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601.
Fletcher QE Boutin S Lane JE LaMontagne JM McAdam AG Krebs CJ Humphries MM 《Ecology》2010,91(9):2673-2683
Mast seeding involves the episodic and synchronous production of large seed crops by perennial plants. The predator satiation hypothesis proposes that mast seeding maximizes seed escape because seed predators consume a decreasing proportion of available seeds with increasing seed production. However, the seed escape benefits of masting depend not only on whether predators are satiated at high levels of seed production, but also on the shape of their functional response (type II vs. type III), and the actual proportion of available seeds that they consume at different levels of seed production. North American red squirrels (Tamiasciurus hudsonicus) are the primary vertebrate predator of white spruce (Picea glauca) mast seed crops in many boreal regions because they hoard unopened cones in underground locations, preempting the normal sequence of cone opening, seed dispersal, and seed germination. We document the functional response of cone-hoarding by red squirrels across three non-mast years and one mast year by estimating the number of cones present in the territories of individual red squirrels and the proportion of these cones that they hoarded each autumn. Even though red squirrels are not constrained by the ingestive and on-body (fat reserves) energy reserve limitations experienced by animals that consume seeds directly, most squirrels hoarded < 10% of the cones present on their territories under mast conditions. Cone availability during non-mast years also reached levels that satiated the hoarding activity of red squirrels; however, this occurred only on the highest-quality territories. Squirrels switched to mushroom-hoarding when cone production was low and mushrooms were abundant. This resulted in type III functional response whereby the proportional harvest of cones was highest at levels of cone availability that were intermediate within non-mast years. Overall, more cones escaped squirrel cone-hoarding during a mast event than when cone production was low in non-mast years, which supports the predator satiation hypothesis. However, the highly variable seed escape in non-mast years may help to explain why all spruce cone production is not concentrated into fewer, larger, mast years. 相似文献
602.
Frequency, not relative abundance, of temperate tree species varies along climate gradients in eastern North America 总被引:1,自引:0,他引:1
There have been many attempts to model the impacts of climate change on the distributions of temperate tree species, but empirical analyses of the effects of climate on the distribution and abundance of tree species have lagged far behind the models. Here, we used forest inventory data to characterize variation in adult tree abundance along climate gradients for the 24 most common tree species in the northeastern United States. The two components of our measure of species abundance--local frequency vs. relative abundance--showed dramatically different patterns of variation along gradients of mean annual temperature and precipitation. Local frequency (i.e., the percentage of plots in a given climate in which a species occurred) varied strongly for all 24 species, particularly as a function of temperature. Relative abundance when present in a plot, on the other hand, was effectively constant for most species right up to their estimated climatic range limits. Although the range limits for both temperature and precipitation were quite broad for all of the species, the range of climates within which a species was common (i.e., high frequency) was much narrower. Because frequency in sites within a given climate shows a strong sensitivity to temperature, at least, this suggests that the processes determining canopy tree recruitment on new sites also vary strongly with climate. 相似文献
603.
Beasley Lake is a Conservation Effects Assessment Program (CEAP) watershed in the intensively cultivated Mississippi Delta, USA. Lake sediment quality at three sites was evaluated in 2004 and 2008 for biological impairment and uptake (animal tissue pesticide residues) from 14 pesticides and three metabolites using Hyalella azteca (Saussure). Eleven pesticides and three metabolites were detected in sediment among the three sites in 2004 and all 17 compounds examined were detected among the three sites in 2008, with the herbicide atrazine having the greatest concentrations. Twenty-eight-day H. azteca survival and growth (mg w/w) indicated no survival effects at any site for either year, but growth impairment occurred in H. azteca exposed to sediments in 2004, whereas growth enhancement occurred in H. azteca exposed to sediments at one site in 2008. Pesticides observed in animal tissue pesticide residues occurred more frequently and in greater concentrations in 2004 compared with 2008. Thirteen pesticides were detected in animal tissue pesticide residues in 2004, with chlorpyrifos occurring in the greatest concentrations, and six pesticides were detected in 2008, with p,p′-DDT occurring in the greatest concentrations. H. azteca tissue pesticide residues of seven pesticides, two herbicides, three insecticides, one insecticide metabolite, and p,p′-DDT, were associated with growth. 相似文献
604.
