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301.
Mean age and length at onset of maturity were estimated for orange roughy (Hoplostethus atlanticus) populations off New Zealand, Namibia, and Great Britain. Significant between-area differences were apparent in both these
parameters. Implications of the between-area differences on stock structure of orange roughy in New Zealand waters are discussed.
A proportional relationship between age at onset of maturity and modal size of fish in the mature population is demonstrated.
This is consistent with later-maturing fish experiencing a longer period at a pre-maturity growth rate that is relatively
faster than the rate of somatic growth after maturity.
Received: 22 December 1997 / Accepted: 5 May 1998 相似文献
302.
Adult zebraperch, Hermosilla azurea, were found to be functional herbivores in that animal matter constituted <0.01% of the total dry weight of stomach contents
of fish collected off Santa Catalina Island in southern California waters. The diet of these fish consisted mainly of red
algae (88.2% by dry wt) and also small amounts of brown (7.8%) and green (4.0%) algae. The most important dietary item, the
filamentous red algae Polysiphonia spp., was found in >78% of the stomachs and comprised >60% of the contents by dry weight. The digestive tract was long, on
average 4.0 times the standard length of the fish, and was composed of the stomach, pyloric caeca, intestine, hindgut chamber
with a blind caecum, and rectum. The mean pH of the cardiac stomach was acidic (3.9), whereas that of the intestine was nearly
neutral (6.9) and that of the hindgut and blind caecum slightly acidic (6.3 and 6.6, respectively). Algal foods are apparently
digested by acid lysis in the stomach and by microbial fermentation in the hindgut. Zebraperch assimilated nutritional constituents
from six species of algae with varying degrees of efficiency: carbon (73.7 to 89.7%), nitrogen (72.4 to 84.5%), and protein
(71.9 to 94.9%). The fish assimilated these constituents as efficiently or more efficiently from three species of nondietary
brown algae as from three species of dietary red and green algae. These results show that zebraperch, like their tropical
and subtropical relatives (members of the genus Kyphosus), can digest a wide variety of algae including brown algae containing defensive secondary compounds.
Received: 3 November 1997 / Accepted: 19 June 1998 相似文献
303.
304.
305.
Lock K De Schamphelaere KA Becaus S Criel P Van Eeckhout H Janssen CR 《Environmental pollution (Barking, Essex : 1987)》2007,147(3):626-633
A Biotic Ligand Model was developed predicting the effect of cobalt on root growth of barley (Hordeum vulgare) in nutrient solutions. The extent to which Ca(2+), Mg(2+), Na(+), K(+) ions and pH independently affect cobalt toxicity to barley was studied. With increasing activities of Mg(2+), and to a lesser extent also K(+), the 4-d EC50(Co2+) increased linearly, while Ca(2+), Na(+) and H(+) activities did not affect Co(2+) toxicity. Stability constants for the binding of Co(2+), Mg(2+) and K(+) to the biotic ligand were obtained: logK(CoBL)=5.14, logK(MgBL)=3.86 and logK(KBL)=2.50. Limited validation of the model with one standard artificial soil and one standard field soil showed that the 4-d EC50(Co2+) could only be predicted within a factor of four from the observed values, indicating further refinement of the BLM is needed. 相似文献
306.
Sampling method, storage and pretreatment of sediment affect AVS concentrations with consequences for bioassay responses 总被引:1,自引:0,他引:1
De Lange HJ Van Griethuysen C Koelmans AA 《Environmental pollution (Barking, Essex : 1987)》2008,151(1):243-251
Sediment treatment and sediment storage may alter sediment toxicity, and consequently biotic response. Purpose of our study was to combine these three aspects (treatment-toxicity-biotic response) in one integrated approach. We used Acid Volatile Sulfide (AVS) concentrations as a proxy of the disturbance of the sediment. AVS and Simultaneously Extracted Metal (SEM) concentrations were compared to bioassay responses with the freshwater benthic macroinvertebrate Asellus aquaticus. Storage conditions and sediment treatment affected AVS but not SEM levels. AVS can be used as a proxy for sediment disturbance. The best way to pretreat the sediment for use in a bioassay in order to maintain initial AVS conditions was to sample the sediment with an Ekman grab, immediately store it in a jar without headspace, and freeze it as soon as possible. In a survey using seven different sediments, bioassay responses of A. aquaticus were correlated with SEM and AVS characteristics. 相似文献
307.
