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951.
In the absence of predators, pollinators can often maximize their foraging success by visiting the most rewarding flowers.
However, if predators use those highly rewarding flowers to locate their prey, pollinators may benefit from changing their
foraging preferences to accept less rewarding flowers. Previous studies have shown that some predators, such as crab spiders,
indeed hunt preferentially on the most pollinator-attractive flowers. In order to determine whether predation risk can alter
pollinator preferences, we conducted laboratory experiments on the foraging behavior of bumble bees (Bombus impatiens) when predation risk was associated with a particular reward level (measured here as sugar concentration). Bees foraged in
arenas containing a choice of a high-reward and a low-reward artificial flower. On a bee’s first foraging trip, it was either
lightly squeezed with forceps, to simulate a crab spider attack, or was allowed to forage safely. The foragers’ subsequent
visits were recorded for between 1 and 4 h without any further simulated attacks. Compared to bees that foraged safely, bees
that experienced a simulated attack on a low-reward artificial flower had reduced foraging activity. However, bees attacked
on a high-reward artificial flower were more likely to visit low-reward artificial flowers on subsequent foraging trips. Forager
body size, which is thought to affect vulnerability to capture by predators, did not have an effect on response to an attack.
Predation risk can thus alter pollinator foraging behavior in ways that influence the number and reward level of flowers that
are visited. 相似文献
952.
Sexually deceptive orchids of the genus Ophrys attract male insects for pollination. Pollinator attraction is achieved by mimicking sex pheromones of virgin females of
their pollinators, mostly bee species. In earlier investigations, we showed that the phylogenetically distinct Ophrys species O.
chestermanii and O. normanii on Sardinia attract their pollinator, males of the cuckoo bumblebee B. vestalis, with the same bouquets of relatively polar volatile compounds. In this investigation, we studied the sex pheromone of virgin
females of B. vestalis with the aim of identifying male-attracting compounds and of comparing them with labellum extracts of the two orchids, which
were found to release male-attracting compounds in earlier investigations (G?gler et al. 2009). In bioassays, shock-frozen females, cuticle extracts and polar fractions of cuticle extracts of virgin females stimulated
mating behaviour in the males. Using gas chromatography coupled with electroantennography (GC-EAD) and gas chromatography
coupled with mass spectrometry (GC-MS), we detected in polar fractions of cuticle extracts of B. vestalis females the same electrophysiologically active compounds as in labellum extracts of both orchid species, including aldehydes,
esters, fatty acids and alcohols. Since statistical comparisons of the relative proportions of esters showed strong similarities
between virgin females and orchids, our results support the hypotheses that this highly specialized Ophrys–pollinator relationship represents another case of chemical mimicry and that esters play a key role in male attraction. 相似文献
953.
Zohra Belala Mejdi Jeguirim Meriem Belhachemi Fatima Addoun Gwena?lle Trouv�� 《Environmental Chemistry Letters》2011,9(1):65-69
The removal of toxic metals from wastewaters by biosorption, based on the metal-binding capacities of various biological materials,
has received much interest. However, the success of this approach depends on economic feasibility, which can be obtained by
optimization of the environmental conditions. This paper evaluates, for the first time, the use of low-cost biosorbent (date
stones (DS) and palm-tree waste (PTW)) to eliminate Cu(II) from aqueous solutions. The effect of some parameters on copper
biosorption has been studied using date stones and palm-tree waste as solid sorbents. Results show that the highest percentage
of copper adsorption was obtained for the smallest size of the sorbent particles. The biosorption process was found to occur
rapidly, i.e. the maximum sorption capacity was reached within 20 min. The process involved pseudo-second-order kinetics with
an activation energy value within the normal range considered for processes, where a physical interaction between the sorbate
and the sorbent solid predominated. The thermodynamic parameters of the copper ions uptake onto the solid sorbents indicated
that, the process was endothermic and proceeds spontaneously from the date stones. However, the thermodynamic studies of the
adsorption of copper on palm-tree waste indicated that the process was exothermic and proceeds spontaneously. 相似文献
954.
Modified ��-cyclodextrins as prospective agents for improving water solubility of organic pesticides
The drawback of some organic pesticides is their low water solubility. Cyclodextrins are used as agents for improving pesticides
water solubility. However, the stabilization of the crystalline lattice can reduces to a large extent the solubility of cyclodextrins,
especially β-cyclodextrin. Here, searching for the water soluble β-cyclodextrin derivatives, a set of new “host” compounds
were prepared by the reaction of β-cyclodextrin with methyl epoxycinnamate. The reactants ratio was varied in to study the
substitution degree of the obtained derivatives. The structure was determined by the 1H-NMR and FT IR spectra. The average degree of substitution was determined by integration of the corresponding NMR signals
and by elemental analysis. The solubility of four selected pesticides: dimethoate, simazine, linuron and thiram, in water
with and without addition of the new modified β-cyclodextrin was measured by ultraviolet spectrophotometry. Our results showed
that the modified β-cyclodextrins significantly improve solubility of pesticides. 相似文献
955.
