全文获取类型
收费全文 | 30349篇 |
免费 | 344篇 |
国内免费 | 457篇 |
专业分类
安全科学 | 951篇 |
废物处理 | 1439篇 |
环保管理 | 3675篇 |
综合类 | 5066篇 |
基础理论 | 7952篇 |
环境理论 | 18篇 |
污染及防治 | 8028篇 |
评价与监测 | 2070篇 |
社会与环境 | 1773篇 |
灾害及防治 | 178篇 |
出版年
2023年 | 140篇 |
2022年 | 322篇 |
2021年 | 316篇 |
2020年 | 240篇 |
2019年 | 284篇 |
2018年 | 478篇 |
2017年 | 477篇 |
2016年 | 742篇 |
2015年 | 568篇 |
2014年 | 885篇 |
2013年 | 2416篇 |
2012年 | 1060篇 |
2011年 | 1434篇 |
2010年 | 1168篇 |
2009年 | 1196篇 |
2008年 | 1437篇 |
2007年 | 1485篇 |
2006年 | 1263篇 |
2005年 | 1093篇 |
2004年 | 982篇 |
2003年 | 1075篇 |
2002年 | 949篇 |
2001年 | 1238篇 |
2000年 | 863篇 |
1999年 | 517篇 |
1998年 | 347篇 |
1997年 | 358篇 |
1996年 | 356篇 |
1995年 | 423篇 |
1994年 | 446篇 |
1993年 | 352篇 |
1992年 | 374篇 |
1991年 | 352篇 |
1990年 | 386篇 |
1989年 | 341篇 |
1988年 | 296篇 |
1987年 | 278篇 |
1986年 | 223篇 |
1985年 | 248篇 |
1984年 | 265篇 |
1983年 | 256篇 |
1982年 | 241篇 |
1981年 | 222篇 |
1980年 | 175篇 |
1979年 | 194篇 |
1978年 | 176篇 |
1975年 | 140篇 |
1974年 | 117篇 |
1972年 | 130篇 |
1971年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A. V. M. Subba Rao Arun K. Shanker V. U. M. Rao V. Narsimha Rao A. K. Singh Pragyan Kumari C. B. Singh Praveen Kumar Verma P. Vijaya Kumar B. Bapuji Rao Rajkumar Dhakar M. A. Sarath Chandran C. V. Naidu J. L. Chaudhary Ch. Srinivasa Rao B. Venkateshwarlu 《Environmental Modeling and Assessment》2016,21(1):17-30
992.
993.
Kusum Komal Karati G. Vineetha N. V. Madhu P. Anil M. Dayana B. K. Shihab A. I. Muhsin C. Riyas T. V. Raveendran 《Environmental monitoring and assessment》2017,189(12):653
El Niño, an interannual climate event characterized by elevated oceanic temperature, is a prime threat for coral reef ecosystems worldwide, owing to their thermal threshold sensitivity. Phytoplankton plays a crucial role in the sustenance of reef trophodynamics. The cell size of the phytoplankton forms the “master morphological trait” with implications for growth, resource acquisition, and adaptability to nutrients. In the context of a strong El Niño prediction for 2015–2016, the present study was undertaken to evaluate the variations in the size-structured phytoplankton of Kavaratti reef waters, a major coral atoll along the southeast coast of India. The present study witnessed a remarkable change in the physicochemical environment of the reef water and massive coral bleaching with the progression of El Niño 2015–2016 from its peak to waning phase. The fluctuations observed in sea surface temperature, pH, and nutrient concentration of the reef water with the El Niño progression resulted in a remarkable shift in phytoplankton size structure, abundance, and community composition of the reef waters. Though low nutrient concentration of the waning phase resulted in lower phytoplankton biomass and abundance, the diazotroph Trichodesmium erythraeum predominated the reef waters, owing to its capability of the atmospheric nitrogen fixation and dissolved organic phosphate utilization. 相似文献
994.
A. M. Stellacci A. Castrignanò A. Troccoli B. Basso G. Buttafuoco 《Environmental monitoring and assessment》2016,188(3):199
Hyperspectral data can provide prediction of physical and chemical vegetation properties, but data handling, analysis, and interpretation still limit their use. In this study, different methods for selecting variables were compared for the analysis of on-the-ground hyperspectral signatures of wheat grown under a wide range of nitrogen supplies. Spectral signatures were recorded at the end of stem elongation, booting, and heading stages in 100 georeferenced locations, using a 512-channel portable spectroradiometer operating in the 325–1075-nm range. The following procedures were compared: (i) a heuristic combined approach including lambda-lambda R2 (LL R2) model, principal component analysis (PCA), and stepwise discriminant analysis (SDA); (ii) variable importance for projection (VIP) statistics derived from partial least square (PLS) regression (PLS-VIP); and (iii) multiple linear regression (MLR) analysis through maximum R-square improvement (MAXR) and stepwise algorithms. The discriminating capability of selected wavelengths was evaluated by canonical discriminant analysis. Leaf-nitrogen concentration was quantified on samples collected at the same locations and dates and used as response variable in regressive methods. The different methods resulted in differences in the number and position of the selected wavebands. Bands extracted through regressive methods were mostly related to response variable, as shown by the importance of the visible region for PLS and stepwise. Band selection techniques can be extremely useful not only to improve the power of predictive models but also for data interpretation or sensor design. 相似文献
995.
996.
997.
998.
999.
1000.