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In the Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) process, the spent waste from the electrochemical cell, which is integrated with the scrubber columns, contains high concentrations of precious silver as dissolved ions in both the anolyte and the catholyte. This work presents an electrochemical developmental study for the recovery of silver from simulated waste water from Ag(II)/Ag(I) based MEO process. Galvanostatic method of silver deposition on Ti cathode in an undivided cell was used, and the silver recovery rate kinetics of silver deposition was followed. Various experimental parameters, which have a direct bearing on the metal recovery efficiency, were optimized. These included studies with the nitric acid concentration (0.75-6M), the solution stirring rate (0-1400 rpm), the inter-electrode distance between the anode and the cathode (2-8 cm), the applied current density (29.4-88.2 mA cm(-2)), and the initial Ag(I) ion concentration (0.01-0.2M). The silver recovered by the present electrodeposition method was re-dissolved in 6M nitric acid and subjected to electrooxidation of Ag(I) to Ag(II) to ascertain its activity towards Ag(II) electrogeneration from Ag(I), which is a key factor for the efficient working of MEO process. Our studies showed that the silver metal recovered by the present electrochemical deposition method could be reused repeatedly for MEO process with no loss in its electrochemical activity. Some work on silver deposition from sulfuric acid solution of different concentrations was also done because of its promising features as the catholyte in the Ag(II) generating electrochemical cell used in MEO process, which include: (i) complete elimination of poisonous NO(x) gas liberation in the cathode compartment, (ii) reduced Ag(+) ion migration across Nafion membrane from anolyte to catholyte thereby diminished catholyte contamination, and (iii) lower cell voltage and hence lesser power consumption. 相似文献
223.
There is a long and rich history of research on the concept of leader emergence. Much of this research positions leader emergence alongside leadership effectiveness as an epiphenomenal criterion in leadership research. Although this view has enhanced our understanding of factors that influence leader emergence and leadership effectiveness individually, our understanding of the potential alignment or misalignment of these concepts remains opaque. Following from this, we are left with unanswered questions concerning how, why, and under what conditions do the right or wrong leaders emerge or fail to emerge. Theory that develops insights into these questions is needed to advance our understanding of leadership and to cope with challenges of identifying and developing effective leaders and maximizing leadership potential in organizations. By integrating theories of leader emergence and leadership effectiveness—and considering their implications jointly—we provide a conceptual basis for identifying and understanding a more complete range of leader emergence than has been suggested in the literature. Importantly, our theoretical frame explains how our leader emergence types—over-emergence, under-emergence, congruent emergence, and congruent non-emergence—are differentially associated with a common set of factors. In doing so, we illuminate tradeoffs that might accompany different interventions intended to enhance leadership in organizations. 相似文献
224.
Konstantinos Kostarelos Daniela Reale Dimitris Dermatas Ennio Rao Deok Hyun Moon 《Water, Air, & Soil Pollution: Focus》2006,6(1-2):171-189
The presence of hexavalent chromium, Cr(VI), in soil is an environmental concern due to its effect on human health. The concern
arises from the leaching and the seepage of Cr(VI) from soil to groundwater. In this paper, a stabilization technology to
prevent this problem was simulated on an artificial soil contaminated with hexavalent chromium. The process is a physico-chemical
treatment in which the toxic pollutant is physically entrapped within a solid matrix formed by the pozzolanic reactions of
lime and fly ash to reduce its leachability and, therefore, its toxicity. This paper presents the optimum ratio of fly ash
and lime in order to stabilize artificial soils contaminated with 0.4 wt.% of Cr (VI) in a brief term process. The degree
of chromium released from the soil was evaluated using a modified Toxicity Characteristic Leaching Procedure (TCLP) by US
Environmental Protection Agency (EPA). Overall, experimental results showed reduced leachability of total and hexavalent chromium
from soils treated with both fly ash and quicklime, and that leachability reduction was more effective with increasing amount
of fly ash and quicklime. Stabilization percentages between 97.3% and 99.7% of the initial chromium content were achieved,
with Cr(VI) concentration in the TCLP leachates below the US EPA limit for chromium of 5 mg/l. Adequate treatment was obtained
after 1 day of curing with just 25% fly ash and 10% quicklime. 相似文献
