首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   289篇
  免费   0篇
  国内免费   1篇
安全科学   10篇
环保管理   25篇
综合类   1篇
基础理论   240篇
污染及防治   5篇
评价与监测   1篇
灾害及防治   8篇
  2014年   20篇
  2013年   26篇
  2012年   4篇
  2011年   12篇
  2010年   23篇
  2009年   21篇
  2008年   16篇
  2007年   21篇
  2006年   18篇
  2005年   26篇
  2004年   27篇
  2003年   11篇
  2002年   3篇
  2001年   5篇
  2000年   1篇
  1999年   1篇
  1997年   5篇
  1996年   5篇
  1995年   5篇
  1994年   1篇
  1993年   4篇
  1992年   2篇
  1991年   8篇
  1990年   6篇
  1989年   4篇
  1988年   6篇
  1987年   6篇
  1982年   2篇
  1980年   1篇
排序方式: 共有290条查询结果,搜索用时 187 毫秒
11.
The application of environmental psychology principles and findings to the work of criminal investigators is gaining ground. This paper presents one particular application of these principles to the study of those very rare criminals, serial killers. An environmental psychology perspective looks on the rational processes that may underlie these disturbing and highly emotive crimes. For, although the murders committed by serial killers may not be considered rational, but rather a consequence of heightened emotion and lack of impulse control, environmental psychology hypotheses predict that their choice of disposal site location may be guided by a recognisable rationality. Support for this rationality would be evident through their spatial patterns of disposal locations, but these spatial patterns themselves would vary depending on the range over which the offender was operating. It was therefore hypothesised that their spatial patterns would reflect the importance of a) the centrality of the home location for determining the disposal site locations, b) the relevance of maintaining distance between sequential disposal site locations themselves. Further, c) the nature of the influences of home and sequence would vary with the size of the area over which the offender disposed of his victims' bodies.The hypotheses were tested by examining three sub-sets of a sample of 120 American serial murderers, each sub-set travelling a different average distance from their homes to their crimes. The Multidimensional Scaling Procedure, Smallest Space Analysis (SSA-I) was used in order to examine the trends across the distances between each disposal site and every other and their distances from the offender's homes. A three dimensional space was used so that the ‘dimension’ of temporal sequence could be revealed as well as the two dimensions of geographical distances. All hypotheses were supported. Firstly, the home was central to the SSA disposal patterns for each of the three sub-sets. Secondly, the location of each subsequent disposal location tended to be in a different direction from that immediately prior to it. However, thirdly, this sequential process was strongest for the sub-set of 36 offenders who travelled on average less than 10 km and weakest for those 40 offenders who travelled on average greater than 30 km. The implications these results have for modelling offenders' geographical behaviour are discussed.  相似文献   
12.

Extraction is an important procedure for samples that contain soil because other compounds in soil may affect analysis of estrogens. This study was conducted to evaluate three different extraction methods for 17β-estradiol in soil. Sand, bentonite, and organic-rich silt loam were spiked with 1 mg kg? 1 of 17β-estradiol as a model compound of estrogens. 17β-estradiol and its metabolites, estrone and estriol, were extracted using (i) a modified Bligh and Dyer extraction, (ii) a pressurized fluid extraction, and (iii) a diethyl ether extraction, and measured by liquid chromatography tandem mass spectrometry. There were significant differences in the extraction efficiency for 17β-estradiol among the extraction methods and the soils: the efficiencies ranged from 10% to 97%. Overall, the diethyl ether extraction method had the largest efficiency of 17β-estradiol with 45% and 57% for bentonite and silt loam, respectively. Transformation of 17β-estradiol to estrone and estriol in the different extraction methods was less than 3.6% during the extraction procedures. This study underlined the importance of sample preparation for estrogen analysis in soil samples.  相似文献   
13.
