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461.
全尺寸隧道火灾实验研究与烟气逆流距离的理论预测 总被引:2,自引:1,他引:2
在建成的隧道中实施全尺寸火灾试验,得到隧道火灾自然通风模式下的烟气温度纵向变化数据和纵向蔓延情况。用OriginPro7.5软件对实验数据进行处理、拟合,得到3次实验的烟气逆流的顶棚射流温度随着离开火源距离纵向衰减规律,建立了计算烟气逆流距离的预测公式。根据隧道实体火灾实验的测量结果与理论模型的预测结果的对比,验证了理论模型的有效性,为市政公路隧道建设采用自然通风模式提供科学依据。 相似文献
462.
实际应用的饮食业油烟净化设备(以下简称油烟净化设备)中,以静电式、机械过滤式、湿式,以及由上述三种技术组成的复合式产品为主。荷电湿式油烟净化器的开发应用,将具有很强的市场竞争力,未来几年,静电式技术将继续被广泛采用,机械式技术将更多地作为预处理手段与其他技术组合使用,湿法技术因兼有部分除味和去除柴油灶燃烧颗粒的功能等特点将更有针对性地应用于适当的场所。优化组合而成的经济高效的复合式技术在未来市场中将占据主导地位。 相似文献
463.
运行旅客列车隧道火灾模拟实验研究 总被引:6,自引:5,他引:1
笔者以相似理论为依据 ,以旅客列车卧铺车厢 1∶5的模型为研究对象 ,利用燃烧风洞提供的流场模拟列车在隧道中运行的速度场 ,在车厢模型中加入等比例的火灾载荷 ,进行了旅客列车隧道火灾模拟实验。研究了不同列车运行速度、不同列车火灾载荷、不同火源位置以及旅客卧铺车厢的不同状况下旅客列车火灾特征及火灾中烟气蔓延规律 ,提出了满足火灾救援和旅客疏散的要求 ,为隧道方案设计提供了可信的技术依据 相似文献
464.
Extending livestock grazing to the steep slopes has led to unstable grazing systems in the East African Highlands, and new
solutions and approaches are needed to ameliorate the current situation. This work was aimed at studying the effect of livestock
grazing on plant attributes and hydrological properties. The study was conducted from 1996 to 2000 at the International Livestock
Research Institute at Debre Ziet Research Station. Two sites were selected: one at 0–4% slope, and the other at 4–8% slope.
The treatments were: (1) no grazing (control); (2) light grazing, 0.6 animal unit months per hectare (aum/ha); (3) moderate
grazing, 1.8 aum/ha; (4) heavy grazing, 3.0 aum/ha; (5) very heavy grazing, 4.2 aum/ha; (6) initially plowed and continuously
very heavily grazed, 4.2 aum/ha. The result showed that species richness, infiltration rate, bare ground, and soil loss significantly
varied with grazing pressure. Species richness was higher in grazed plots compared to nongrazed plots. Biomass yield improved
on heavily grazed plots as cow dung accumulated over years. Cynodon dactylon plant species persisted with livestock grazing pressure in both sites. Infiltration rate improved and soil erosion declined
in all treatments after the first year. 相似文献
465.
Understanding the problems of grazing land in vertisol areas and seeking long-lasting solutions is the central point where
mixed crop livestock is the second stay for the majority of the population. In order to understand this, the current study
was conducted at two sites, one with 0–4% slope and the other with 4–8% slope at Ginchi watershed, 80 km west of Addis Ababa,
Ethiopia. The specific objectives of the study were to quantify changes in plant species richness, biomass, plant cover, and
soil physical and hydrological properties. The grazing regimes were: moderate grazing (regulated), heavy grazing (free grazing),
and no grazing (closed to any grazing), which was considered the control treatment. The results showed that the biomass yield
in nongrazed plots was higher than in the grazed plots. However, the biomass yield in grazed plots improved over the years.
Species richness and percentage of dominant species attributes were better in medium grazed plots than the other treatments.
