全文获取类型
收费全文 | 269篇 |
免费 | 13篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 3篇 |
环保管理 | 60篇 |
综合类 | 105篇 |
基础理论 | 84篇 |
污染及防治 | 17篇 |
评价与监测 | 15篇 |
社会与环境 | 18篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 5篇 |
2009年 | 27篇 |
2008年 | 12篇 |
2007年 | 31篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有306条查询结果,搜索用时 250 毫秒
91.
Local extinction of native species and colonization of non-native species are commonly invoked as responsible for changes in species similarity among biotas of different regions. In this study we used a model of species similarity between islands to assess the emergent, and unexplored, effects of changes in colonization by native species, extinction of non-native species, and propagule pressure on species similarity among insular communities. The model predicts that extinction probability of endemic species has a positive but asymptotic effect on species similarity, which is exacerbated by increasing colonization and reducing extinction of non-native species. Species similarity tends to increase with increasing colonization probability by non-native species, however this effect may be reduced, or even reverted, when the islands are exposed to an elevated number of non-native species that are prone to extinction, high levels of endemic species loss, and an initially large number of native species shared between islands. Species similarity was positively affected by the propagule pressure rate of non-native species only when their colonization and extinction probabilities were large and small enough, respectively. A negative effect of propagule pressure rate can be caused by an increase in the pool size of non-native species, which involves the introduction of different species into different islands, promoting biotic differentiation between islands. Our results indicate that the interactions between colonization, extinction and species pool lead to nonlinear responses and unexpected scenarios of biotic change. In order to validate model predictions, future research programs should focus on understanding the dynamics on such complex meta-communities where coexist native, non-native and endemic species. 相似文献
92.
运用能值分析的理论和方法,以中国第三大岛崇明岛为研究对象,定量分析和评价了1980~2003年岛内“社会-经济-自然”复合生态系统的能值自给率、人均能值用量、能值密度、环境负荷率、人口承载量以及基于能值分析的可持续发展指数等多项指标的变化趋势,并将2003年的数据进行了国内外对比。针对崇明建设生态岛的目标,分析了崇明岛的优势和不足,为其可持续发展提出了对应的建议和措施。研究表明:虽然良好的生态环境提升了人民的生活质量,但由于缺乏经济和科技竞争力,崇明岛的发展水平处于全国平均水平,与所处的长三角地区整体发展水平相差较大。但岛屿系统现状良好,运行稳定、健康、有活力,可持续性高。未来崇明岛的发展应当合理权衡和协调绎济发展和环境保护的关系,维持系统的可持续性。 相似文献
93.
Xiangrong Wang Yi Yong Shixiong Wang Hao Zhang Hing Hon Ho Pingjian Wang Shoubing Wang Weizhen Chen 《Frontiers of Environmental Science & Engineering in China》2008,2(2):178-186
The background, concept, connotation, principles, and methods of eco-planning for an Eco-Demonstration Park (EDP) and sustainability
were examined based on a case study of the Luhua EDP in the Chongming Island of Shanghai, China, which is an important part
of Shanghai Eco-city planning and construction in the 21st century. By analyzing natural, social and economic conditions,
calculating population using the land capacity eco-model, eco-function zoning, and eco-construction, an innovative eco-industrial
structure and technical chain were formulated. A comprehensive eco-planning scheme for the EDP was proposed, including planning
and management strategies for subsystems of efficient industry, good quality human settlement, high standard eco-construction
and eco-tourism as well as effective environmental protection and attractive landscape. The EDP should be an area with coordinated
and sustainable economic, social and environmental subsystems. Eco-planning for the EDP should be a very important part of
eco-city planning and sustainability. The paper aims to set up a theoretical framework and practical basis for eco-planning
and promoting harmony between human and nature. 相似文献
94.
