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571.
The expected impact of the “Peace Conduit” project (the Red Sea - Dead Sea pipeline) on the Dead Sea
Ittai?GavrieliEmail author Amos?Bein Aharon?Oren 《Mitigation and Adaptation Strategies for Global Change》2005,10(4):759-777
The Dead Sea is a severely disturbed ecosystem, greatly damaged by anthropogenic intervention in its water balance. During
the 20th century, the Dead Sea level dropped by more than 25 meters, and presently (2003) it is at about 416 meters below
mean sea level. This negative water balance is mainly due to the diversion of water from the catchment area of the lake by
Israel, Jordan and Syria. During the 2002 World Summit on Sustainable Development Israel and Jordan jointly announced their
interest in saving the Dead Sea by constructing the “Peace Conduit” that will pipe water from the Red Sea to the Dead Sea.
The inflow of seawater (or reject brine after desalinization) into the Dead Sea will have a major impact on its limnology,
geochemistry and biology. During the filling stage, relatively diluted surface water will form and the rate of evaporation
will therefore increase. Dilution of the surface water will most likely result in microbial blooming whose duration is not
known, while the lower water layer is likely to develop reducing conditions, including bacterial sulfate reduction and presence
of hydrogen sulfide (H2S). Mixing between the calcium-rich Dead Sea brine and the sulfate-rich seawater will result in gypsum precipitation (CaSO4⋅ 2H2O). Once the target level is reached, inflow will be outbalanced by evaporation and salinity of the surface water will increase
due to accumulation of seawater-salts. The water column will re-mix when the density of the surface water will equal that
of the lower water column. In spite of its large volume and high salinity relative to that of the inflowing water, over the
long run the composition of this unique lake will change. Before a decision is made on the planning and construction of the
Conduit, it is essential that the long term evolution and characteristics of the “renewed” Dead Sea be known and anticipated
changes examined. Once decided upon, the planning and construction of the Conduit should be conducted so as to minimize possible
negative impacts of seawater introduction on the Dead Sea. This can only be achieved through a thorough understanding of the
expected changes in the limnological physical/chemical characteristics of the Dead Sea and its unique brine. 相似文献
572.
Ernst Mayr: the doyen of twentieth century evolutionary biology 总被引:1,自引:0,他引:1
Hölldobler B 《Die Naturwissenschaften》2004,91(6):249-254
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Al/Si configurations in some natural and synthetic Rb-feldspars have been examined carefully by EMPA and XPS analyses. Our results indicate that a small amount of H2O and excess Si and Al are incorporated in hydrothermally synthesized Rb-feldspar. The quantities of excess Al are 0.056 atoms per formula unit and are negatively correlated with those of the Rb, suggesting the presence of excess Al occupying non-tetrahedral sites in feldspar structures. This leads to incorporation of Al(Al3Si)O8 endmember into Rb-feldspars, estimated as one appropriate endmember indication for unusual chemistry of feldspars. In addition, Si2p, Al2p and O1s XPS signals of Rb-feldspars shift drastically toward the higher energy side than those of any natural feldspars. These provide conclusive evidence not only for existence of perceptible excess Si and Al, but also for Al at both extra-framework and tetrahedral sites in feldspar structures. 相似文献
576.
The mechanism of caste differentiation in a social aphid Tuberaphis styraci, which has a sterile soldier caste in the 2nd instar, was investigated using an artificial diet rearing system. High aphid density induced soldier production. Combinatorial prenatal and postnatal density treatments revealed that (1) either prenatal high density or postnatal high density is sufficient for soldier induction; (2) thus, embryos in the maternal body and newborn 1st instar nymphs are both responsive to high density; (3) the combination of prenatal high density and postnatal high density enhances soldier differentiation in a synergistic manner; and (4) the final determination of soldier differentiation occurs postnatally, probably at a late 1st instar stage. This study first throws light on the developmental aspects of caste differentiation in a social aphid. 相似文献
577.
Food sharing among unrelated same-sex individuals has received considerable interest from primatologists and evolutionary biologists because of its apparent altruistic nature and implications for the evolution of complex social cognition. In contrast to primates, food sharing in birds has received relatively little attention. Here we describe three types of food sharing in jackdaws, with the initiative for the transfer either with the receiver or the giver. The latter situation is of particular interest because the food transfer takes place through active giving. Compared to primates, jackdaws show high rates of food sharing. Finally we discuss the implications of food sharing in jackdaws, and in birds in general. 相似文献
578.
579.
Social insect colonies respond to challenges set by a variable environment by reallocating work among colony members. In many social insects, such colony-level task allocation strategies are achieved through individual decisions that produce a self-organized adapting group. We investigated colony responses to parasitoids and native ant competitors in the red imported fire ant (Solenopsis invicta). Parasitoid flies affected fire ants by decreasing the proportion of workers engaged in foraging. Competitors also altered colony-level behaviours by reducing the proportion of foraging ants and by increasing the proportion of roaming majors, whose role is colony defence. Interestingly, the presence of both parasitism and competition almost always had similar effects on task allocation in comparison to each of the biotic factors on its own. Thus, our study uniquely demonstrates that the interactive effect of both parasitism and competition is not necessarily additive, implying that these biotic factors alter colony behaviour in distinct ways. More generally, our work demonstrates the importance of studying the dynamics of species interactions in a broader context. 相似文献
580.
Multiple behavioral and chemical studies indicate that ant nestmate recognition cues are low-volatile substances, in particular hydrocarbons (HCs) located on the cuticular surface. We tested the hypothesis that in the ant Camponotus fellah, nest environment, in particular nest volatile odors, can modulate nestmate-recognition-mediated aggression. Workers were individually confined within their own nest in small cages having either a single mesh (SM = limited physical contact permitted) or a double mesh (DM = exposed to nest volatiles only) screen. Individual workers completely isolated outside their nest (CI) served as control. When reintroduced into a group of 50 nestmates, the CI workers were attacked as alien ants after only 2 weeks of separation, whereas the SM workers were treated as nestmates even after 2 months of separation. Aggression towards DM ants depended on the period of isolation. Only DM workers isolated for over 2 months were aggressed by their nestmates, which did not significantly differ from the CI nestmates. Cuticular HC analyses revealed that the profile of the non-isolated ants (NI) was clearly distinct from that of CI, SM and DM ants. Profile differences matched the aggressive response in the case of CI ants but were uncorrelated in the case of SM or DM ants. This suggests that keeping the ants within the nest environment affected nestmate recognition in additional ways than merely altering their HC profile. Nest environment thus appears to affect label–template mismatch by modulating aggressive behavior, as well as the direction at which cuticular HCs diverged during the separation period. 相似文献