956.
B?a?ej Kud?ak Lidia Wolska Jacek Namie?nik 《Environmental monitoring and assessment》2011,174(1-4):509-516
The sensitivity of Heterocypris incongruens to selected heavy metal ions is discussed. Although the Ostracodtoxkit ${\textregistered}$ has been present on the market for a few years, data on its selectivity and sensitivity to toxicants is scarce; such data is indispensable when interpreting the results of sediment toxicity. The LC50 and EC50 results with the Ostracodtoxkit ${\textregistered}$ are compared with those obtained with other commercially available ??direct-contact?? tests (utilizing Hyalella azteca and Chironomus riparius) and microbiotests for assessing the toxicity of aqueous samples (Vibrio fischeri, Daphnia magna, and Selenastrum capricornatum). The sensitivity of H. incongruens to metal ions (Cd2?+?>?>Hg2?+?> Cu2?+?>Cr6?+?>Ni2?+???Mn7?+?>Zn2?+?>Pb2?+?>Li1?+?> Fe3?+?) was found to be similar to that of H. azteca and of C. riparius. The Ostracodtoxkit ${\textregistered}$ has shown itself to be an efficient and reliable element of test batteries for toxicity determination. 相似文献
957.
?i?dem Co?kun Hepcan Mehmet B��lent ?zkan 《Environmental monitoring and assessment》2011,174(1-4):157-170
The study involves the Çe?me?CUrla Peninsula, where habitat fragmentation and loss, which threaten biological diversity, have become an urgent matter of concern in recent decades. The study area has been subjected to anthropogenic pressures and alterations due to ongoing and impending land uses. Therefore, ecological networks, as an appropriate way to deal with habitat fragmentation and loss and to improve ecological quality, were identified in the study area as one of the early attempts in the country to maintain its rich biodiversity. In this sense, core areas and ecological linkages as primary components of ecological networks were established on the basis of sustaining natural habitats. A GIS-based model was created to identify core areas and to facilitate the ecological connectivity. The modeling process for core areas and corridors combined 14 and 21 different variables, respectively. The variables were used as environmental inputs in the model, and all analyses were materialized in ArcGIS 9.2 using grid functions of image analysis and spatial analyst modules. As a result, six core areas and 36 corridor alternatives were materialized. Furthermore, some recommendations for the implementation and management of the proposed ecological networks were revealed and discussed. 相似文献
958.
Kuznetsova T Tilk M Pärn H Lukjanova A Mandre M 《Environmental monitoring and assessment》2011,183(1-4):341-350
The investigation was carried out in 8-year-old Scots pine (Pinus sylvestris L.) and lodgepole pine (Pinus contorta var. latifolia Engelm.) plantations on post-mining area, Northeast Estonia. The aim of the study was to assess the suitability of lodgepole pine for restoration of degraded lands by comparing the growth, biomass, and nutrient concentration of studied species. The height growth of trees was greater in the Scots pine stand, but the tree aboveground biomass was slightly larger in the lodgepole pine stand. The aboveground biomass allocation to the compartments did not differ significantly between species. The vertical distribution of compartments showed that 43.2% of the Scots pine needles were located in the middle layer of the crown, while 58.5% of the lodgepole pine needles were in the lowest layer of the crown. The largest share of the shoots and stem of both species was allocated to the lowest layer of the crown. For both species, the highest NPK concentrations were found in the?needles and the lowest in the stems. On the basis of the present study results, it can be concluded that the early growth of Scots pine and lodgepole pine on oil shale post-mining landscapes is similar. 相似文献
959.
Richard Owen Flamm John Elliot Reynolds III Craig Harmak 《Environmental management》2013,51(1):154-166
We used southwestern Florida as a case study to lay the groundwork for an intended and organized decision-making process for managing warm-water habitat needed by endangered manatees to survive winters in Florida. Scientists and managers have prioritized (a) projecting how the network of warm-water sites will change over the next 50 years as warmed industrial discharges may expire and as flows of natural springs are reduced through redirection of water for human uses, and (b) mitigating such changes to prevent undue consequences to manatees. Given the complexities introduced by manatee ecology; agency organizational structure; shifting public demands; fluctuating resource availability; and managing within interacting cultural, social, political, and environmental contexts, it was clear that a structured decision process was needed. To help promote such a process, we collected information relevant to future decisions including maps of known and suspected warm-water sites and prototyped a characterization of sites and networks. We propose steps that would lead to models that might serve as core tools in manatee/warm-water decision-making, and we summarized topics relevant for informed decision-making (e.g., manatee spatial cognition, risk of cold-stress morbidity and mortality, and human dimensions). A major impetus behind this effort is to ensure proactively that robust modeling tools are available well in advance of the anticipated need for a critical management decision. 相似文献
960.