Abstract: The EDGE (evolutionarily distinct and globally endangered) conservation program ( http://www.edgeofexistence.org ) uses a composite measure of threat and phylogenetic isolation to rank species for conservation attention. Using primates as a test case, we examined how species that rank highly with this metric represent the collective from which they are drawn. We considered the ecological and morphological traits, including body mass, diet, terrestriality, and home range size, of all 233 species of primates. Overall, EDGE score and the level of deviance from the mean of 20 different ecological, reproductive, and morphological variables were correlated (mean correlation r =0.14, combined p =1.7 × 10?14). Although primates with a high EDGE score had characteristics that made them seem odd, they did not seem to express more ancestral characteristics than expected. Sets of primate species with high EDGE scores will, therefore, collectively capture a broader than expected range of the biology of the clade. If similar patterns hold in other groups, the EDGE metric may be useful for prioritizing biodiversity for conservation.  相似文献   
14.
Abstract: Success of captive‐breeding programs centers on consistent reproduction among captive animals. However, many individuals do not reproduce even when they are apparently healthy and presented with mates. Mate choice can affect multiple parameters of reproductive success, including mating success, offspring production, offspring survival, and offspring fecundity. We investigated the role of familiarity and preference on reproductive success of female Columbia Basin pygmy rabbits (Brachylagus idahoensis) as measured by litter production, litter size, average number of young that emerged from the burrow, and average number of young that survived to 1 year. We conducted these studies on pygmy rabbits at the Oregon Zoo (Portland, Oregon, U.S.A.) and Washington State University (Pullman, Washington, U.S.A.) from February to June 2006, 2007, and 2008. Before mating, we housed each female adjacent to 2 males (neighbors). Female preference for each potential mate was determined on the basis of behavioral interactions observed and measured between the rabbits. We compared reproductive success between females mated with neighbor and non‐neighbor males and between females mated with preferred and nonpreferred males. Our findings suggest that mating with a neighbor compared with a non‐neighbor and mating with a preferred neighbor compared with a nonpreferred neighbor increased reproductive success in female pygmy rabbits. Litter production, average number of young that emerged, and average number of young that survived to 1 year were higher in rabbits that were neighbors before mating than in animals who were not neighbors. Pairing rabbits with a preferred partner increased the probability of producing a litter and was significantly associated with increased litter size. In captive breeding programs, mates are traditionally selected on the basis of genetic parameters to minimize loss of genetic diversity and inbreeding coefficients. Our results suggest that integrating genetic information with social dynamics and behavioral measures of preference may increase the reproductive output of the pygmy rabbit captive‐breeding program. Our findings are consistent with the idea that allowing mate choice and familiarity increase the reproductive success of captive‐breeding programs for endangered species.  相似文献   
15.
In November 1928 there was an eruption of Mount Etna, Sicily, which led to lava largely destroying the town of Mascali, situated low on the eastern flank of the volcano. Destruction of the town took just over a day but there was an orderly evacuation of its inhabitants and, with help from the military, families were able to remove furniture and fittings from their houses. Evacuees were relocated to nearby towns staying with relatives, friends or in hired apartments. Rebuilding Mascali provided an opportunity for the fascist government of the time to demonstrate efficient centralised planning. A completely new town was built on a grid-iron plan with many of the buildings reflecting the 'fascist architecture' of the time. The town was complete by 1937 and housing condztzons were very advanced in comparison with other towns in the region. The 1928 eruption is important as it was the most destructive on Etna since 1669 when the city of Catania was overwhelmed. In terms of hazard and risk assessment the 1928 eruption demonstrates that lava can reach the lower flanks of the volcano within a short period after the onset of an eruption.  相似文献   
16.
