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521.
522.
William C. Anderson Sukanta Basu Chris W. Letchford 《Environmental Fluid Mechanics》2007,7(3):195-215
Several non-dynamic, scale-invariant, and scale-dependent dynamic subgrid-scale (SGS) models are utilized in large-eddy simulations
of shear-driven neutral atmospheric boundary layer (ABL) flows. The popular Smagorinsky closure and an alternative closure
based on Kolmogorov’s scaling hypothesis are used as SGS base models. Our results show that, in the context of neutral ABL
regime, the dynamic modeling approach is extremely useful, and reproduces several establised results (e.g., the surface layer
similarity theory) with fidelity. The scale-dependence framework, in general, improves the near-surface statistics from the
Smagorinsky model-based simulations. We also note that the local averaging-based dynamic SGS models perform significantly
better than their planar averaging-based counterparts. Lastly, we find more or less consistent superiority of the Smagorinsky-based
SGS models (over the corresponding Kolmogorov’s scaling hypothesis-based SGS models) for predicting the inertial range scaling
of spectra. 相似文献
523.
Summary The linked gas chromatographical/electroan-tennogram (GC/EAG) technique revealed that the parasitic reindeer nose bot fly is able to specifically sense components produced by the interdigital pheromone gland of reindeer. The head-space extraction technique, with Porapak Q as the collecting polymer, was used to trap pheromone gland and urine components used to assess fly responses. One component from reindeer urine also was a potent stimulus for the sensory neurons of the fly. These components can be important chemical signals to the flies for long distance orientation towards host animals. This is the first report on EAG in Oestridae. 相似文献
524.
David R. Anderson Gary C. White Kenneth P. Burnham 《Environmental and Ecological Statistics》1995,2(2):91-115
We present three empirical methods for risk assessment in field studies of free-ranging vertebrates. First, we advocate statistical inference concerning population recruitment or mortality in response to ecological hazards. Second, if inferences about both recruitment and mortality are available, one can use a Leslie- Lefkovitch matrix to estimate the finite rate of population change () as a function of ecological hazards. Third, designed experiments can be conducted on samples of marked animals in natural environments to assess impacts and risks. These methods rely on either sophisticated capture-recapture or radio-tracking models, and on well-developed analysis theory. The use of uniquely marked animals is somewhat analogous to the use of tracers in other areas of risk assessment. We present examples of each approach and discuss some limitations. 相似文献
525.
Environmental Cleanliness as a Public Good: Welfare and Policy Implications of Nonconvex Preferences
Siwan Anderson Patrick Francois 《Journal of Environmental Economics and Management》1997,34(3):256-274
This paper explores the implications of a form of nonconvexity in individual preferences over the public good “cleanliness.” The implications of this nonconvexity on equilibrium outcomes, welfare analysis, the process of development, and optimal government policy are examined. The nonconvexity can imply a role for government in providing a commitment to a clean environment even if the government has a cost disadvantage in cleaning compared with individuals. By providing a credible commitment to a clean environment the government can induce private individuals to undertake optimal levels of cleaning on their own. 相似文献
526.
Uptake of organic material by aquatic invertebrates. VI. Role of epiflora in apparent uptake of glycine by marine crustaceans 总被引:1,自引:0,他引:1
Soft-bodied marine invertebrates from most invertebrate phyla are capable of taking up amino acids from seawater. Marine crustaceans were originally reported not to accumulate amino acids. Artemia salina, Limnoria tripunctata, Tigriopus californicus, and Corophium acherusicum were examined for their ability to accumulate C14-labelled glycine from dilute solution in seawater. In initial experiments with Artemia and Limnoria the organisms were found to become very radioactive. When animals were preincubated in streptomycin or in a mixture of antibiotics, uptake of the C14-glycine was drastically reduced. Microorganisms associated with the arthropods and in the culture media were found capable of accumulating C14-labelled glycine. Efforts to demonstrate removal of amino acids from seawater by colorimeteric determination of material remaining in the medium were unsuccessful. The microorganisms responsible for the uptake are apparently associated with the exoskeleton of the organisms and not the gut. There is probably no substantial contribution to the nutrition of these crustaceans by the epiflora. Preincubation in the antibiotic mixture depressed the uptake of C14-glucose and C14-acetate by about an order of magnitude. It is concluded that there is no evidence for accumulation or assimilation of small organic compounds by the small crustaceans examined. 相似文献
527.
