全文获取类型
收费全文 | 4294篇 |
免费 | 364篇 |
国内免费 | 376篇 |
专业分类
安全科学 | 1058篇 |
废物处理 | 51篇 |
环保管理 | 709篇 |
综合类 | 1785篇 |
基础理论 | 437篇 |
环境理论 | 1篇 |
污染及防治 | 119篇 |
评价与监测 | 293篇 |
社会与环境 | 340篇 |
灾害及防治 | 241篇 |
出版年
2024年 | 17篇 |
2023年 | 56篇 |
2022年 | 93篇 |
2021年 | 147篇 |
2020年 | 161篇 |
2019年 | 117篇 |
2018年 | 94篇 |
2017年 | 173篇 |
2016年 | 205篇 |
2015年 | 194篇 |
2014年 | 213篇 |
2013年 | 301篇 |
2012年 | 370篇 |
2011年 | 419篇 |
2010年 | 293篇 |
2009年 | 259篇 |
2008年 | 192篇 |
2007年 | 267篇 |
2006年 | 262篇 |
2005年 | 205篇 |
2004年 | 156篇 |
2003年 | 145篇 |
2002年 | 97篇 |
2001年 | 88篇 |
2000年 | 86篇 |
1999年 | 63篇 |
1998年 | 53篇 |
1997年 | 40篇 |
1996年 | 45篇 |
1995年 | 39篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 24篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 6篇 |
排序方式: 共有5034条查询结果,搜索用时 531 毫秒
381.
382.
THERON MORGAN‐BROWN SUSAN K. JACOBSON KENNETH WALD BRIAN CHILD 《Conservation biology》2010,24(2):563-572
Abstract: Scientific understanding of the role of development in conservation has been hindered by the quality of evaluations of integrated conservation and development projects. We used a quasi‐experimental design to quantitatively assess a conservation and development project involving commercial butterfly farming in the East Usambara Mountains of Tanzania. Using a survey of conservation attitudes, beliefs, knowledge, and behavior, we compared 150 butterfly farmers with a control group of 170 fellow community members. Due to the nonrandom assignment of individuals to the two groups, we used propensity‐score matching and weighting in our analyses to control for observed bias. Eighty percent of the farmers believed butterfly farming would be impossible if local forests were cleared, and butterfly farmers reported significantly more participation in forest conservation behaviors and were more likely to believe that conservation behaviors were effective. The two groups did not differ in terms of their general conservation attitudes, attitudes toward conservation officials, or knowledge of conservation‐friendly building techniques. The relationship between butterfly farming and conservation behavior was mediated by dependency on butterfly farming income. Assuming unobserved bias played a limited role, our findings suggest that participation in butterfly farming increased participation in conservation behaviors among project participants because farmers perceive a link between earnings from butterfly farming and forest conservation. 相似文献
383.
Sonia Labatt 《Environmental management》1991,15(2):163-178
This article reviews the existing models of corporate social responsiveness and develops a theoretical framework with which
to examine corporations' discretionary performance with respect to one social issue, that of the environment. Discretionary
indicators of corporate response to environmental issues are developed and tested within this framework. Twelve companies
from five different sectors were selected for the survey, based on prior knowledge of their commitment to environmental concerns.
Primary data was collected from personal interviews, and secondary data was obtained from company documents, annual reports,
and other forms of publically disclosed information. Empirical results varied, but certain voluntary indicators, such as composition
of the board of directors, the environmental affairs function, community support, and the annual report are considered to
provide strong indications of discretionary corporate performance. Philanthropy and company products proved to be less satisfactory
indicators of corporate commitment to the environment. The aggregated results revealed a correlation between the final rankings
of firms' discretionary environmental performance and whether those companies are process or product oriented. Linkages between
discretionary elements and those of economic and legal requirements were not explored. 相似文献
384.
