全文获取类型
收费全文 | 25483篇 |
免费 | 1256篇 |
国内免费 | 3491篇 |
专业分类
安全科学 | 1363篇 |
废物处理 | 471篇 |
环保管理 | 7222篇 |
综合类 | 12008篇 |
基础理论 | 2500篇 |
环境理论 | 3篇 |
污染及防治 | 1701篇 |
评价与监测 | 1991篇 |
社会与环境 | 2535篇 |
灾害及防治 | 436篇 |
出版年
2024年 | 60篇 |
2023年 | 264篇 |
2022年 | 470篇 |
2021年 | 540篇 |
2020年 | 649篇 |
2019年 | 492篇 |
2018年 | 462篇 |
2017年 | 741篇 |
2016年 | 896篇 |
2015年 | 919篇 |
2014年 | 1063篇 |
2013年 | 1600篇 |
2012年 | 1558篇 |
2011年 | 1872篇 |
2010年 | 1210篇 |
2009年 | 1401篇 |
2008年 | 1204篇 |
2007年 | 1710篇 |
2006年 | 1584篇 |
2005年 | 1289篇 |
2004年 | 1188篇 |
2003年 | 1183篇 |
2002年 | 1053篇 |
2001年 | 855篇 |
2000年 | 904篇 |
1999年 | 767篇 |
1998年 | 558篇 |
1997年 | 496篇 |
1996年 | 409篇 |
1995年 | 374篇 |
1994年 | 353篇 |
1993年 | 302篇 |
1992年 | 231篇 |
1991年 | 166篇 |
1990年 | 127篇 |
1989年 | 103篇 |
1988年 | 104篇 |
1987年 | 96篇 |
1986年 | 78篇 |
1985年 | 57篇 |
1984年 | 67篇 |
1983年 | 68篇 |
1982年 | 79篇 |
1981年 | 80篇 |
1980年 | 89篇 |
1979年 | 86篇 |
1978年 | 59篇 |
1977年 | 50篇 |
1973年 | 50篇 |
1971年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Rudra P. Pradhan Mahendhiran S. Nair Mak B. Arvin John H. Hall 《Natural resources forum》2023,47(3):435-483
This article postulates strong endogenous relationships in lower income countries between institutional quality, financial development and sustained economic growth. These associations were investigated using the vector-error correction model (VECM) and Granger causality method for a sample of 79 countries from 2005 to 2022. The findings show that (1) these variables reinforce each other in the short run. (2) In the long run, both institutional quality and financial development can fuel economic growth. (3) The positive effect of institutional quality on economic growth is greater than that of financial development. Policy implications of these findings are that careful attention should be paid to co-development policies to enhance the institutional quality and the financial system in these economies. Policies should also consider economic growth strategies to enable sustainable economic growth rates. 相似文献
2.
Bodhipaksha Krishna Geethani Thilakarathne Stephen Schensul Sujithra K. Weeragoda Rohan Weerasooriya Ng Wun Jern 《环境质量管理》2023,32(4):371-378
Fifty percent of the dry zone areas in Sri Lanka have fluoride levels above 1 ppm. This paper discusses the ground conditions and recommends an appropriate range of fluoride in drinking water which can support preventive practices for improving the oral health of children 8-years old and younger. In efforts to address the Chronic Kidney Disease of Unknown etiology (CKDU), water treatment to reduce contaminant level in potable water has been implemented. Such treatment would also remove fluoride and has resulted in potable water with various fluoride levels, depending on concentrations in the raw water. While it is important to reduce fluoride levels, it is important to have appropriate residual levels for prevention of dental caries. It needs, however, to be noted fluoride in excess can cause dental fluorosis. In Sri Lanka's dry zone areas increasing prevalence of dental fluorosis with decreasing prevalence of dental caries has been noted. Consumption of tea and powdered milk could increase total intake of fluoride. Fluoridated toothpaste, when used properly, may, however, result in negligible intake of fluoride. Sri Lanka's hot tropical climate which results in substantial intake of fluids reinforces the need to consider reduction in water fluoride. Consideration of local studies and international standards indicate fluoride levels should be in the range of 0.225–0.500 ppm. In the range of 0.225–0.500 ppm, the prevalence of dental fluorosis and caries was only 14% and 8%, respectively, in an endemic district. When fluoride levels are above 0.500 ppm, the issue of dental fluorosis shall need to be addressed. When levels are below 0.225 ppm, oral health care services shall need to be directed at preventing dental caries. 相似文献
3.
Waste accumulation is a grave concern and becoming a transboundary challenge for environment. During Covid-19 pandemic, diverse type of waste were collected due to different practices employed in order to fight back the transmission rate of the virus. Covid-19 was proved to be capricious catastrophe of this 20th century and even not completely eradicated from the world. The havoc created by this imperceptible quick witted, pleomorphic deadly virus can't be ignored. Though a number of vaccines have been developed by the scientists but there is a fear of getting this virus again in our life. Medical studies prove that immunity drinks will help to reduce its reoccurrences. Coconut water is widely used among all drinks available globally. Its massive consumption created an incalculable pile of green coconut shells around the different corners of the world. This practice generating enormous problem of space acquisition for the environment. Both the environment and public health will benefit from an evaluation of quantity of coconut waste that is being thrown and its potential to generate value added products. With this context, present article has been planned to study different aspects like, coconut waste generation, its biological properties and environmental hazards associated with its accumulation. Additionally, this review illustrates, green technologies for production of different value added products from coconut waste. 相似文献
4.
