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61.
Net emissions of CH4 and CO2 in Alaska: implications for the region's greenhouse gas budget. 总被引:1,自引:0,他引:1
Q Zhuang J M Melillo A D McGuire D W Kicklighter R G Prinn P A Steudler B S Felzer S Hu 《Ecological applications》2007,17(1):203-212
We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are approximately 3 Tg CH4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr). 相似文献
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63.
生物降解途径的理论预测与QSBR研究 总被引:4,自引:1,他引:4
本文把有机污染生生物降解途径理论预测的结果与QSBR模型中化合物选择相结合,所遵循相同理论生物降解途径作为化合物分组的原则,以分子连接性接数和EHOMO作为结构参数与电性参数,采用逐步回归的方法建立了新的QSBR模型,新模型的预测民实验结果能较好地吻合。 相似文献
64.
在浓度场基础上,利用总磷、总氮和COD三项指标的综合指数法,结合管理部门提供的资料,划分了滇不不环境保护功能区,给出了划分指标值及功能区划分图。 相似文献
65.
拓扑指数在定量结构生物降解性关系中的应用 总被引:10,自引:3,他引:10
本文采用二氧化碳生成量实验,对训练组有机物,利用逐步回归分析程序,从计算和十四种分子连接性指数中筛选出与生物降解性最为相关的分子结构描述参数,建立定量结构-生物降解性关系模型,其相关系数为0.931,利用该模型对预测组质的预测结果表明,此模型对芳香化合物的好氧生物降解性具有良好的预测能力,其正确预测率达83.3%。 相似文献
66.
汞矿地区人发中甲基汞的气相色谱测定 总被引:6,自引:0,他引:6
本文采用气相色谱法测定人发中甲基汞,对人发的酸度,浸取时间,人发与酸液的比例,以及无机汞存在的影响作了测定和选择,方法的平均回收率96.6%,精确度2.8%,方法可靠性用氢化物原子荧光法核对,结果一致,并对我国某矿区职工,儿童及产妇发样分析结果作了讨论。 相似文献
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68.
Pulse jet fabric filters (PJFFs) have become an attractive option of particulate collection utilities, because they can meet stringent particulate emission limits regardless of variation in operating conditions. Despite their wide applications, the present control algorithm for PJFFs can best be described as rudimentary. In this paper, a modeling and control strategy based on the local model network (LMN) is proposed. An extended self-organizing map (ESOM) network is developed to construct the LMN model of the filtration process using the filter's input-output data. Subsequently, these ESOM local models are incorporated into the design of local generalized predictive controllers (GPC), and the proposed controller design is obtained as the weighted sum of these local controllers. Simulation results show that the proposed controller design yields a better performance than both conventional GPC and proportional plus integral (PI) controllers yield. 相似文献
69.
70.
Virus retention and transport through Al-oxide coated sand columns: effects of ionic strength and composition 总被引:11,自引:0,他引:11
Knowledge of the factors that influence the fate and transport of viruses in porous media is very important for accurately determining groundwater vulnerability and for developing protective regulations. In this study, six saturated sand column experiments were performed to examine the effects of a positively charged Al-oxide, which was coated on sand particles, on the retention and transport of viruses (phiX174 and MS-2) in background solutions of different ionic strength and composition. We found that the Al-oxide coating on sand significantly removed viruses during their transport in a phosphate buffered saline (PBS) solution. Mass balance calculations showed that 34% of the input MS-2 was inactivated/irreversibly sorbed on the surface of Al-oxide coated sand whereas 100% of phiX174 was recovered. Results from this study also indicated that higher ionic strength facilitated the transport of both phiX174 and MS-2 through the Al-oxide coated sand. This was attributed to the effect of ion shielding, which at higher ionic strength decreased the electrostatic attraction between the viral particles and the sand surface and consequently decreased virus sorption. Strong effect of the ionic strength indicates that an outer-sphere complexation mechanism was responsible for the virus sorption on the Al-oxide coated sand. Ion composition of the background solutions was also found to be a significant factor in influencing virus retention and transport. Virus transport was enhanced in the presence of phosphate (HPO(4)(2-)) as compared to bicarbonate (HCO(3)(-)), and the effect of HPO(4)(2-) was more significant on MS-2 than on phiX174. The presence of bivalent cations (Ca(2+) and Mg(2+)) increased virus transport because the cations partially screened the negative charges on the viruses therefore decreased the electrostatic attraction between the positively charged sand surface and the negatively charged viruses. Mass recovery data indicated that bivalent cations gave rise to a certain degree of inactivation/irreversibly sorption of phiX174 on the surface of Al-oxide coated sand. On the contrary, the bivalent cations appeared to have protected MS-2 from inactivation/irreversibly sorption. This study provides some insights into the mechanisms responsible for virus retention and transport in porous media. 相似文献