The land evaluation and site assessment (LESA) method has been used extensively in the United States to assess agricultural
land suitability for different localities. Despite widespread use, LESA models rarely have been evaluated in a systematic,
comprehensive manner. This article discusses development of a LESA system for Hawaii, the first statewide application of the
LESA methodology. The empirical model was implemented with a computerized geographic information system (GIS). The system's
efficiency, ability to discriminate among land parcels, and robustness to subjective model parameter values are evaluated
with statistical analyses and map overlays of GIS data. Results show great potential to simplify the original model specification,
primarily through deletion of marginal site assessment factors. System output was generally insensitive to the numeric values
selected for model parameters, with exception of the ratio used to combine the land evaluation (LE) and site assessment (SA)
component scores. Relative supplies of the differing land attributes measured by the two components must be considered in
determining an appropriate LE:SA ratio for a given area. 相似文献
385.
本文根据灰色关联分析的基本性质,提出一种环境质量综合评价的新方法。该方法用待评价样本各指标值组成参考数列,环境质量分级标准值组成被比较数列,通过计算参考数列与被比较数列的关联度,按最优关联识别原则综合评价环境质量等级。用4个实例与其它方法进行了对比,取得满意的效果。 相似文献
386.
Edward J. Phlips F J. Aidridge C. Hanlon 《Journal of the American Water Resources Association》1994,30(2):229-238
ABSTRACT: A 17-year record of chlorophyll a at eight limnetic sampling stations was used to evaluate putative changes in the trophic status of Lake Okeechobee, a shallow polymictic lake located in the subtropical environment of South Florida. Significant spatial differences were observed in the temporal patterns and variability of chlorophyll a concentrations. The highest chlorophyll a values were found in the northern and northwestern regions of the lake. The center of the lake, subject to high levels of non-algal suspended solids, exhibited relatively low chlorophyll a values and coefficient of variation. The lowest chlorophyll a values were observed at the southernmost sampling station in the lake. This was also the station that showed a significant upward trend in annual mean chlorophyll a values over the 17-year period of record. Examination of the relationship between chlorophyll a and three key environmental variables (i.e., total phosphorus concentration, phosphorus loading, and lake stage) revealed significant correlations at two out of the eight stations. The overall results of this study indicate that spatial and temporal disparities in the distribution and dynamics of chlorophyll a in Lake Okeechobee mandate more temporally and spatially intense approaches to the evaluation of trophic state than used in previous studies. 相似文献
387.
选择北京市四家锅炉厂的电焊工56名,即从事手把焊、氩弧焊、CO2气体保护焊、电弧气爆等特种工种作业人员。通过调查,提出单项四级评分标准,再依模糊数学模型,进行综合评价。按B=A·R,求得B中最大元为0.707。最后总评为甲级。此结果与权数分配有关。此方法,可为劳动卫生管理(防护措施评级)提供依据。 相似文献
388.
黄土滑坡稳定性评价的反演分析 总被引:2,自引:0,他引:2
本文根据黄土滑坡的变形监测结果,同时考虑了边坡的初期应变分布状况,通过有限元反分析法,反推出边坡地基的力学参数,为黄土滑坡的稳定性评价和预报提供了可靠的依据。 相似文献
389.
A method is described for the rapid survey and determination of the ecological value of woodlots. The three dominant tree species in a stand are given a visual ranking that is converted to awoodlot index through the use of species adaptation values. The woodlot index is scaled by presettlement vegetation type to yield awoodlot scale. The ecologically most valuable woodlots in a region are identified by using the woodlot scale and data on woodlot area, human disturbance, and tree density. The woodlot index corresponds closely to results from conventional methods of woodlot surveys. This method should be valuable to land-use planners for environmental impact assessment and regional planning. 相似文献
390.
Construction of guilds for habitat assessment 总被引:1,自引:0,他引:1
Thomas H. Roberts 《Environmental management》1987,11(4):473-477
This article outlines a procedure for developing guilds for use in habitat assessment studies. It is based on a matrix constructed around layers of vegetation and other physical features of the environment used by vertebrate species for feeding and breeding. Modifications to permit inclusion of other life requirements such as cover are discussed. Examples are used to illustrate how species are assigned to guild cells based on their use of habitat, and how the association between a species and its environment does not have to be direct to influence the species' placement within the matrix. 相似文献