Land degradation is a global problem that seriously threatens human society. However, in China and elsewhere, ecological restoration still largely relies on a traditional approach that focuses only on ecological factors and ignores socioeconomic factors. To improve the effectiveness of ecological restoration and maximize its economic and ecological benefits, a more efficient approach is needed that provides support for policy development and land management and thereby promotes environmental conservation. We devised a framework for assessing the value of ecosystem services that remain after subtracting costs, such as the opportunity costs, costs of forest protection, and costs for the people who are affected by the program; that is, the net value of ecosystem services (NVES). To understand the difference between the value of a resource and the net value of the ecosystem service it provides, we used data on VES, timber sales, and afforestation costs from China's massive national afforestation programs to calculate the net value of forest ecosystem services in China. Accounting for the abovementioned costs revealed an NVES of ¥6.1 × 1012 for forests in 2014, which was 35.9% less than the value calculated without accounting for costs. As a result, the NVES associated with afforestation was 55.9% less than the NVES of natural forests. In some regions, NVES was negative because of the huge costs of human-made plantations, high evapotranspiration rates (thus, high water opportunity costs), and low forest survival rates. To maximize the ecological benefits of conservation, it is necessary to account for as many costs as possible so that management decisions can be based on NVES, thereby helping managers choose projects that maximize both economic and ecological benefits. 相似文献
5.
A sequencing batch reactor was modeled using multi-layer perceptron and radial basis function artificial neural networks (MLPANN and RBFANN). Then, the effects of influent concentration (IC), filling time (FT), reaction time (RT), aeration intensity (AI), SRT and MLVSS concentration were examined on the effluent concentrations of TSS, TP, COD and NH4+-N. The results showed that the optimal removal efficiencies would be obtained at FT of 1 h, RT of 6 h, aeration intensity of 0.88 m3/min and SRT of 30 days. In addition, COD and TSS removal efficiencies decreased and TP and NH4+-N removal efficiencies did not change significantly with increases of influent concentration. The TSS, TP, COD and NH4+-N removal efficiencies were 86%, 79%, 94% and 93%, respectively. The training procedures of all contaminants were highly collaborated for both RBFANN and MLPANN models. The results of training and testing data sets showed an almost perfect match between the experimental and the simulated effluent of TSS, TP, COD and NH4+-N. The results indicated that with low experimental values of input data to train ANNs the MLPANN models compared to RBFANN models are more precise due to their higher coefficient of determination (R2) and lower root mean squared errors (RMSE) values. 相似文献
6.
基于复杂系统建模的水管理政策研究进展 总被引:3,自引:0,他引:3
基于Agent的建模方法(ABSS)通过自下而上的方式,考察系统中主体的不同状态和行为特征、主体与环境的作用、主体之间的作用,来表征系统的宏观特征,是进行复杂社会环境系统分析和政策研究的重要手段,在水资源、水环境管理系统中得到了有效的应用。本文在大量文献调研的基础上,讨论了ABSS建模方法的基本原理、主要特征、系统构成、分类方法和开发工具等特征,总结了其供水系统发展、水资源分配和流域水资源管理、农业土地和水资源利用、居民用水行为、农业污染控制及人类活动的水环境影响等方面的应用,分析了其在研究内容、研究方法、研究结果等方面的发展趋势,讨论了利用该方法研究我国水资源管理和水污染控制政策的必要性和重要性。 相似文献
7.
F. Pricope Ştefănescu G. Tiţescu I. Cărăuş D. Ureche 《Environmental Chemistry Letters》2003,1(2):149-151
During the artificial reproduction of salmonides, the fecundity can be increased either by improving the viability of spermatozoa,
or by extending the time period during which a roe micropile remains open, thus allowing its fecundation. Practically, this
can be achieved by the use of some fertilising techniques suitable for fish species. Here, we show that the reproduction of
rainbow trout in a 1:1 solution of deuterium-depleted water and distilled water led to a significant increase in survival
of roes during their embryonic development. Moreover, the addition of glucose and fructose into the deuterium-depleted fertilising
solutions led to a further increase in roe survival during embryonic development. The increase in survival is mainly explained
by an increase in the motility of spermatozoa. 相似文献
8.
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
9.
J. B. Harcum Jim C. Loftis Robert C. Ward 《Journal of the American Water Resources Association》1992,28(3):469-478
ABSTRACT: The use of nonparametric tests for monotonic trend has flourished in recent years to support routine water quality data analyses. The validity of an assumption of independent, identically distributed error terms is an important concern in selecting the appropriate nonparametric test, as is the presence of missing values. Decision rules are needed for choosing between alternative tests and for deciding whether and how to pre-process data before trend testing. Several data pre-processing procedures in conjunction with the Mann-Kendall tau and the Seasonal Kendall test (with and without serial correlation correction) are evaluated using synthetic time series with generated serial correlation and missing data. A composite test (pre-testing for serial correlation followed by one of two trend tests) is evaluated and was found to perform satisfactorily. 相似文献
10.
Tanay B. Yıldırım Tutku Ak Zuhal Ölmez 《Environment, Development and Sustainability》2008,10(6):871-881
While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined. 相似文献