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541.
Size distribution of polycyclic aromatic hydrocarbons in urban and suburban sites of Beijing, China 总被引:9,自引:0,他引:9
PAHs in five-stage size segregated aerosol particles were investigated in 2003 at urban and suburban sites of Beijing. The total concentration of 17 PAHs ranged between 0.84 and 152 ng m(-3), with an average of 116 ng m(-3), in urban area were 1.1-6.6 times higher than those measured in suburban area. It suggested a serious pollution level of PAHs in Beijing. PAHs concentrations increased with decreasing the ambient temperature. Approximately 68.4-84.7% of PAHs were adsorbed on particles having aerodynamic diameter 2.0 microm. Nearly bimodal distribution was found for PAHs with two and three rings, more than four rings PAHs, however, followed unimodal distribution. The overall mass median diameter (MMD) for PAHs decreased with increasing molecular weight. Diagnostic ratios and normalized distribution of PAHs indicated that the PAHs in aerosol particles were mainly derived from fossil fuel combustion. Coal combustion for domestic heating was probably major contributor to the higher PAHs loading in winter, whereas PAHs in other seasons displayed characteristic of mixed source of gasoline and diesel vehicle exhaust. Biomass burning and road dust are minor contributors to the PAHs composition of these aerosol particles. Except for source emission, other factors, such as meteorological condition, photochemical decay, and transportation from source to the receptor site, should to be involved in the generation of the observed patterns. 相似文献
542.
As a component of a multi-level study of the anthropogenic lead cycle for year 2000 (52 countries, 8 regions, and the planet), we have estimated the lead flows in seven emission streams: tailings, slag, fabrication and manufacturing, dissipation from use, hibernation, landfilling, and dispersion following product discard. For every 1 kg of lead put into end use, 0.5 kg is lost to the environment, largely due to landfilling and dissipation from use. From the standpoint of the receiving media, 1/3 of the losses are to uncontained solids on land and 48% of the losses are to containment facilities on land. On a country basis, the largest losses occur in the United States and China, which between them are responsible for about 32% of total global lead losses. On a per capita basis, the highest lead losses occurred in the United Kingdom, Belgium-Luxembourg, and Ireland. 相似文献
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545.
Wang Xianmin Mao Hang 《Environmental science and pollution research international》2022,29(11):15681-15702
Environmental Science and Pollution Research - Spatio-temporal evolution of post-seismic landslides and debris flows provides a new perspective to understand post-earthquake evolution of geological... 相似文献
546.
Pine needles collected from 22 sites of six areas in Beijing city, China, were analyzed by instrumental neutron activation analysis (INAA) combined with organic extraction for extractable organohalogens (EOX) and extractable persistent organohalogens (EPOX). The concentrations of EOX (EOX = ECl + EOBr + EOI) were in the order of EOCl > EOBr > EOI. About 1.6-34% of EOCl remained as extractable persistent organochlorine (EPOCl) after treatment with concentrated sulfuric acid, which suggested that major fractions of EOCl in pine needles were an acid-liable or acid-soluble fraction. The fact that pine needle contained higher EOCl contents in chemical industrial and traffic hub areas indicated that chemical industries and exhaust emission from vehicle were the main sources of organochlorines in the Beijing's air. The relative proportions of the known organochlorines (such as HCHs, DDTs, chlordanes, HCB and PCBs) to total EOCl and EPOCl were 0.32-0.76% and 2.5-11.4%, respectively, which implied that a major portion of the EOCl and EPOCl measured in pine needles was unknown. The organochlorinated pesticides (OCPs) and PCBs concentrations in six areas were as follows: sigma HCH (sigma HCH = alpha- + beta- + gamma- + delta-HCH), 11.7-20.8 ng/g; sigma DDT (p,p'-DDT + p,p'-DDE + p,p'-DDD), 12.5-113.3 ng/g; hexachlorobenzene (HCB), 1.1-5.3 ng/g; sigma chlordane (cis-chlordane + trans-chlordane + heptachlor), 1.7-9.5 ng/g, sigma PCB, 41.8-270.5 ng/g, on dry weight basis. The samples from chemical industrial area and residential area nearby chemical industries contained the highest concentrations of sigma DDT, HCB, sigma chlordane and sigma PCB, while the contamination levels of most OCPs and PCBs in iron-steel industrial area were the lowest. The ratios of alpha/gamma-HCH (ranged from 0.9-1.5) and p,p'-DDT/DDTs (ranged from 72.1% to 91.0%) revealed the presence of the recent use of lindane and DDTs or impure dicofol in Beijing. 相似文献
547.
利用2005-2017年夏半年国家大监站的逐小时降水量资料,14个要素被设计来进行多角度分析。多数要素与地形高度有良好的负相关关系。时段雨量最大值主要集中地是四川盆地西部,其次是贵州南部,云南南部边缘地带有少许站点,云贵高原主体及其与青藏高原交接带内没有最大值出现。多个要素在9到12时出现日变化最高峰。月际变化一般在7月出现最大值。随月份推进,强降水区会在贵州西南部、云南南部边缘出现后,跳跃到川渝地区出现。时段累积雨量最大值随时间增加而增加,多个要素的时间增加一倍时雨量增大10%到20%。以小时而言,西南地区降水几率平均为1/10,最多的可以达到1/4,最少的不到1/14。6月份降水时数最多,10月的雨时数仅次于6月,4月最少。连续时段与标准日界时段雨量的显著差异出现在川渝地区;白天12 h降水与夜间12 h降水的显著差异也出现在川渝地区。总体而言,连续时段的累积雨量大于标准日界的相同时间长度的累积雨量,白天降水量大于夜间降水量。 相似文献
548.
毛竹枯梢病病原菌毒素的生物测定及成分研究 总被引:3,自引:0,他引:3
毛竹枯梢病病原菌培养液的不同浓度粗提液对高粱胚根抑制率明显大于对胚芽抑制率,胚根对毒素的敏感性大于胚芽对毒素的敏感性;在121℃加热15分钟,胰蛋白酶处理2hr后,培养滤液对胚根和胚芽的抑制作用与对照比较无差异;培养滤液及粗提液经过透析后,毒性显著降低,并且透析后的培养滤液对胚根已无抑制作用;通过α-萘酚反应、班乃德反应和茚三酮反应等化学测定和薄层层析进一步分析表明毒素为一种分子量较小、且含有葡萄糖和果糖或两者其一的还原性多糖。 相似文献
549.
钒的停流──诱导光度法测定及价态分析 总被引:1,自引:1,他引:1
依据V~(4+)对Cr~(6+-)I~-氧化还原反应的诱导作用,建立了微量V~(4+)的停流—动力学光度测定方法。方法的线性范围为0~2.1mg·l~(-1):最低检测浓度为0.008mg·l~(-1)。10倍量的V~(5+)不影响测定。测得V~(4+)后,还原V~(5+)为V~(4+),测定总钒量,进而对钒进行价态分析。 相似文献
550.