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281.
Bioenergetics of ephyra larvae of the scyphozoan jellyfish Aurelia aurita in relation to temperature and salinity 总被引:3,自引:0,他引:3
The body mass of Aurelia aurita ephyrae was better correlated with the diameter of the central disc than with the distance between opposite rhopaliae or
distance between opposite lappet tips. Body dry weight (y, in μg) related to the disc diameter (x, in mm) through the equation y = 22.33 x
1.99. The exponent 1.99 was significantly lower than that for the medusa stage, indicating a tendency to grow in diameter rather
than in weight through the ephyra stage. The average ash-free dry weight (AFDW) of ephyrae was 38.0% of the dry weight. The
AFDW/diameter relationship was used to convert measured diameters to body AFDW and calculate succession in body mass, daily
ration, daily growth rate and gross growth efficiency. Effects of temperature (6, 9.5, 12, 15 and 18 °C) and salinity (17.5,
22, 26, 30.5 and 35 PSU) on these parameters and feeding were studied at saturated prey concentration (222 Artemia nauplii l−1 initial concentration) by daily measurements over 10 d. There was a strong effect of temperature for total ingestion, growth
rate, growth efficiency and final body mass of individual ephyrae, whereas the daily ration was not significantly different
between the different temperatures. The experimental group kept at the highest temperature (18 °C) diverged the most, and
ephyrae at this temperature ingested 2.7 times more and increased in weight 5.4 times more than at 6 °C. The average daily
growth rate and gross growth efficiency of these ephyrae were 34.5% and 25.1%, respectively, significantly higher than at
6, 9.5 and 15 °C. Significant effects of salinity were shown for total ingestion, daily ration, daily growth rate and final
weight, although only total ingestion and daily ration diverged sufficiently to show effects in a post-hoc test. This test
showed that total ingestion was significantly different for all salinities except between 22 and 35 PSU and between 17.5 and
26 PSU. The daily ration for 35 PSU diverged from all other salinities, whereas none of the other salinities showed any significant
differences. Thus, provided food in excess A. aurita can double its weight every 2 to 4 d, dependent on temperature and can therefore develop to the medusa stage in short time.
Differences in environmental salinity in the range 17.5 to 35 PSU have little or no effect on growth rate and growth efficiency,
whereas our results indicate that the full seawater salinity (35 PSU) causes significantly higher ingestion rate compared
to lower salinities.
Received: 11 January 1999 / Accepted: 11 May 1999 相似文献
282.
The purpose of this study was to examine the potential of a native wild bird, Lagopus lagopus, as a monitor of environmental metal levels, in particular with respect to the influence of atmospheric deposition of metals from long-range transport. Specimens of willow ptarmigan were collected from ten different locations in Norway. The concentrations of cadmium, zinc and copper were determined in kidneys of birds from all sites. Mean cadmium levels in adult ptarmigan kidney ranged from 6.6 to 48.5 microg g(-1) (wet weight), with individual concentrations up to 71.0 microg g(-1). These are among the highest cadmium levels reported in wild birds. The kidneys of adult birds contained 3-10 times higher cadmium levels than kidneys from juvenile birds in the same collection area, and most of the high cadmium levels probably reflect natural exposure, rather than atmospheric pollution. Concentrations of elements in kidney tissues were highly correlated with each other. 相似文献
283.
Summary Evidence suggests that males incur costs in producing ejaculates. Therefore some discrimination should be expected with respect to their pattern of allocating ejaculates. In a laboratory study, males of the European swallowtail butterfly Papilio machaon were mated with conspecific virgin females up to six times. The weight of the spermatophore and of the accessory substances delivered by males, the duration of mating, and the number of sperm in ejaculates were measured. The weight of the first spermatophore was related to male weight but that of accessory substances was not. The weight of the spermatophore delivered by males upon remating was always less than that of the first spermatophore. Second spermatophores Produced by males were smallest when delivered on the day after the first mating and increased asymptotically to about half the initial size with time elapsed since the first mating. Copula duration was highest for males remating on the day after the first mating but decreased to the duration of the first mating for males that were remated on the third day after the first mating or later. The weight of accessory substances delivered by males and the number of sperm in ejaculates were also higher in first matings compared to all subsequent matings. Both of two males that were handpaired on three consecutive days after the first mating produced a cumulative ejaculate mass equalling that transferred at the first mating. Thus the fact that males delivered smaller ejaculates upon remating on the third day after the first mating or later requires explanation, especially in view of the fact that copulations were not prolonged. We argue that the male ejaculate delivery strategy in mildly polyandrous species should be to mate for the first time with virgin females, when a maximum size ejaculate should be delivered, and then to maximize the number of matings. The rationale behind the male shift towards smaller ejaculate sizes delivered at subsequent matings is that: (1) the size of the ejaculate that can be produced is dependent on the time elapsed since the last mating; (2) the abundance of virgin females decreases as the flight season proceeds; and (3) there is an inverse relationship between the size and number of ejaculates that a male can produce in his life-time. 相似文献
284.