Various approaches have been used to classify large geographical areas into smaller regions of similar water quality or extrapolate water-quality data from a few streams to other unmonitored streams. A combination of some of the strengths of existing techniques is used to develop a new approach for these purposes. In this new approach, referred to here as SPARTA (SPAtial Regression-Tree Analysis), environmental characteristics for each monitored stream are first quantified using a Geographic Information System (GIS) and then regression-tree analysis is used to determine which characteristics are most statistically important in describing the distribution of a specific water-quality constituent. GIS coverages of only the most statistically significant environmental characteristics are then used to subdivide the area of interest into relatively homogeneous environmental water-quality zones. Results from the regression-tree analysis not only define the most important environmental characteristics, but also describe how to subdivide the coverage of the specific characteristic (for example, areas with <26% or ≥26% soil clay content). The resulting regionalization scheme is customized for each water-quality constituent based on the environmental characteristics most statistically related to that constituent. SPARTA was used to delineate areas of similar phosphorus, nitrogen, and sediment concentrations (by including land-use characteristics) and areas of similar potential water quality (by excluding land-use characteristics). The SPARTA approach reduced the variability in water-quality concentrations (phosphorus, total nitrogen, Kjeldahl nitrogen, and suspended sediment) within similarly classified zones from that obtained using the US Environmental Protection Agency's nutrient ecoregions.  相似文献   
17.
We examined the impact of single-tree selective logging and fuel reduction burns on the abundance of hollow-nesting bird species at a regional scale in southeastern Queensland, Australia. Data were collected on species abundance and habitat structure of dry sclerophyll production forest at 36 sites with known logging and fire histories. Sixteen bird species were recorded with most being resident, territorial, obligate hollow nesters that used hollows that were either small (<10 cm diameter) or very large (>18 cm diameter). Species densities were typically low, but combinations of two forest management and three habitat structural variables influenced the abundances of eight bird species in different and sometimes conflicting ways. The results suggest that habitat tree management for biodiversity in production forests cannot depend upon habitat structural characteristics alone. Management histories appear to have independent influence (on some bird species) that are distinguishable from their impacts on habitat structure per se. Rather than managing to maximize species abundances to maintain biodiversity, we may be better off managing to avoid extinctions of populations by identifying thresholds of acceptable fluctuations in populations of not only hollow-nesting birds but other forest dependent wildlife relative to scientifically valid forest management and habitat structural surrogates.  相似文献   
18.
Policy makers often must rely on the cumulative impact of independent actions taken by local landowners to achieve environmental goals. The connection between policy, regulation, and local action, however, is often not well understood and, thus, the impact of proposed policies may be difficult to predict. In this study we evaluate the effectiveness of alternative policy scenarios for agricultural set aside programs (e.g., the conservation reserve program administered by the United States Department of Agriculture) in reducing nonpoint pollution. Two alternative policy scenarios are developed and analyzed; one based on the erodibility index (detachment), the other sediment yield (transport). An estimate of the cumulative impact of associated land use change on nonpoint pollution is made using the AGNPS distributed parameter watershed model. This work is completed within the Cypress Creek watershed in southern Illinois. An analysis of the resulting data suggests that the most efficacious regulatory strategy for achieving nonpoint water pollution goals depends, in part, on place-specific land use patterns. This conclusion provides a solid argument for place-based regulatory strategies.  相似文献   
19.
A method is proposed to quantify disturbance impact on isolated habitats. For every landscape patch, the breakpoint distance, defined as the penetration distance for which equality of interior and edge habitat is observed, can be calculated. Disturbance with equal impact at all patch sides is assumed. Effects of patch compactness, size, convolution, and perforation are discussed. The potential use of the measure for nature reserve design is discussed. The breakpoint distance follows the reserve design guidelines for individual patches, based on island biogeography and is consistent with the form and function principle. A large breakpoint distance is preferred for natural habitats. Small size, small compactness, intense convolution, and the occurrence of many gaps depress the breakpoint distance.  相似文献   
20.
Es esencial desarrollar esfuaos intensives para proteger el habitat de la pantera de Florida (Felis concolor coryi) en terrenos privados para asegurar la supervivencia de esta especie en peligro. Apmimadamente la mitad del área de distribucion de esta panteras, en el sur de Florida, se encuentra en propiedades privadas, donde el desarrollo urbano y agnícola avanzan rápidamente. La estrategiu de conseruación para la pantera debe ir más allá de la adquisición tradicional de tierras por parte del gobierno, e incluir programas económicos para conservar terrenos críticos en propiedades privadas.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号