全文获取类型
收费全文 | 15539篇 |
免费 | 158篇 |
国内免费 | 126篇 |
专业分类
安全科学 | 374篇 |
废物处理 | 666篇 |
环保管理 | 1794篇 |
综合类 | 2540篇 |
基础理论 | 4308篇 |
环境理论 | 4篇 |
污染及防治 | 4025篇 |
评价与监测 | 1057篇 |
社会与环境 | 963篇 |
灾害及防治 | 92篇 |
出版年
2022年 | 127篇 |
2021年 | 104篇 |
2020年 | 100篇 |
2019年 | 106篇 |
2018年 | 195篇 |
2017年 | 233篇 |
2016年 | 326篇 |
2015年 | 266篇 |
2014年 | 452篇 |
2013年 | 1202篇 |
2012年 | 491篇 |
2011年 | 692篇 |
2010年 | 613篇 |
2009年 | 581篇 |
2008年 | 671篇 |
2007年 | 713篇 |
2006年 | 589篇 |
2005年 | 513篇 |
2004年 | 521篇 |
2003年 | 507篇 |
2002年 | 489篇 |
2001年 | 647篇 |
2000年 | 475篇 |
1999年 | 254篇 |
1998年 | 173篇 |
1997年 | 206篇 |
1996年 | 205篇 |
1995年 | 236篇 |
1994年 | 234篇 |
1993年 | 180篇 |
1992年 | 195篇 |
1991年 | 183篇 |
1990年 | 203篇 |
1989年 | 187篇 |
1988年 | 151篇 |
1987年 | 162篇 |
1986年 | 153篇 |
1985年 | 156篇 |
1984年 | 148篇 |
1983年 | 140篇 |
1982年 | 125篇 |
1981年 | 120篇 |
1980年 | 115篇 |
1979年 | 124篇 |
1978年 | 100篇 |
1977年 | 113篇 |
1975年 | 87篇 |
1974年 | 87篇 |
1973年 | 96篇 |
1972年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
831.
Background, aim, and scope In the district List of Hanover (Lower Saxony) radioactive contaminations of the ground were detected at a site of a former chemical plant. Due to the lack of an ordinance regarding intervention regulations in the case of radioactive contaminations in Germany this situation had to be assessed on the basis of scales and methods of the German regulations concerning soil protection and contaminated sites. In particular it was necessary to develop methods and levels for the assessment of radioactive contaminations. Materials and methods Because radioactivity can be considered as a carcinogenic substance the methodical approaches of the BBodSchV for this group of substances were used in order to derive test thresholds for radioactive contaminations at children’s play areas, residential areas as well as parks and recreation facilities. Results For the assessment of radioactive soil contaminations with naturally occurring radionuclides at children’s play areas and residential areas the ingestion of soil is the decisive pathway of exposure. For children’s play areas a threshold level of 0.2?Bq/g for the sum U-238,max?+?Th-232,max was obtained. At areas with only impacts of ambient radiation from the contaminated ground test thresholds of 0.5?µSv/h are recommended. A special pathway is the migration of radon from the contaminated soil into basement floors of buildings. Taking into account the natural background levels of radon a concentration of 260?Bq/m³ is suggested as a test threshold in the framework of soil protection benchmarks. Discussion and conclusions will be described in Part 2 of the paper. 相似文献
832.
CARLOS CARROLL JOHN A. VUCETICH MICHAEL P. NELSON DANIEL J. ROHLF MICHAEL K. PHILLIPS 《Conservation biology》2010,24(2):395-403
Abstract: The U.S. Endangered Species Act (ESA) defines an endangered species as one “at risk of extinction throughout all or a significant portion of its range.” The prevailing interpretation of this phrase, which focuses exclusively on the overall viability of listed species without regard to their geographic distribution, has led to development of listing and recovery criteria with fundamental conceptual, legal, and practical shortcomings. The ESA's concept of endangerment is broader than the biological concept of extinction risk in that the “esthetic, ecological, educational, historical, recreational, and scientific” values provided by species are not necessarily furthered by a species mere existence, but rather by a species presence across much of its former range. The concept of “significant portion of range” thus implies an additional geographic component to recovery that may enhance viability, but also offers independent benefits that Congress intended the act to achieve. Although the ESA differs from other major endangered‐species protection laws because it acknowledges the distinct contribution of geography to recovery, it resembles the “representation, resiliency, and redundancy” conservation‐planning framework commonly referenced in recovery plans. To address representation, listing and recovery standards should consider not only what proportion of its former range a species inhabits, but the types of habitats a species occupies and the ecological role it plays there. Recovery planning for formerly widely distributed species (e.g., the gray wolf [Canis lupus]) exemplifies how the geographic component implicit in the ESA's definition of endangerment should be considered in determining recovery goals through identification of ecologically significant types or niche variation within the extent of listed species, subspecies, or “distinct population segments.” By linking listing and recovery standards to niche and ecosystem concepts, the concept of ecologically significant type offers a scientific framework that promotes more coherent dialogue concerning the societal decisions surrounding recovery of endangered species. 相似文献
833.