Life cycle changes that allow populations of the toxic dinoflagellate Gonyaulax tamarensis Lebour to inhabit the benthos and the plankton alternately are important factors regulationg the initiation and decline of blooms in restricted embavments. When the dynamics of these estuarine populations were monitored during “bloom” and “non bloom” years, it was shown that: (1) each year, germination of benthie cysts inoculated the overlying waters during the vernal warming period, but a large residual population remained in the sediments throughout the blooms; (2) the resulting planktonic population began growth under suboptimal temperature conditions; (3) the populations developed from this inoculum through asexual reproduction until sexuality (and cyst formation) were induced; (4) encystment was not linked to any obvious environmental cue and occurred under apparently optimal conditions; and (5) an increase in the number of non-mitotic swimming cells (planozygotes, the precursors to dormant cysts) accompanied the rapid decline of the planktonic population. Thus encystment, in combination with hypothesized losses due to advection and grazing, contributed substantiatly to the decline of the vegetative cell population. We conclude that the encystment/excystment cycle temporally restricts the occurrence of the vegetative population and may not be optimized for rapid or sustained vegetative growth and bloom formation in shallow embayments. The factors that distinguish “bloom” from “non-bloom” years thus appear to be operating on the growth of the planktonic population. 相似文献
528.
Grass shrimp, Palaemonetes pugio, were capable of hypo- and hyper-osmotic regulation of body fluids. Hemolymph chloride and osmotic concentrations were maintained at relatively stable levels over a wide salinity range. Following an abrupt transfer from intermediate (14 and 17) to high (31 and 35) or low (1 and 2) salinities, hemolymph chloride levels exhibited initial overshoot and undershoot, respectively, of new steady-state levels. Osmotic concentrations exhibited an initial undershoot at low, but not overshoot at high salinity. Chloride space in salinity-acclimated shrimp was relatively stable at salinities from 1 to 35. Changes in chloride space following salinity transfer paralleled those of hemolymph chloride levels, and are discussed in the light of alterations in intracellular sodium concentrations reported earlier. Rate constants for chloride turnover indicated independent exchanges of sodium and chloride ions. Water-turnover measurements showed that permeability of P. pugio was greatest at the isosmotic salinity (17) and reduced at salinities which were associated with active osmoregulation. Exposure to sublethal and 96-h LC50 levels of Aroclor® 1254 did not seriously alter hemolymph chloride and osmotic concentrations, chloride space or chloride-exchange kinetics in adult shrimp. Disruption of hemolymph chloride regulation in juvenile shrimp was associated with large mortalities not observed in adults. Shrimp exposed to Aroclor 1254 at 17 S exhibited reduced water permeability similar to levels previously observed in controls at high and low salinities in response to osmotic or ionic gradients. Exposure to PCBs did not result in further reduction in permeability at the latter salinities. 相似文献
529.
530.
Edward E. DeMartini Todd W. Anderson Alan M. Friedlander James P. Beets 《Marine Biology》2011,158(11):2437-2447
Group incidence and size are described for recruit parrotfishes, wrasses, and damselfishes on Hawaiian reefs over 3 years
(2006–2008) at sites spanning the archipelago (20–28°N, 155–177°W). Coral-poor and coral-rich areas were surveyed at sites
with both low (Hawaii Island) and high (Midway Atoll) predator densities, facilitating examination of relations among predator
and recruit densities, habitat, and group metrics. Predator and recruit densities varied spatially and temporally, with a
sixfold range in total recruit densities among years. Group (≥2 recruits) metrics varied with time and tracked predator and
recruit densities and the proportion of schooling species. Groups often included heterospecifics whose proportion increased
with group size. A non-saturating relationship between group size and recruit density suggests that the anti-predator benefits
of aggregation exceeded competitive costs. Grouping behavior may have overarching importance for recruit survival–even at
high recruit densities–and merits further study on Hawaiian reefs and elsewhere. 相似文献