全文获取类型
收费全文 | 28093篇 |
免费 | 5574篇 |
国内免费 | 29414篇 |
专业分类
安全科学 | 2605篇 |
废物处理 | 1386篇 |
环保管理 | 2357篇 |
综合类 | 38327篇 |
基础理论 | 4792篇 |
环境理论 | 1篇 |
污染及防治 | 9251篇 |
评价与监测 | 2217篇 |
社会与环境 | 1105篇 |
灾害及防治 | 1040篇 |
出版年
2024年 | 42篇 |
2023年 | 369篇 |
2022年 | 1084篇 |
2021年 | 1015篇 |
2020年 | 1446篇 |
2019年 | 2437篇 |
2018年 | 2678篇 |
2017年 | 2821篇 |
2016年 | 2523篇 |
2015年 | 3120篇 |
2014年 | 3914篇 |
2013年 | 4407篇 |
2012年 | 4061篇 |
2011年 | 3736篇 |
2010年 | 3306篇 |
2009年 | 3334篇 |
2008年 | 3138篇 |
2007年 | 2882篇 |
2006年 | 2496篇 |
2005年 | 1768篇 |
2004年 | 1465篇 |
2003年 | 1288篇 |
2002年 | 1129篇 |
2001年 | 1028篇 |
2000年 | 1211篇 |
1999年 | 1010篇 |
1998年 | 764篇 |
1997年 | 738篇 |
1996年 | 713篇 |
1995年 | 606篇 |
1994年 | 426篇 |
1993年 | 345篇 |
1992年 | 390篇 |
1991年 | 315篇 |
1990年 | 263篇 |
1989年 | 212篇 |
1988年 | 161篇 |
1987年 | 79篇 |
1986年 | 85篇 |
1985年 | 53篇 |
1984年 | 56篇 |
1983年 | 42篇 |
1982年 | 54篇 |
1981年 | 34篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1976年 | 2篇 |
1972年 | 8篇 |
1971年 | 7篇 |
1958年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
多波长法用于减小浊度对水源水中甲醛测定结果的影响 总被引:1,自引:1,他引:0
比较了减小水样浊度对样品结果影响的各种方法,包括过滤法、双波长法、三波长法,3种方法均基于乙酰丙酮分光光度法,测定波长均为414 nm。结果表明,以480 nm为参比波长的双波长法所得方法检出限为0.027 mg/L,采用470 nm与360 nm、460 nm与370 nm、450 nm与380 nm 3对参比波长的三波长法测得方法检出限为0.025~0.028 mg/L,这些方法用于检测0.100 mg/L标准点样品时,检测结果 RSD介于8.0%~8.6%。双波长法适合低浊度样品的直接分析,而浊度较高或双波长法测得结果大于方法检出限时,应采用三波长法进行定量分析,他们的使用有助于提高方法的准确度及减少工作量。用于地表水样品分析时,0.200、0.400 mg/L加标样品的回收率介于90.3%~101%,对应RSD介于0.0%~4.2%。 相似文献
53.
54.
A fragment constant QSAR model for evaluating the EC50 values of organic chemicals to Daphnia magna.
Shu Tao Xiaohuan Xi Fuliu Xu Bengang Li Jun Cao R Dawson 《Environmental pollution (Barking, Essex : 1987)》2002,116(1):57-64
The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests. 相似文献
55.
三峡库区水土流失特点及其环境危害防治措施探讨 总被引:15,自引:0,他引:15
水土流失是三峡库区主要环境问题之一,也是库区产生大量泥沙的根本因素,更是造成库区人民生活贫困的根源。本文就三峡库区水土流失的特点及其环境危害作了分析,提出了相应的防治措施,为水土流失防治工程提供科学依据。 相似文献
56.
Kennedy N. Igbokwe 《中国人口.资源与环境(英文版)》2005,(1)
1 INTRODUCTIONIn the past, natural resources management initiatives havefocused on large but specific sector projects such as dams,reservoirs for water supply schemes, irrigation systems,crop production, at forestation, etc. Often these projectswere treated as technical and administrative issues ratherthan as a socio-economic and political one. However, thehigh social and environmental cost of such schemes haveled to a change of paradigm since the 1980s towards small-scale community projec… 相似文献
57.
可张孔曝气器曝气能耗试验研究 总被引:1,自引:0,他引:1
通过试验研究,总结出可张孔曝气阻力损失的影响因素,以优化产品的结构设计参数,降低产品在工程应用中的能耗,获取更好的经济效益。 相似文献
58.
59.
Enhanced sludge solubilization by microbubble ozonation 总被引:7,自引:0,他引:7
A microbubble ozonation process for enhancing sludge solubilization was proposed and its performance was evaluated in comparison to a conventional ozone bubble contactor. Microbubbles are defined as bubbles with diameters less than several tens of micrometers. Previous studies have demonstrated that microbubbles could accelerate the formation of hydroxyl radicals and hence improve the ozonation of dyestuff wastewater. The results of this study showed that microbubble ozonation was effective in increasing ozone utilization and improving sludge solubilization. For a contact time of 80 min, an ozone utilization efficiency of more than 99% was obtained using the microbubble system, while it gradually decreased from 94% to 72% for the bubble contactor. The rate of microbial inactivation was obviously faster in the microbubble system. At an ozone dose of 0.02 g O3 g−1 TSS, about 80% of microorganisms were inactivated in the microbubble system, compared with about 50% inactivation for the bubble contactor. Compared to the bubble contactor, more than two times of COD and total nitrogen, and eight times of total phosphorus content were released from the sludge into the supernatant by using the microbubble system at the same ozone dosage. The application of microbubble technology in ozonation processes may provide an effective and low cost approach for sludge reduction. 相似文献
60.
The endocrine response of crucian carp injected intraperitoneally with extracted microcystins (MC) was investigated in this study. Fish were injected intraperitoneally either with 0.75% NaCl (control) and Microcystis extract corresponding to 150 and 600 microg microcystins per kg body weight. The plasma levels of triiodothyronine (T(3)), thyroxine (T(4)), free triiodothyronine (FT(3)), free thyroxine (FT(4)), and cortisol were determined at 0, 1, 3, 12, 24, and 48h post-administration of MC-containing extract. Treated fish displayed abnormal behaviors, such as a startle response and disoriented swimming, as well as changes in ventilation rates. Plasma cortisol concentrations of fish in both dose groups significantly increased after administration of extracted MC and remained high throughout the experiment, which suggested that MC elicited a stress response in treated fish. The profiles of cortisol changes in treated fish appeared to be dose dependent, indicating that fish in the high dose group experienced greater MC-induced disturbance. Mortality occurred after 12h in the high dose group. Plasma levels of T(4), T(3), FT(4), and FT(3) did not vary significantly between the control fish. In contrast to this, fish exposed to MC-containing extract showed significant declines in T(3), FT(4), and FT(3) levels in a dose-dependent manner throughout the experiment. Plasma T(4) levels, however, did not vary significantly in the low dose group, whereas they decreased significantly at 48h post injection in the high dose group. This study demonstrates that administration of microcystins-containing extract causes a stress response and reduces the plasma levels of thyroid hormones in crucian carp. These results illustrate that microcystins exerted potent effects on the endocrine system of crucian carp, through activating their hypothalamus-pituitary- interrenal axis and disturbing thyroid function. 相似文献