In a short-term (162 h) accumulation experiment with mussels Mytilus edulis exposed to 100 ppb Cd and fed algal cells (Phaeodactylum tricornutum) in 1986, it was found that uptake via food played an insignificant role compared to direct uptake from ambient water (19 S). From measurements of the filtration rate and Cd uptake rate, it was estimated that the fraction of Cd taken up per liter of water filtered was about 0.15%. The initial uptake of Cd was linear with time and about three times higher in fed than in starved mussels. From the measured uptake of Cd in starved mussels collected in 1982 and exposed to 10, 100 and 200 ppb in long-term experiments (up to 242 d), it was found that the Cd Accumulation rate was not linear with time, and that the Cd uptake was not directly proportional with the exposure concentration. Values as high as 100 to 1 300 ppm Cd (dry wt of soft parts) were measured. It was found that the Cd elimination rate was not directly proportional with the Cd body burden in long-term exposed mussels, thus indicating that a certain fraction of Cd may have been immobilized to metallothioneins. 相似文献
285.
Filtration rate,using a new indirect technique,in thirteen species of suspension-feeding bivalves 总被引:14,自引:0,他引:14
A method for determining filtration rates in undisturbed suspension-feeding bivalves is described. Concentrations of particulate matter in the water collected in the inhalant (C
i) and exhalant (C
e) currents were estimated with an electronic particle counter. The clearance was calculated as
, where Fl=flow rate through the tube collecting exhalant water. Only above critical levels of water flow (Fl) were clearances representative of filtration rates. At 10° to 13°C, the filtration rates (F, 1 h-1) within one or two orders of magnitude of dry weight (w, g), in Cardium echinatum L., C. edule L., Mytilus edulis L., Modiolus modiolus (L.) and Arctica islandica (L.) followed the allometric equations: 4.22w
0.62, 11.60w
0.70, 7.45w
0.66, 6.00w
0.75 and 5.55w
0.62, respectively. Five species of bivalves [Spisula subtruncata (da Costa), Hiatella striata (Fleuriau), Cultellus pellucidus (Pennant), Mya arenaria L. and Venerupis pullastra (Montagu)] filtered with the same rates as individuals of Cardium echinatum and A. islandica of equivalent soft weight. In Pecten furtivus and P. opercularis filtration rates were about twice the rates measured in individuals of Mytilus edulis of comparable body weight. The gill area in M. edulis increases with size at the same rate as the filtration rate. 相似文献
286.
Accumulation rates of Cd have been studied in the common mussel Mytilus edulis L. under different laboratory conditions. Semi-static and through-flow experiments were carried out at Cd concentrations of 200 ppb and 50/100 ppb in the water, respectively. A linear uptake of Cd throughout the experimental periods of 36 or 124 d was found in all experiments. The accumulation rate was 3.10 ppm d-1 at 50 ppb in the through-flow water experiment, 4.1 ppm d-1 in starved and 6.6 ppm d-1 in fed mussels in the semi-static experiments with 200 ppb Cd in the water. The Cd-accumulation rate in various fractions of soft parts decreased in the order: body>mantle>muscles. Elution patterns obtained from gel-filtrations showed an increasing amount of Cd-binding proteins (metallothioneins) when the body burden of Cd increased. The Cd content in the body fraction of mussels transferred to clean water for 42 d after first being exposed to Cd during 124 d decreased from 564 ppm on a dry weight basis to 417 ppm while the fraction of Cd bound to metallothioneins rose from 22 to 78% during the same period. 相似文献
287.
