全文获取类型
收费全文 | 2693篇 |
免费 | 213篇 |
国内免费 | 418篇 |
专业分类
安全科学 | 565篇 |
废物处理 | 99篇 |
环保管理 | 446篇 |
综合类 | 1194篇 |
基础理论 | 362篇 |
环境理论 | 5篇 |
污染及防治 | 272篇 |
评价与监测 | 119篇 |
社会与环境 | 128篇 |
灾害及防治 | 134篇 |
出版年
2024年 | 8篇 |
2023年 | 29篇 |
2022年 | 42篇 |
2021年 | 59篇 |
2020年 | 74篇 |
2019年 | 78篇 |
2018年 | 79篇 |
2017年 | 130篇 |
2016年 | 130篇 |
2015年 | 121篇 |
2014年 | 155篇 |
2013年 | 216篇 |
2012年 | 205篇 |
2011年 | 184篇 |
2010年 | 159篇 |
2009年 | 156篇 |
2008年 | 120篇 |
2007年 | 181篇 |
2006年 | 184篇 |
2005年 | 148篇 |
2004年 | 120篇 |
2003年 | 129篇 |
2002年 | 88篇 |
2001年 | 84篇 |
2000年 | 75篇 |
1999年 | 61篇 |
1998年 | 48篇 |
1997年 | 33篇 |
1996年 | 34篇 |
1995年 | 37篇 |
1994年 | 25篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1972年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有3324条查询结果,搜索用时 15 毫秒
71.
72.
对采用共沉淀法制备的纳米Fe3O4颗粒进行表征,并探究在中温(35 ℃)厌氧消化过程中纳米Fe3O4浓度对产气性能的影响。结果表明:纳米Fe3O4浓度为100 mg/L时可使厌氧体系中的氨氮浓度维持在600~1 200 mg/L,pH为7~8,TCODCr以及SCODCr去除率分别提高了8.35%和9.90%;该浓度下厌氧体系中产生的挥发性脂肪酸(VFA)浓度最大,可达4 300 mg/L,且强化了对乙酸的利用;该试验组的产气性能最好,相对于空白组,其累积产气量提高了28.08%,产气周期缩短了2 d,甲烷浓度提高了6%。 相似文献
73.
煤气化技术的应用是我国能源战略的重要一环,但同时也会产生大量的煤气化炉渣,亟需研究可批量消纳的资源化利用技术。煤炭灰分中各种矿物相在气化炉内会随温度发生变化,通过对该变化的研究和总结,描述了煤炭灰分中各种矿物相在气化炉内的物化反应过程,并指出煤炭灰分对煤气化炉渣的最终形态特点具有决定性的影响;对煤气化炉渣中残碳的组成及其变化特点的研究表明,残碳对煤气化炉渣的最终利用途径具有重要影响;此外,通过分析煤气化炉渣利用技术研究现状,指出建材化利用技术和掺烧循环流化床原料技术是目前的主流途径;最后,展望了煤气化炉渣利用技术的发展方向,并提出了煤气化炉渣用于混凝土和水泥原料以及井下回填的技术途径。 相似文献
74.
以农业废弃物核桃青果皮为原料、F127为微结构调控剂、硝酸铝为中心配位离子,通过中心组合设计,螯合辅助共组装策略制备了系列铝基多孔碳材料并对制备参数进行优化分析。选择硝酸铝浓度、铝基复合材料与F127的质量比和碳化温度作为优化因素,研究各因素的不同水平对系列碳材料比表面积的影响。得到制备的最优条件为硝酸铝浓度1 mol·L-1,铝基复合材料与F127质量比为2.5及碳化温度850 °C。在此条件下,制备得到的碳样品的比表面积为1 505.86 m2·g-1,与预测值1 503.77 m2·g-1接近,说明与响应方程模型高度拟合。 相似文献
75.
为提高海洋红球菌SY095发酵产生物表面活性剂的能力,研究发酵培养基中碳源及氮源的影响,并通过响应面分析法优化培养基各组分的含量。首先通过单因素实验,确定培养基最佳碳源、氮源分别为大豆油和尿素,在此基础上,利用Plackett-Burman实验设计筛选出2个对表面活性剂产量有显著影响的因子为尿素和K2HPO4,通过最陡爬坡实验和响应面分析法对显著影响因子进行优化,获得海洋红球菌产表面活性剂的最佳培养基配方为:大豆油2%(体积分数),尿素2.35 g·L-1,K2HPO40.69 g·L-1,KH2PO4 1.0 g·L-1,MgSO4 0.5 g·L-1。使用该优化培养基配方,海洋红球菌发酵液的表面张力为29.254 mN·m-1,与预测值接近,表面张力活性比优化前提高了12.9%。 相似文献
76.
