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991.
Ryoko Fujiyoshi Yukihide Haraki Takashi Sumiyoshi Hikaru Amano Ivan Kobal Janja Vaupotič 《Environmental geochemistry and health》2010,32(1):73-82
Radon (222Rn) and carbon dioxide were monitored simultaneously in soil air under a cool-temperate deciduous stand on the campus of Hokkaido
University, Sapporo, Japan. Both 222Rn and CO2 concentrations in soil air varied with atmospheric (soil) temperature in three seasons, except for winter when the temperature
in soil air remained constant at 2–3°C at depth of 80 cm. In winter, the gaseous components were influenced by low-pressure
region passing through the observation site when the ground surface was covered with snow of ~1 m thickness. Carbon isotopic
analyses of CO2 suggested that CO2 in soil air may result from mixing of atmospheric air and soil components of different origins, i.e. CO2 from contemporary soil organic matter and old carbon from deeper source, to varying degrees, depending on seasonal meteorological
and thus biological conditions. 相似文献
992.
Marco Ghisalberti 《Environmental Fluid Mechanics》2010,10(3):329-343
Obstructed shear flows (i.e. those over permeable media) are common in the environment. An archetypal example, flow over a
submerged vegetation canopy, is investigated here. Like any flow through complex geometry, canopy flows are characterised
by strong spatial gradients. The focus of this experimental study is the three-dimensionality of aquatic canopy flow, in particular
that of the coherent interfacial vortices that govern mixing into and out of the canopy. It is shown here that the vortices
have a finite lateral scale that is comparable to their vertical scale; both are of the order of the drag length scale of
the canopy, (C
D
a)−1, where a is the frontal area density and C
D
is a bulk drag coefficient. The finite lateral extent of the vortices generates strong lateral hydrodynamic gradients, both
instantaneously and in the long-term. The instantaneous gradients, which can contribute greatly to the dispersion of dissolved
and particulate species, are far more pronounced. Finally, the potential for canopies to generate differential roughness secondary
circulation is examined. In the consideration of vertical scalar transport, this circulation can be of the same order as turbulent
diffusion. 相似文献
993.
Persistence models for mark-recapture 总被引:1,自引:0,他引:1
The stable of models available for analyzing mark-recapture data (Otis et al. Wild Momogr 66:135, 1978) includes those having
behavioral characteristics, time variation, heterogeneity, along with combinations of those characteristics. This paper proposes
use of a series of models based on the persistence model of Ramsey and Usner (Biometrics 59:331–339, 2003). We show that persistence
can be modeled in combination with behavior and with time variation. We apply the persistence model to situations in which
capture occasions are not equally-spaced in time. Two case studies illustrate the use of these extended persistence models. 相似文献
994.
Anthropogenic influence on surface water quality of the Nhue and Day sub-river systems in Vietnam 总被引:2,自引:0,他引:2
Pham Thi Minh Hanh Suthipong Sthiannopkao Kyoung-Woong Kim Dang The Ba Nguyen Quang Hung 《Environmental geochemistry and health》2010,32(3):227-236
In order to investigate the temporal and spatial variations of 14 physical and chemical surface water parameters in the Nhue
and Day sub-river systems of Vietnam, surface water samples were taken from 43 sampling sites during the dry and rainy seasons
in 2007. The results were statistically examined by Mann–Whitney U-test and hierarchical cluster analysis. The results show that water quality of the Day River was significantly improved during
the rainy season while this was not the case of the Nhue River. However, the river water did not meet the Vietnamese surface
water quality standards for dissolved oxygen (DO), biological oxygen demand (BOD5), chemical oxygen demand (COD), nutrients, total coliform, and fecal coliform. This implies that the health of local communities
using untreated river water for drinking purposes as well as irrigation of vegetables may be at risk. Forty-three sampling
sites were grouped into four main clusters on the basis of water quality characteristics with particular reference to geographic
location and land use and revealed the contamination levels from anthropogenic sources. 相似文献
995.
Biogeochemical model (BGC-ES) and its basin-level application for evaluating ecosystem services under forest management practices 总被引:1,自引:0,他引:1
It is important for humans to live in harmony with ecosystems. Evaluation of ecosystem services (ES) may be helpful in achieving this objective. In Japan, forest ecosystems need to be re-evaluated to prevent their degradation due to lack of forest management.In order to evaluate the effects of forest management on forest ES, we developed a process-based biogeochemical model to estimate water, carbon, and nitrogen cycles in forest ecosystems (BGC-ES). This model consists of four submodels: biomass, water cycle, carbon-nitrogen (CN) cycles, and forest management. The biomass submodel can calculate growth of forest biomass under forest managements.Several parameters of the model were calibrated using data from observations of evapotranspiration flux and quality of stream flow in forests. The model results were compared with observations of runoff water from a dam catchment site and with carbon flux observations.Our model was coupled with a basin-level GIS database of forests. Evaluations under various forest management scenarios were carried out for forests in a basin contained in the Ise Bay basin (Chubu region, Japan), where plantations (artificial forests) seemed to have degraded from poor forest management.Comparing our simulation results with those of forests without management in the basin, we found that the amounts of absorbed carbon and runoff were larger in managed forests. In addition, the volume of harvested timber was larger and its quality (diameter) was better in managed forests. Changes of ES within the various scenarios were estimated for their economic value and were compared with the cost of forest management. 相似文献
996.
997.
