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1.
景观中存在着某些关键性的局部、位置和空间联系,它们构成某种战略性的格局--景观安全格局,对维护景观中某种过程的健康和安全有着至关重要的作用。以北京香山滑雪场和规划过程为例,本文系统地探讨了景观生态安全格局、景观礼觉安全格局和景观文化安全格局的判别及其敏感地段的场地规划办法。地理信息系统在场地规划中的有着广阔的应用前景。  相似文献
2.
Nitrate removal in zero-valent iron packed columns   总被引:25,自引:0,他引:25  
Westerhoff P  James J 《Water research》2003,37(8):1818-1830
Nitrate removal by laboratory and field continuous-flow zero-valent iron (Fe(0)) packed bed columns was evaluated for different influent water qualities (pH, dissolved oxygen (DO), nitrate concentration) and several months of operation (600-1500 bed volumes (BVs)). In contrast to previous batch experiments with Fe(0) where nitrate was stoichiometrically converted to ammonium, only 70% of the applied nitrogen was recovered as nitrate, ammonium, or nitrite (<0.1mg/L) during shorter-term column tests (2-20 BVs) and less than 25% of the applied nitrogen was recovered during longer-term field testing (500-1000 BVs) at elevated nitrate levels (approximately 25mg N/L). Nitrate removal was accompanied by a pH increase, DO decrease, and soluble iron increase. During longer-term operation (500-1500 BVs) iron and calcium precipitates were observed, by SEM and EDX analyses, to form in the packed columns. Precipitation led to cementation and reduction in permeability for the Fe(0)/sand media in the packed column. Different abiotic and microbial-mediated mechanisms may be involved during shorter- and longer-term operation of Fe(0) systems and the role of iron precipitates should be further evaluated.  相似文献
3.
铁、炭流化床预处理染料废水研究   总被引:21,自引:2,他引:19  
用铁、炭流化床反应器所进行的染料废水预处理试验结果表明,该工艺克服了固定床铁、炭反应器易钝化、结块的缺点、运行管理方便。在原水CODcr为3750mg/L、色度为1500倍时,两者的去除率分别达到了77%和90%。  相似文献
4.
Zeng L  Li X  Liu J 《Water research》2004,38(5):1318-1326
This study explored the feasibility of utilizing industrial waste iron oxide tailings for phosphate removal in laboratory experiments. The experimental work emphasized on the evaluation of phosphate adsorption and desorption characteristics of the tailing material. The adsorption isotherm, kinetics, pH effect and desorption were examined in batch experiments. Five isotherm models were used for data fitting. The three-parameter equations (Redlich-Peterson and Langmuir-Freundlich) showed more applicability than the two-parameter equations (Freundlich, Langmuir and Temkin). A modified equation for calculation of the separation factor using the Langmuir-Freundlich equation constants was developed. The initial phosphate adsorption on the tailings was rapid. The adsorption kinetics can be best described by either the simple Elovich or power function equation. The phosphate adsorption on the tailings tended to decrease with an increase of pH. A phosphate desorbability of approximately 13-14% was observed, and this low desorbability likely resulted from a strong bonding between the adsorbed PO(4)(3-)and iron oxides in the tailings. Column flow-through tests using both synthetic phosphate solution and liquid hog manure confirmed the phosphate removal ability of the tailings. Due to their low cost and high capability, this type of iron oxide tailings has the potential to be utilized for cost-effective removal of phosphate from wastewater.  相似文献
5.
红粘土有效胶结特征的初步研究   总被引:19,自引:2,他引:17       下载免费PDF全文
 本文通过时红粘土有效胶结铁含量确定方法的探讨,系统地研究了一种典型红粘土的胶结特征。结果表明:游离氧化铁起胶结作用的只是其中一部分,其含量可通过动态化学选择溶解法确定,有效胶结铁的溶蚀给红粘土的工程特性带来明显的影响。  相似文献
6.
