全文获取类型
收费全文 | 1256篇 |
免费 | 27篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 51篇 |
废物处理 | 47篇 |
环保管理 | 323篇 |
综合类 | 132篇 |
基础理论 | 381篇 |
污染及防治 | 192篇 |
评价与监测 | 106篇 |
社会与环境 | 45篇 |
灾害及防治 | 15篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 22篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 43篇 |
2015年 | 31篇 |
2014年 | 29篇 |
2013年 | 75篇 |
2012年 | 73篇 |
2011年 | 72篇 |
2010年 | 53篇 |
2009年 | 45篇 |
2008年 | 58篇 |
2007年 | 68篇 |
2006年 | 75篇 |
2005年 | 52篇 |
2004年 | 48篇 |
2003年 | 55篇 |
2002年 | 37篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 19篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有1292条查询结果,搜索用时 31 毫秒
881.
Alan N. Hodgson Will J. F. Le Quesne Stephen J. Hawkins John D. D. Bishop 《Marine Biology》2007,150(3):415-426
Laboratory experiments were undertaken to examine fertilization success in the intertidal prosobranch limpets Patella ulyssiponensis and Patella vulgata. Alkalization of eggs (10 min in pH 9.0 sea water) prior to fertilization trials improved fertilization rates greatly. Fertilization success was found to be a function of sperm concentration, gamete age and contact time. Sperm concentration needed for optimum fertilization success in vivo ranged between 105 and 107 sperm ml−1 for both species although at higher concentrations the number of normally developing trochophore larvae decreased. For P. vulgata, sperm longevity (at a concentration of 106 sperm ml−1) did not exceed 6 h, whereas eggs of both species were fertilizable for up to 12 h. Maximum fertilization success occurred after 15–30 min gamete contact time. The Vogel et al. (Math Biosci 58:189–216, 1982) fertilization kinetics model is developed to allow for non-complete fertilizations under optimal sperm concentrations, and a new parameter fitting technique is developed to improve estimates of fertilization success for short gamete contact times. 相似文献
882.
Summary Modern population ecology is becoming increasingly spatially-explicit. For insect hervibores, spatial variation in plant quality is a critical component of distribution and abundance. We argue that populationlevel measurements of phytochemical variation among individual plants has not kept pace with recent developments in population ecology. With examples from our own work, we demonstrate the importance of spatial variation in plant chemistry for insect herbivores, and suggest that phytochemistry should play a central role in the development of any spatially-based ecological theory. 相似文献
883.
Stephen Ameyaw 《The Environmentalist》1992,12(4):267-275
Summary This paper focuses on the characteristics of sustainable development as manifested in localized contexts and situations. It examines the KASHA project in Botswana, and suggests an important conceptual link between the community and sustainable development. To convey the message that there is hope and that "Sustainable Development" is possible, the paper suggests the need to document, share, describe and talk about successful programmes like KASHA.Dr Stephen Ameyaw is currently Assistant Professor of Planning in the Faculty of Environmental Design, University of Calgary. His research interests are focused on women and development, community development, regional planning, policy and institutional development. He has conducted research in Canada, Ghana and Botswana. 相似文献
884.
A total of 25 scenes representing the five visual quality objectives in the US Department of Agriculture Forest Service visual management system were presented to 18 professional and public interest groups in western Montana. The results indicate that nearly all the groups have similar rank orderings of the scenes in terms of visual preference. However, the groups differ according to the absolute values of their ratings. Most groups were unable, in a statistical sense, to differentiate the scenic quality of areas in the preservation and retention visual quality objectives. Landscape architects tended to rate scenes in a way similar to professional forest management groups. 相似文献
885.
