全文获取类型
收费全文 | 19704篇 |
免费 | 1377篇 |
国内免费 | 3929篇 |
专业分类
安全科学 | 2587篇 |
废物处理 | 329篇 |
环保管理 | 2974篇 |
综合类 | 10917篇 |
基础理论 | 2320篇 |
环境理论 | 12篇 |
污染及防治 | 2042篇 |
评价与监测 | 1129篇 |
社会与环境 | 1641篇 |
灾害及防治 | 1059篇 |
出版年
2024年 | 55篇 |
2023年 | 277篇 |
2022年 | 488篇 |
2021年 | 607篇 |
2020年 | 568篇 |
2019年 | 553篇 |
2018年 | 518篇 |
2017年 | 686篇 |
2016年 | 843篇 |
2015年 | 835篇 |
2014年 | 924篇 |
2013年 | 1180篇 |
2012年 | 1404篇 |
2011年 | 1582篇 |
2010年 | 1175篇 |
2009年 | 1275篇 |
2008年 | 948篇 |
2007年 | 1352篇 |
2006年 | 1344篇 |
2005年 | 1135篇 |
2004年 | 908篇 |
2003年 | 1003篇 |
2002年 | 800篇 |
2001年 | 678篇 |
2000年 | 623篇 |
1999年 | 600篇 |
1998年 | 455篇 |
1997年 | 367篇 |
1996年 | 308篇 |
1995年 | 297篇 |
1994年 | 268篇 |
1993年 | 224篇 |
1992年 | 179篇 |
1991年 | 130篇 |
1990年 | 91篇 |
1989年 | 47篇 |
1988年 | 49篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1973年 | 9篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Two Gram (+) bacterial strains, BSB6 and BSB12, showing resistance and potential for Se(IV) reduction among 26 moderately halotolerant isolates from the Bhitarkanika mangrove soil were characterized by biochemical and 16S rDNA sequence analyses. Both of them were strictly aerobic and able to grow in a wide range of pH (4-11), temperature (4-40 °C) and salt concentration (4-12%) having an optimum growth at 37 °C, pH ∼7.5 and 7% salt (NaCl). The biochemical characteristics and 16S rDNA sequence analysis of BSB6 and BSB12 showed the closest phylogenetic similarity with the species Bacillus megaterium. Both the strains effectively reduced Se(IV) and complete reduction of selenite (up to 0.25 mM) was achieved within 40 h. SEM with energy dispersive X-ray and TEM analyses revealed the formation of nano size spherical selenium particles in and around the bacterial cells which were also supported by the confocal micrograph study. The UV-Vis diffuse reflectance spectra and XRD of selenium precipitates revealed that the selenium particles are in the nanometric range and crystalline in nature. These bacterial strains may be exploited further for bioremediation process of Se(IV) at relatively high salt concentrations and green synthesis of selenium nanoparticles. 相似文献
922.
Wölz J Grosshans K Streck G Schulze T Rastall A Erdinger L Brack W Fleig M Kühlers D Braunbeck T Hollert H 《Chemosphere》2011,85(5):717-723
Bankside groundwater is widely used as drinking water resource and, therefore, contamination has to be avoided. In the European Union groundwater protection is explicit subject to Water Framework Directive. While groundwater pollution may originate from different sources, this study investigated on impacts via flood events.Groundwater was sampled with increasing distance to the river Rhine near Karlsruhe, Germany. Samples were HPLC-MS-MS analyzed for the river contaminant carbamazepine to indicate river water infiltration, giving permanent presence in 250 m distance to the river (14-47 μg L−1). Following a flood event, concentrations of about 16-20 μg L−1 could also be detected in a distance of 750 m to the river. Furthermore, estrogenic activity as determined with the Yeast Estrogen Screen assay was determined to increase up to a 17β-ethinylestradiol equivalent concentration (E-EQ) = 2.9 ng L−1 near the river, while activity was initially measured following the flood with up to E-EQ = 2.6 ng L−1 in 750 m distance. Detections were delayed with increasing distance to the river indicating river water expansion into the aquifer.Flood suspended matter and floodplain soil were fractionated and analyzed for estrogenic activity in parallel giving up to 1.4 ng g−1 and up to 0.7 ng g−1, respectively. Target analysis focusing on known estrogenic active substances only explained <1% of measured activities.Nevertheless, river water infiltration was shown deep into bankside groundwater, thus, impacting groundwater quality. Therefore, flood events have to be in the focus when aiming for groundwater and drinking water protection as well as for implementation of Water Framework Directive. 相似文献
923.