ANNE K. SALOMON SARAH K. GAICHAS NICK T. SHEARS JENNIFER E. SMITH ELIZABETH M. P. MADIN STEVEN D. GAINES 《Conservation biology》2010,24(2):382-394
Abstract: Trophic cascades triggered by fishing have profound implications for marine ecosystems and the socioeconomic systems that depend on them. With the number of reported cases quickly growing, key features and commonalities have emerged. Fishery‐induced trophic cascades often display differential response times and nonlinear trajectories among trophic levels and can be accompanied by shifts in alternative states. Furthermore, their magnitude appears to be context dependent, varying as a function of species diversity, regional oceanography, local physical disturbance, habitat complexity, and the nature of the fishery itself. To conserve and manage exploited marine ecosystems, there is a pressing need for an improved understanding of the conditions that promote or inhibit the cascading consequences of fishing. Future research should investigate how the trophic effects of fishing interact with other human disturbances, identify strongly interacting species and ecosystem features that confer resilience to exploitation, determine ranges of predator depletion that elicit trophic cascades, pinpoint antecedents that signal ecosystem state shifts, and quantify variation in trophic rates across oceanographic conditions. This information will advance predictive models designed to forecast the trophic effects of fishing and will allow managers to better anticipate and avoid fishery‐induced trophic cascades. 相似文献
834.
MATTHEW SOMMERVILLE E.J. MILNER‐GULLAND MICHAEL RAHAJAHARISON JULIA P.G. JONES 《Conservation biology》2010,24(6):1488-1498
Abstract: Despite the growing interest in conservation approaches that include payments for environmental services (PES), few evaluations of the influence of such interventions on behaviors of individuals have been conducted. We used self‐reported changes in six legal and illegal forest‐use behaviors to investigate the way in which a PES for biodiversity conservation intervention in Menabe, Madagascar, influenced behavior. Individuals (n =864) from eight intervention communities and five control communities answered questions on their forest‐use behaviors before and after the intervention began, as well as on their reasons for changing and their attitudes to various institutions. The payments had little impact on individuals’ reported decisions to change behaviors, but it had a strong impact on individuals’ attitudes. Payments appeared to legitimize monitoring of behaviors by the implementing nongovernmental organization (NGO), but did not act as a behavioral driver in their own right. Although there were no clear differences between changes in behaviors in the intervention and control communities, the intervention did influence motivations for change. Fear of local forest associations and the implementing NGO were strong motivators for changing behavior in communities with the PES intervention, whereas fear of the national government was the main reason given for change in control communities. Behavioral changes were most stable where fear of local organizations motivated the change. Our results highlight the interactions between different incentives people face when making behavioral decisions and the importance of considering the full range of incentives when designing community‐based PES interventions. 相似文献
835.
道南膜技术测定CaCl2溶液体系中汞的化学形态 总被引:1,自引:0,他引:1
尝试并探索道南膜技术(DMT)测定溶液体系中Hg化学形态的方法条件.结果表明,0.01mol·1-1CaCl2作为背景溶液时,跨过阳离子交换膜的Hg主要形态并非阳离子而是HgCl2和HgCl3.Hg在阳离子交换膜内扩散为限制Hg跨膜传输的主要因素.Hg在阳离子交换膜内的吸附除静电吸附外还存在结合力更强的化学吸附,成为限制道南膜技术用于Hg形态测定的主要因素.采用动力学DMT方法,缩短试验时间至8h以内,可在一定程度上降低Hg的化学吸附,为DMT方法测定土壤溶液体系中Hg的化学形态提供可能. 相似文献
836.
We tracked the long-term movements of 70 parrotfishes, surgeonfishes and goatfishes captured inside a small (1.3 km2) marine protected area (MPA: Kealakekua Bay Marine Life Conservation District, Hawaii) by implanting them with small transmitters
and deploying underwater monitoring devices inside the bay and along 100 km of the adjacent west Hawaii coastline. Individual
fish were detected inside Kealakekua Bay for up to 612 days but many were detected for much shorter periods (median = 52 days).
There were species-specific differences in the scale of movements and habitats used, but most fish utilized between 0.2 and
1.6 km of coastline, and individuals of each species showed some degree of diel habitat shift. A wide variety of reef fishes
captured inside the MPA swam back and forth across an MPA boundary intersecting continuous reef (i.e., this boundary was porous
to reef fish movements), but only 1 of 11 species tagged crossed a wide sandy channel inside Kealakekua Bay suggesting that
this feature may function as a natural barrier to movements. Results indicate relatively small MPAs (<2 km of coastline) could
provide effective, long-term protection for multi-species assemblages of reef fishes provided that boundaries are situated
along major habitat breaks (e.g., large sand channels between reefs) that may serve as natural barriers to reef fish movements.
It is crucial that a multi-species approach be used when assessing MPA effectiveness. 相似文献
837.