煤矿安全风险预控与隐患闭环管理信息系统设计研究 总被引:2,自引:1,他引:2
从事故风险管理理论出发,借鉴国外风险管理的流程和方法,总结国内煤矿安全管理中隐患治理的先进实践经验,设计了满足煤矿危险源辨识、评价、管理标准与措施制定流程的风险预控管理,隐患治理中的反馈式闭环管理以及员工"三违"的流程管理需求的煤矿安全管理信息系统。通过安全管理信息系统的实施,能够使煤矿的风险管理系统化、规范化,煤矿生产中的潜在危险源得到有效管理,隐患及人员不安全行为能够得到及时控制,避免或减少煤矿事故的发生。 相似文献
77.
Eugene L. Peck 《Journal of the American Water Resources Association》1997,33(1):125-134
ABSTRACT: Many users of hydrometeorological records are not aware of the number of inconsistencies and biases that occur in hydrometeorological records. Examples are presented illustrating how the exposures of sites for measurement of precipitation, wind, snow on the ground, and evaporation determine to a large extent how useful the records are for estimating areal conditions. For areas where precipitation in the form of snow produces a significant portion of the runoff, a smaller number of quality records may be more valuable for modeling than a much larger number of records of lower quality. Information is presented to show that the overall value of an operational hydrometeorological network is dependent upon how consistent and representative of average conditions the collected records are, especially for mountainous areas in cold regions. 相似文献
78.
Improving the Urban Stream Restoration Effort: Identifying Critical Form and Processes Relationships 总被引:1,自引:0,他引:1
Stream restoration projects are often based on morphological form or stream type and, as a result, there needs to be a clear tie established between form and function of the stream. An examination of the literature identifies numerous relationships in naturally forming streams that link morphologic form and stream processes. Urban stream restoration designs often work around infrastructure and incorporate bank stabilization and grade control structures. Because of these imposed constraints and highly altered hydrologic and sediment discharge regimens, the design of urban channel projects is rather unclear. In this paper, we examine the state of the art in relationships between form and processes, the strengths and weaknesses of these existing relationships, and the current lack of understanding in applying these relationships in the urban environment. In particular, we identify relationships that are critical to urban stream restoration projects and provide recommendations for future research into how this information can be used to improve urban stream restoration design. It is also suggested that improving the success of urban restoration projects requires further investigation into incorporating process-based methodologies, which can potentially reduce ambiguity in the design and the necessity of using an abundant amount of in-stream structures. 相似文献
79.
L. M. Cox W. J. Rawls J. F. Zuzel 《Journal of the American Water Resources Association》1975,11(5):1009-1012
ABSTRACT: Snow, one of Nature's greatest reservoirs, supplies most of the usable water in the Western United States. Reliable predictions of the quantity and timing of the release of this water are used in making management decisions involving irrigation, stock water and municipal water supplies, hydro-power generation, recreation, navigation, and pollution control Practically oriented research is vital for the proper development and management of this resource. In southwestern Idaho, the Northwest Watershed Research Center, ARS, USDA, is conducting intensive investigations for assessing snow Volumes, snow water content, and snow-melt over a watershed. Application of these research findings will result in better development and management of the water stored as snow in Nature's reservoir. 相似文献
80.
Jérémy Bonvoisin 《International Journal of Sustainable Engineering》2017,10(4-5):198-206
AbstractIn pursuit of coping mechanisms for the challenges of sustainable manufacturing, systematic methods have been developed to allow engineers to improve the ratio between products’ utility and environmental impact. These necessary efforts remain however limited if the surrounding production and consumption practices are not called into question at the same time. This article introduces open source product development as a potential approach for unlocking the limits of existing sustainable product design practices and to lead towards alternative and eco-efficient production and consumption practices termed as participative production. First, it discusses the potential advantages of this emerging practice in terms of environmental sustainability. Second, it provides a screened qualitative environmental analysis of 18 exemplary open source hardware products. Specific sustainable design principles implemented by these products are highlighted and discussed in order to identify challenges for further common research in the field of open source and sustainable product development. 相似文献