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441.
Biosynthetic studies on marking pheromones of bumblebee males 总被引:2,自引:0,他引:2
Anna Luxová Irena Valterová Karel Stránský Olďrich Hovorka Aleš Svatoš 《Chemoecology》2003,13(2):81-87
442.
443.
444.
Hybrid zones are often found in areas where the environmental characteristics of native habitat of both parental species meet.
One of the plausible mechanisms that maintain species distinctiveness, or limit hybridization, is the existence of local species-specific
preferences for the natal habitat type. We evaluated this hypothesis for two passerine bird species, the pied Ficedula hypoleuca and collared flycatcher F. albicollis, in their narrow hybrid zone in Central Europe. Both species have quite distinct habitat distributions, and they have also
been reported to differ in their foraging niches. In a series of aviary experiments, we demonstrated that both species show
distinct preferences for trees from their native area. The pied flycatcher preferred coniferous vegetation, while the collared
flycatcher favored deciduous vegetation. In addition, both species differed in foraging substrate preferences. The pied flycatcher
preferred to forage in the lower strata on the ground than the canopy, whereas the collared flycatcher foraged more at the
canopy level. Both males and females of each species were highly consistent in their preference patterns. Due to the widespread
nature of hybrid zones as places with transitional habitat features and the well-known habitat tight associations of various
animal taxa with particular habitat types, we propose that habitat preferences might be an important and common mechanism
that enhances the formation of conspecific pairs. 相似文献
445.
The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies
and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings
and the socioeconomic status of the parents. As parasite infection affects many immunological and physiological parameters
of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born
from 1996 to 2004 contained information regarding the mother’s age, concentration of anti-Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest
that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of
a boy can increase up to a value of 0.72, C.I.95 = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of
anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced
survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis
on the human population might be considerable. 相似文献
446.
Adam Dušek Luděk Bartoš František Sedláček 《Behavioral ecology and sociobiology》2011,65(12):2209-2217
The issue of adaptive adjustment of offspring sex ratio (proportion of male births) in polytocous mammals, producing several
offspring per litter, is controversial because females of these species can maximize their fitness mainly by adjusting offspring
number. To address this issue, we examined the effect of maternal condition at mating, experimentally decreased by pre-mating
food restriction, on the sex ratio variation in 137 female mice. We tested two basic sex allocation hypotheses plausible for
polytocous mammals: (1) the Myers hypothesis, predicting that cheaper sex should be favored in poor environmental conditions
to maximize offspring number; and (2) the Williams hypothesis, predicting maximum fitness returns by adjusting size- and sex-specific
composition of the litter according to the maternal condition. The food-restricted mothers produced larger litters with a
higher proportion of cheaper daughters than the control mothers. By contrast, the control mothers optimized size and sex composition
of the litter according to their weight at mating. In addition, the offspring of the food-restricted mothers suffered less
from pre-weaning mortality than those of the control mothers. Therefore, when comparing the groups, the Myers hypothesis had
a general significance while the Williams hypothesis was plausible only for the control mothers. Furthermore, some of the
food-restricted mothers partly coped with the pre-mating food restriction and increased the proportion of sons in the litter
with the increasing maternal weight loss (during the period of food restriction). The sex ratio variation was thus a result
of three sex allocation strategies depending on the maternal condition at mating. 相似文献
447.
Jirí Gabriel Marina Capelari Petr Rychlovský Milan Krenželok František Zadražil 《毒物与环境化学》2013,95(1-4):141-146
The presence of Cd in substrate (wheat straw) strongly depressed the growth and mineralization of substrate by Agrocybe perfecta. Pleurolus ostreatoroseus was only slightly depressed and Pleurotus sp. CCB 068 increased degradation by the two highest Cd concentration. Mineralization rate of fungal substrate were increased by indigenous soil flora. However increase in Cd concentrations added to the soil depressed mineralisation of organic matter. Cadmium also affected the fruitbody yield and only Pleurotus sp. was able to fructify in high Cd concentrations. Translocation and accumulation of Cd in fruitbodies increased with the increase of Cd concentrations in substrate. 相似文献
448.
