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Etienne Paul Delmira Beatriz Wolff Juan Carlos Ochoa Rejane Helena Ribeiro da Costa 《Water environment research》2007,79(7):765-774
The reduction of organic and nitrogen pollution of wastewater was investigated in two hybrid reactors and compared with the reduction obtained by using a conventional activated sludge reactor (ASR) run as a control. Both HR-1 and HR-2 were activated sludge systems where a low-density carrier, P1 (polyethylene) for HR-1 and P2 (recycled plastics) for HR-2, was added. Firstly, the three reactors were operated at 10 days Suspended Solid Retention Time (SRT(SS)), leading to a complete nitrification. Secondly, the SRT(SS) for each reactor was lowered to 3 days. Nitrification was lost for the ASR but remained complete for HR's. Respirometric techniques were used to measure fixed or suspended biomass activities for heterotrophic and autotrophic biomass. More than 90% of the autotrophic activity was found on the supports whatever the SRT(SS) used. The results may underline the role of the carrier geometry or surface characteristics on the autotrophic/heterotrophic microorganism distribution. 相似文献
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J. Gasperi C. Sebastian V. Ruban M. Delamain S. Percot L. Wiest C. Mirande E. Caupos D. Demare M. Diallo Kessoo M. Saad J. J. Schwartz P. Dubois C. Fratta H. Wolff R. Moilleron G. Chebbo C. Cren M. Millet S. Barraud M. C. Gromaire 《Environmental science and pollution research international》2014,21(8):5282-5283
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Vivian C. Goerlich Cor Dijkstra Ton G. G. Groothuis 《Behavioral ecology and sociobiology》2010,64(4):599-606
Primary sex ratio adjustment in birds has been extensively studied, yet the underlying physiological mechanisms are far from
understood. Avian females are the heterogametic sex (ZW), and the future sex of the offspring is determined at chromosome
segregation during meiosis I, shortly before the oocyte is ovulated. Assuming that the mother can detect the sex of the developing
oocyte before ovulation, it has been suggested that a follicle of the un-preferred sex could selectively be induced to become
atretic and regress instead of being ovulated (selective follicle abortion). This potential mechanism has been proposed to
underlie biased primary sex ratios in birds, including the homing pigeon (Columba livia domestica), which produces a modal clutch size of two eggs. However, without replacement by an additional, already mature follicle,
abortion of a preovulatory follicle would most likely result in either reduced clutch sizes or laying gaps, since a not-yet-recruited
follicle still needed to undergo the whole maturation phase. In the current study we killed female pigeons, which were adjusting
embryo sex of first eggs according to change in body mass. We examined ovaries for signs of follicle abortion but did not
find any supporting evidence. All females produced one or two mature follicles but only two out of the 56 experimental birds
produced an additional third mature follicle. Therefore, our results do not corroborate the hypothesis that pigeon mothers
manipulate primary offspring sex by selectively aborting follicles of the un-preferred sex. 相似文献
60.
Dennis F. Kahlbaum Jon M. Heuss George T. Wolff 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1070-1078
ABSTRACT Because the U. S. Environmental Protection Agency (EPA) has changed the National Ambient Air Quality Standards (NAAQS) for ambient particulate matter (PM), there is a great deal of interest in determining recent PM trends. This paper examines trends in PM10 (i.e., particulate matter less than 10 micrometers in diameter) for areas of the United States based on their attainment status—for PM10 and ozone nonattainment and attainment areas. The analysis also focuses on urban, suburban, and rural areas, and eastern and western areas. The time period of evaluation is from 1988 through 1995. To shed further light on the ambient PM10 trends, trends in ambient SO2, NO2, and volatile organic compounds (VOCs) are also analyzed. Finally, trends in emission inventories of SO2, NOx, VOCs, and PM10 are evaluated. Results of the analysis show that widespread and similar reductions in PM10 levels have occurred over the last seven years. Annual reductions range from 3.0% to 3.8%, with the greatest reductions coming in PM10 nonattainment areas, but with very significant reductions also in PM10 attainment areas, ozone attainment areas, and rural areas. The widespread reductions appear to be due to a set of controls or common factors that are having a fairly uniform effect in all of the areas. The consistency of the reductions in different areas suggests that the reductions may also be primarily in the fine particles (i.e., those less than 2.5 micrometers in diameter, or PM2.5), which are more readily transported than coarse particles. 相似文献