Ali Akbar Safari Sinegani Hossein Mirahamdi Araki 《Environmental Chemistry Letters》2010,8(4):323-330
Sequential extraction has been used as a suitable method for fractionation of chemical forms of trace elements and study of
their plant availability. Surface soils were sampled from Guilan and Hamadan provinces in north and northwest of Iran with
temperate and semiarid climates. The chemical forms of Pb in the Pb(NO3)2-treated (400 μg Pb g−1) soils have been studied in solid state incubation (FC) at 27°C in sterile and unsterile conditions. After 20 min and 3600 h
a sequential extraction scheme was also used to fractionate Pb of incubated samples into soluble-exchangeable (Sol-Exch),
carbonates associated (ACar), organic matter associated (AOM), Mn oxide associated (AMnOx), Fe oxide associated (AFeOx), and
residual (Res) forms. Temperate soil samples had higher clay content, cation exchange capacity (CEC), dichromate oxidable
organic carbon (OC), total Kjeldahl-nitrogen (TN), biological activity, amorphous and crystalline Fe and Al, but semiarid
soil samples had higher sand content, pH, equivalent calcium carbonate (ECC), available P and K. Soil lead fractionation revealed
that in both groups of soils Pb largely changed to exchangeable, carbonates associated and organic associated forms after
20 min. The chemical forms of Pb differed widely among soils after 3600-h incubation. The conversion rate of Pb from more
available forms to less available forms was higher in temperate soils with higher Fe–Mn oxides and OM contents compared to
semiarid soils. In temperate soils after 3600-h incubation, greater content of Pb was observed in Res (68%), AOM (14%), ACar
(7%), and AMnOx (5%) fractions. However, in semiarid soils greater content of Pb was observed in Res (61%), ACar (16%), Sol-Exch
(8%), and AOM (8%) fractions. The sum of AMnOx and AFeOx chemical forms for Pb in semiarid soils compared to temperate soils
was lower. It was only 7% against 9% in temperate soils. Soil microorganisms in unsterile soils had significant effect on
AOM, AFeOx and Res fractions of Pb. They not only increased AOM and AFeOx fractions of Pb in soils but also decreased Res
fraction of Pb significantly. 相似文献
998.
Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments
on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three different diatom strains (9B, 1G, and 7J) induced widely different effects on Acartia tonsa physiology, and the 9B strain induced different effects for the three copepods. In contrast, different strains induced no
or small alterations in the distribution, swimming behavior, and turning frequency of the copepods. 22:6(n-3) fatty acid (DHA)
and sterol content of the diet typically showed a positive effect on either egg production (A. tonsa) or hatching success (P. elongatus), while other measured compounds (PUA, other long-chain polyunsaturated fatty acids) of the algae had no obvious effects.
Our results demonstrate that differences between strains of a given diatom species can generate effects on copepod physiology,
which are as large as those induced by different algae species or groups. This emphasizes the need to identify the specific
characteristics of local diatoms together with the interacting effects of different mineral, biochemical, and toxic compounds
and their potential implications on different copepod species. 相似文献
999.
Spatial distribution and temporal variation of epibenthic assemblages of coralligenous biogenic rocky outcrops occurring in
the northern Adriatic Sea (45°04′–45°24′N; 12°23′–12°43′E) were investigated by photographic sampling from 2003 to 2006 at
12 randomly selected sites. The dominant reef-forming organisms were the encrusting calcareous algae (Lithophyllum stictaeforme, Lithothamnion minervae and Peyssonnelia polymorpha), while the main bioeroders were boring sponges (Cliona viridis, C. celata, C. thoosina, C. rhodensis, Piona vastifica) and the bivalve Gastrochaena dubia. Composition of the assemblages varied thorough years and among sites. Spatial heterogeneity, at local and regional scale,
prevailed over temporal variation. This variability was related both to the geo-morphological features of the outcrops and
to environmental variables. Sites clearly differed in the percent cover of reef builder and bioeroder species while only limited
temporal variation within site was found. Some taxa revealed complex intra-site temporal trends. These results provide valuable
information on the diversity and variability of epibenthic assemblages of the northern Adriatic coralligenous reefs, essential
for the management and conservation of these unique biogenic habitats. 相似文献
1000.
Shrimp trawling is common throughout the southeastern and Gulf of Mexico coasts of the USA and is the primary contributor
to fisheries discards in these regions. Tens of thousands of nearshore seabirds nest near shrimp trawling grounds in the USA,
but to date, there has been no assessment of the relationship between seabirds and shrimp trawlers. We examined the taxonomic
composition of bycatch, rate at which seabirds scavenged bycatch, and energy density of discarded bycatch in a nearshore commercial
shrimp fishery. Bycatch was primarily comprised of demersal fish that are not typically accessible to the plunge-diving and
surface-feeding seabirds that occur in the area. Hence, seabird diets in the region appear to be broadened taxonomically by
the availability of discards. Results from discard experiments indicated that 70% of the nearly 5,500 items discarded by hand
were scavenged by seabirds and that the fate of a discarded item was most strongly predicted by its taxonomic order. Laughing
gulls scavenged the greatest proportion of discards, although brown pelicans were the only species to scavenge more discards
than predicted based upon their abundance. Because this is the first such study in the region, it is difficult to ascertain
the extent or intensity of the impact that discards have on nearshore seabirds. Nonetheless, our results suggest that it will
be difficult for managers to clearly understand fluctuations in local seabird population dynamics without first understanding
the extent to which these species rely upon discards. This may be especially problematic in situations where seabird populations
are recovering following natural or anthropogenic stressors. 相似文献