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191.
Using individual‐condition measures to predict the long‐term importance of habitat extent for population persistence
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Habitat loss and fragmentation are causing widespread population declines, but identifying how and when to intervene remains challenging. Predicting where extirpations are likely to occur and implementing management actions before losses result may be more cost‐effective than trying to reestablish lost populations. Early indicators of pressure on populations could be used to make such predictions. Previous work conducted in 2009 and 2010 identified that the presence of Eastern Yellow Robins (Eopsaltria australis) in 42 sites in a fragmented region of eastern Australia was unrelated to woodland extent within 500 m of a site, but the robins’ heterophil:lymphocyte (H:L) ratios (an indicator of chronic stress) were elevated at sites with low levels of surrounding woodland. We resurveyed these 42 sites in 2013 and 2014 for robin presence to determine whether the H:L ratios obtained in 2009 and 2010 predicted the locations of extirpations and whether the previous pattern in H:L ratios was an early sign that woodland extent would become an important predictor of occupancy. We also surveyed for robins at 43 additional sites to determine whether current occupancy could be better predicted by landscape context at a larger scale, relevant to dispersal movements. At the original 42 sites, H:L ratios and extirpations were not related, although only 4 extirpations were observed. Woodland extent within 500 m had become a strong predictor of occupancy. Taken together, these results provide mixed evidence as to whether patterns of individual condition can reveal habitat relationships that become evident as local shifts in occupancy occur but that are not revealed by a single snapshot of species distribution. Across all 85 sites, woodland extent at scales relevant to dispersal (5 km) was not related to occurrence. We recommend that conservation actions focus on regenerating areas of habitat large enough to support robin territories rather than increasing connectivity within the landscape. 相似文献
192.
Steffen KallbekkenStephan Kroll Todd L. Cherry 《Journal of Environmental Economics and Management》2011,62(1):53-64
Tax-aversion reduces the likelihood that price rationing can be a politically viable tool for environmental protection. We examine the case of the classic Pigouvian tax to control a negative externality, and consider how recycling the revenues, labeling of the tax and information about its purpose affects the support for taxation. We test the support for taxation within a single-price market experiment, in which purchases by some buyers impose external costs on others. Observing behavior consistent with tax-aversion, we also find that recycling the revenues to more narrowly targeted groups seems to increase support for taxation. In the absence of narrow revenue recycling, labeling a Pigouvian instrument as a ‘tax’ may significantly lower the likelihood of voter support. 相似文献
193.
P. Vann Bush Todd R. Snyder Ramsay L. Chang 《Journal of the Air & Waste Management Association (1995)》2013,63(3):361-372
Baghouse performance at utility coal-fired power plants is determined by baghouse design, operating procedures, and the characteristics of the ash that is collected as a dustcake on the fabric filter. The Electric Power Research Institute has conducted laboratory research to identify the fundamental variables that influence baghouse performance. A database was assembled including measured characteristics of coal and dustcake ash, and data describing operating parameters and performance of full-scale and pilotscale baghouses. Predictions of performance can be based on physical characteristics of the ash to be filtered (discussed in Part I of this article), as well as chemical characterizations of the ash, or empirical correlations with the alkali content of the source coal The effects of design and operational variables can be included in these predictions. Baghouse performance can be optimized by exercising proper operating practices and by selecting a filtering fabric and cleaning method matched to the cohesivity of the ash to be collected. 相似文献
194.
195.
