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11.
Russell LM Rasch PJ Mace GM Jackson RB Shepherd J Liss P Leinen M Schimel D Vaughan NE Janetos AC Boyd PW Norby RJ Caldeira K Merikanto J Artaxo P Melillo J Morgan MG 《Ambio》2012,41(4):350-369
Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some regions. Two types of geoengineering activities that have been proposed are: carbon dioxide (CO(2)) removal (CDR), which removes CO(2) from the atmosphere, and solar radiation management (SRM, or sunlight reflection methods), which reflects a small percentage of sunlight back into space to offset warming from greenhouse gases (GHGs). Current research suggests that SRM or CDR might diminish the impacts of climate change on ecosystems by reducing changes in temperature and precipitation. However, sudden cessation of SRM would exacerbate the climate effects on ecosystems, and some CDR might interfere with oceanic and terrestrial ecosystem processes. The many risks and uncertainties associated with these new kinds of purposeful perturbations to the Earth system are not well understood and require cautious and comprehensive research. 相似文献
12.
Mary B. Janicki Christopher G. Fernandez Dorothy Wakefield Jonathan P. Shepherd Reinaldo Figueroa 《黑龙江环境通报》2020,40(2):223-231
To determine if using a checklist of specific ultrasound image criteria to screen the fetal heart improves the cardiac exam completion rate, defined as the ability to classify the heart as normal or abnormal. This is a retrospective cohort study of patients with singleton pregnancies who underwent a fetal anatomy survey between 18 and 28 weeks' gestation. A checklist was used from 1 September 2015 to 31 March 2016 to categorize exams as complete-normal, complete-abnormal, or incomplete. Performance was compared with a 7-month period prior to checklist introduction (1 December 2014 to 30 June 2015). Checklist utilization improved the cardiac exam completion rate by 8.9%. With the checklist, 1083 of 1202 exams (90.1%) were completed compared to 987 of 1193 (82.7%) pre-checklist, P < .001. We did not detect a change in cases classified as abnormal and referred for echocardiography: 25 (2.1%) with the checklist and 16 (1.3%) pre-checklist, P = .16. We did not detect more congenital heart disease (CHD), 12 (1.0%) with checklist screening, 5 (0.4%) pre-checklist, P = .14. Critical CHD was not missed in either group. Using the checklist improved the cardiac exam completion rate. There was no change in congenital heart disease detection. 相似文献
13.
To examine the impact of development rate on swimming performance, escape response, and morphology, yolk-sac larvae of American
plaice (Hippoglossoides platessoides, Fabricius) were reared at two temperatures (5 and 10 °C). Videomicroscopy and silhouette collimation videography were used
to examine swimming, escape behaviour, and morphology (standard length, finfold area, and yolk-sac area) of individual larvae.
Larvae were examined from 0 d post hatch (dph) to 14 dph for the 5 °C treatment group and from 0 to 6 dph for the 10 °C treatment
group (3 August to 17 August 1996). Since larvae were not fed, yolk-sac reserves were essentially exhausted by 14 and 6 dph
for the 5 and 10 °C treatment groups, respectively. To control for the effect of testing temperature on behaviour, larvae
from each temperature treatment were tested at both 5 and 10 °C. Testing temperature had an effect on some swimming parameters
but not on escape response. Swimming performance, escape response, and morphology varied with age, while only morphology and
escape response varied with development rate. Morphology and swimming performance, and morphology and escape response were
found to be correlated as determined by canonical correlation. This study suggests that both types of swimming behaviours
should be examined when developing models of the impacts of predation on the early life history of larval fish.
Received: 13 September 1999 / Accepted: 21 June 2000 相似文献
14.
The concentration of glutamine in Tridacna gigas haemolymph increased >35-fold following exposure to sea water supplemented with ammonium (20 μM), but no increase was observed with nitrate (20 μM). Lack of a diel cycle, no decrease in haemolymph glucose levels, the expression patterns of glutamine synthetase in zooxanthellae
and host, and the lack of glutamine release in response to nitrate supplementation all support the proposition that the increase
in haemolymph glutamine is a product of the host and not the zooxanthellae. Unlike ammonium, nitrate accumulates rapidly in
the haemolymph. It has no effect on the concentration of glutamine in the haemolymph, but there is an increase in arginine,
histidine and lysine in the haemolymph, suggesting the release of these essential amino acids from zooxanthellae. Glutamine
synthetase (GS) activity decreased markedly in the gill and less so in the mantle over a period of 6 d exposure to elevated
ammonium (20 μM). In contrast, GS activity in zooxan- thellae doubled. The response of zooxanthellae in situ was confirmed by incubating
freshly isolated zooxanthellae for 4 d in ammonium, which resulted in a ten-fold increase in GS activity. Comparison of the
in situ response of zooxanthellae with that obtained in vitro indicates that the symbionts are likely to be exposed to ammonium
concentrations lower than that found in the haemolymph.
Received: 14 November 1997 / Accepted: 28 April 1998 相似文献
15.
