter G. Ashton James B. Pickens Coryell Ohlander Bruce Benninghoff 《Journal of the American Water Resources Association》1980,16(4):738-744
ABSTRACT: Decisionmaking associated with the Nation's 1.7 billion acres of forest and range land has become increasingly complicated because of the rise in competition for resource use and in the awareness of environmental and social effects. This system analysis approach uses four models to synthesize pertinent masses of information into measures of economic, environmental, and social impacts. The system results can be used to help evaluate alternative national programs. The models are:
89.
Suravuth Pratishthananda A. Bruce Bishop 《Journal of the American Water Resources Association》1977,13(3):611-625
ABSTRACT: A nonlinear multilevel transportation model is developed to study large-scale allocations in a water resources system. The model uses a modified transportation matrix formulated with nonlinear cost functions as the basic subregional model and the goal coordination method for multilevel decomposition and optimization of the overall regional system. The model is applied to projected water requirements for Salt Lake County in 1985. Sources of water supply - surface water, ground water, import water, and reuse of reclaimed wastewater on a restricted basis - are available to satisfy water requirements for municipal, industrial, and agricultural sectors in four subregions. The conjugate gradient projection method is used to optimize the first level subregional models having cost functions of the form of C = aXb, and the second level problem is solved using the conjugate gradient method. 相似文献
90.
美国应急信息交互协议与规范 总被引:1,自引:0,他引:1
应急信息交互和共享的目标是实现事故现场、应急管理中心、应急指挥中心以及公共安全服务等机构之间应用系统的无缝联接,信息完全共享。本文主要讨论当前有关应急信息交互与共享技术的研究和系统开发,并对今后该领域的研究问题做一陈述。 相似文献