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91.
This study examines factors that affect foraging rate of free-flying bumblebees, Bombus terrestris, when collecting nectar, and also what factors determine whether they collect pollen or nectar. We show that nectar foraging rate (mass gathered per unit time) is positively correlated with worker size, in accordance with previous studies. It has been suggested that the greater foraging rate of large bees is due to their higher thermoregulatory capacity in cool conditions, but our data suggest that this is not so. Workers differing in size were not differentially affected by the weather. Regardless of size, naïve bees were poor foragers, often using more resources than they gathered. Foraging rate was not maximised until at least 30 trips had been made from the nest. Foraging rates were positively correlated with humidity, perhaps because nectar secretion rates were higher or evaporation of nectar lower at high humidity. Temperature, wind speed and cloud cover did not significantly influence foraging rate, within the summertime range that occurred during the study. Weather greatly influenced whether bees collected pollen or nectar. Pollen was preferably collected when it was warm, windy, and particularly when humidity was low; and preferably during the middle of the day. We suggest that bees collect pollen in dry conditions, and avoid collecting pollen when there is dew or rain-water droplets on the vegetation, which would make grooming pollen into the corbiculae difficult. Availability of sufficient dry days for pollen collection may be an important factor determining the success of bumblebee colonies.Communicated by M. Giurfa 相似文献
92.
Marcela K. Castelo Muriel Ney-Nifle Juan C. Corley Carlos Bernstein 《Behavioral ecology and sociobiology》2006,61(2):231-243
For parasitoids, host finding is a central problem that has been solved through a variety of behavioural mechanisms. Among species in which females do not make direct contact with hosts, as is the case for many dipteran parasitoids, eggs must be laid in an appropriate part of the host habitat. The asilid fly Mallophora ruficauda lays eggs in clusters on tall vegetation. Upon eclosion, pollen-sized larvae fall and parasitize soil-dwelling scarab beetle larvae. We hypothesized that wind dissemination of M. ruficauda larvae is important in the host-finding process and that females lay eggs at heights that maximize parasitism of its concealed host. Through numerical and analytical models resembling those used to describe seed and pollen wind dispersal, we estimated an optimal oviposition height in the 1.25- to 1.50-m range above the ground. Our models take into account host distribution, plant availability and the range over which parasitic larvae search for hosts. Supporting our findings, we found that the results of the models match heights at which egg clusters of M. ruficauda are found in the field. Generally, work on facilitation of host finding using plants focuses on plants as indicators of host presence. We present a case where plants are used in a different way, as a means of offspring dispersal. For parasitoids that carry out host searching at immature stages rather than as adults, plants are part of a dissemination mechanism of larvae that, as with minute seeds, uses wind and a set of simple rules of physics to increase offspring success. 相似文献
93.
Hajo Holzmann Axel Munk Max Suster Walter Zucchini 《Environmental and Ecological Statistics》2006,13(3):325-347
We introduce a new class of circular time series based on hidden Markov models. These are compared with existing models, their
properties are outlined and issues relating to parameter estimation are discussed. The new models conveniently describe multi-modal
circular time series as dependent mixtures of circular distributions. Two examples from biology and meteorology are used to
illustrate the theory. Finally, we introduce a hidden Markov model for bivariate linear-circular time series and use it to
describe larval movement of the fly Drosophila.
Received: September 2003 / Revised: March 2004 相似文献
94.
上海地区风速,风向,稳定度联合频率的计算及分析 总被引:1,自引:0,他引:1
以上海龙华气象测站5年(1981-1985年)的逐日气象资料为基础,计算了上海地区的气象联合频率,并进行了一定的分析讨论。计算结果可为大气污染浓度的计算,大气污染防治,及环境规划等提供参考依据。 相似文献
95.
《环境科学学报(英文版)》2023,35(4):633-643
The present study evaluates ground-based downward surface shortwave radiation (Rs) over the coastal region of Alicante (Southeastern Spain). Hourly measurements collected over the eleven-year period 2010-2020 are used. Two weather stations located over the region capital, Alicante, have been selected as representative of urban and suburban typologies. Two additional weather stations far from the city have been selected representing rural typologies. Rs is significantly reduced over the urban station during the morning hours within the winter season compared to the observations recorded over the suburban and rural stations, with a global mean difference of -81 and -120 W/m2 at 10 LT, respectively. However, no significant differences are obtained during the midday sun, with a global mean difference of -20 W/m2 between the urban and rural stations. With the aim of explaining these differences, the current paper investigates the relationship between Rs and different air pollutants: NOx, SO2, and fine particulate matter (PM2.5 and PM10) as well as the wind field measured at the urban and suburban stations. The results found in this work point towards a close relationship between Rs and NOx concentrations annual cycles, which are also influenced by the prevailing wind circulations observed over the study area. A global mean NOx concentration of 107 µg/m3 is observed over the urban station at 10 LT during the winter season. In contrast, these high concentrations are significantly reduced over the suburban station, with global mean value of 40 µg/m3 at 10 LT, for this period of the year. 相似文献
96.
Zoe S. Nivolianitou Barbara M. Synodinou Olga N. Aneziris 《Journal of Loss Prevention in the Process Industries》2004,17(6):419-429
This paper presents a methodology for the calculation of atmospheric stability classes in correlation with wind velocities for six sites of the Greek territory, namely Ellinikon (Athens), Elefsis, Megara, Heraklion, Chania and Patras, based on real data obtained from meteorological observations in these sites and on computations related with their geographic position. In addition to that, a comparison is presented of the atmospheric stability classes produced with online measurements for the Ellinikon (Athens) site with significant coincidence in the results.
These calculated values of the meteorological parameters (particularly of atmospheric stability) are most appropriate for uncertainty calculations in quantified risk assessments (QRAs) of hazardous installations sited in the above-mentioned areas, especially when risk and safety-related decisions need to be taken. Consequent results obtained with these parameters are more realistic compared to the “classical” assumption of D5/F2, which leads to significant diversification in the estimation of risk. 相似文献
97.
内蒙古天晧水泥有限公司将"挡风抑尘墙"技术成功应用在石灰石预均化堆场和煤场,对消减石灰石预均化堆场和煤场风力,抑制石灰石预均化堆场和煤场扬尘起到了很好的作用,解决了大型堆场扬尘治理的一个技术难题。现就"挡风抑尘墙"的工作机理、结构特点及其抑尘效果等进行分析介绍,以促进该技术的推广和应用。 相似文献
98.
99.
100.
风障减少尘埃飞起的风洞模拟研究 总被引:12,自引:1,他引:11
在环境风洞中对具有相同孔率但孔径不同的11种风障模型(金属网)的流场特性及网后煤堆模型的起尘特性进行模拟实验?结果表明,风障(网)的屏蔽作用取决于网的孔率;孔径雷诺数Re*存在着临界值(该实验为1200),当Re*小于临界值时,网后附近气流的湍流运动受到抑制,此时煤堆模型的起尘率随Re*的减小而减小,且对来流的湍流结构很敏感,当Re*大于临界值时,起尘率基本上不再随Re*变化而变化? 相似文献