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461.
文章分析了垃圾焚烧技术的利弊,详述了垃圾焚烧发电厂必要的配套设施的项目内容,指出这是垃圾焚烧发电系统不可分割的部分。认为垃圾焚烧发电发展前景广阔。 相似文献
462.
463.
Male mating biases may be a widespread feature of animal mating systems but the phenotypic consequences of these biases are often unclear, especially in species for which the operational sex ratio is strongly male-biased. In Colias butterflies, male choice is thought to be one of the factors responsible for maintaining a female-limited genetic color polymorphism, in which female wings appear either yellowish-orange or white (the “alba” variant). Previous studies have indicated that alba females of two montane Colias species mate fewer times during their lifetime, possibly as a partial consequence of this bias. Here we report the results of a field study of male mating behavior and female mating biology in Colias eurytheme, conducted under conditions of high (summer) and low (spring) population densities. Our data show that despite a substantial male bias in approaching alba vs yellowish-orange phenotypes [ratios of 0.08:1 (spring) and 0.28:1 (summer)], alba females did not contain, on average, fewer or smaller spermatophores. Not one of the 308 sampled females was virgin, but females of both phenotypes accumulated spermatophores with age, and tended to carry fewer, larger spermatophores in spring. These data suggest that significantly fewer (or lighter) spermatophores need not be an obligatory or simple consequence of a strong male bias in butterflies. We discuss these findings in light of the known, thermally and density-dependent complexities of alba reproductive biology and of the Colias mating system. 相似文献
464.
Summary. Two common components, identified as
(E)-11-hexadecenal (E11-16:Ald) and (E,E)-10,12-hexadecadienal
(E10E12-16:Ald), were found in the extract of virgin females of two sympatric pyralid moths, Terastia subjectalis
Lederer, and Agathodes ostentalis (Geyer). The amount of E11-16:Ald and E10E12-16:Ald was 0.12 and 2.8 ng/female
for T. subjectalis and 2.0 and 1.8 ng/female for A. ostentalis,
respectively. Hexadecanal (16:Ald) was also found at
0.7 ng/female in the extract of A. ostentalis, but EAG activity was unclear. In the field, T. subjectalis and
A. ostentalis
males were captured with species specific blends in the proportions
of 5:95 and 50:50 blends. Blends attractive to one
species did not attract the opposite one. Rubber septa loaded
with 1 mg each of 5:95 and 50:50 blends of E11-16:Ald and
E10E12-16:Ald were as attractive as two virgin females of
T. subjectalis and
A. ostentalis
, respectively. This demonstrated
that different ratios of shared pheromone components could
provide species specific cues for critical mate location in the
two sympatric pyralid moths. It is suggested that directional
selection probably occurs in the pheromone blends in opposite
directions in both species. 相似文献
465.
俞宪忠 《中国人口.资源与环境》2004,14(5):86-90
对中国农村人口问题有两种不弼的理论主张和政策导向:一是城市化。二是城镇化。由于“城镇化”模型的基本结构是:“城镇化”=“城市化“ “乡镇化”其框架所明含的“乡镇化”倾向必然存在下述显著弊端:选择了不可能从根本上解决农民问题的农村化乡镇框架;将会对中国现代化进程中的农村人口压力产生短期缓解而长期困抗的不良后果;将会导致资泊配置的浪费;将会导致后果严重的长期环境污染;违背了农村人口的最优化理性选择;乡镇企业存在和发展主妻理由已经基本上不复存在。中国农村人口目艇t性发展的战略框架是:必须和只能走新型城市化道路;尽快理智而清晰地确立城市化的惟一发展战略;尽快建构“教育化 城市化”的提升国民素质的社会发展框架;尽快把县级城市作为中国城市化发展战略的根本空间选择和主要社会载体。中国在这方面具有广阔的制度创新空间。应尽快通过镧度现代化而开辟出一条农民市民化和人口现代化的制度通道。 相似文献
466.
Chad C. Smith 《Behavioral ecology and sociobiology》2007,61(9):1349-1358
Operational sex ratio (the ratio of sexually active males to fertilizable females) has a major influence on male competition
for mates and male–female interactions. The contributions of male and female density per se to mating system dynamics, however,
are rarely examined, and the fitness consequences are often inferred rather than quantified. Male mosquitofish (Gambusia affinis) compete aggressively and frequently harass females for copulations, a behavior thought to reduce female fitness. Female
fitness can also be reduced by increases in female density, which may affect food availability, cannibalism rates, and chemical
interactions between females. I manipulated male and female densities of G. affinis to measure their effects on male–male aggression, male harassment toward females, and female fitness. I found that males
chased rivals more often and attempted fewer copulations when female density decreased, but surprisingly male density had
no significant effect on the frequency of these male behaviors. In contrast, males’ agonistic displays toward other males
increased with male density, but display behavior was unaffected by female density. These results suggest that male and female
density do not always contribute equally or at all to the patterns of behavior we observe. Female fitness declined as female
density increased, the opposite pattern expected if male harassment is costly to females. This suggests that a strong, negative
effect of female density overwhelmed any potential costs of male harassment. Sources of female density dependence and the
consequences of changes in male and female density to patterns of male behavior are discussed. 相似文献
467.
