全文获取类型
收费全文 | 6792篇 |
免费 | 391篇 |
国内免费 | 1317篇 |
专业分类
安全科学 | 463篇 |
废物处理 | 202篇 |
环保管理 | 1573篇 |
综合类 | 3230篇 |
基础理论 | 1304篇 |
环境理论 | 3篇 |
污染及防治 | 580篇 |
评价与监测 | 335篇 |
社会与环境 | 680篇 |
灾害及防治 | 130篇 |
出版年
2024年 | 36篇 |
2023年 | 113篇 |
2022年 | 194篇 |
2021年 | 189篇 |
2020年 | 199篇 |
2019年 | 198篇 |
2018年 | 199篇 |
2017年 | 264篇 |
2016年 | 289篇 |
2015年 | 330篇 |
2014年 | 310篇 |
2013年 | 430篇 |
2012年 | 436篇 |
2011年 | 612篇 |
2010年 | 388篇 |
2009年 | 442篇 |
2008年 | 436篇 |
2007年 | 527篇 |
2006年 | 466篇 |
2005年 | 331篇 |
2004年 | 263篇 |
2003年 | 289篇 |
2002年 | 204篇 |
2001年 | 185篇 |
2000年 | 167篇 |
1999年 | 134篇 |
1998年 | 93篇 |
1997年 | 98篇 |
1996年 | 99篇 |
1995年 | 65篇 |
1994年 | 59篇 |
1993年 | 45篇 |
1992年 | 39篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 29篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1975年 | 10篇 |
1974年 | 9篇 |
排序方式: 共有8500条查询结果,搜索用时 375 毫秒
91.
Numerous studies support that biodiversity predict most to ecosystem functioning, but whether other factors display a more significant direct impact on ecosystem functioning than biodiversity remains to be studied. We investigated 398 samples of the phytoplankton phosphorus resource use efficiency (RUEP = chlorophyll-a concentration/dissolved phosphate) across two seasons in nine plateau lakes in Yunnan Province, China. We identified the main contributors to phytoplankton RUEP and analyzed their potential influences on RUEP at different lake trophic states. The results showed that total nitrogen (TN) contributed the most to RUEP among the nine lakes, whereas community turnover (measured as community dissimilarity) explained the most to RUEP variation across the two seasons. Moreover, TN also influenced RUEP by affecting biodiversity. Species richness (SR), functional attribute diversity (FAD2), and dendrogram-based functional diversity (FDc) were positively correlated with RUEP in both seasons, while evenness was negatively correlated with RUEP at the end of the rainy season. We also found that the effects of biodiversity and turnover on RUEP depended on the lake trophic states. SR and FAD2 were positively correlated with RUEP in all three trophic states. Evenness showed a negative correlation with RUEP at the eutrophic and oligotrophic levels, but a positive correlation at the mesotrophic level. Turnover had a negative influence on RUEP at the eutrophic level, but a positive influence at the mesotrophic and oligotrophic levels. Overall, our results suggested that multiple factors and nutrient states need to be considered when the ecosystem functioning predictors and the biodiversity-ecosystem functioning relationships are investigated. 相似文献
92.
超临界二氧化碳流体萃取土壤中有机污染物的研究进展 总被引:4,自引:0,他引:4
就近年来人们利用超临界二氧化碳流体对有机污染物污染的土壤所做的研究工作以及所取得的成果进行了总结。 相似文献
93.
从城市的结构和功能出发,提出推广生态建筑,提倡生态工艺,搞好城乡生态和加强宏观调控的城市可持续发展策略,为人们科学认识现代城市的发展趋势提供新思路。 相似文献
94.
95.
不同车速下,对四种通风模式(A关闭通风口和风扇、B关闭通风口打开风扇、C打开通风口关闭风扇、D打开通风口和风扇)车内二氧化碳浓度进行分析研究。通风口关闭的状态,无论是否打开风扇及车速快慢,车内CO2浓度严重超标。通风口打开:不开风扇,以50km/h速度行驶,车内CO2浓度高于标准限量;速度提高到80km/h,车内CO2浓度可低于标准限量,通风口和缝隙的换气可以保障车内的空气质量;而打开风扇可以有效排除车内污染物。车速提高,各种通风模式的换气量都增加,属于缝隙换气贡献的比例增加,属于风扇换气贡献的比例减小,属于通风口换气贡献比例变化不大。基于研究结果,提出了一些减少车内污染的通风方式建议。 相似文献
96.
针对沈阳市区二氧化硫污染现状 ,结合本市经济发展的实际 ,就如何削减二氧化硫的排放量 ,提出了 5项对策及有关的监督控制管理措施。 相似文献
97.
99.
Rob H.G.Jongman 《环境科学学报(英文版)》2003,15(2):173-181
The paper gives an overview of approaches towards ecological networks throughout Europe.It does not intend to present a complete picture,but to highlight comon developments within countries and regions and show common principles and differences between countries and regions that have to be taken into account when developing a joint European intiative,Countries or regions that have not been included can be active in the same way ,but information was not accessible to be authors for different reasons.This overview shows the comparable trends in decline of landscapes and the diversity in approaches to biodiversity conservation and nature conservation planning.Understanding the differences and common issues are of utmost imprtance to generalise common principles and to understand the way neighbours and other European partners approach problems. 相似文献
100.
The influence of source and timing of nitrogen fertilizers on yield and nitrogen use efficiency of four sweet potato cultivars 总被引:2,自引:0,他引:2
R. O. Ankumah V. Khan K. Mwamba K. Kpomblekou-A 《Agriculture, ecosystems & environment》2003,100(2-3):201
Nitrogen (N) availability is a very important determinant of crop yield. It is also one of the most expensive inputs in crop production. Thus, the efficient management of N by farmers with limited resource is a very important part of successful soil and crop management system. A field study was conducted on a Norfolk sandy loam soil at the George Washington Carver Agricultural Experiment Station, Tuskegee, AL, to evaluate the influence of fertilizer source and timing on the yield of four sweet potato [Ipomoea batatas (L.)] cultivars. Two N sources (urea, CO(NH2)2 and ammonium nitrate, NH4NO3), four sweet potato cultivars (‘Georgia Jet’, GA-Jet; ‘TU-82-155’, TU-155; ‘TU-1892’; and ‘Rojo Blanco’, Rojo-Bl) and three times (zero, single, and split applications) were used in a factorial designed experiment. Plants were harvested after 80 and 120 days and total and marketable yields determined. Nitrogen recovery efficiency, yield efficiency and physiological efficiency were also determined. Total and marketable yields of early maturing cultivars were significantly higher than of late maturing cultivars (P<0.05). The single application of N resulted in significantly higher yield in storage roots than split application (P<0.05). Physiological efficiency values were highly correlated with total marketable yields. Recovery rates increased with time. Late maturing cultivars tended to have higher N recovery and physiological efficiency than early maturing cultivars. These results suggest that cultivar maturity group should play an important part in N fertilization recommendations for sweet potato. 相似文献