The origin of viscid capture silk in orb webs, from cribellate silk-spinning ancestors, is a key innovation correlated with significant diversification of web-building spiders. Ancestral cribellate silk consists of dry nanofibrils surrounding a stiff, axial fiber that adheres to prey through van der Waals interactions, capillary forces, and physical entanglement. In contrast, viscid silk uses chemically adhesive aqueous glue coated onto a highly compliant and extensible flagelliform core silk. The extensibility of the flagelliform fiber accounts for half of the total work of adhesion for viscid silk and is enabled by water in the aqueous coating. Recent cDNA libraries revealed the expression of flagelliform silk proteins in cribellate orb-weaving spiders. We hypothesized that the presence of flagelliform proteins in cribellate silk could have allowed for a gradual shift in mechanical performance of cribellate axial silk, whose effect was masked by the dry nature of its adhesive. We measured supercontraction and mechanical performance of cribellate axial silk, in wet and dry states, for two species of cribellate orb web-weaving spiders to see if water enabled flagelliform silk-like performance. We found that compliance and extensibility of wet cribellate silk increased compared to dry state as expected. However, when compared to other silk types, the response to water was more similar to other web silks, like major and minor ampullate silk, than to viscid silk. These findings support the punctuated evolution of viscid silk mechanical performance. 相似文献
196.
Despite an array of policies at the federal and state level aimed at regulating stormwater discharges, engineered solutions
enforced by local governments often fall short of meeting water quality standards. Although the implications of land use planning
and development regulations are important for stormwater management, they are often overlooked as critical initial steps to
improving water quality. This study explores the role of ‘form-based’ regulations as tools for achieving urban planning and
water quality objectives. Form-based codes are a new generation of development codes aimed at regulating urban development
based on urban form and density, rather than land use. We present an exploratory case study of the feasibility of form-based
codes in the Jordan Lake Watershed in North Carolina, a rapidly growing region where fragmented local governments face stringent
nutrient reduction standards under new state regulations. Through program analysis and interviews, we explore the viability
of form-based codes for reducing development impacts on Jordan Lake’s water quality. We consider the legal feasibility of
code enforcement, regional and local barriers and opportunities, and implementation given existing regulatory frameworks.
Our findings suggest that high quality information and data modeling are foundational to gaining support for a consensus agreement
on the sources and degree of water quality impairment. Furthermore, implementing form-based solutions for water quality is
greatly aided by (1) experienced regional planning bodies that have regulatory authority, and (2) local governments whose
staff are experienced in implementing complex development ordinances, reviewing architectural renderings, and communicating
development requirements with the public and developers. 相似文献
197.
Population distribution and structure of the free-living nematodes of Long Island Sound 总被引:2,自引:0,他引:2
J. H. Tietjen 《Marine Biology》1977,43(2):123-136
The distribution and structure of nematode populations in 4 sedimentary environments (muds, muddy sands, fine sands and medium-coarse sands) in Long Island Sound were studied. Mean population densities were highest in muds and muddy sands. Cluster analysis suggested the presence of two basic faunistic units; a mud unit characterized by high species dominance, low species diversity and low species endemism, and a sand unit characterized by low species dominance, high species diversity and high species endemism. Species diversity in all habitats was a direct function of both species richness and equitability. Limited niche separation among deposit feeders, usually the dominant nematode trophic type in muddy sediments, is proposed as the cause for the high species dominance so often characteristic of shallow marine muds. The study afforded the opportunity to examine the quantitative and qualitative aspects of population structure in relation to environmental impact (as indicated by large differences in the heavy metal and organic carbon concentrations within each of the 4 sedimentary regimes). Within each sediment type no differences in population densities, species composition or species diversity of nematodes existed between heavily impacted and apparently non-impacted sediments, or between Long Island Sound and similar coastal regions. These findings cast doubt on (1) the use of heavy metal and organic carbon concentrations as indicators of environmental stress for marine nematodes; (2) the use of diversity indices alone as indicators of environmental deterioration; and (3) the usefulness of field monitoring studies alone for the assessment of pollution impact on marine nematodes.Contribution no. 100 from the Institute of Marine and Atmospheric Sciences, City College of New YorkCommunicated by M.R. Tripp, Newark 相似文献
198.