Gonçalo C. Cardoso Paulo Gama Mota Violaine Depraz 《Behavioral ecology and sociobiology》2007,61(9):1425-1436
We tested if male or female behavior towards manipulated song indicates intra- or inter-sexual selection of two characteristics
of serin song that are extreme and evolutionarily derived in this species: high frequency and fast syllable rate. In a first
experiment, we monitored vocal responses and attendance to song playbacks. Female behavior indicated a preference for high-frequency
song and suggested an aggressive function for fast syllable rates, as fast songs inhibited vocal response. Males did not show
discrimination of frequency or syllable rate with this experimental design. The second experiment used a simple approach/no
approach design, and in this experiment, males showed stronger discrimination between stimuli than did females. Therefore,
sex differences in discrimination appear not to result from differences in perceptual abilities but from differences in the
context of stimulus presentation. The second experiment also supported a role of song frequency in female choice, as the effect
of frequency was limited to females: males did not respond differently to song frequency and approached high-frequency songs
less than females did. Results of this experiment also supported an aggressive function for fast syllable rates, as the effect
of fast songs did extend to male behavior. Taken together, our results indicate that the high frequency and fast syllable
rate of serin song cannot result from a single selection process: while high frequency may have evolved by inter-sexual selection,
syllable rate provokes a pattern of response that is more consistent with intra-sexual selection. 相似文献
468.
The benefits of strategic environmental considerations in the process of siting a repository for low- and intermediate-level radioactive waste (LILW) are presented. The benefits have been explored by analyzing differences between the two site selection processes. One is a so-called official site selection process, which is implemented by the Agency for radwaste management (ARAO); the other is an optimization process suggested by experts working in the area of environmental impact assessment (EIA) and land-use (spatial) planning. The criteria on which the comparison of the results of the two site selection processes has been based are spatial organization, environmental impact, safety in terms of potential exposure of the population to radioactivity released from the repository, and feasibility of the repository from the technical, financial/economic and social point of view (the latter relates to consent by the local community for siting the repository). The site selection processes have been compared with the support of the decision expert system named DEX. The results of the comparison indicate that the sites selected by ARAO meet fewer suitability criteria than those identified by applying strategic environmental considerations in the framework of the optimization process. This result stands when taking into account spatial, environmental, safety and technical feasibility points of view. Acceptability of a site by a local community could not have been tested, since the formal site selection process has not yet been concluded; this remains as an uncertain and open point of the comparison. 相似文献
469.
Domestic animals potentially affect the reproductive output of plants by direct removal of aboveground plant parts but also could alter the structure and fertility of the upper soil and the integrity of biological crusts through trampling. We asked whether sheep selectivity of plant patches along grazing paths could lead to negative changes in biological crusts and soil seed banks. We randomly selected ten floristically homogeneous vegetation stands distributed across an area (1250 ha) grazed by free ranging sheep. Vegetation stands were differently selected by sheep as estimated through sheep-collaring techniques combined with remote imagery mapping. At each stand, we extracted 15 paired cylindrical soil cores from biological crusts and from neighboring soil without crusts. We evaluated the crust cover enclosed in each core and incubated the soil samples at field capacity at alternating 10-18 °C during 24 months. We counted the emerged seedlings and identified them by species. Sheep selectivity along grazing paths was largest at mid-distances to the watering point of the paddock. Increasing sheep selectivity was associated with the reduction of the cover of biological crusts and the size and species number of the soil seed bank of preferred perennial grasses under biological crusts. The size of the soil seed bank of annual grasses was reduced with increasing sheep selectivity under both crust and no crust soil conditions. We did not detect changes in the soil seed banks of less- and non- preferred species (shrubs and forbs) related to sheep selectivity. Our findings highlight the negative effects of sheep selectivity on biological crusts and the soil seed bank of preferred plant species and the positive relationship between biological crusts and the size of the soil seed bank of perennial grasses. Accordingly, the state of conservation of biological crusts could be useful to assess the state of the soil seed banks of perennial grasses for monitoring, conservation and planning the sustainable management of grazing lands. 相似文献
470.