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831.
832.
The short-sighted selection hypothesis for parasite virulence predicts that winners of within-host competition are poorer at transmission to new hosts. Social parasitism by self-replicating, female-producing workers occurs in the Cape honeybee Apis mellifera capensis, and colonies of other honeybee subspecies are susceptible hosts. We found high within-host virulence but low transmission rates in a clone of social parasitic A. m. capensis workers invading the neighbouring subspecies A. m. scutellata. In contrast, parasitic workers from the endemic range of A. m. capensis showed low within-host virulence but high transmission rates. This suggests a short-sighted selection scenario for the host-parasite co-evolution in the invasive range of the Cape honeybee, probably facilitated by beekeeping-assisted parasite transmission in apiaries. 相似文献
833.
Carotenoid pigments cannot be synthesized by vertebrates but must be ingested through the diet. As they seem to be a limited
resource, carotenoid-based ornaments are particularly interesting as possible honest signals of individual quality, in particular
of foraging efficiency and nutritional status. Some studies have demonstrated the condition dependence of carotenoid-based
plumage in birds. However, many other carotenoid-pigmented bare parts (i.e. skin, caruncles, bills, cere, and tarsi) are present
in birds but, in comparison with plumage, little is known about these traits as indicators of individual quality. Here, we
show that the eye ring pigmentation and bill redness of the red-legged partridge (Alectoris rufa) are positively associated to body condition and recent changes in body mass. Also, we found a negative relationship between
these two traits and heterophil-to-lymphocyte ratio, an indicator of physiological stress (the relationship with bill redness
being significant only for males). In an experiment, we found that after a period of reduction in food intake (with the consequent
loss of body mass), food-restricted birds showed lower eye ring pigmentation than ad-libitum-fed birds. Therefore, different
ornaments seem to reflect changes in body condition but at different speeds or intensities (eye ring, a fleshy ornament, appears
to respond more rapidly to changes in the nutritional status than a keratinized structure as the bill). These results indicate
that carotenoid-based ornaments are condition-dependent traits in the red-legged partridge, being therefore susceptible to
be employed as honest signals of quality in sexual selection. 相似文献
834.
水生维管束植物在修复受损水环境中的选择与配置 总被引:2,自引:0,他引:2
水生维管柬植物通过对污染物的吸收、富集,与藻类的竞争或他感抑制作用以及根际水生生态系统的协同作用等方式实现对受损水环境的修复,是一种与建设污水处理厂互补的水环境修复技术。着重指出利用水生维管束植物在修复受损水环境应用中的科学选择与配置,尤其是应优先考虑选择少量先锋物种,以便尽快恢复水环境生态系统的基本结构和功能以及生物多样性;重视各种生活型水生植物的合理搭配,优势互补,稳定有效地发挥各自的生态功能;注意考虑水生植物种群配置在生长期上的密切衔接及群落优势中的季节性演替等;并佐以实例为实际应用提供参考。 相似文献
835.
The queenless ant Pristomyrmex punctatus (Hymenoptera: Myrmicinae) has a unique society that differs from those of other typical ants. This species does not have
a queen, and the workers lay eggs and produce their clones parthenogenetically. However, a colony of these ants does not always
comprise members derived from a single clonal line. In this study, we examined whether P. punctatus changes its “assembling behavior” based on colony genetic structure. We prepared two subcolonies—a larger one comprising
200 individuals and a smaller one comprising 100 individuals; these subcolonies were established from a single stock colony.
We investigated whether these subcolonies assemble into a single nest. The genetically monomorphic subcolonies (single clonal
line) always fused into a single nest; however, the genetically polymorphic subcolonies (multiple clonal lines) did not tend
to form a single colony. The present study is the first to demonstrate that the colony genetic structure significantly affects
social viscosity in social insects. 相似文献
836.
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
837.
在水力停留时间为1~7 d的条件下,研究石菖蒲、美人蕉、水芋、杜鹃、一叶兰和袖珍椰子等6种植物湿地系统在表面流情况下对二级出水中NH3-N、TP的去除效果.结果显示,6种植物湿地系统对二级出水中NH3-N、TP的去除效果存在差异,但随着水力停留时间的加长,各系统的总体变化趋势较为接近.分析认为,植物的吸收不是污水中N、P去除的主要原因,但植物的环境适应性对NH3-N的去除有一定影响.在中水回用的设计中,湿地植物的选择可以从美学角度出发,选择具有较强环境适应性的湿地或水生植物,以增加湿地系统的景观效果;同时在以二级出水为原水的表面流人工湿地设计中,水力停留时间不宜大于4 d. 相似文献
838.
Selective predation can be an important force driving the evolution of organisms. In particular, sex-biased predation is expected to have implications for sexual selection, sex allocation and population dynamics. In this study, we analysed sex differences in the predation of the western green lizard (Lacerta bilineata) by the Eurasian kestrel (Falco tinnunculus) during the reproductive season. In addition, we investigated whether the rate of predation differed during the 8-year study period and among the three habitats studied. We collected lizard remains from nest boxes of kestrels. Freshly killed lizards were sexed by visual inspection, whilst the sex of head remains was assigned by analysing the cephalic scale morphology using geometric morphometrics. Our results show that the risk of being predated by a kestrel in our population was overall about 3.55 times higher for males than for females. To our knowledge this is the first study showing a male-biased predation in a lizard species. The selective predation of males was consistent between years over the 8-year study period (1999-2006) and also consistent between the three types of kestrel hunting habitat. Overall predation rates on lizards differed between habitats, depending on the year. We propose that the observed sex-biased predation is mainly due to sex differences in lizard behaviour. 相似文献
839.
840.