全文获取类型
收费全文 | 2241篇 |
免费 | 174篇 |
国内免费 | 63篇 |
专业分类
安全科学 | 127篇 |
废物处理 | 17篇 |
环保管理 | 1041篇 |
综合类 | 597篇 |
基础理论 | 365篇 |
环境理论 | 2篇 |
污染及防治 | 50篇 |
评价与监测 | 57篇 |
社会与环境 | 129篇 |
灾害及防治 | 93篇 |
出版年
2023年 | 26篇 |
2022年 | 51篇 |
2021年 | 49篇 |
2020年 | 52篇 |
2019年 | 51篇 |
2018年 | 60篇 |
2017年 | 85篇 |
2016年 | 94篇 |
2015年 | 92篇 |
2014年 | 77篇 |
2013年 | 121篇 |
2012年 | 80篇 |
2011年 | 130篇 |
2010年 | 89篇 |
2009年 | 105篇 |
2008年 | 97篇 |
2007年 | 113篇 |
2006年 | 107篇 |
2005年 | 82篇 |
2004年 | 70篇 |
2003年 | 75篇 |
2002年 | 51篇 |
2001年 | 56篇 |
2000年 | 53篇 |
1999年 | 68篇 |
1998年 | 41篇 |
1997年 | 37篇 |
1996年 | 42篇 |
1995年 | 40篇 |
1994年 | 27篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1975年 | 10篇 |
1973年 | 16篇 |
1972年 | 14篇 |
1971年 | 16篇 |
排序方式: 共有2478条查询结果,搜索用时 3 毫秒
981.
982.
Kristen C. Ruegg Ryan J. Harrigan James F. Saracco Thomas B. Smith Caz M. Taylor 《Conservation biology》2020,34(6):1482-1491
Migratory animals are declining worldwide and coordinated conservation efforts are needed to reverse current trends. We devised a novel genoscape-network model that combines genetic analyses with species distribution modeling and demographic data to overcome challenges with conceptualizing alternative risk factors in migratory species across their full annual cycle. We applied our method to the long distance, Neotropical migratory bird, Wilson's Warbler (Cardellina pusilla). Despite a lack of data from some wintering locations, we demonstrated how the results can be used to help prioritize conservation of breeding and wintering areas. For example, we showed that when genetic, demographic, and network modeling results were considered together it became clear that conservation recommendations will differ depending on whether the goal is to preserve unique genetic lineages or the largest number of birds per unit area. More specifically, if preservation of genetic lineages is the goal, then limited resources should be focused on preserving habitat in the California Sierra, Basin Rockies, or Coastal California, where the 3 most vulnerable genetic lineages breed, or in western Mexico, where 2 of the 3 most vulnerable lineages overwinter. Alternatively, if preservation of the largest number of individuals per unit area is the goal, then limited conservation dollars should be placed in the Pacific Northwest or Central America, where densities are estimated to be the highest. Overall, our results demonstrated the utility of adopting a genetically based network model for integrating multiple types of data across vast geographic scales and better inform conservation decision-making for migratory animals. 相似文献
983.
The Convention on Biological Diversity's (CBD) strategic plan will expire in 2020, but biodiversity loss is ongoing. Scientists call for more ambitious targets in the next agreement. The nature-needs-half movement, for example, has advocated conserving half of Earth to solve the biodiversity crisis, which has been translated to protecting 50% of each ecoregion. We evaluated current protection levels of ecoregions in the territory of one of the CBD's signatories, the European Union (EU). We also explored the possible enlargement of the Natura 2000 network to implement 30% or 50% ecoregion coverage in the EU member states’ protected area (PA) network. Based on the most recent land-use data, we examined whether ecoregions have enough natural area left to reach such high coverage targets. We used a spatially explicit mixed integer programing model to estimate the least-cost expansion of the PA network based on 3 scenarios that put different emphasis on total conservation cost, ecological representation of ecosystems, or emphasize an equal share of the burden among member states. To realize 30% and 50% ecoregion coverage, the EU would need to add 6.6% and 24.2%, respectively, of its terrestrial area to its PA network. For all 3 scenarios, the EU would need to designate most recommended new PAs in seminatural forests and other semi- or natural ecosystems. Because 15 ecoregions did not have enough natural area left to implement the ecoregion-coverage targets, some member states would also need to establish new PAs on productive land, allocating the largest share to arable land. Thirty percent ecoregion coverage was met by protecting remaining natural areas in all ecoregions except 3, where productive land would also need to be included. Our results support discussions of higher ecoregions protection targets for post-2020 biodiversity frameworks. 相似文献
984.
Spatial,socio‐economic,and ecological implications of incorporating minimum size constraints in marine protected area network design 下载免费PDF全文
Kristian Metcalfe Gregory Vaughan Sandrine Vaz Robert J. Smith 《Conservation biology》2015,29(6):1615-1625
Marine protected areas (MPAs) are the cornerstone of most marine conservation strategies, but the effectiveness of each one partly depends on its size and distance to other MPAs in a network. Despite this, current recommendations on ideal MPA size and spacing vary widely, and data are lacking on how these constraints might influence the overall spatial characteristics, socio‐economic impacts, and connectivity of the resultant MPA networks. To address this problem, we tested the impact of applying different MPA size constraints in English waters. We used the Marxan spatial prioritization software to identify a network of MPAs that met conservation feature targets, whilst minimizing impacts on fisheries; modified the Marxan outputs with the MinPatch software to ensure each MPA met a minimum size; and used existing data on the dispersal distances of a range of species found in English waters to investigate the likely impacts of such spatial constraints on the region's biodiversity. Increasing MPA size had little effect on total network area or the location of priority areas, but as MPA size increased, fishing opportunity cost to stakeholders increased. In addition, as MPA size increased, the number of closely connected sets of MPAs in networks and the average distance between neighboring MPAs decreased, which consequently increased the proportion of the planning region that was isolated from all MPAs. These results suggest networks containing large MPAs would be more viable for the majority of the region's species that have small dispersal distances, but dispersal between MPA sets and spill‐over of individuals into unprotected areas would be reduced. These findings highlight the importance of testing the impact of applying different MPA size constraints because there are clear trade‐offs that result from the interaction of size, number, and distribution of MPAs in a network. 相似文献
985.