Khanal SK  Huang JC 《Water research》2003,37(9):2053-2062
A series of chemostat studies were conducted at a constant influent total organic carbon of 3750 mg/L (equivalent chemical oxygen demand (COD) of 10,000 mg/L) but at different influent sulfates of 1000, 3000 and 5000 mg/L in order to investigate the feasibility of online sulfide toxicity control through periodic oxygenation to the recycled biogas stream. The oxygen dosing for sulfide oxidation was regulated by using oxidation-reduction potential (ORP) as a controlling parameter. During oxygenation at elevated ORPs of -230 and -180 mV (50 and 100 mV above natural ORP of -280 mV, respectively), the dissolved and gaseous sulfides were completely eliminated which resulted in a concomitant improvement in methane yield by 56.3% at 5000 mg/L influent sulfate. However, at influent sulfates of 1000 and 3000 mg/L, both methane generation rate and sulfate removal efficiency were dropped appreciably at elevated ORPs. Facultative heterotrophs were found to consume as high as 66.3% of the influent COD during oxygenation. For effective sulfide oxidation at lower sulfate levels, it was no longer required to raise the ORP by as much as 50 or 100 mV. The actual needed ORP increase depended on the influent sulfate. This study had proven that the ORP-controlled oxygenation was reliable for achieving consistent online sulfide control during anaerobic treatment of high-sulfate wastewater.  相似文献
7.
Chemical reduction of nitrate by nanosized iron: kinetics and pathways   总被引:17,自引:0,他引:17  
Yang GC  Lee HL 《Water research》2005,39(5):884-894
This study was conducted to investigate chemical reduction of nitrate by nanoscale zero-valent iron (ZVI) in aqueous solution and related kinetics and pathways. In the last decade, employment of micro-scale ZVI has gained its popularity in nitrate reduction. To further study chemical reduction of nitrate, nanosized iron was synthesized and tested in this work. It has a size in the range of 50-80 nm and a BET surface area of 37.83 m(2)g(-1). Chemical reduction of nitrate by nanosized iron under various pHs was carried out in batch experiments. Experimental results suggest that nitrate reduction by nanosized ZVI primarily is an acid-driven surface-mediated process. A stronger acidic condition is more favorable for nitrate reduction. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. Additional test results also showed that the reduction rate of nitrate increased as the dose of nanosized ZVI increased. In all tests, reaction rate equations developed do not obey the first- or pseudo-first-order reaction kinetics with respect to the nitrate concentration. Based on the research findings obtained, two possible reaction pathways for nitrate reduction by nanoscale iron particles have been proposed in this work.  相似文献
8.
生物固锰除锰机理与生物除铁除锰技术   总被引:16,自引:4,他引:12  
在pH中性条件下生物接触滤层中Mn^2 的氧化是生物氧化,滤层中以除锰菌为核心的生物群系的平衡与稳定是除锰活性的基础。生物滤层不但可以同时氧化去除Fe^2 、Mn^2 ,而且对进入滤层前已氧化成Fe^3 的微细颗粒也有良好的截留作用。以此生物固锰除锰机制为基础开发了弱曝气、一级过滤的生物除铁除锰简缩流程,确定了相应的设计与运行参数并指导了沈阳市开发区生物除铁除锰水厂的设计与运行。投产一年多来出水水质良好,总铁为痕量,锰<0.0.05mg/L。  相似文献
9.
厌氧下的PHB和聚磷酸盐及其生化机理研究   总被引:15,自引:2,他引:13  
用氧化还原电位仪严格监测反应过程,准确测定了在厌氧状况下PHB的合成量与聚酸盐的释放量;对活性污泥细胞内的PHB颗粒和聚磷粒进行了大量染色及显微镜检验分析。通过试验证明,厌氧状况发生了PHB大量合成与聚磷酸盐大量释放,并得出二者关系曲线图,对其生化机理进行了深入研究。  相似文献
10.
铁屑过滤/生化法处理糠醛废水   总被引:14,自引:0,他引:14  
由于糠醛废水酸性较强(pH值为2~3),因此很难通过传统的酸碱中和来调整pH值,从而影响生物处理效果.而采用铁屑过滤池处理时,利用铁和氢离子的氧化还原反应调节废水的pH值,并结合厌氧/好氧生化法去除COD、BOD5,可使出水达到<污水综合排放标准>(GB8978-1996)的一级标准.  相似文献
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