Tracing the sources of refractory dissolved organic matter in a large artificial lake using multiple analytical tools 总被引:2,自引:0,他引:2
Structural and chemical characteristics of refractory dissolved organic matter (RDOM) from seven different sources (algae, leaf litter, reed, compost, field soil, paddy water, treated sewage) were examined using multiple analytical tools, and they were compared with those of RDOM in a large artificial lake (Lake Paldang, Korea). Treated sewage, paddy water, and field soil were distinguished from the other sources investigated by their relatively low specific UV absorbance (SUVA) values and more pronounced fulvic-like versus humic-like fluorescence of the RDOM samples. Microbial derived RDOM from algae and treated sewage showed relatively low apparent molecular weight and a higher fraction of hydrophilic bases relative to the total hydrophilic fraction. For the biopolymer types, the presence of polyhydroxy aromatics with the high abundance of proteins was observed only for vascular plant-based RDOM (i.e., leaf litter and reed). Molecular weight values exhibited positive correlations with the SUVA and the hydrophobic content among the different RDOM, suggesting that hydrophobic and condensed aromatic structures may be the main components of high molecular weight RDOM. Principal component analysis revealed that approximately 77% of the variance in the RDOM characteristics might be explained by the source difference (i.e., terrestrial and microbial derived) and a tendency of further microbial transformation. Combined results demonstrated that the properties of the lake RDOM were largely affected by the upstream sources of field soil, paddy water, and treated sewage, which are characterized by low molecular weight UV-absorbing and non-aromatic structures with relatively high resistance to further degradation. 相似文献
924.
McGoldrick DJ Durham J Leknes H Kierkegaard A Gerhards R Powell DE McLachlan MS 《Chemosphere》2011,85(8):1241-1247
Cyclic volatile methyl siloxanes (cVMS) are high volume production chemicals used in a wide range of industrial and consumer products. Three cVMS compounds (D4, D5, and D6) have and are undergoing environmental risk evaluations in several countries and have been proposed for legal regulation in Canada. As interest in monitoring concentrations of these chemicals in the environment increase, there is a need to evaluate the analytical procedures for cVMS in biological matrices in order to assess the quality of data produced. The purpose of this study was to determine laboratory testing performance for measuring residues of D4, D5, and D6 in a standard set of fish homogenate samples and to estimate limits of determination for each substance. The samples sent to each laboratory consisted of homogenized whole body tissues of hatchery raised rainbow trout which were fed food fortified with D4, D5, and D6 (dosed) and trout that were fed standard food rations (control). The participants analyzed each sample using their analytical method of choice using their own standards and procedures for quantification and quality control. With a few exceptions, participating laboratories generated comparable results for D4, D5, and D6 in both the dosed and control samples having z-scores between 2 and −2. Method detection limits for the whole fish matrix were on average 2.4 ng g−1 ww for D4, 2.3 ng g−1 ww for D5, and 1.8 ng g−1 ww for D6. 相似文献
925.
926.
壳聚糖的物理/化学改性及其对含酚废水的处理 总被引:1,自引:0,他引:1
将壳聚糖物理改性为球形颗粒,然后在微波辐射下,球形壳聚糖与柠檬醛接枝反应,再与NaBH4还原反应,制备一种新型环保材料--物化改性壳聚糖.采用红外光谱仪(IR)、X衍射仪(XRD)、电子显微镜(SEM)和比表面测定及孔径分析仪(BET)结构表征改性壳聚糖.通过含酚制药废水的动态小柱吸附实验,研究了时间、柱高和出水流速等... 相似文献
927.
928.
929.
化学实验中,经常会出现空白值异常的情况。文中从可能对空白值产生影响的各个因素逐一进行分析,并在此基础上提出了控制空白值的手段和措施。 相似文献
930.
针对农村面源污染日渐突出的问题,以农村饮用水源地黄沙港为例分析了农村面源污染的现状和成因,并从乡镇规划、生活污水处理工艺选择、畜禽水产业污染治理、农药化肥的施用、农业废弃物利用技术等方面提出防治措施。 相似文献