Summary This study tests the general prediction that discrimination among potential mates increases with the availability of potential mates. Specifically, we conducted two experiments that examined mate choice by male zaprochiline katydids in relation to their prior encounter rate with females. The probability of mate acceptance or rejection was measured for males given either frequent or no contact with females in the laboratory (experiment 1) and males taken directly from natural areas of either high or low female abundance (experiment 2). In both experiments, males with low female encounter rates were more likely to mate than males with high female encounter rates. In both cases, the decreased mating probability of males in the high encounter treatment resulted from their tendency to reject lighter (and less fecund) females. Despite the presumed advantage to males of selecting heavier females, field data indicate that, unlike females, males do not aggregate in rich food patches. Possible explanations for this finding are discussed.
Offprint requests to: T.E. Shelly at the present address 相似文献
199.
Daniel R. Fuka M. Todd Walter Charlotte MacAlister Tammo S. Steenhuis Zachary M. Easton 《Journal of the American Water Resources Association》2014,50(5):1349-1353
The Soil and Water Assessment Tool (SWAT) model (Arnold et al., 1998) is a popular watershed management tool. Currently, the SWAT model, actively supported by the U.S. Department of Agriculture and Texas A&M, operates only on Microsoft® Windows, which hinders modelers that use other operating systems (OS). This technical note introduces the Comprehensive R Archive Network (CRAN) distributed “SWATmodel” package which allows SWAT 2005 and 2012 to be widely distributed and run as a linear model‐like function on multiple OS and processor platforms. This allows researchers anywhere in the world using virtually any OS to run SWAT. In addition to simplifying the use of SWAT across computational platforms, the SWATmodel package allows SWAT modelers to utilize the analytical capabilities, statistical libraries, modeling tools, and programming flexibility inherent to R. The software allows watershed modelers to develop a simple hydrological watershed model conceptualization of the SWAT model and to obtain a first approximation of the minimum expected results a more complicated model should deliver. As a proof of concept, we test the SWAT model by initializing and calibrating 314 U.S. Geological Survey stream gages in the Chesapeake Bay watershed and present the results. 相似文献
200.
Adsorption and release of perchlorate in a variety of soils, minerals, and other media were studied when the solid media were exposed to low and high aqueous solutions of perchlorate salts. Low level ClO4- exposure was investigated by subjecting triplicate 5.0 g portions of a solid medium (38 different soils, minerals, or dusts) to 25 mL of an aqueous ammonium perchlorate (NH4ClO4) solution containing 670 ng mL(-1) (6.8 microM) perchlorate. This corresponds to a perchlorate-to-soil ratio of 3.4 microg g(-1) (34 nmol g(-1)). At this level of exposure, more than 90% of the perchlorate was recovered in the aqueous phase, as determined by ion chromatography. In some cases, more than 99% of the perchlorate remained in the aqueous phase. In some cases, the apparent loss of aqueous perchlorate was not clearly distinguishable from the variation due to experimental error. The forced perchlorate anion exchange capacities (PAECs) were studied by soaking triplicate 5.0 g portions of the solid media in 250 mL of 0.20 M sodium perchlorate (NaClO4) followed by repeated deionized water rinses (overnight soaks with mixing) until perchlorate concentrations fell below 20 ng mL(-1) in the rinse solutions. The dried residua were leached with 15.0 mL of 0.10 M sodium hydroxide. The leachates were analyzed by ion chromatography and the perchlorate concentrations thus found were subsequently used to calculate the PAECs. The measurable PAECs of the insoluble and settleable residua ranged from 4 to 150 nmol g(-1) (micromol kg(-1)), with most in the 20-50 nmol g(-1) range. In some soils or minerals, no sorption was detectable. The mineral bentonite was problematic, however. Overall, the findings support the widely accepted idea that perchlorate does not appreciably sorb to soils and that its mobility and fate are largely influenced by hydrologic and biologic factors. They also generally support the idea that intrasoil perchlorate content is depositional rather than sorptive. On the other hand, sorption (anion replacement) of perchlorate appears to occur in some soils. Therefore, the measurement of perchlorate in soils requires accounting for ion exchange phenomena; leaching with water alone may give inaccurate results. If perchlorate anion exchange is confirmed to be negligible, then leaching procedures may be simplified accordingly. 相似文献