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901.
为揭示半填半挖黄土路基的变形规律及其影响因素,为高填方黄土路基稳定性的评估提供科学依据。以国道G310典型半填半挖黄土路基为例,运用Settle3D软件对不同工况条件下的黄土路基进行精确建模与系统分析。结果表明:自然条件下路基左右侧沉降量差别不大,而降雨条件下原状黄土侧的沉降大于压实黄土侧的沉降,土层交界处沉降差异显著;降雨条件下中心点的沉降曲线在原填土交界处发生转折,表明压实效果显著;各施工阶段间沉降量差值呈非线性减小趋势,但降雨条件下的稳定时间更长。因此施工中控制路基压实度和采取合理的路基防水排水措施非常重要。 相似文献
902.
采用微宇宙培养法,分析了不同水动力条件(不循环、水循环和泥循环)对微污染景观水体富营养化模拟过程中藻类演替的影响.结果表明,水循环和泥循环使得水体的TP值前期增加后期减少,前期藻类生长主要受TP影响,而后期浊度成了重要的影响因素;水循环引起的TP值减少及蓝藻聚集状态的破坏,导致了藻类的生长明显减缓,但优势种的演化过程却... 相似文献
903.
Silvie Pavlickova Anja Klancnik Magda Dolezalova Sonja Smole Mozina Ivan Holko 《Journal of environmental science and health. Part. B》2017,52(8):570-576
Attachment of pathogenic bacteria to food contact surfaces and the subsequent biofilm formation represent a serious threat for the food industry, since these bacteria are more resistant to antimicrobials or possess more virulence factors. The main aim of this study was to investigate the correlation between antibiotic resistance against 13 antibiotics, distribution of 10 virulence factors and biofilm formation in 105 Escherichia coli strains according to their origin. The high prevalence of antibiotic resistance that we have found in wildlife isolates could be acquired by horizontal transfer of resistance genes from human or domestic or farm animals. Consequently, these commensal bacteria might serve as indicator of antimicrobial usage for human and veterinary purposes in the Czech Republic. Further, 46 out of 66 resistant isolates (70%) were able to form biofilm and we found out statistically significant correlation between prevalence of antibiotic resistance and biofilm formation ability. The highest prevalence of antibiotic resistance was observed in weak biofilm producers. Biofilm formation was not statistically associated with any virulence determinant. However, we confirmed the correlation between prevalence of virulence factors and host origin. Chicken isolates possessed more virulence factors (66%), than isolates from wildlife (37%). We can conclude that the potential spread of antibiotic resistance pattern via the food chain is of high concern for public health. Even more, alarming is that E. coli isolates remain pathogenic potential with ability to form biofilm and these bacteria may persist during food processing and consequently lead to greater risks of food contamination. 相似文献
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GUO Zhao-hai YANG Min ZHANG Yu PEI Yi-shan ZHANG Jing-song FAN Jie Junji HIROTSUJI 《环境科学学报(英文版)》2006,18(2):209-213
The effectiveness of preozonation was evaluated on treating a bromide-bearing dam source water in south China through batch-scale experiments. Preozonation at ozone doses of 0.5-1.0 mg/L (at ozone consumption base) enhanced total organic carbon (TOC) removal through coagulation, and resulted in an almost linear reduction of ultraviolet absorbance at 254 nm (LW2s4). The removals of TOC (after coagulation) and UV254 at the ozone dose of 1.0 mg/L were 36% and 70%, respectively. Preozonation at an ozone dose between 0.5 and 1.0 mg/L resulted in the removal of disinfection byproducts formation potential (DBFP) including trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP) for about 50%. The removals of THMFP and HAAFP decreased with the further increase of ozone dose. Ozonation of bromide-bearing water (bromide concentration, 34 μg/L) produced a bromate concentration under the detection limit(2μg/L) at ozone doses 〈1.5 mg/L. However, bromate 〉10μg/L could be produced when the bromide concentration was increased to 96 μg/L. 相似文献
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Cohen MJ Dabral S Graham WD Prenger JP Debusk WF 《Environmental monitoring and assessment》2006,116(1-3):427-457
Rapid, repeatable assessment of ecological condition is critical for quantitative ecosystem monitoring. Soils provide a sensitive,
integrative indicator for which sampling and analysis techniques are well defined. We evaluated soil properties as indicators
of ecological condition (subjectively classified into minimally/moderately/severely degraded based on vegetative, hydrologic
and edaphic cues) at 526 sites within Ft. Benning military installation (Georgia, USA). For each sample, we measured 17 biogeochemical
parameters, and collected high-resolution diffuse reflectance spectra using visible/near infrared reflectance spectroscopy
(VNIRS). VNIR spectra have been related to numerous soil attributes — we examine them here for diagnosing integrated response
(i.e., ecological condition). We used ordinal logistic regression (OLR) and classification trees (CT) to discriminate between
condition categories using both sets of predictors (biogeochemistry and spectra). Sixteen biogeochemical parameters were significantly
different across condition categories; however, multivariate models greatly improved discrimination ([calibration, validation]
accuracy of [69%, 66%] and [96%, 73%] for OLT and CT models, respectively). Important predictors included total C, total P,
and Mehlich K/Ca/Mg. VNIR spectra further improved discrimination ([calibration, validation] accuracy of [74%, 70%] and [96%,
75%] for OLR and CT models, respectively). While spectra were comparably effective at discriminating minimally degraded sites,
they were significantly more effective at discriminating severely degraded sites. Error rates across confounding factors suggest
that watershed of origin and landscape position were the only important confounders, likely due to imbalanced sampling. We
conclude that multivariate diagnosis improves accuracy, and that VNIR spectroscopy, which yields substantial cost and logistical
improvements over conventional analyses, provides an effective tool for rapid condition diagnosis. 相似文献
909.
微生物絮凝剂高产菌株的筛选及培养条件的研究 总被引:4,自引:0,他引:4
采用随机分离的方法,从旱地、水田和池塘的污泥中分选出12种产絮凝剂的菌株。其中随机标号为I2、F11和G菌株的絮凝效果比较好,进一步根据不同培养时间、碳源、氮源和助凝离子,对此3株菌进行了培养条件及絮凝条件的研究。又依据絮凝反应时凝聚团产生的快慢和大小,确定菌株I2、F11有最好的絮凝效果。实验过程中还发现了筛选产絮凝剂菌株的新方法。 相似文献
910.