Soil compaction was higher in very heavily grazed plots than in nongrazed and medium-grazed plots. In contrast to that, the
soil water content and infiltration rate were better in nongrazed plots than in grazed plots. Soil loss in grazed plots decreased
with the increase of biomass yields and as the soil was more compacted by livestock trampling during the wet season. Finally
since the medium stocking rate is better in species richness and plant attributes, and lies between nongrazed and heavily
grazed plots in the rest of the measured parameters, it could be the appropriate stocking rate to practice by the smallholder
farmer. 相似文献
466.
467.
Shun'ichi Honda Naoyuki Miyata Keisuke Iwahori 《Journal of Material Cycles and Waste Management》2002,4(1):46-50
In our previous work, the primary sludge from wastewater treatment plants was shown to contain a considerable amount of cellulose
(about 20%, based on suspended solids) owing to the discharge of toilet paper. For the purpose of using the cellulose as a
biomass resource, this study examined a simple method for its recovery. When fibrous cellulose was suspended in 0.3% sulfuric
acid and autoclaved at 130°C for 60 min, 85%–88% of the initial solids remained without dissolving. Under these conditions,
an activated sludge sample not containing cellulose was strongly hydrolyzed and only 7% of the initial solids remained. The
prescribed amounts of cellulose added to the activated sludge sample were quantitatively recovered by the autoclaving treatment.
In the treatment of primary sludge containing >20% cellulose, residual solids with relatively high levels of cellulose (>69%)
could be obtained. The results indicate that the method proposed here could recover cellulose practically from waste sewage
sludge for biomass utilization.
Received: July 17, 2000 / Accepted: July 4, 2001 相似文献
468.
水喷淋控制烟气输运的大涡模拟研究 总被引:4,自引:0,他引:4
本文采用大涡模拟方法研究了烟气输运和水喷淋之间的相互作用问题。研究目的是探讨水喷淋(或细水雾)对烟气输运的控制和抑制的有效性和要行性。为了有效地模拟烟气输运过程,本文采用了低马赫数近似下的三维可压缩滤波形式的Navier-Stokes方程进行有限差分法数值求解。烟气的生成和运动采用携带燃烧反应热的Lagrangian粒子(热元模型)来模拟,同时喷淋器喷出的细水雾也采用模型模拟。在本文的研究中,烟气由一个独立的火池产生并且被一股来流(或风)驱动,从而在一个方形槽道里形成烟气输运,在火池下游槽道的顶部布置若干个喷淋器并喷出水雾,以便探讨水雾对烟气输运的控制作用。本文着重分析讨论了不同喷淋角和水雾半径下水雾对烟气输运的控制和抑制效果。 相似文献
469.
470.
Fred J. Brenner Elaine K. Brenner Patricia E. Brenner Richard P. Steiner 《Environmental management》1994,18(2):307-315
Current surface mine regulations as ascribed under the Surface Mining Control and Reclamation Act of 1977 require that mine
lands be returned to the approximate original contours (AOC) with an area coverage of at least 70% and to biological productivity
equal to or greater than that which existed prior to mining. Six different procedures were evaluated on nine mine sites in
northwestern Pennsylvania as to their suitability to estimate aboveground biomass on mines reclaimed as hayland and pastures.
Biomass estimates determined by different procedures were compared to those obtained by random clip plots and with landowner
estimates of the annual yield from each site. Biomass estimates determined from a disk meter and landowner interviews varied
approximately ±10% from those obtained from random clip plots compared to a variation of ±8%–37% for the other procedures.
The number of samples required to obtain reliable estimates within ±10% of the mean at 95% confidence intervals varied among
the different sampling procedures according to the variance in biomass on the site. Although all procedures may be used either
singly or in combination to estimate above ground biomass on reclaimed mine lands, the combination of the disk meter, profile
board, and vegetation height is recommended because of their ease of measurement compared to the other procedures. 相似文献