Samuel Veloz Leonardo Salas Bob Altman John Alexander Dennis Jongsomjit Nathan Elliott Grant Ballard 《Conservation biology》2015,29(4):1217-1227
Systematic conservation planning aims to design networks of protected areas that meet conservation goals across large landscapes. The optimal design of these conservation networks is most frequently based on the modeled habitat suitability or probability of occurrence of species, despite evidence that model predictions may not be highly correlated with species density. We hypothesized that conservation networks designed using species density distributions more efficiently conserve populations of all species considered than networks designed using probability of occurrence models. To test this hypothesis, we used the Zonation conservation prioritization algorithm to evaluate conservation network designs based on probability of occurrence versus density models for 26 land bird species in the U.S. Pacific Northwest. We assessed the efficacy of each conservation network based on predicted species densities and predicted species diversity. High‐density model Zonation rankings protected more individuals per species when networks protected the highest priority 10‐40% of the landscape. Compared with density‐based models, the occurrence‐based models protected more individuals in the lowest 50% priority areas of the landscape. The 2 approaches conserved species diversity in similar ways: predicted diversity was higher in higher priority locations in both conservation networks. We conclude that both density and probability of occurrence models can be useful for setting conservation priorities but that density‐based models are best suited for identifying the highest priority areas. Developing methods to aggregate species count data from unrelated monitoring efforts and making these data widely available through ecoinformatics portals such as the Avian Knowledge Network will enable species count data to be more widely incorporated into systematic conservation planning efforts. 相似文献
986.
Larry Larsen Terri Morrell Gretchen Schalge Meghan Gallione Joseph Bell Kip Petersen Frederick Steiner 《Environmental management》1991,15(4):549-563
This article is the third in a series prepared to explain the Teller County growth management planning process. Once it was
determined by local decision-makers that Teller County, Colorado, would pursue a policy of directed growth, concepts based
on this policy were developed. These concepts presented visions and options for the future. Landscape plans then were developed
for Teller County and the City of Woodland Park planning area so that these options could be visualized by local leaders and
the public. The landscape plans were used as part of the ongoing citizen involvement process to inform the public about the
options for growth management. To provide even more information, detailed designs were developed for specific areas in the
county. From the landscape plan, public involvement effort, and detailed designs, specific implementation measures were identified,
discussed, and adopted. These measures included guidelines for administration, so that county and city goals could be linked
to the actual day-to-day management of development proposals.
Paper 3 in a series of 3. 相似文献
987.
William Whipple 《Journal of the American Water Resources Association》1991,27(6):895-902
ABSTRACT: Water quality controls of storm water runoff and infiltration should be a major part of a nonpoint source control program. Although surface runoff and ground water controls are often approached separately, coordination between the two is essential. For practical reasons, a rather simplified technology-based approach appears to be desirable. Areas affected vary greatly as to their sensitivity to pollution; and the various classes of pollutant source vary greatly as to their potential harmfulness. In effect, a matrix approach appears best, in which both vulnerability of the area and harmfulness of the pollutant source would have weight in determining which level of best management practices (BMP) would be appropriate, whether standard, special, or complete prohibition of the type facility under given circumstances. 相似文献
988.
James G. Titus 《Environmental management》1991,15(1):39-58
Climatologists generally expect an anthropogenic global warming that could raise sea level 30–150 cm in the next century and
more thereafter. One of the impacts would be the loss of coastal wetlands. Although the inundation of adjacent dryland would
enable new wetlands to form, much of this land is or will soon be developed. If developed areas are protected, wetlands will
be squeezed between an advancing sea and the land being protected, which has already happened in China and the Netherlands,
where people have built dikes for centuries.
Unlike those countries, the United States has enough land to accommodate the landward migration of wetlands; but governments
lack the funds to purchase all the coastal lowlands that might be inundated and the legal authority to prohibit their development.
We propose a third approach: allowing property owners to use coastal lowlands today as they choose, but setting up a legal
mechanism to ensure that the land is abandoned if and when sea level rises enough to inundate it. Although compensation may
be required, this approach would cost less than 1% as much as purchasing the land, and would be (1) economically efficient
by enabling real estate markets to incorporate expectations of future sea level rise; (2) constitutional by compensating property
owners; and (3) politically feasible by pleasing people who care about the long-term fate of the coastal environment without
disturbing people who either are unconcerned about the distant future or do not believe sea level will rise.
This article demonstrates that it would be irrational to delay policy formulation until sea level rise projections are more
precise. The cost will be small if we act now but great if we wait, and sea level is already rising along most coasts. The
US government should develop a strategy in the next three years.
The opinions expressed in this paper do not necessarily reflect the views of EPA and no official endorsement should be inferred. 相似文献
989.
O. W. R. Lucas 《Journal of Environmental Planning and Management》1983,26(2):98-104
The value placed by the public on the nation's rural landscapes is emphasised by vociferous criticism of insensitive, large‐scale afforestation. As forestry causes massive changes in the landscape in the short term, with results that last for decades, the opportunity provided to improve and conserve should be positively grasped. There is evidence that concensus exists over a considerable part of landscape and design, and this paper explores some of the major factors in landscape design which are consistently important in forest landscapes. 相似文献
990.