Pengcheng Xun Kiang Liu J. Steve Morris Joanne M. Jordan Ka He 《Environmental science and pollution research international》2013,20(3):1423-1430
Since data on mercury (Hg) levels in Caucasians and African Americans (AAs) of both genders are lacking, this study aims to present toenail Hg distributions and explore the potential determinants using data from the Coronary Artery Risk Development in Young Adults Trace Element Study. Data from 4,344 Americans, aged 20–32 in 1987, recruited from Oakland, Chicago, Minneapolis, and Birmingham were used to measure toenail Hg levels by instrumental neutron-activation method. The Hg distribution was described with selected percentiles and geometric means. Multivariable linear regression (MLR) was used to examine potential determinants of Hg levels within ethnicity–gender subgroups. The geometric mean of toenail Hg was 0.212 (95 % CI?=?0.207–0.218)?μg/g. Hg levels varied geographically with Oakland the highest [0.381 (0.367–0.395) μg/g] and Minneapolis the lowest [0.140 (0.134–0.147) μg/g]. MLR analyses showed that male gender and AA ethnicity were negatively associated with toenail Hg levels, and that age, living in Oakland city, education level, alcohol consumption, and total fish intake were positively associated with toenail Hg concentrations within each ethnicity–gender subgroup. Current smokers were found to have higher Hg only in AA men. This study suggested age, gender, ethnicity, study center, alcohol, education level, and fish consumption consistently predict toenail Hg levels. As fish consumption was the key determinant, avoiding certain types of fish that have relatively high Hg levels may be crucial in reducing Hg intake. 相似文献
449.
Dragan M. Marković Ivana R. Milošević Dragica Vilotić 《Environmental science and pollution research international》2013,20(1):136-145
As an indicator of environmental pollution, we collected tree rings and bark of linden (Tilia platyphyllos Scop.) from four sampling locations in Serbia. Mn and Pb were determined with a spectrochemical method that has an argon-stabilized U-shaped DC arc with aerosol supply as excitation source. Increased concentrations of Mn in linden tree rings and bark were found at the Debeli Lug location, where the Mn transfer factors were largest. The availability of Mn in soil and tree rings was greatly influenced by pH. Since 1950, Mn level decreased more noticeably on acidic soils. Higher concentrations of Pb were found in linden tree rings and bark at the locations Fru?ka Gora and Zemun. Proximity of the road to Novi Sad at both sites may be a possible reason for this. The Pb transfer factor was highest at Fru?ka Gora. The ratio of bioavailable elements in soil for Mn and Pb were also calculated. Close correlations between Mn and Pb concentrations in linden tree rings and the ratio of bioavailable elements in soil were seen at all four locations. 相似文献
450.
Flood management: prediction of microbial contamination in large-scale floods in urban environments 总被引:1,自引:0,他引:1
Taylor J Lai KM Davies M Clifton D Ridley I Biddulph P 《Environment international》2011,37(5):1019-1029
With a changing climate and increased urbanisation, the occurrence and the impact of flooding is expected to increase significantly. Floods can bring pathogens into homes and cause lingering damp and microbial growth in buildings, with the level of growth and persistence dependent on the volume and chemical and biological content of the flood water, the properties of the contaminating microbes, and the surrounding environmental conditions, including the restoration time and methods, the heat and moisture transport properties of the envelope design, and the ability of the construction material to sustain the microbial growth. The public health risk will depend on the interaction of these complex processes and the vulnerability and susceptibility of occupants in the affected areas. After the 2007 floods in the UK, the Pitt review noted that there is lack of relevant scientific evidence and consistency with regard to the management and treatment of flooded homes, which not only put the local population at risk but also caused unnecessary delays in the restoration effort. Understanding the drying behaviour of flooded buildings in the UK building stock under different scenarios, and the ability of microbial contaminants to grow, persist, and produce toxins within these buildings can help inform recovery efforts. To contribute to future flood management, this paper proposes the use of building simulations and biological models to predict the risk of microbial contamination in typical UK buildings. We review the state of the art with regard to biological contamination following flooding, relevant building simulation, simulation-linked microbial modelling, and current practical considerations in flood remediation. Using the city of London as an example, a methodology is proposed that uses GIS as a platform to integrate drying models and microbial risk models with the local building stock and flood models. The integrated tool will help local governments, health authorities, insurance companies and residents to better understand, prepare for and manage a large-scale flood in urban environments. 相似文献