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91.
For dioecious species, choosing a mate of the same sex can have reproductive costs. For sex-changing animals, however, a lack
of sex recognition may not carry a reproductive cost, as pairs that were initially same-sex can become opposite-sex pairs
as one partner changes sex. The strength of sex discrimination in sex changers, then, should depend on the duration of mating
associations and whether the time of sex change is influenced by social situation (“flexible” sex change). We studied two
species of marine snails that change sex from male to female, one with flexible sex change and long-term or permanent mating
associations (Crepidula fornicata) and one with short-term pairings and relatively fixed time of sex change (Crepidula convexa), to determine whether either species exhibits sex recognition and whether members of C. convexa show stronger sex discrimination. In laboratory experiments, small males, the choosing animals, were placed with either a
male or a female conspecific (no-choice experiments) or given a choice of a male or female (choice experiments). We controlled
for shell length in all experiments, as relative size may influence sex change or choice. Males of both species paired more
often with females than males, but, as predicted, males of C. convexa showed stronger discrimination: When given a choice, no C. convexa male paired with another male. In contrast, some C. fornicata males always chose other males even when given the choice of a female. These results suggest that sex recognition can be
adaptive even for sex changers but demonstrate that the level of sex recognition will depend on other aspects of reproductive
behavior. 相似文献
92.
A contingent valuation survey was undertaken to estimate the public benefits of landscapechanges that could arise from reductions in grazing levels using the example of the Central Southern Uplands of Scotland. A dichotomous choice with continuous follow-up format was used to quantify the environmentalbenefit in terms of the willingness to pay of the general public and visitors. The paper discusses the merits of this format and the evidence of starting-point bias. In addition, the results are compared with the preferences of locals and interest groups as expressed through focus group sessions and subsets of the survey. A strong preference for more tree cover was evident, a landscape feature not well represented in the current landscape. 相似文献
93.
Daverede IC Kravchenko AN Hoeft RG Nafziger ED Bullock DG Warren JJ Gonzini LC 《Journal of environmental quality》2004,33(4):1535-1544
Excessive fertilization with organic and/or inorganic P amendments to cropland increases the potential risk of P loss to surface waters. The objective of this study was to evaluate the effects of soil test P level, source, and application method of P amendments on P in runoff following soybean [Glycine max (L.) Merr.]. The treatments consisted of two rates of swine (Sus scrofa domestica) liquid manure surface-applied and injected, 54 kg P ha(-1) triple superphosphate (TSP) surface-applied and incorporated, and a control with and without chisel-plowing. Rainfall simulations were conducted one month (1MO) and six months (6MO) after P amendment application for 2 yr. Soil injection of swine manure compared with surface application resulted in runoff P concentration decreases of 93, 82, and 94%, and P load decreases of 99, 94, and 99% for dissolved reactive phosphorus (DRP), total phosphorus (TP), and algal-available phosphorus (AAP), respectively. Incorporation of TSP also reduced P concentration in runoff significantly. Runoff P concentration and load from incorporated amendments did not differ from the control. Factors most strongly related to P in runoff from the incorporated treatments included Bray P1 soil extraction value for DRP concentration, and Bray P1 and sediment content in runoff for AAP and TP concentration and load. Injecting manure and chisel-plowing inorganic fertilizer reduced runoff P losses, decreased runoff volumes, and increased the time to runoff, thus minimizing the potential risk of surface water contamination. After incorporating the P amendments, controlling erosion is the main target to minimize TP losses from agricultural soils. 相似文献
94.
95.
Passaretti María Gabriela Ninago Mario D. Villar Marcelo A. López Olivia V. 《Journal of Polymers and the Environment》2022,30(10):4394-4405
Journal of Polymers and the Environment - Multifunctional horticultural mulches satisfy different agronomic needs: control weeds and insects, reduction of water evaporation and soil erosion, as... 相似文献