全文获取类型
收费全文 | 5452篇 |
免费 | 839篇 |
国内免费 | 1043篇 |
专业分类
安全科学 | 1718篇 |
废物处理 | 544篇 |
环保管理 | 689篇 |
综合类 | 2880篇 |
基础理论 | 406篇 |
环境理论 | 4篇 |
污染及防治 | 542篇 |
评价与监测 | 383篇 |
社会与环境 | 103篇 |
灾害及防治 | 65篇 |
出版年
2024年 | 11篇 |
2023年 | 83篇 |
2022年 | 174篇 |
2021年 | 215篇 |
2020年 | 234篇 |
2019年 | 204篇 |
2018年 | 177篇 |
2017年 | 250篇 |
2016年 | 286篇 |
2015年 | 341篇 |
2014年 | 334篇 |
2013年 | 475篇 |
2012年 | 555篇 |
2011年 | 487篇 |
2010年 | 354篇 |
2009年 | 360篇 |
2008年 | 216篇 |
2007年 | 355篇 |
2006年 | 372篇 |
2005年 | 266篇 |
2004年 | 204篇 |
2003年 | 214篇 |
2002年 | 191篇 |
2001年 | 169篇 |
2000年 | 158篇 |
1999年 | 114篇 |
1998年 | 108篇 |
1997年 | 95篇 |
1996年 | 91篇 |
1995年 | 63篇 |
1994年 | 49篇 |
1993年 | 30篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有7334条查询结果,搜索用时 15 毫秒
991.
John Cairns 《Journal of the American Water Resources Association》1970,6(6):868-878
Discharge of heated waste water may affect the entire aquatic ecosystem–the interrelated biological, chemical, physical system–and, if the temperature change is large, may destroy the capacity of the ecosystem to serve a variety of beneficial purposes. However, it is possible to discharge heated waste water in carefully controlled amounts without seriously degrading the aquatic ecosystem. There are four basic alternatives which are open to us with regard to the heated waste water problem which we may choose singly or in various combinations: (1) Placing all heated, waste water in streams, lakes, and oceans without regard to the effects. Thus considering the environmental damage as a necessary consequence of our increased power demand. (2) Using, but not abusing, existing ecosystems. This means regulating the heated waste water discharge to fit the receiving capacity of the ecosystem. (3) Finding alternative ways to dissipate or beneficially use waste heat. (4) Modifying ecosystems to fit the new temperature conditions. We are all dependent upon a life-support system which is partly industrial and partly ecological. Unfortunately, we have reached a stage of development where the non-expandable, ecological portion of our life-support system is endangered by the expanding industrial portion. Optimal function and full beneficial use of both portions of our life-support system will only be possible if a variety of disciplines and diverse points of view can cooperate and work together effectively. Since wastes in amounts that are acceptable taken one at a time may be lethal collectively, environmental management should be on a regional basis. 相似文献
992.
Emmet M. Owens Steven W. Effler Francesco Trama 《Journal of the American Water Resources Association》1986,22(2):219-227
ABSTRACT: The thermal stratification characteristics of a flow-augmentation reservoir, Round Valley Reservoir, New Jersey, and attendant driving conditions were documented and analyzed for portions of three years. Substantial differences in the thermal stratification regime of the reservoir occurred in response to the documented changes in meteorological, operating, and light penetration conditions. The features of stratification that were affected included: the depth of the upper mixed layer, the average temperature of the epilimnion, the temperature gradient in the metalimnion, and the average temperature in the hypolimnion. 相似文献
993.
994.
995.
996.
化学品突发性事故预测的不确定性分析 总被引:1,自引:0,他引:1
介绍化学品突发性事故预测的不确定性概率统计和模糊数学分析方法。对参数和模式的不确定性分别进行了讨论,计算机系统包括化学品常用数据库、事故识别模块,事故后果分析模块和不确定性分析模块,对液氯泄漏排放事故、液化气(丙烷)两相闪蒸爆炸和管道煤气(CO)泄漏伤害模式实例进行了分析。对连续源和瞬时源的讨论说明泄漏时间的确定对事故分析极为重要。 相似文献
997.
火灾中双层窗玻璃破裂机理的研究 总被引:1,自引:0,他引:1
把单层窗玻璃破裂的模型作为研究基础,基于原有的单层窗玻璃破裂的计算软件开发设计了双层窗玻璃破裂的模型,并对双层玻璃的内表面及其空隙的热传递过程和连续发生的玻璃破裂机理进行了研究。 相似文献
998.
999.
Waste plastics recycling by an entrained-flow gasifier 总被引:1,自引:0,他引:1
Takatoshi Shoji Kenjiro Shindoh Hironori Ozaki Atsushi Sodeyama 《Journal of Material Cycles and Waste Management》2001,3(2):75-81
We studied an entrained-flow gasification process which efficiently converts waste plastics to energy at a high energy recovery
rate. Waste plastics, after being shredded to <8 mm or <14 mm, were fed into an entrained-flow gasifier with air and oxygen.
In the gasifier, organic substances were pyrolyzed, partially combusted, and then converted into synthetic gas (CO, H2) at a high temperature (over 1600 K). The clarified gasification characteristics were that the lower heat value (LHV) of
the product gas was over 4.2 MJ/Nm3 and the cold gas efficiency was approximately 60%. Other inert substances in the wastes such as ashes and metals were melted
into slag and condensed on bag filters. The bag filters and a water scrubber removed impurities such as dusts, heavy metals,
and hydrogen halides from the product gases. Solid hydrocarbons, which include char and soot, were removed at a hot cyclone
and on the bag filters.
Received: July 19, 2000 / Accepted: October 3, 2000 相似文献
1000.
改进BP算法在煤与瓦斯突出预测中的应用 总被引:19,自引:7,他引:12
为了正确预测煤与瓦斯突出的趋势与危险性 ,基于反向BP神经网络 ,笔者提出了一种改进的BP网络模型 :为了加快BP网络的收敛速度 ,增强其跳出局部极小点的能力 ,采用了自适应变步长法和改进模拟退火法 (SA法 )相结合的方法。实际应用表明 ,该模型收敛速度快 ,准确性高 ,具有较高的可靠性和实用性 ,是一种十分有效的煤与瓦斯突出危险性预测方法。 相似文献