McDonald K Shepherd M 《Journal of the Air & Waste Management Association (1995)》2004,54(9):1061-1068
Canada has recently established standards for the management of particulate matter (PM) air quality. National networks currently measure PM mass concentrations and chemical speciation. Methods used in the U.S. IMPROVE network are applied to the 1994--2000 Canadian fine PM data to obtain a regional reconstruction of the visibility based on particle composition. Nationally, the greatest light extinction occurs in the Windsor-Quebec City corridor. Variations in the dominant chemical species responsible for the reduction in visibility are presented for regions across the country. In most regions, sulfate and nitrate contribute most greatly to reduced visibility. The visibility implications of achieving the Canada-Wide Standard (CWS) across the country are evaluated, with the greatest improvement in visibility associated with achieving the CWS in southern Ontario. Elsewhere in the country, achieving the CWS will actually result in deteriorating air quality. Improving current estimates of visibility requires higher spatially and temporally resolved measurements of organic and elemental carbon fractions and particulate nitrate. 相似文献
16.
Determinants of consumer behavior related to organic foods 总被引:1,自引:0,他引:1
There have been many studies of what influences consumers in their decisions to purchase or consume organic foods, mainly concerned with fresh organic foods. These show a discrepancy between attitudes and behavior with people being positive about organic foods but often not purchasing them. This discrepancy seems to be explained by the fact that consumers do not consider "organically produced" to be an important purchase criterion, that organic foods are not perceived to surpass conventional foods regarding taste and shelf life (two qualities rated to be of great importance), and because of the perceived premium prices of organic foods. In two Swedish studies, health benefits were demonstrated to be more strongly related to attitudes and behavior toward organic foods than were perceived environmental benefits. A new European Union (EU) project will investigate the influences on both fresh and processed organic foods and investigate the role of moral, ethical, and affective influences on choice across eight EU countries. 相似文献
17.
Climate change can cause significant (un)foreseen changes in the fisheries sector. However, adaptation has the potential to moderate some of the impacts. This paper explores the challenges faced by both freshwater and marine fisheries sector in addressing climate change and teases out intervention measures from 21 African countries. The paper uses document analysis and draws selected analysis parameters from the grounded theory. The data are obtained from the United Nations Framework Convention on Climate Change National Communication reports. Among the key adaptation measures emerging from the analysis are: fish breeding, integrated coastal management, putting in place appropriate policies, water and flood management as well as research and development. The study concludes that adaptation in the African fisheries sector should be prioritised, an aspect that could also apply elsewhere in the world to enhance food security. 相似文献
18.
Given the substantial impact that new ventures have on the global economy, understanding what motivates entrepreneurs is of both practical and theoretical importance. Although research on the nature, causes, and consequences of entrepreneurial motivation has grown rapidly, it has evolved in distinct theoretical silos that tend to isolate motives based on the phase of business development (e.g., initiation, growth, and exit) rather than acknowledge that individuals often traverse all these phases and experience multiple types of motivation throughout their entrepreneurial journey. To advance the study of motivation in the fields of entrepreneurship and organizational behavior and provide a means through which these advancements can contribute to our understanding of how motivation drives the start-up, growth, and exiting of businesses, we organize and review the extant literature on entrepreneurial motives based on the phases of the new venture process. In doing so, this article develops a roadmap of the current state of entrepreneurial motivation research and its nomological network and provides suggestions to guide future research in extending our understanding of motivation in the entrepreneurship domain as well as in traditional organizational settings. 相似文献
19.
20.
Modeling China's semiconductor industry fluorinated compound emissions and drafting a roadmap for climate protection 总被引:1,自引:0,他引:1
Scott C. Bartos Nina Kshetry C. Shepherd Burton 《International Journal of Greenhouse Gas Control》2008,2(4):665
Fluorinated compounds (FC) are high-global warming potential (GWP) greenhouse gases used and emitted during the manufacture of silicon semiconductor devices. Following the U.S. EPA's PFC Emissions Vintage Model (PEVM), uncontrolled FC emissions are modeled as proportional to total manufactured layer area (TMLA) of silicon. FC emissions of World Semiconductor Council (WSC) charter member countries (Europe, Japan, Korea, Taiwan and the United States), which voluntarily committed in 1999 to lower FC emissions by 2010 to 10% of baseline year emissions, are modeled for the period 1995–2020. For this same period, emissions from Chinese manufacturers under alternative emission reduction scenarios are modeled. If Chinese manufacturers were to adopt a baseline year of 2005 and a reduction target of 10% below baseline year emissions to be achieved by 2020, emissions would be 3.4 MMTCO2eq, comparable to the similarly projected controlled emissions of an average WSC charter member country (=16.3/5 MMTCO2eq) in 2020. The relative stringency of the alternative reduction scenarios considered for China vary between 50 and 95% reduction compared to business as usual (BAU). This is comparable to the stringency of the WSC charter members’ goals for which FC emission reduction technologies are currently available. 相似文献