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Thalassa McMurdo Hamilton Stefano Canessa Katie Clark Pani Gleeson Fiona Mackenzie Troy Makan Gena Moses-Te Kani Shona Oliver Kevin A. Parker John G. Ewen 《Conservation biology》2021,35(4):1162-1173
Ko koe ki tēnā, ko ahau ki tēnai kīwai o te kete (you at that, and I at this handle of the basket). This Māori (New Zealanders of indigenous descent) saying conveys the principle of cooperation—we achieve more through working together, rather than separately. Despite decades of calls to rectify cultural imbalance in conservation, threatened species management still relies overwhelmingly on ideas from Western science and on top-down implementation. Values-based approaches to decision making can be used to integrate indigenous peoples’ values into species conservation in a more meaningful way. We used such a values-based method, structured decision making, to develop comanagement of pekapeka (Mystacina tuberculata) (short-tailed bat) and tara iti (Sternula nereis davisae) (Fairy Tern) between Māori and Pākehā (New Zealanders of European descent). We implemented this framework in a series of workshops in which facilitated discussions were used to gather expert knowledge to predict outcomes and make management recommendations. For both species, stakeholders clearly stated their values as fundamental objectives from the start, which allowed alternative strategies to be devised that naturally addressed their diverse values, including mātauranga Māori (Māori knowledge and perspectives). On this shared basis, all partners willingly engaged in the process, and decisions were largely agreed to by all. Most expectations of conflicts between values of Western science and Māori culture were unfounded. Where required, positive compromises were made by jointly developing alternative strategies. The values-based process successfully taha wairua taha tangata (brought both worlds together to achieve the objective) through codeveloped recovery strategies. This approach challenges the traditional model of scientists first preparing management plans focused on biological objectives, then consulting indigenous groups for approval. We recommend values-based approaches, such as structured decision making, as powerful methods for development of comanagement conservation plans between different peoples. 相似文献
229.
Daniel Andres Tim H. Clutton-Brock Loeske E. B. Kruuk Josephine M. Pemberton Katie V. Stopher Kathreen E. Ruckstuhl 《Behavioral ecology and sociobiology》2013,67(8):1249-1258
In several primates, the presence of mothers affects the growth, survival and reproduction of their offspring, but similar effects have not yet been demonstrated in ungulates. Here, we investigate the effects of the mother’s presence in a population of red deer (Cervus elaphus) on the Isle of Rum, Scotland, which is the subject of a long-term, individual-based study. We compared measures of performance including antler growth in young males and age at first reproduction in females and survival of deer with mothers still alive against those that have lost their mothers (orphans). We show that orphaning both before and after weaning increases the risk of a natural death for both sexes. For males, no maternal benefit was detectable past 24 months of age while, for females, post-weaning benefits continued throughout life. Orphaning resulted in compromised male physical condition as measured by a reduced probability of growing antlers by 16 months of age while no evidence for compromised reproduction was found in females. These results support assertions that post-weaning maternal associations affect the development and survival of offspring. 相似文献
230.
Katie E. Slocombe Tanja Kaller Laurel Turman Simon W. Townsend Sarah Papworth Paul Squibbs Klaus Zuberbühler 《Behavioral ecology and sociobiology》2010,64(12):1959-1966
Chimpanzees produce acoustically distinct calls when encountering food. Previous research on a number of species has indicated
that food-associated calls are relatively widespread in animal communication, and the production of these calls can be influenced
by both ecological and social factors. Here, we investigate the factors influencing the production of food-associated calls
in wild chimpanzees and examine whether male chimpanzees produce food-associated calls selectively in the presence of important
social partners. Male chimpanzees form stable long-term social relationships with each other, and these social bonds are vital
in enabling a range of cooperative activities, such as group hunting and territory defence. Our data show that males were
significantly more likely to produce food-associated calls if an important social partner was nearby, regardless of the size
of the audience or the presence of oestrus females. Call production was also mediated by the size of the food patch and by
whether or not the food could be monopolised. The presence of important social partners explained most of the variation in
male calling behaviour, indicating that food-associated calls are socially directed and serve a bonding function. 相似文献