全文获取类型
收费全文 | 3421篇 |
免费 | 306篇 |
国内免费 | 545篇 |
专业分类
安全科学 | 984篇 |
废物处理 | 79篇 |
环保管理 | 272篇 |
综合类 | 1967篇 |
基础理论 | 441篇 |
污染及防治 | 199篇 |
评价与监测 | 56篇 |
社会与环境 | 59篇 |
灾害及防治 | 215篇 |
出版年
2024年 | 39篇 |
2023年 | 104篇 |
2022年 | 124篇 |
2021年 | 132篇 |
2020年 | 93篇 |
2019年 | 148篇 |
2018年 | 93篇 |
2017年 | 108篇 |
2016年 | 88篇 |
2015年 | 140篇 |
2014年 | 362篇 |
2013年 | 142篇 |
2012年 | 193篇 |
2011年 | 196篇 |
2010年 | 151篇 |
2009年 | 131篇 |
2008年 | 292篇 |
2007年 | 298篇 |
2006年 | 278篇 |
2005年 | 202篇 |
2004年 | 179篇 |
2003年 | 105篇 |
2002年 | 125篇 |
2001年 | 102篇 |
2000年 | 81篇 |
1999年 | 61篇 |
1998年 | 35篇 |
1997年 | 51篇 |
1996年 | 42篇 |
1995年 | 50篇 |
1994年 | 32篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有4272条查询结果,搜索用时 15 毫秒
81.
WAHG Ren-zhong 《环境科学学报(英文版)》2002,14(1):20-26
Population demography, seed production, biomassallocation, net photosynthesis and transpiration of two Leymus chinensis divergence populations and between two years in Songnenplain, northeast China were compared. Strong differences betweenthe dry 1997 and moist 1998 occurred in vegetative shoot and sexualshoot densities, sexual differentiation and tiller densities, aswell as in the lengths of inflorescence, seed numbers perinflorescence, seed weights and biomass allocation in eachpopulation respectively (P<0.01). While strong differences betweenthe two populations occurred in vegetative shoot densities, sexualshoot densities, sexual differentiation and seed weights in eachyear (P<0.01). The differences between the two populations intiller densities and in biomass allocation to sexual shoots were significant (P<0.05). But there were no significant differences between the two populations in the lengths of inflorescence, seed numbers per inflorescence and biomass allocation to rhizomes and vegetative shoots (P>0.05). Excepting the transpiration rate in the early June, the differences between the two populations in net photosynthesis and transpiration rate of vegetative shoots and sexual shoots were strongly significant in the early June and July respectively (P<0.01). Relative stable variations in population demography and physiological traits between the two populations indicated that they are divergently in the Songnen Plain. 相似文献
82.
83.
84.
广东境内河涌密布,对于环保部门而言,确保水环境安全是一件关系民生的大事.随着珠三角经济的高速发展,广东省环境压力持续增大,水环境状况同样不容乐观. 相似文献
85.
沈阳市城市降雨综合利用途径探讨 总被引:1,自引:0,他引:1
降雨是城市的宝贵水资源,开发利用雨水资源已成为当前的重要研究课题.在调查目前沈阳市水资源和降水资源的特点和状况的基础上,分析了沈阳市降水水质.同时借鉴了国内其它城市和世界上其它国家在降雨利用方面的先进技术和经验,提出了针对沈阳市降雨特点的雨水综合利用的途径和措施,为缓解沈阳市水资源短缺问题具有一定的指导作用. 相似文献
86.
87.
XU Min ZENG Guang-ming XU Xin-yi HUANG Guo-he SUN Wei JIANG Xiao-yun 《环境科学学报(英文版)》2005,17(6):946-952
Bayesian regularized BP neural network(BRBPNN) technique was applied in the chlorophyll-α prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of the network were obtained. After the selection of input variables using stepwise/multiple linear regression method in SPSS i1.0 software, the BRBPNN model was established between chlorophyll-α and environmental parameters, biological parameters. The achieved optimal network structure was 3-11-1 with the correlation coefficients and the mean square errors for the training set and the test set as 0.999 and 0.000?8426, 0.981 and 0.0216 respectively. The sum of square weights between each input neuron and the hidden layer of optimal BRBPNN models of different structures indicated that the effect of individual input parameter on chlorophyll- α declined in the order of alga amount 〉 secchi disc depth(SD) 〉 electrical conductivity (EC). Additionally, it also demonstrated that the contributions of these three factors were the maximal for the change of chlorophyll-α concentration, total phosphorus(TP) and total nitrogen(TN) were the minimal. All the results showed that BRBPNN model was capable of automated regularization parameter selection and thus it may ensure the excellent generation ability and robustness. Thus, this study laid the foundation for the application of BRBPNN model in the analysis of aquatic ecological data(chlorophyll-α prediction) and the explanation about the effective eutrophication treatment measures for Nanzui water area in Dongting Lake. 相似文献
88.
89.
《安全.健康和环境》2004,4(3):13
2004年2月18日,伊朗一列满载多种化学材料的货车在伊东北部脱轨,起火后并发生一连串爆炸,导致发生200余人丧生、350余人受伤的惨剧。据伊朗官方通讯社消息,共有5个村庄在爆炸中遭到严重损坏。 该列货车共有51节车厢,当时正停靠在内沙布尔市附近的阿布穆斯林这个小站,车上满载硫磺、燃油以及其他化学工业品。由于列车车厢在没有引擎牵引的情况下突然移动,而且没有列车员控制其方向,当列车滑行到卡亚姆车站时,终于翻车脱轨,并引发熊熊大火。 相似文献
90.