全文获取类型
收费全文 | 843篇 |
免费 | 17篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 13篇 |
废物处理 | 65篇 |
环保管理 | 78篇 |
综合类 | 96篇 |
基础理论 | 173篇 |
污染及防治 | 319篇 |
评价与监测 | 73篇 |
社会与环境 | 49篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 11篇 |
2022年 | 57篇 |
2021年 | 39篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 38篇 |
2017年 | 38篇 |
2016年 | 60篇 |
2015年 | 37篇 |
2014年 | 58篇 |
2013年 | 82篇 |
2012年 | 60篇 |
2011年 | 59篇 |
2010年 | 39篇 |
2009年 | 42篇 |
2008年 | 56篇 |
2007年 | 31篇 |
2006年 | 31篇 |
2005年 | 17篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有871条查询结果,搜索用时 46 毫秒
821.
The growth pattern of Loxechinus albus in southern Chile was studied using size-at-age data obtained by reading growth bands on the genital plates. The scatter
plots of sizes-at-age for samples collected in three different locations indicated that growth is linear between ages 2 and
10. Five different growth models, including linear, asymptotic and non-asymptotic functions, were fitted to the data, and
model selection was conducted based on the Akaike information criteria (AIC) and the Bayesian information criteria (BIC).
The AIC identified the Tanaka model as the most suitable for two of the three sites. However, the BIC led to the selection
of the linear model for all zones. Our results show that the growth pattern of L. albus is different from the predominantly asymptotic pattern that has been reported for other sea urchin species. 相似文献
822.
With the discovery of previously unreported populations of hemoglobin-possessing Ophiactis from the Texas coast in the Gulf of Mexico, an investigation into its population structure, including populations of O. simplex from the Pacific coast of California and O. rubropoda from the Atlantic coast of Florida, was undertaken using DNA sequence data from the mitochondrial COI gene. The reconstructed
haplotype network suggests that California populations contain the ancestral source of mtDNA variation, and there is no evidence
of recent introductions into Texas. Population genetic analyses reveal the California, Florida, and Texas Ophiactis populations to each be significantly differentiated from one another. Sequence divergence among the three areas is shallower
than would be predicted given biogeographic history. Texas and Florida populations are equally genetically diverged from California
populations as they are to one another, despite the greater potential for gene flow between these areas. The genetic distinctiveness
of the Texas populations and the concordance of this pattern with phylogeographic patterns in other brittle star systems indicate
an isolated and independent evolutionary history and we hypothesize that the three geographic regions included in this study
each serve as hypotheses of population-level lineages that remain to be tested with independent sources of data. 相似文献
823.
The Bahia Blanca Estuary is located in southern Buenos Aires province, Argentina. The area is linked to a petrochemical industrial complex, whose raw materials and final products contaminate the surrounding areas via atmospheric pollution and effluents, which are dumped in the estuary waters. To establish the effects of the industrial waste disposal on the nearest coastal soils, 17 samples were taken at different distances from the loading dock and the outfall pipes of the industrial complex. Later, the physicochemical characteristics of the soil samples, their hydrocarbon contents, sulfides, sulfates, Zn, Cu, and Pb were analyzed and a comparison was made to control samples, which were not affected by the industrial outfall. Hydrocarbons, Zn, Cu, and Pb contents were found at levels that modified the physical and chemical characteristics of the soils. The resistance to penetration shows that the thinner the film of water that surrounds the particles or aggregates, the smaller the migration of organic micelle, which settle on the surface of the contact material. This is demonstrated by the degree of cohesion reached by the particles and the strong influence on the index of hydrophobicity. The high porosity shows that the continuity of the porous space of the soil matrix is impeded by the presence of pollutants, which generate areas that are highly limiting to water flow. The oxidation-reduction potential and the low concentrations of soluble forms of Cu and Pb compared with their concentrations precipitated as sulfides confirm the action of the pollutants. 相似文献
824.
Management practices as antecedents of safety culture within the trucking industry: similarities and differences by hierarchical level 总被引:1,自引:0,他引:1
PROBLEM: A homogeneous perception of safety is important for the achievement of a strong safety culture; however, employees may differ in their safety perceptions, depending on their position and/or hierarchical level within the organization. Moreover, there is limited information on the antecedents of safety culture. This study examines how safety training, driver scheduling autonomy, opportunity for safety input, and management commitment to safety influence individuals' perceptions of safety culture. METHOD: Data for this study were drawn from 116 trucking firms, stratified by three safety performance levels. The data were collected from drivers (lowest hierarchical level), dispatchers (medium hierarchical level), and safety directors (highest hierarchical level), regarding their perceptions of their respective corporate safety cultures. Perceptions of safety culture were analyzed through a linear regression using dummy variables to differentiate among the three hierarchical groups. The resulting model allowed for examination of the specific antecedents of safety culture for the three employee groups and the extent to which the hierarchical groups were in agreement with each other. RESULTS: Driver fatigue training, driver opportunity for safety input, and top management commitment to safety were perceived to be integral determinants of safety culture in all three groups. IMPACT ON INDUSTRY: Trucking firms seeking to strengthen employees' perceptions of safety culture might begin by improving these safety management practices while appreciating that they may have a different impact depending on the employee's hierarchical position (e.g., drivers' perceptions of safety culture are more influenced by top management commitment and driver fatigue training). A fourth safety practice examined, driver scheduling autonomy, was not found to be instrumental in shaping safety culture for any of the three hierarchical levels. Consistent with previous research, implementation of stronger safety cultures should result in fewer accidents. 相似文献
825.
