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In a bivouacked swarm of honey bees, most individuals are quiescent while a small minority (the scouts) are active in choosing the swarm's future nest site. This study explores the way in which the members of a swarm warm their flight muscles for take-off when the swarm eventually decamps. An infrared camera was used to measure the thoracic (flight muscle) temperatures of individual bees on the surface of a swarm cluster. These are generally the coolest bees in a swarm. The warming of the surface-layer bees occurred mainly in the last 10 min before take-off. By the time a take-off began, 100% of the bees had their flight muscles heated to at least 35°C, which is sufficient to support rapid flight. Take-offs began only a few seconds after all the surface-layer bees had their flight muscles warmed to at least 35°C, but exactly how take-offs are triggered remains a mystery. 相似文献
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Martin Heil Brigitte Fiala K. Eduard Linsenmair Thomas Boller 《Die Naturwissenschaften》1999,86(3):146-149
Many plant species have evolved mutualistic associations with ants, protecting their host against detrimental influences
such as herbivorous insects. Letourneau (1998) reported in the case of Piper that ants defend their plants principally against stem-boring insects and also reduce fungal infections on inflorescences.
Macaranga plants that were experimentally deprived of their symbiotic Crematogaster ants suffered heavily from shoot borers and pathogenic fungi (Heil 1998). Here we report that ants seem to reduce fungal infections
actively in the obligate myrmecophyte Macaranga
triloba (Euphorbiaceae), while ant-free plants can be easily infected. We also found extremely low chitinase activity in Macaranga plants. The plants' own biochemical defense seems to be reduced, and low chitinase activity perhaps may represent a predisposition
for the evolution of myrmecophytism. These plants are therefore highly dependent on their ants, which obviously function not
only as an antiherbivore defense but also as an effective agent against fungal pathogens.
Received: 5 August 1998 / Accepted in revised form: 18 November 1998 相似文献
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Herbicides and nitrogen fallout were studied in France at six sites from west to east. Atrazine, a herbicide widely used in France and forbidden in some European countries was found. Its fallout was quantified to 400 kg on the river Marne catchment (13 500 km2), an agricultural region located east of Paris. The average fallout contribution to the Marne river contamination was estimated at 20 ng/l from March to August. Independently of the wind direction, only a small part of this atmospheric contamination can reach adjacent countries. 相似文献
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Frédéric Soulignac Brigitte Vinçon-Leite Bruno J. Lemaire José R. Scarati Martins Céline Bonhomme Philippe Dubois Yacine Mezemate Ioulia Tchiguirinskaia Daniel Schertzer Bruno Tassin 《Environmental Modeling and Assessment》2017,22(4):309-322
Urban lakes provide many ecosystem services, e.g., flood control, nature protection, coolness island, recreation. Hydrodynamic models will increasingly be used to enhance these benefits. We present the first validation of a three-dimensional (3D) hydrodynamic model on a small shallow lake with high resolution and high frequency measurements. Lake Créteil, France (area 0.4 km2, mean depth 4.5 m, and catchment area 1 km2) is a former gravel pit and now part of a regional park. The model Delft3D-FLOW was calibrated on a one-month period, with continuous measurements of temperature at five depths at the center of the lake and at three depths at two other stations, and with current speed profiles at the centre of the lake. The model was then verified on 18 1-month periods with similar temperature measurements. The model reproduced very well the temperature dynamics, including the alternation between mixing and stratification periods and internal wave patterns. The mean absolute errors over the five depths at the central point remained below 0.55°C in spring and summer, the most favorable seasons for phytoplankton growth. Horizontal temperature differences, which rose up to 3°C at the beginning of stratification periods, were also well reproduced, as well as current speeds. These results are very promising for assessing nutrient and pollutant diffusion, settling and resuspension, as well as for understanding how phytoplankton blooms start in small shallow lakes. 相似文献
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Diana W. Bianchi Tim Van Mieghem Lisa G. Shaffer Brigitte H. W. Faas Lyn S. Chitty Alessandro Ghidini Jan Deprest 《黑龙江环境通报》2014,34(1):1-5
本文提出怎样理解产学研相结合的问题,并从产学研不同层面进行分析,提出以市场为目标、以制度为保证实现产学研有效结合的思路。 相似文献
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