全文获取类型
收费全文 | 29107篇 |
免费 | 2189篇 |
国内免费 | 4192篇 |
专业分类
安全科学 | 3474篇 |
废物处理 | 504篇 |
环保管理 | 8140篇 |
综合类 | 14396篇 |
基础理论 | 2972篇 |
环境理论 | 54篇 |
污染及防治 | 1626篇 |
评价与监测 | 2049篇 |
社会与环境 | 1760篇 |
灾害及防治 | 513篇 |
出版年
2024年 | 93篇 |
2023年 | 353篇 |
2022年 | 529篇 |
2021年 | 701篇 |
2020年 | 844篇 |
2019年 | 736篇 |
2018年 | 672篇 |
2017年 | 1069篇 |
2016年 | 1253篇 |
2015年 | 1324篇 |
2014年 | 1360篇 |
2013年 | 1941篇 |
2012年 | 2014篇 |
2011年 | 2204篇 |
2010年 | 1630篇 |
2009年 | 1699篇 |
2008年 | 1244篇 |
2007年 | 1933篇 |
2006年 | 1878篇 |
2005年 | 1539篇 |
2004年 | 1403篇 |
2003年 | 1285篇 |
2002年 | 1095篇 |
2001年 | 962篇 |
2000年 | 933篇 |
1999年 | 722篇 |
1998年 | 511篇 |
1997年 | 483篇 |
1996年 | 403篇 |
1995年 | 383篇 |
1994年 | 274篇 |
1993年 | 270篇 |
1992年 | 198篇 |
1991年 | 152篇 |
1990年 | 117篇 |
1989年 | 111篇 |
1988年 | 97篇 |
1987年 | 91篇 |
1986年 | 70篇 |
1985年 | 51篇 |
1984年 | 68篇 |
1983年 | 63篇 |
1982年 | 69篇 |
1981年 | 86篇 |
1980年 | 93篇 |
1979年 | 92篇 |
1978年 | 62篇 |
1977年 | 53篇 |
1972年 | 49篇 |
1971年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
841.
L. A. Kelly J. Stellwagen A. Bergheim 《Journal of the American Water Resources Association》1996,32(5):1017-1025
ABSTRACT: Recent studies suggest that waste generation from the freshwater phase of Atlantic salmon (Salmo salar L.) production varies considerably on an annual basis. A fish farm on the West Coast of Scotland was visited regularly during a two-year period to determine inflow and outflow water quality. Waste output budgets of suspended solids (SS), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), total ammonia nitrogen (TAN = NH3+NH4+), dissolved reactive phosphorus (DRP) and total phosphorus (TP) were produced. The annual waste loadings obtained were 71 kg TN t fish?1 yr?1 (one year of data only), 10.9–11.1 kg TP t fish?1 yr?1, 1.2–2.1 kg DRP t fish?1 yr?1, 422–485 kg BOD5 t fish?1 yr?1, 327–337 kg SS t fish?1 yr?1, and 30–35 kg TAN-N t fish?1 yr?1. Simple linear regression models relating waste parameter production to water temperature and feeding regime were developed. When compared to existing data for other salmonid production systems, greater ranges of daily waste loadings were observed. Wide variations in concentrations of these parameters during a daily cycle were also observed, suggesting that mass balance estimates of waste production will provide more robust estimates of waste output than frequent monitoring of outflow water quality. 相似文献
842.
Liang Chen Syed H. Imam Sherald H. Gordon Richard V. Greene 《Journal of Polymers and the Environment》1997,5(2):111-117
Starch-PVOH cast films were prepared with and without crosslinking agent (hexamethoxymethylmelamine) in the absence of plasticizer.
Moisture absorption in films without crosslinking agent at a low relative humidity was similar to that of PVOH and increased
as the relative humidity increased. Films with crosslinking agent showed moisture absorption linearly proportional to the
relative humidity. Significant improvement in resistance to water disintegration for crosslinked starch-PVOH films was observed.
While the tensile strength decreased with increased relative humidity, crosslinking significantly improved the tensile strength.
