收费全文 | 12563篇 |
免费 | 562篇 |
国内免费 | 4501篇 |
安全科学 | 853篇 |
废物处理 | 807篇 |
环保管理 | 951篇 |
综合类 | 6999篇 |
基础理论 | 2067篇 |
环境理论 | 6篇 |
污染及防治 | 4444篇 |
评价与监测 | 484篇 |
社会与环境 | 443篇 |
灾害及防治 | 572篇 |
2024年 | 3篇 |
2023年 | 209篇 |
2022年 | 599篇 |
2021年 | 498篇 |
2020年 | 375篇 |
2019年 | 372篇 |
2018年 | 501篇 |
2017年 | 571篇 |
2016年 | 534篇 |
2015年 | 713篇 |
2014年 | 982篇 |
2013年 | 1298篇 |
2012年 | 1041篇 |
2011年 | 1204篇 |
2010年 | 875篇 |
2009年 | 856篇 |
2008年 | 895篇 |
2007年 | 702篇 |
2006年 | 662篇 |
2005年 | 489篇 |
2004年 | 356篇 |
2003年 | 441篇 |
2002年 | 389篇 |
2001年 | 315篇 |
2000年 | 344篇 |
1999年 | 399篇 |
1998年 | 331篇 |
1997年 | 312篇 |
1996年 | 295篇 |
1995年 | 261篇 |
1994年 | 177篇 |
1993年 | 157篇 |
1992年 | 114篇 |
1991年 | 94篇 |
1990年 | 65篇 |
1989年 | 54篇 |
1988年 | 44篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1961年 | 2篇 |
1959年 | 3篇 |
1955年 | 1篇 |
Boro rice, an emerging low-risk crop variety of rice, cultivated using residual or stored water after Kharif season. To enhance the quality and production of rice, potassium (K) and phosphorus (P) are the common constituents of agricultural fertilizers. However, excess application of fertilizers causes leaching of nutrients and contaminates the groundwater system. Therefore, assessment and optimization of fertilizer dose are needed for better management of fertilizers. Towards this, the present study determines the path, persistence, and mobility of K and P under the Boro rice cropping system. The experimental site consisted of four plots having Boro rice with four different fertilizer doses of nitrogen (N), P, K viz. 100%, 75%, 50%, and 25% of the recommended dose. Disturbed soil samples were analysed for K and P from pre-sown land to tillering stage at 0–5, 5–10, 10–15, 15–30, 30–45, and 45–60 cm depths. Simultaneously, K and available P were also simulated in the subsurface soil layers through the HYDRUS-1D model. The statistical comparisons were made with RMSER, E, and PBIAS between the modelled values and laboratory-measured values. Although, the results showed that all the treatments considered had agreeable simulations for both K and P, the K simulations were found to be better as compared to P simulations except for 25% where P simulations outperformed K. The simulated concentration at all doses was found most appropriate when measured for the subsurface layers (up to 45 cm), while showed an underestimation in the bottom layers (45–60 cm) of soil.
相似文献A process combining catalyzed Fe(0)-carbon microelectrolysis (IC-ME) with activated carbon (AC) adsorption was developed for advanced reclaimed water treatment. Simultaneous nitrate reduction and chemical oxygen demand (COD) removal were achieved, and the effects of composite catalyst (CC) addition, AC addition, and initial pH were investigated. The reaction kinetics and reaction mechanisms were calculated and analyzed. The results showed that CC addition could enhance the reduction rate of nitrate and effectively inhibit the production of ammonia. Moreover, AC addition increased the adsorption capacity of biorefractory organic compounds (BROs) and enhanced the degradation of BRO. The reduction of NO3?–N at different pH values was consistently greater than 96.9%, and NH4+–N was suppressed by high pH. The presence of CC ensured the reaction rate of IC-ME at high pH. The reaction kinetics orders and constants were calculated. Catalyzed iron scrap (IS)-AC showed much better nitrate reduction and BRO degradation performances than IS-AC and AC. The IC-ME showed great potential for application to nitrate and BRO reduction in reclaimed water.
相似文献