Neighborhood and habitat effects on vital rates: expansion of the Barred Owl in the Oregon coast ranges 总被引:1,自引:0,他引:1
In this paper, we modify dynamic occupancy models developed for detection-nondetection data to allow for the dependence of local vital rates on neighborhood occupancy, where neighborhood is defined very flexibly. Such dependence of occupancy dynamics on the status of a relevant neighborhood is pervasive, yet frequently ignored. Our framework permits joint inference about the importance of neighborhood effects and habitat covariates in determining colonization and extinction rates. Our specific motivation is the recent expansion of the Barred Owl (Strix varia) in western Oregon, USA, over the period 1990-2010. Because the focal period was one of dramatic range expansion and local population increase, the use of models that incorporate regional occupancy (sources of colonists) as determinants of dynamic rate parameters is especially appropriate. We began our analysis of 21 years of Barred Owl presence/nondetection data in the Tyee Density Study Area (TDSA) by testing a suite of six models that varied only in the covariates included in the modeling of detection probability. We then tested whether models that used regional occupancy as a covariate for colonization and extinction outperformed models with constant or year-specific colonization or extinction rates. Finally we tested whether habitat covariates improved the AIC of our models, focusing on which habitat covariates performed best, and whether the signs of habitat effects are consistent with a priori hypotheses. We conclude that all covariates used to model detection probability lead to improved AIC, that regional occupancy influences colonization and extinction rates, and that habitat plays an important role in determining extinction and colonization rates. As occupancy increases from low levels toward equilibrium, colonization increases and extinction decreases, presumably because there are more and more dispersing juveniles. While both rates are affected, colonization increases more than extinction decreases. Colonization is higher and extinction is lower in survey polygons with more riparian forest. The effects of riparian forest on extinction rates are greater than on colonization rates. Model results have implications for management of the invading Barred Owl, both through habitat alteration and removal. 相似文献
605.
Jessica R. Frost Anneke Denda Clive J. Fox Charles A. Jacoby Rolf Koppelmann Morten Holtegaard Nielsen Marsh J. Youngbluth 《Marine Biology》2012,159(2):239-253
The ecology of small, gelatinous zooplankton is not integrated into management of Dogger Bank (54° 00′ N, 3° 25′ E to 55°
35′ N, 2° 20′ E). In pursuit of this goal, gelatinous zooplankton and their potential prey were sampled along a transect across
the bank on June 10–16, 2007. Eleven species of small medusae and ctenophores were collected, with six abundant taxa occurring
in greater numbers below the thermocline and in the shallower, southeastern portion of the bank. There were no statistically
significant diel changes in distribution. In contrast, potential prey were distributed more evenly across the bank and throughout
the water column. Isotopic analyses revealed that gelatinous zooplankton fed on both smaller (100–300 μm) and larger (>300 μm)
mesozooplankton, but also potentially on each other. These ecological insights suggest that small medusae and ctenophores
should be integrated into sustainable management of Dogger Bank. 相似文献
606.
There currently exists a large push for the use, improvement, and expansion via landscape modification of dedicated biofuel crops (feedstocks) in the United States and in many parts of the world. Ecological concerns have been voiced because many biofuel feedstocks exhibit characteristics associated with invasiveness, and due to potential negative consequences of agronomic genes in native wild populations. Seed purity concerns for biofuel feedstock cultivars whose seeds would be harvested in agronomic fields also exist from the agribusiness sector. The common thread underlying these concerns, which have regulatory implications, is gene flow; thus detailed knowledge of gene flow in biofuel crop plants is important in the formulation of environmental risk management plans. Here, we synthesize the current state of knowledge of gene flow in an exemplary biofuel crop, switchgrass (Panicum virgatum L.), which is native to eastern North America and is currently experiencing conventional and technological advances in biomass yields and ethanol production. Surprisingly little is known regarding aspects of switchgrass pollen flow and seed dispersal, and whether native populations of conspecific or congeneric relatives will readily cross with current agronomic switchgrass cultivars. We pose that filling these important gaps will be required to confront the sustainability challenges of widespread planting of biofuel feedstocks. 相似文献
607.