Increased PVOH content improved elongation of films even when the relative humidity was 80% or higher. Biodegradation studies
revealed that the degradation rate was negatively correlated with the PVOH content in films and crosslinking generated more
converged degradation curves.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
843.
通过对变流量冷冻水系统的分析指出,在运用平衡调温调湿方式的空调系统中,应用变流量冷冻水系统可以较大地节约能源和投资;并提出了实现这种应用的方法。 相似文献
844.
中国可持续发展与国家安全文化战略的新对策 总被引:2,自引:0,他引:2
金磊 《中国安全科学学报》1997,7(3):3-8
“可持续发展”战略的实质是社会、经济发展与资源、环境相协调的一种发展模式。值得注意,这一人类社会发展模式中跨世纪重大转变的策略,尚未引起安全与减灾科技界的普遍关注,不仅在安全减灾战略研究中很少涉及,严重的是它阻碍了安全减灾诸领域跨世纪及决策课题研究的深度,造成与国际接轨进程缓慢。为此,立足可持续发展思路,并以全新视角、系统地讨论适宜安全减灾文化战略的总体对策,可望能为中国二十一世纪安全保障及科技发展提供科学指南 相似文献
845.
846.
Nada Horvatinčić José Luis Briansó Bogomil Obelić Jadranka Barešić Ines Krajcar Bronić 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):475-485
The process of eutrophication in form of intense plant growth has been observed in some lakes and water streams at the Plitvice
Lakes National Park in central Croatia. Here we investigate whether this phenomenon is a consequence of anthropogenic pollution
or due to naturally produced organic matter in the lakes. We applied chemical analysis of water at two springs and four lakes
(nutrients, dissolved organic carbon (DOC), trace elements) and measurements of surface lake sediments (mineral and organic
fraction analyses, trace elements) in four different lakes/five sites. The chemical composition of water does not indicate
recent anthropogenic pollution of water because the concentrations of most trace elements are below detection limits. The
concentrations of DOC and nutrients are slightly higher in the area of increased eutrophication-plant growth. Also the content
of organic matter in the sediment is at the highest level in areas with highest C/N ratio indicating that the organic fraction of this sediment is mainly of terrestrial origin. There is no significant difference
among the trace element concentration in the upper segment of all cores, deposited approximately during last 50 years when
higher anthropogenic influence is expected due to development and touristic activity, and the lower part of the cores, corresponding
to the period approximately 100–200 years before present. The content of trace elements and organic matter in sediments decreases
from the uppermost lake downstream. According to our results there is no indication of recent anthropogenic pollution in water
and sediment. Higher concentrations of DOC in water as well as phosphorus and some other elements in the lake sediment can
be a consequence of input of natural organic matter to the lake water. 相似文献
847.
介绍了河北马头电厂废水处理工艺系统流程、设计及系统调试运行指标。处理后的电厂废水作为循环冷却水的补水,减少了新鲜水用量和污水排放量,对北方地区厂区废水回收利用具有借鉴意义,在火电厂废水资源利用方面有很好的应用前景。 相似文献
848.
介绍了河津发电厂目前的用水、排水情况及工业废水零排放实施方案,对方案实施后的效果进行了预测,同时对废水零排放实施后运行中可能出现的问题进行了分析并提出了建议。 相似文献
849.
电力工业发展与环境保护 总被引:6,自引:3,他引:6
从我国电力工业发展历程、面临的主要环境问题、污染控制等方面全面简述我国电力工业环境保护取得的发展与成就;展望“十一五”电力发展目标及电力环保指标;分析了为实现环境目标需要实施的污染控制措施。 相似文献
850.
针对仪化热电厂将循环水用作冲灰水,导致浓缩倍率只有1.6,以及凝汽器铜管腐蚀结垢严重等问题,提出了隔断循环水与冲灰水的直接联系,实现闲路循环,对凝汽器铜管进行酸洗,并对循环水实施加缓蚀阻垢荆、杀菌剂和旁流过滤等办法,全部实施后产生了很好的效益,值得借鉴。 相似文献