This paper presents a scan statistic, progressive upper level set (PULSE) scan statistic, for geospatial hotspot detection
and its software implementation. Like ULS, the PULSE scan statistic is based on the arbitrarily shaped scan window and can
be adapted for a network setting. PULSE is a refinement of the upper level set (ULS) scan statistic. Like some other likelihood
based scanning devices, the ULS scan statistic identifies maximum likelihood estimate (MLE) zones that tend to be ‘stringy’
and sprawling. Its search path increases possibility of inclusion of extraneous cells in its MLE zones and, to a smaller extent,
of exclusion of cells that belong to a true hotspot from its MLE zone. The PULSE scan statistic achieves improvement over
the ULS scan statistic in two ways. First, it begins its search for a most likely zone with a large population of candidate
zones obtained by modifying the ULS tree structure and continues its search using a genetic algorithm. Secondly, to reduce
chances of generating an MLE that is excessively stringy and that includes extraneous cells in the MLE zone, PULSE uses cardinality
and compactness of zones along with their likelihoods as the fitness function in the genetic algorithm and uses several pertinent
criteria including evenness of intra-zone cellular response ratios to determine the MLE zone. To reduce computation, Gumbel
distribution of extreme values is used to determine the p-value of the MLE zone. Better results come at the cost of increased processing time. An evaluative performance study is presented. 相似文献
838.
We equipped individual tiger (Galeocerdo cuvier Péron and Lesueur, 1822) and Galapagos (Carcharhinus galapagensis Snodgrass and Heller, 1905) sharks with both acoustic and satellite transmitters to quantify their long-term movements in
the Papahanaumokuakea Marine National Monument (Northwestern Hawaiian Islands). Tiger sharks exhibited two broad patterns
of behavior. Some individuals were detected at French Frigate Shoals (FFS) year round, whereas others visited FFS atoll in
summer to forage on fledging albatross, then swam thousands of kilometers along the Hawaiian chain, or out into open ocean
to the North Pacific transition zone chlorophyll front, before returning to FFS in subsequent years. These patterns suggest
tiger sharks may use cognitive maps to navigate between distant foraging areas. Different patterns of spatial behavior may
arise because cognitive maps are built up through individual exploration, and each tiger shark learns a unique combination
of foraging sites. Galapagos shark detections were all associated with FFS, suggesting these sharks may be more resident around
oceanic islands. Both Galapagos and tiger sharks primarily used the mixed layer (<100 m depth) and made occasional deeper
dives through the thermocline down to 680 m. Results show reef-associated sharks utilize a wide variety of habitats ranging
from shallow atoll lagoons to deep reefs and open ocean and may provide important trophic links between these habitats. 相似文献
839.
G. Verreydt I. Van Keer J. Bronders L. Diels P. Vanderauwera 《Environmental geochemistry and health》2012,34(6):725-736
A site- and receptor-specific risk management strategy for groundwater pollution based on the measurement of contaminant mass flux is proposed. The approach is useful and compatible with the demands formulated in the European Water Framework Directive, its Groundwater Daughter Directive and the regulations applicable in the EU member states. The proposed CMF method focuses on the following: (1) capture zones, (2) the location of control planes, (3) the definition of the maximum allowed contaminant mass discharge and (4) contaminant mass flux measurements. For every control plane, such a maximum allowed contaminant mass discharge is derived and is crucial for the receptor risk management strategy. The method is demonstrated for a large area of groundwater pollution present in the industrial area of Vilvoorde–Machelen located in Flanders, Belgium. 相似文献
840.
In southern Taiwan, brooded larvae of Pocillopora damicornis and Seriatopora caliendrum are released year-round in synchrony with new moons, and each larval release occurs over multiple days. Using P. damicornis and S. caliendrum as a model system, we describe within-brood variation in larval phenotypes and test for release-day effects that influence larval performance in the pelagic phase. Research was conducted in 2010 using larvae from corals collected in June and July from Nanwan Bay (21°56.179??N, 120°44.85??E). In June, larval phenotypes of both species were characterized immediately following release, and their competency to settle assessed. In July, larvae of P. damicornis were collected on 3?days over the peak release period and incubated for 7?C11?days at 28.0?°C and 320???mol?quanta?m?2?s?1; their phenotypes and settlement competency were measured every 2?days. P. damicornis larvae released close to peak release were 1.6 times larger in size, contained twice the number of Symbiodinium larva?1, and were 44?% more likely to settle in the first 24?h than larvae released early in the brood. In addition, peak-release larvae respired at a lower rate than larvae released late in the brood. Similarly, S. caliendrum larvae released close to peak release were 1.4 times larger in size and were 33?% more likely to settle in the first 5?h than larvae released early in the brood. In July, P. damicornis larvae differed between early (2?days prior to peak), peak, and late (2?days after peak) release. Protein content of early-release larvae was lower than peak- and late-release larvae, and this difference persisted throughout the development. Further, release day affected the way larval respiration varied throughout development. By showing that brooded coral larvae differ between release days and display maternal effects influencing performance in the swimming phase, our results suggest that pocilloporid corals utilize bet-hedging to increase reproductive success. 相似文献