全文获取类型
收费全文 | 26537篇 |
免费 | 646篇 |
国内免费 | 5544篇 |
专业分类
安全科学 | 1250篇 |
废物处理 | 1380篇 |
环保管理 | 2791篇 |
综合类 | 10225篇 |
基础理论 | 5700篇 |
环境理论 | 9篇 |
污染及防治 | 8277篇 |
评价与监测 | 1276篇 |
社会与环境 | 1118篇 |
灾害及防治 | 701篇 |
出版年
2023年 | 282篇 |
2022年 | 772篇 |
2021年 | 640篇 |
2020年 | 484篇 |
2019年 | 521篇 |
2018年 | 687篇 |
2017年 | 796篇 |
2016年 | 901篇 |
2015年 | 1045篇 |
2014年 | 1419篇 |
2013年 | 2492篇 |
2012年 | 1611篇 |
2011年 | 1835篇 |
2010年 | 1368篇 |
2009年 | 1425篇 |
2008年 | 1528篇 |
2007年 | 1431篇 |
2006年 | 1271篇 |
2005年 | 1019篇 |
2004年 | 766篇 |
2003年 | 906篇 |
2002年 | 831篇 |
2001年 | 876篇 |
2000年 | 769篇 |
1999年 | 681篇 |
1998年 | 552篇 |
1997年 | 507篇 |
1996年 | 494篇 |
1995年 | 472篇 |
1994年 | 423篇 |
1993年 | 344篇 |
1992年 | 282篇 |
1991年 | 257篇 |
1990年 | 230篇 |
1989年 | 211篇 |
1988年 | 160篇 |
1987年 | 144篇 |
1986年 | 143篇 |
1985年 | 104篇 |
1984年 | 123篇 |
1983年 | 128篇 |
1982年 | 129篇 |
1981年 | 120篇 |
1980年 | 97篇 |
1979年 | 114篇 |
1978年 | 75篇 |
1977年 | 77篇 |
1975年 | 80篇 |
1973年 | 72篇 |
1967年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
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
23.
I Chu D C Villeneuve B McDonald V E Secours V E Valli 《Journal of environmental science and health. Part. B》1987,22(3):303-317
Pentachlorotoluene (PCT) and pentabromotoluene (PBT) are environmental contaminants detected in the Great Lakes ecosystem. In view of the paucity of toxicity data and the potential for human exposure, a subacute (28 day) and a subchronic (91 day) study were conducted in the rat. In the subacute study, groups of 10 male and 10 female rats were fed the diet containing PCT or PBT at 0, 0.5, 5.0, 50 or 500 ppm for 28-days. In the subchronic study, the group size was increased to 15, the dose levels were 0, 0.05, 0.5, 5.0, 50 and 500 ppm in the diet and the exposure period was 91 days. Growth rate and food consumption were not affected by exposure to either chemical in the subacute and subchronic study. Clinical observations revealed no abnormalities. Decreased hemoglobin was observed in female rats fed 5.0 ppm PCT and higher levels in the subacute (28 day) study. In the same study the hematocrit value and erythrocyte numbers of females fed 5.0 or 500 ppm PCT diets were significantly lower than the control. In both subacute and subchronic studies mild dose-dependent histopathological changes were observed in the thyroid, liver and kidney of rats fed PCT and PBT diets. In general male rats were more susceptible than females to the treatment of PCT and PBT. Based on these data, it was concluded that the no observable adverse effect level for PCT was 50 ppm in the diet (3.5 mg/kg b.w./day) and that of PBT was 5.0 ppm (0.35 mg/kg b.w./day). 相似文献
24.
25.
王新茹 《防灾科技学院学报》2007,9(1):111-113
布鲁纳在20世纪60年代以结构主义理论为基础领导了美国的课程改革运动.虽然此次课程改革以失败而告终,但是发现式学习方法及其教学方法的提出却受到了广泛的关注.布鲁纳也曾就发现式学习进行了专门的论述.本文从发现式学习法的特点、作用出发来探求我国目前正在进行的第八轮新课程改革,试图为我国新课程改革中学习、教学方法的改革提供一个新的视角. 相似文献
26.
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
27.
Wang Degang Huang Xiaoting 《中国人口.资源与环境(英文版)》2006,4(1):45-53
At present, internal rural tourism is at the stage of upgrading and renewing, and ecotourism has been considered to be the main direction. This paper discussed the concepts and criteria of rural tourism and ecotourism, analyzed a typical case of Nongke Village of Chengdu City-being considered to be the first rural tourism site in China, went deep into the problems of the contents and criteria of the development of rural ecotourism, and tried to probe into the principles of the development of rural ecotourism both theoretically and practically so as to understand the rules of the development of rural ecotourism . 相似文献
28.
29.
30.