Codfishes, the Gadiformes, are quite abundant in modern temperate and polar waters with a fossil record ranging back into
the Palaeogene. The oldest records are from the Danian and Selandian of Europe and South Australia. The bipolar distribution
early in their evolutionary history implies that their origin must have occurred quite early in the Palaeocene, or even in
the Late Cretaceous with subsequent rapid diversification. By the Eocene, gadiforms were highly abundant and widespread. With
the exception of gadiforms, no Eocene Antarctic teleostean group is present in the modern Antarctic fauna. Here, we review
the early evolution and diversification of gadiforms in general and of macrouroids in particular. We also describe the undoubtedly
oldest skeletal macrourid specimen with otoliths preserved in situ. It is the first definitive record of this group from the
Eocene of Antarctica filling a gap in its stratigraphic distribution. The fossil record of gadiforms in general and macrouroids
in particular indicates that the origin of both was in shallow shelf environments but with adaptations to deep-water settings
early in their evolution. While gadoids seemingly originated in the earliest Palaeogene and rapidly experienced a first major
radiation event in the eastern North Atlantic and/or North Sea Basin, macrouroids evolved in the Southern Ocean and migrated
northwards into the South Atlantic before the establishment of the circum-Antarctic current and subsequent isolation of the
Antarctic fish fauna. These two timely and regional separated adaptive radiation events in the Palaeogene gave rise to their
modern taxonomic diversity and global distribution. 相似文献
95.
The bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and palaeontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into ‘non-avian’ and ‘avian’ modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying—or terrestrial and arboreal—categories may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an ‘interpretive asymptote’ for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and palaeontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables. 相似文献
96.
淇澳岛红树林生态系统中重金属含量相关性 总被引:3,自引:1,他引:2
采集珠海淇澳岛北部大围湾的红树林区潮间带沉积物和植物组织样品若干,测定各样品中Cu、Zn、Cd和Pb的含量,四种重金属含量在各沉积物中、各植物组织中以及沉积物和植物组织之间的相关性。研究表明,沉积物中Pb和Zn含量呈极强正相关,Pb、Zn与Cd含量之间呈强正相关,其他各类重金属之间的相关性不显著。四种重金属与沉积物颗粒形态相关性均不显著。红树植物各组织对四种重金属的富集系数范围为0.001~0.72,0.006~0.39,0.053~1.97和0.004~0.24,富集能力与林龄正相关,其中对Zn、Cd和Pb的富集系数与土壤中含量呈负相关,表明在过高重金属污染胁迫的环境中红树植物有自行降低富集能力以避免被伤害的趋势。 相似文献
97.
The evolution of bird migration—a synthesis 总被引:1,自引:1,他引:0
We approach the problem of the evolution of bird migration by asking whether migration evolves towards new breeding areas
or towards survival areas in the non-breeding season. Thus, we avoid the ambiguity of the usually discussed “southern-home-theory”
or “northern-home-theory”. We argue that migration evolved in birds that spread to seasonal habitats through gradual dispersal
to enhance survival during the non-breeding season; this in contrast to the alternative idea suggesting that migration evolved
towards new breeding areas to increase reproductive success. Our synthesis is based on the threshold model explaining how
migratory traits can change rapidly through microevolutionary processes. Our model brings former theories together and explains
how bird migration, with the appropriate direction and time program, evolves through selection after genetically non-directed
events such as dispersal and colonization. The model does not need the former untested assumptions such as competition as
a reason for migration and for the disappearance of sedentary populations or higher reproductive success in temperate breeding
areas. Our theory offers answers to questions such as how birds with a southern origin may gradually reach northern latitudes,
why migration routes may follow historical expansion routes and why birds leave an area for the non-breeding season and move
back instead of breeding on their wintering grounds. The theory proposes gradual change through selection and not sudden changes
such as long distance dispersal or mutations and can be applied to migration at all latitudes and in all directions. The scenario
provides a reasonable concept to understand most of the existing migratory phenomena on the basis of the ecology and genetics
of migratory behaviour. 相似文献
98.
99.
100.
舟山六横岛附近海域沉积物重金属污染及潜在生态风险评价 总被引:2,自引:1,他引:1
根据2010年3月、6月对舟山六横岛邻近海域表层沉积物重金属调查资料,采用单因子指数法和Hakanson生态风险指数法对Cu、Pb、Cd、Zn、Hg、As、Cr元素进行分析与评价,并与2010年8月舟山嵊泗近岸海域表层沉积物质量进行比较。研究结果表明:该海域沉积物综合污染程度为中等水平,各种元素污染程度高低依次为Zn>Cu>Cd>Pb>Cr>As>Hg,主要重金属污染因子为Zn、Cu、Cd元素。总体而言,该海域沉积物潜在生态风险性低,风险程度高低依次为Cd>Hg>Cu>Pb>As>Cr>Zn,其中各站位Cd的生态风险参数均值大于40,Cd为该海域的最大潜在生态风险因子。 相似文献