全文获取类型
收费全文 | 42368篇 |
免费 | 8045篇 |
国内免费 | 30362篇 |
专业分类
安全科学 | 6100篇 |
废物处理 | 1559篇 |
环保管理 | 3762篇 |
综合类 | 46653篇 |
基础理论 | 7042篇 |
污染及防治 | 8809篇 |
评价与监测 | 2829篇 |
社会与环境 | 2077篇 |
灾害及防治 | 1944篇 |
出版年
2024年 | 159篇 |
2023年 | 798篇 |
2022年 | 2320篇 |
2021年 | 2253篇 |
2020年 | 2874篇 |
2019年 | 2929篇 |
2018年 | 3076篇 |
2017年 | 3297篇 |
2016年 | 2861篇 |
2015年 | 3743篇 |
2014年 | 4412篇 |
2013年 | 5161篇 |
2012年 | 5363篇 |
2011年 | 5015篇 |
2010年 | 4538篇 |
2009年 | 4332篇 |
2008年 | 4092篇 |
2007年 | 3959篇 |
2006年 | 3520篇 |
2005年 | 2544篇 |
2004年 | 1936篇 |
2003年 | 1577篇 |
2002年 | 1380篇 |
2001年 | 1214篇 |
2000年 | 1346篇 |
1999年 | 1028篇 |
1998年 | 706篇 |
1997年 | 681篇 |
1996年 | 671篇 |
1995年 | 579篇 |
1994年 | 393篇 |
1993年 | 311篇 |
1992年 | 378篇 |
1991年 | 301篇 |
1990年 | 256篇 |
1989年 | 207篇 |
1988年 | 155篇 |
1987年 | 79篇 |
1986年 | 82篇 |
1985年 | 53篇 |
1984年 | 55篇 |
1983年 | 40篇 |
1982年 | 47篇 |
1981年 | 34篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1958年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
81.
82.
Fenton法氧化处理水中土霉素的研究 总被引:2,自引:0,他引:2
为了评价Fenton法预处理抗生素生产废水中残留的高浓度土霉素的可行性,对Fenton试剂(Fe2 -H2O2)法催化氧化降解水溶液中的土霉素进行了研究.探讨了H2O2与Fe2 投加比例、投加量以及起始pH值对降解效果的影响,同时考察了土霉素废水中大量共存的草酸根离子对氧化过程的影响.结果表明,当H2O2与Fe2 按照5:1的比例投加时降解效率最高,最佳初始pH值在3.0-4.0之间.在最佳投加比例下,H2O2投加量为0.9 mmol/L,100 mg/L的土霉素可在10 min内得到完全降解.最佳反应条件下经过处理后土霉素水溶液TOC的去除率达40%左右,可生化性(BOD5/COD)也得到明显的改善.水中共存的草酸根离子对氧化效率具有明显的影响,但通过增加亚铁离子的量可以消除草酸的影响. 相似文献
83.
Processes involved in uptake and release of nitrogen dioxide from soil and building stones into the atmosphere 总被引:1,自引:0,他引:1
Atmospheric NO2 was taken up by samples of various soils and building stones. The NO2 uptake rate constants were highest in soil samples taken during the summer months. However, the NO2 uptake rate constants of the soils and building stones were not significantly correlated with any of the following variables: moisture, pH, ammonium, nitrite, or nitrate. NO2 uptake by soil and stone was not abolished by autoclaving indicating a chemical uptake process. NO2 uptake by acidic and air-dry soils and stones resulted in nearly stoichiometric reduction of NO2 to NO. This reduction was enhanced by the addition of ferrous iron and was further enhanced by incubation under 1 ppmv SO2. The results suggest that NO2 reduction may be coupled to oxidation of ferrous to ferric iron which may be reduced again by atmospheric SO2 thus regenerating the ferrous iron content of the soil or stone. Conversion of NO2 to NO was not observed in neutral or/and moist soils and stones. NO2 was also taken up by purified and sterilized quartz sand moistend with water. This uptake was enhanced by addition of humic material but not by addition of bacteria which both had been extracted from genuine soil. Under most conditions, only uptake but no release of NO2 was observed. However, NO2 was released in air-dry soils that were heated to 45–65°C, or in ammonium-fertilized soil or stone that was drying up at room temperature. Under the latter conditions mimicking field practice, the NO2 release reached rates that were similar to the NO release rates. 相似文献
84.
4种不同生境的蟹类金属硫蛋白cDNA的克隆与比较 总被引:2,自引:0,他引:2
利用Carcinus maenas金属硫蛋白氨基酸序列资料,用全简并引物从鳃组织总RNA中扩增并克隆了首个甲壳类金属硫蛋白cDNA片段序列,3'-RACE获得了其编码区全长cDNA。之后,用部分简并的引物扩增并克隆了其它3种国内常见蟹类的金属硫蛋白cDNA编码区全长序列。序列分析结果表明,几种蟹的金属硫蛋白cDNA序列存在差异,推知的氨基酸序列也不完全相同,比较不同蟹的cDNA和氨基酸序列数据不能证明不同生态环境对金属硫蛋白的分子进化起重要作用。图4表1参15 相似文献
85.
86.
Xiang Laisheng Guo Yajun Li Zhanfang . School of Management Northeastern University Shenyang Liaoning China . Development Research Center of Liaoning People’s Government Shenyang Liaoning China 《中国人口.资源与环境(英文版)》2007,5(2):49-52
In the high technology industry, small and medium sized technology enterprises (SMSTEs) play a pivotal role in advancing the whole industry. To achieve sustainable development, they need to extend their scope of business activities beyond a national view and exploit international market actively to meet international competitions that increase quickly in the form of allocating resources within the scope of the world. However, the SMSTEs are also facing risks associated with themselves during the process of exploiting international market owing to their own restrictions, so what they should do is to consider risk evaluations in exploiting the international market. 相似文献
87.
88.
89.
浅谈消防部队抢险救援的几个问题 总被引:2,自引:2,他引:0
随着经济建没的快速发展,火灾和其他突发事故呈直线上升趋势,抑制火灾和做好其他突发事故的抢险救援工作,成了消防部队的历史使命.本文详尽地阐述了消防部队抢险救援的主要任务和在抢险救援中所面临的主要问题,并针对消防队员在抢险救援中存在的风险,应用安全系统工程的方法,对抢险救援中的风险因素识别、评估及风险控制进行分析,提出消防队员在抢险救援中预防风险的措施. 相似文献
90.
Li Hongxin Electronic Commerce Institute Dongbei University of Finance & Economics Dalian China 《中国人口.资源与环境(英文版)》2004,2(3)
According to the United Nations population projections, the population of the elderly is expected to roughly triple in China from 2000 to 2050, particularly when the generations who were born between the 1950s and 1970s move through the age structure, and also because people are living longer and fertility rates have fallen, population aging is expected to put pressure on government's fiscal balance through higher old-age security benefits and health-care expenditures. This work draws together the broad range of elements involved within a consistent framework, based on a computable dynamic general equilibrium model with an overlapping generation structure. Further analysis using model simulation illustrates that the alternative schemes for the benefit rate, retirement age and technological progress are likely to be beneficial, and that an obvious slow-down in the growth of living standards is likely to be avoided. 相似文献