826.
Water quality levels and loads of nutrients transported by the Agüera stream (northern Spain) were studied for a year to assess
the self-purification capacity of this system. The main villages produce an increase of nutrient concentrations and a degradation
of water quality. Nevertheless, the high retention capacity, especially for phosphate, allows the stream to recover its previous
levels of quality after a short reach. The retention of nutrients depends on a complex combination of the flow level, hydrologic
stability and the development of periphytic communities. 相似文献
827.
Sabine Perch-Nielsen Ana Sesartic Matthias Stucki 《Environmental Science & Policy》2010,13(2):131-140
Greenhouse gas intensity is a ratio comparing the greenhouse gas (GHG) emissions of an activity or economic sector to the economic value it generates. In recent years, many countries have calculated the GHG intensity of their economic sectors as a basis for policy making. The GHG intensity of tourism, however, has not been determined since tourism is not measured as an economic sector in the national accounts. While for tourism-reliant countries it would be useful to know this quantity, a number of difficulties exist in its determination. In this study, we determine the GHG intensity of tourism's value added in Switzerland by means of a detailed bottom-up approach with the main methodological focus on how to achieve consistent system boundaries. For comparison, we calculate the tourism sector's GHG intensity for selected European countries using a simpler top-down approach. Our results show that the Swiss tourism sector is more than four times more GHG intensive than the Swiss economy on average. Of all tourism's sub-sectors, air transport stands out as the sector with by far largest emissions (80%) and highest GHG intensity. The results for other countries make similar, if not as pronounced, patterns apparent. We discuss the results and possible mitigation options against the background of the goal to prevent dangerous climate change. 相似文献
828.
Investigation at the scene of a crime begins with the search for clues. In the case of bloodstains, the most frequently used
reagents are luminol and reduced phenolphthalein (or phenolphthalin that is also known as the Kastle–Meyer colour test). The
limitations of these reagents have been studied and are well known. Household cleaning products have evolved with the times,
and new products with active oxygen are currently widely used, as they are considered to be highly efficient at removing all
kinds of stains on a wide range of surfaces. In this study, we investigated the possible effects of these new cleaning products
on latent bloodstains that may be left at a scene of a crime. To do so, various fabrics were stained with blood and then washed
using cleaning agents containing active oxygen. The results of reduced phenolphthalein, luminol and human haemoglobin tests
on the washed fabrics were negative. The conclusion is that these new products alter blood to such an extent that it can no
longer be detected by currently accepted methods employed in criminal investigations. This inability to locate bloodstains
means that highly important evidence (e.g. a DNA profile) may be lost. Consequently, it is important that investigators are
aware of this problem so as to compensate for it.
相似文献
Fernando Verdú (Corresponding author)Email: |
829.
Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO2 mixing ratios. Meteorological observations were obtained from a RASS sodar and CO2 mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread
over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two
classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation,
and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this
paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between
the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale
partially with recirculation. CO2 observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily
described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO2 mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal
of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing
ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high.
A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided
a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby
cities. 相似文献
830.
Sofía Copello Ana I. Dogliotti Domingo A. Gagliardini Flavio Quintana 《Marine Biology》2011,158(6):1247-1257
The study of how and why marine animals distribute themselves at sea has important conservation and management implications
of the species and their habitats. We characterize the oceanographic and biological landscapes of the marine areas used by
breeding Southern Giant Petrels (Macronectes giganteus) at Patagonian colonies and explore inter-sexual and inter-colony differences. The at-sea movements of 16 adults (7 males
and 9 females) were studied by means of satellite telemetry techniques during 1999, 2000, 2002, and 2004 breeding seasons.
Southern Giant Petrels utilized an oceanographic scenario characterized by high productivity, warm sea surface temperature,
and shallow waters. The biological landscape was characterized by a high availability of squid and carrion nearby colonies.
Females spent more time in the shelf break and exploited deeper waters than males. In contrast, males spent more time in coastal
areas and they showed a higher spatial overlap with areas of high squid density than females. Such a prosperous foraging scenario
for both sexes may play a key role in the growth of the breeding population of Southern Giant Petrel Patagonian colonies. 相似文献