Florence Mouchet Christian Gancet Emmanuel Flahaut Eric Pinelli Jean–Charles Boutonnet Laury Gauthier 《毒物与环境化学》2016,98(8):829-847
The classical approach in ecotoxicological evaluation of chemical substances consists of conducting standardized bioassays on organism models. In this work, the potential impact of industrial multi-walled carbon nanotubes was investigated by ecotoxicological standardized procedures using aquatic organisms of different trophic levels, namely bacteria, green algae, invertebrates, fish, and amphibians. The results indicated (1) inhibition of growth in amphibians at 50 mg L?1 and higher, and (2) no effects on daphnia and fish up to 100 mg L?1. With the exception of algae (for which Fe deficiency is measured), it seems that the observed toxicity may be due to physiological effects in relation to the ingestion of carbon nanotubes not necessarily related to their intrinsic effects. 相似文献
608.
During the Queensland floods in the summer of 2010–2011, a flood-driven Brisbane River plume extended into Moreton Bay, Queensland, Australia, and then seaward, travelling in a northward direction. It covered approximately 500 km $^{2}$ . This paper presents a three- dimensional hydrodynamic numerical model investigation into the behaviour of the Brisbane River plume. The model was verified by using satellite observations and field measurement data. The present study concludes that the high river discharge was the primary factor determining the plume size and its seaward extensions. A notable finding was that the plume was a bottom-trapped type rather than a buoyant type. Further, the southerly winds were found to have moderately confined the alongshore extension of the plume, and had caused the plume to mix thoroughly with the ocean water. 相似文献
609.
Walter?Q.?BetancourtEmail authorView authors OrcID profile Charles?P.?Gerba 《Food and environmental virology》2016,8(3):161-173
The genus Orthoreovirus contains nonenveloped viruses with double-stranded gene segments encased in a double-layered icosahedral capsid shell. These features constitute major determinants of virion stability in the environment and virion resistance against physical and chemical agents. Reovirus (ReoV) is the general term most commonly used for all virus strains that infect humans and nonhuman animals. Several studies have demonstrated the frequent occurrence of ReoV in wastewaters and natural waters, including surface and ground waters from different geographical areas. Most of these studies have reported higher concentrations of ReoV than any other enteric virus analyzed. They are more commonly isolated in chlorine-disinfected wastewaters than other enteric viruses, and appear to survive longer in water. The ability of ReoV to form large aggregates, even with different types of enteric viruses (e.g., poliovirus) and their ability to undergo mechanisms of gene segment reassortment among different serotypes may also explain their greater stability. Different approaches have been applied for concentration of ReoV from water; however, the recovery efficiency of the filtration methods has not been fully evaluated. Recently, molecular methods for identification of ReoV strains and quantification of virus genome have been developed. Studies have shown that the overall detection sensitivity of ReoV RNA is enhanced through initial replication of infectious virions in cell culture. More studies are needed to specifically address unresolved issues about the fate and distribution of ReoV in the environment since this virus is not commonly included in virological investigations. 相似文献
610.
Andrew N. Kadykalo Rachel T. Buxton Peter Morrison Christine M. Anderson Holly Bickerton Charles M. Francis Adam C. Smith Lenore Fahrig 《Conservation biology》2021,35(6):1725-1737
Calls for biodiversity conservation practice to be more evidence based are growing, and we agree evidence use in conservation practice needs improvement. However, evidence-based conservation will not be realized without improved access to evidence. In medicine, unlike in conservation, a well-established and well-funded layer of intermediary individuals and organizations engage with medical practitioners, synthesize primary research relevant to decision making, and make evidence easily accessible. These intermediaries prepare targeted evidence summaries and distribute them to practitioners faced with time-sensitive and value-laden decisions. To be effective, these intermediaries, who we refer to as evidence bridges, should identify research topics based on the priorities of practitioners; synthesize evidence; prepare and distribute easy-to-find and easy-to-use evidence summaries; and develop and maintain networks of connections with researchers and practitioners. Based on a review of the literature regarding evidence intermediaries in conservation and environmental management, as well as an anonymous questionnaire searching for such organizations, we found few intermediaries that met all these criteria. Few evidence bridges that do exist are unable to reach most conservation practitioners, which include resource managers in government and industry, conservation organizations, and farmers and other private landowners. We argue that the lack of evidence bridges from research to practitioners contributes to evidence complacency and limits the use of evidence in conservation action. Nevertheless, several existing organizations help reduce the gap between evidence and practice and could serve as a foundation for building additional components of evidence bridges in conservation. Although evidence bridges need expertise in research and evidence synthesis, they also require expertise in identifying and communicating with the community of practitioners most in need of clear and concise syntheses of evidence. Article Impact Statement: Evidence-based conservation will not be realized without improved access to evidence. We call for intermediary evidence bridges. 相似文献