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991.
Standard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O 2 g -1 h -1) and "winter" (106.52±39.65 µl O 2 g -1 h -1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage. 相似文献
992.
993.
994.
Inorganic mercury and methylmercury in surface sediments and mussel tissues from a microtidal lagoon (Bizerte, Tunisia) 总被引:1,自引:0,他引:1
N. Mzoughi T. Stoichev M. Dachraoui A. El Abed D. Amouroux O. F. X. Donard 《Journal of Coastal Conservation》2002,8(2):141-145
The aim of this study was to investigate the distribution of mercury compounds in marine sediments and mussel tissues collected
in the lagoon of Bizerte, Tunisia, during two seasons (summer and winter). Inorganic mercury (Hg2+) concentrations in sediments were found to be highly variable, ranging from 0.04 nmol.g1 to 3.22 nmol.g−1 (dry weight) with a mean value of 0.52 nmol.g−1. Anthropogenic sources of Hg2+, most probably metallurgy or tire production industries, have been evidenced. The mean concentration of monomethylmercury
(MeHg+) in the surface sediments is 2.32 pmol g−1 ranging from below the detection limit (0.45 pmol.g−1) to 14.6 pmol.g−1. No significant variation was observed between winter and summer seasons for both mercury species concentration in the sediments.
The Hg2+ concentrations in mussel tissues are also variable, ranging from 0.007 to 1.347 nmol.g−1 (dry weight). The mean concentration is 0.70 nmol.g−1. In these tisssues, Hg2+ is generally the major compound, making up ca. 88% of total mercury concentrations. However, methylmercury concentrations
are significant and homogeneous, ranging from 62 to 121 pmol.g−1 (mean 96 pmol.g−1). The results suggest that a fraction of the inorganic mercury load in the sediments of the lagoon undergoes methylation
pathways. MeHg+ produced is assimilated in the mussels more readily than Hg2+. 相似文献
995.
Methodology of light response curves: application of chlorophyll fluorescence to microphytobenthic biofilms 总被引:1,自引:0,他引:1
The light response curve methodology for microphytobenthic biofilms was studied by comparing the two most usual approaches
used in pulse amplitude modulated (PAM) fluorometry. The non-sequential light curve (N-SLC) method is characterized by independent
measures of the photosynthetic activity across a light gradient whereas the rapid light curve (RLC) method consists of successive
measures on the same sample exposed to a stepwise increase of light intensities. Experiments were carried out on experimental
microphytobenthic biofilms prepared from natural assemblages and acclimated to dark conditions. In preliminary experiments,
N-SLCs were constructed from fluorescence induction curves performed at 12 different photon flux densities (PFDs). A minimum
of 50 s of illumination was necessary to reach a stable light response curve; shorter illumination times resulted in underestimating
the physiological parameters (α the light utilization coefficient in light-limited conditions and rETRmax the maximum rate of photosynthesis efficiency) of the light response curve. For the comparison between N-SLCs and RLCs, the
same time of illumination (50 s) was used for each light step of RLCs so that N-SLCs differed from RLCs only by the way the
amount of light was delivered, i.e., a light dose accumulation for RLC. The experimental results showed the difference between
the two photobiological response curves. In the lower range of PFDs, RLCs exhibited a larger value of α; in this light-limited
part of the response curve the incremental increase of PFDs limited the development of NPQ and resulted in a better optimization
of electron transport rate for RLC. In the higher range of PFDs, the trend was reversed and the RLC showed a lower value of
rETRmax than the N-SLC did; this is attributed to the light dose accumulation which likely led to a more efficient dispersion of
energy, as illustrated by a higher non-photochemical quenching (NPQ). In conclusion, these results confirm that parameters
derived from both methods differ in their value and do not bear the same physiological information. 相似文献
996.
Summary Home ranges, social organization, and nest co-occupancy of Peromyscus californicus were studied using radiotelemetry at the Hastings Natural History Reservation, California. Mated pairs were ascertained by the transfer of fluorescent pigments from lactating females to putative fathers. Mated pairs had largely overlapping home ranges that were not statistically distinguishable, whereas adjacent adults had mostly exclusive, statistically distinguishable home ranges. There was no difference in the mean home range of males and females, but mated females tended to have smaller ranges than their mate. Home range size was extremely variable (range: 150–3788 m2) and averaged 1161 m2 across all individuals. Male home range size was inversely correlated with population density, suggestive of a social influence on home range. Putative fathers spent comparable amounts of time to females in the nest — presumably caring for the young — which supports previous laboratory reports of paternal care in this species. All data collected in this study are consistent with previous suggestions that P. californicus live in semi-permanent family groups and are monogamous.
Offprint requests to: D.O. Ribble 相似文献
997.
Discrimination between nestmate and non-nestmate kin by social wasps (Polistes fuscatus,Hymenoptera: Vespidae) 总被引:1,自引:0,他引:1
George J. Gamboa Jeff E. Klahn Allan O. Parman Ruth E. Ryan 《Behavioral ecology and sociobiology》1987,20(2):125-128
Summary The threespine stickleback,Gasterosteus aculeatus is a voracious cannibal of both its own eggs and those of conspecific neighbours. Females, but not males, can distinguish their progeny from those of other fish and attacked alien eggs more frequently. In experiments to examine nest raiding, females that initiated raids on nests resulting in cannibalism were the first females to spawn in the reconstructed nest. These results support the hypothesis that cannibalism by females may be adaptive in situations where intense female competition for male guardians occurs. 相似文献
998.
The Ecology of Extinctions in Kelp Forest Communities 总被引:5,自引:0,他引:5
999.
1000.
Mariusz O. Jedrysek 《Environmental Chemistry Letters》2005,3(3):100-112
Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates,
which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ13C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich
conditions. Likewise, high δ13C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane
and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand
the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water
column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland.
The highest concentration of sulphate has been detected in rivers (85.47 SO4
2− mg/l) and an artificial lake (70.30 SO4
2− mg/l) located in the extremely SO4
2−-polluted region called the “Black Triangle”. The lowest concentration of sulphate is found in dystrophic and mountain lakes
(from 0.5 SO4
2− to about 3 mg/l). The lowest δ34S(SO4
2−) and δ18O(SO4
2−) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios
are found in a polluted lake in western Poland (δ14S(SO4
2)=12.95‰) and in a dystrophic lake in eastern Poland (δ18O(SO4
2) = 16.15‰) respectively. It is proposed that δ34SO4
2− and (18O(SO4
2−) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations
in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column.
In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ13C(CH4) value from about –35 to about –78‰. However, δ13C value in sedimentary calcite (δ13C vary from –10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes
and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ13C value in methane and low δ13C value in calcite—this is probably due to an enhanced oxidation of methane producing 13C-depleted CO2. In contrast to clean lakes, it is observed that an increase of the δ13C(CH4) value occurs with increasing depth of the water column in a strongly SO4
2−-contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active
oxidation of methane precursors. 相似文献