ABSTRACTThe concept of an agro-production park combines industrial with environmental and animal friendly agriculture. In The Netherlands, academics and government introduced this idea—what we consider a boundary concept—to align economic and environmental ambitions. In this contribution, we argue that boundary concepts are important in deliberations as they create a sphere of engagement that enables participants to scrutinize their routines and to explore new interpretations and practices that replace their normal ways. In this way we ground the notion of ‘reflexive governance’ in deliberative practices for sustainable agriculture. We explored if and how the concept of an agropark induced frame-reflective conversations about conflicting and overlapping interpretations. We conducted a frame analysis of four Dutch national newspapers from which we derived four possible interpretations of an agropark: Pigs in the City, Surviving Farmers, Pigs in the Mud and Surviving Citizens. Next, we analysed 10 deliberative sessions about agroparks to study if reflectivity occurred. Our findings suggest that to move to more sustainable agriculture, the introduction of innovative boundary crossing concepts invites participants to reflect on conflicting frames and engage in reflective governance. However, facilitators and governmental actors need to support this boundary crossing for it to become tangible. 相似文献
308.
Methods for defining and retrieving reference conditions for large rivers were explored with emphasis on hydromorphologic
and biologic quality indicators. For a set of four large rivers in the European Western Plains ecoregion, i.e., the rivers
Meuse, Loire, Allier, and Dordogne, reference reaches were selected based on geomorphologic characteristics. A survey of riparian
land use, vegetation, and bed geometry was done for the selected reaches. Responses of the riparian landscape to hydromorphologic
conditions were determined with a set of existing and newly developed measures of riparian dynamics and forest development.
Strong correlations were observed at the reach and local levels between the ratios of width to depth and embankment and the
developed measures of riparian dynamics and forest. Boundary conditions for riparian forest development were determined for
the hydromorphologic and biologic indicators of riparian dynamics and vegetation structure. These conditions also proved useful
for determining the presence of sustainable populations of Populus nigra and Salix purpurea. From this agreement between abiotic and biotic boundary conditions, a set of useful reference conditions was determined,
and a framework for the definition of reference and good status conditions subsequently evolved. Finally, a proposal for assessment
and monitoring the proposed indicators is discussed for its applicability. 相似文献
309.
Thai Hong Nam Nguyen Tien Dung Nguyen Van Tuan Nguyen Hoang Giang Kawamoto Ken 《Journal of Material Cycles and Waste Management》2022,24(1):34-48
Journal of Material Cycles and Waste Management - Mechanical properties of recycled concrete aggregates (RCA) such as compaction and California bearing ratio (CBR) are important for application as... 相似文献
310.
Influence of pH on the sonolysis of ciprofloxacin: Biodegradability, ecotoxicity and antibiotic activity of its degradation products 总被引:3,自引:0,他引:3
Evelien De Bel Jo Dewulf Bavo De Witte Herman Van Langenhove Colin Janssen 《Chemosphere》2009,77(2):291-295
The presence of antibiotics in the aquatic environment has raised concerns due to the potential risk for the emergence or persistence of antibiotic resistance. Antibiotics are often poorly degraded in conventional wastewater treatment plants. In this study, sonolysis at 520 kHz and 92 W L−1 was used for the degradation of the fluoroquinolone antibiotic ciprofloxacin. In a first experiment at pH 7, 57% of the ciprofloxacin (15 mg L−1) was degraded after 120 min of ultrasonic irradiation at 25 °C. pH proved to be an important parameter determining the degradation rate, since the pseudo first order degradation constant increased almost fourfold when comparing treatment at pH 7 (0.0058 min−1) and pH 10 (0.0069 min−1) with that at pH 3 (0.021 min−1). This effect can be attributed to the degree of protonation of the ciprofloxacin molecule. The BOD/COD ratio of the solutions, which is a measure for their biodegradability, increased from 0.06 to 0.60, 0.17, and 0.18 after 120 min of irradiation depending on the pH (3, 7, and 10, respectively). The solution treated at pH 3 can even be considered readily biodegradable (BOD/COD > 0.4). The antibiotic activity against Escherichia coli (G−) and Bacillus coagulans (G+) of the treated solutions also reduced after sonolysis. The highest decrease was again found when irradiated at pH 3. In contrast, ecotoxicity of the solutions to the alga Pseudokirchneriella subcapitata increased 3- to 10-fold after 20 min of treatment, suggesting the formation of toxic degradation products. The toxicity slowly diminished during further treatment. 相似文献