The very potent greenhouse gas nitrous oxide (N2O) is widely used as a mild anaesthetic for mothers in delivery work in Sweden. As a part of the Stockholm County Council environmental program it was decided in 2002 that the emissions should be drastically reduced. Different ways were theoretically evaluated, and catalytic splitting to nitrogen and oxygen gas (N2 and O2) was chosen for a demonstration installation. A Japanese commercial unit for treatment of mixed anaesthetic gases (Anesclean® from Showa Denko K.K.) was thoroughly modified and installed at the Karolinska University Hospital at Huddinge in Stockholm in 2004. The destruction of N2O was optimised and studied for 2 years. Data from both collection and destruction are given in the article. Of the collected N2O more than 95% was split to N2 and O2 in the very stable system. The overall emission decrease was mainly dependent on the share that could be collected in the specific exhaustion system as compared to the normal room ventilation. Life cycle assessment (LCA) and life cycle costing (LCC) were used to evaluate the actual environmental value and economical cost for the process. Important factors are pointed out. 相似文献
288.
Atmospheric mercury at mediterranean coastal stations 总被引:2,自引:0,他引:2
Ingvar Wängberg John Munthe David Amouroux Maria E. Andersson Vesna Fajon Romano Ferrara Katarina Gårdfeldt Milena Horvat Yaacov Mamane Ety Melamed Mathilde Monperrus Nives Ogrinc Osnat Yossef Nicola Pirrone Jonas Sommar Francesca Sprovieri 《Environmental Fluid Mechanics》2008,8(2):101-116
Mercury in air has been measured at five coastal Mediterranean sites, involving measurements in Spain, France, Italy, Slovenia and
Israel. Four two-weeks long measurements campaigns were performed at the five sites. The measurements were carried out during
autumn 2003 and winter, spring and summer 2004. Total gaseous mercury/elemental gaseous mercury, particulate mercury and divalent
gaseous mercury were measured in parallel at the five sites. The activities constituted a subtask of the EU funded MERCYMS
research project, which also included Mediterranean Sea cruises where both mercury in air and water were measured. The result
from an evaluation of all the coastal air data is presented. Mercury concentrations from the different sites are compared
with similar data obtained in northern Europe and elsewhere. The result shows that the background concentration of mercury
in Mediterranean coastal air is lower than earlier anticipated. Background concentrations of TGM, RGM and TPM corresponded
to 1.75–1.80 ng m−3, 1–13 and 3–23 pg m−3, respectively. The measurements also showed that the mercury concentration occasionally can be very high in some areas due
to local anthropogenic emissions. It is proposed that diurnal variation in RGM concentrations observed during situation with
nocturnal inversion merely is an effect of meteorology rather than due to local photochemistry. 相似文献
289.
The synthesis of the BONUS+ research is introduced. The HELCOM Baltic Sea Action Plan is examined as a case to illustrate the potentials and challenges in building the science–policymaking interface on a macroregional level. The projects address environmental challenges in the Baltic Sea as defined by the Baltic Sea Action Plan, or consider the environmental governance and decision making within the Baltic Sea context in general. Eutrophication, biodiversity, hazardous substances, maritime activities, and the environment governance are addressed, as are crosscutting issues, such as the impact of climate change, maritime spatial planning and impacts of future development on ecosystem services. The projects contributed to relevant policy developments: 37 consultations carried out at EU level, 49 modifications to policy documents and action plans, 153 suggestions for the efficacy of pertinent public policies and governance, and in 570 occasions, scientists working in BONUS+ projects served as members or observers in scientific and stakeholder committees. 相似文献
290.
Belachew Gizachew Rasmus Astrup Pål Vedeld Eliakimu M. Zahabu Lalisa A. Duguma 《Natural resources forum》2017,41(2):92-104
REDD+, a climate change mitigation mechanism that values carbon in tropical forests, is expected to provide Africa with a range of environmental and socio‐economic benefits. Drawing on a vast array of literature and personal experiences, this review analyzed particular features and challenges that REDD+ implementation has faced on the continent. The distinct contexts and major challenges regarding governance, finance and technical capacities are discussed, and mechanisms to fill these gaps are suggested. Radical land tenure reform and a perfect safeguard mechanism that transfers forest land and carbon to the communities are unlikely. REDD+ should rather look for systems that respect local institutional arrangements, and allow forest‐based communities to participate in decision‐making and benefit sharing, particularly benefits from emerging REDD+. Finances for REDD+ infrastructure and the results‐based payment are in short supply. While negotiating for potential external sources in the short term, Africa should generate domestic financial resources and look for additional payments for ecosystem services. Africa should also negotiate for forest monitoring capacity building, while strengthening local community forest monitoring. This review contributes to an improved understanding of the contexts and challenges to consider in the capacity and policy development for REDD+ implementation. 相似文献