Steven W. Effler Carol M. Brooks Mary Gail Perkins Michael Meyer Stephen D. Field 《Journal of the American Water Resources Association》1987,23(6):1193-1201
ABSTRACT: The underwater light field of eight central New York lakes, which represent a wide range of trophic state, was characterized through paired measurements of Sechi disc transparency (SD, m) and diffuse light attenuation (Kd, m?1). A total of 90 paired measurements are included in the data base. Substantial variability in the Kd SD product with time within individual systems, and amongst systems, was observed, which indicates differences in the relative contributions of absorption and scattering to attenuation. More than 50 percent of the temporal variability in Kd was attributable to attendant variations in chlorophyll a (C, mg m?3) in only two of the lakes. Estimates of the adsorption (a, m?1) and scattering (b, m?1) coefficients based on paired Kd and SD measurements compared well with more precise determinations available for one of the lakes. Determinations of a and b for the eight lakes, from SD and Kd measurements, indicated great system-specificity and temporal variability in these characteristics. The temporal variability in relative contributions of a and b to Kd is consistent with covariation of different attenuating components and the lack of correlation between C and Kd in most of the study lakes. 相似文献
886.
The effects of off-road vehicles (ORVs) on the dune system of Fire Island National Seashore, New York, USA, were examined through a detailed, two-year field study. The experimental approach was adopted in order to evaluate the environmental effects of ORVs in this zone. Adjacent control and impact sites were established in two locations. Vehicle impacts were applied at the equivalent rate of one vehicle pass per week. Monitoring of foredune vegetation through sequential quadrat surveys and construction of sea-ward limit maps showed a significant loss of vegetation resulting from ORV impacting. Loss of vegetation resulted in an alteration of the natural foredune profile, which could increase dune erosion during storm wave attack. 相似文献
887.
888.
Stephen R. Kessell 《Environmental management》1979,3(1):29-40
The application of vegetation information to resource management problems is reviewed in four areas: (1) the stratification of vegetation data by classification and gradient analysis, (2) the storage and retrieval of these data, (3) the sources of vegetation information, and (4) the accuracy and resolution requirements posed by different management applications. Conclusions indicate that the successful application of inference methods to resource management problems requires an appropriate integration of these four components. 相似文献
889.
Stephen R. Kessell Meredith W. Potter Collin D. Bevins Larry Bradshaw Bruhe W. Jeske 《Environmental management》1978,2(4):347-363
Recent advances in fire modeling permit quantitative estimations of fire behavior from quantitative inputs that describe the fuel array and conditions, such as weather and site data, under which it will burn. This paper describes the collection, analysis, and stratification of flammable forest fuels data for coniferous forest ecosystems in Montana and then illustrates the resource management application of these data in three areas: the development of the fire behavior model, a determination of the model's sensitivity to input errors as reflected by fire behavior prediction errors, and the development of a fire hazard simulator (TAROT). A new integrated stand simulator, GANDALF, is highlighted.Conclusions center on the need to integrate fire management into the land management planning decision-making process.This work was supported by a USDI National Park Service contract to Gradient Modeling, Inc., a nonprofit research foundation devoted to ecologic research and resource management applications, and by cooperative aid agreements between Gradient Modeling, Inc. and the USDA Forest Service, Intermountain Forest and Range Experiment Station, Northern Forest Fire Laboratory (Fire in Multiple Use Management, R, D, and A Program). 相似文献
890.
Since taking office 1 December 1988, Mexico's incumbent president, Carlos Salinas de Gortari, has introduced important innovations
in environmental policy that distinguish his administration from those of his predecessors. Greater administrative continuity,
improved regulatory capacity achieved through statutory change, focused priorities centering on pollution abatement in Mexico
City, and an aggressive search for external financing for pollution control are hallmarks of Salinas' approach. The success
of these environmental reforms depends heavily on economic recovery, however, and environmental policy still suffers from
underfunding, bureaucratic fragmentation, and heavy reliance on voluntarist enforcement mechanisms. Recently, U.S. congressional
debate on a proposed free trade agreement with Mexico has been a factor in spurring the Salinas government to take new antipollution
and conservation measures. Mexico's growing environmental movement is also an important force behind the government's new
responsiveness in environmental matters. The Salinas administration recognizes the issue's political salience and has sought
to defuse environmental criticism using a large arsenal of resources at its disposal. Salinas' environmental policy strategy
may thus be characterized as both proactive and reactive in nature. While the reforms are evidence that Mexico is beginning
to take environmental matters more seriously, economic recovery and sustained environmental activism remain vital to further
progress. 相似文献