全文获取类型
收费全文 | 22644篇 |
免费 | 1937篇 |
国内免费 | 4354篇 |
专业分类
安全科学 | 1566篇 |
废物处理 | 387篇 |
环保管理 | 5594篇 |
综合类 | 13123篇 |
基础理论 | 2438篇 |
环境理论 | 8篇 |
污染及防治 | 1622篇 |
评价与监测 | 2381篇 |
社会与环境 | 1454篇 |
灾害及防治 | 362篇 |
出版年
2024年 | 62篇 |
2023年 | 343篇 |
2022年 | 504篇 |
2021年 | 602篇 |
2020年 | 700篇 |
2019年 | 582篇 |
2018年 | 498篇 |
2017年 | 799篇 |
2016年 | 967篇 |
2015年 | 1061篇 |
2014年 | 1128篇 |
2013年 | 1577篇 |
2012年 | 1588篇 |
2011年 | 1753篇 |
2010年 | 1237篇 |
2009年 | 1277篇 |
2008年 | 1028篇 |
2007年 | 1626篇 |
2006年 | 1530篇 |
2005年 | 1206篇 |
2004年 | 1045篇 |
2003年 | 1049篇 |
2002年 | 971篇 |
2001年 | 750篇 |
2000年 | 776篇 |
1999年 | 643篇 |
1998年 | 428篇 |
1997年 | 428篇 |
1996年 | 353篇 |
1995年 | 329篇 |
1994年 | 272篇 |
1993年 | 251篇 |
1992年 | 173篇 |
1991年 | 152篇 |
1990年 | 109篇 |
1989年 | 97篇 |
1988年 | 92篇 |
1987年 | 78篇 |
1986年 | 53篇 |
1985年 | 42篇 |
1984年 | 50篇 |
1983年 | 59篇 |
1982年 | 61篇 |
1981年 | 79篇 |
1980年 | 86篇 |
1979年 | 80篇 |
1978年 | 54篇 |
1977年 | 49篇 |
1973年 | 45篇 |
1971年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
961.
Joseph Domagalski 《Journal of the American Water Resources Association》1996,32(5):953-964
ABSTRACT: Pesticides in stormwater runoff, within the Sacramento River Basin, California, were assessed during a storm that occurred in January 1994. Two organophosphate insecticides (diazinon and methidathion), two carbamate pesticides (molinate and carbofuran), and one triazine herbicide (simazine) were detected. Organophosphate pesticide concentrations increased with the rising stage of the hydrographs; peak concentrations were measured near peak discharge. Diazinon oxon, a toxic degradation product of diazinon, made up approximately 1 to 3 percent of the diazinon load. The Feather River was the principal source of organophosphate pesticides to the Sacramento River during this storm. The concentrations of molinate and carbofuran, pesticides applied to rice fields during May and June, were relatively constant during and after the storm. Their presence in surface water was attributed to the flooding and subsequent drainage, as a management practice to degrade rice stubble prior to the next planting. A photo-degradation product of molinate, 4-keto molinate, was in all samples where molinate was detected and made up approximately 50 percent of the total molinate load. Simazine, a herbicide used in orchards and to control weeds along the roadways, was detected in the storm runoff, but it was not possible to differentiate the two sources of that pesticide to the Sacramento River. 相似文献
962.
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
963.
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
964.
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
965.
本文根据常微分方程参数反问题的数学理论,将正交化方法同有限差分法结合用于确定水质模型参数,并与正则化方法、最速下降法和共轭梯度法作了比较。其计算结果对比表明,正交化方法具有快速、简便、可靠的特点。更适合于水质模型参数的确定。 相似文献
966.
967.
高层建筑的消防设计审核是消防执法中的重要环节.以规范为指导,根据我国国情和具体工程设计情况,对高层建筑临时高压消防水系统中有关消防水泵房的出水管的布置、高位消防水箱的容积以及增压设施的设置几方面的规定进行了探讨. 相似文献
968.
969.
城市雨水径流污染控制技术 总被引:4,自引:0,他引:4
城市雨水径流特别是初期雨水污染严重,是水体富营养化、水华以及海域赤潮等环境问题产生的根源之一.分析了径流污染产生的特点,概括了城市雨水径流污染控制的必要性,并着重论述了径流污染控制技术. 相似文献
970.
运用多元回归法,通过预测模型的选择、数学模型的建立、基础数据的整理和回归效果的检验,建立环境污染范围与诸条件的关系,达到快速估算的目的,从而形成一种有效的大气环境污染事故范围预测的方法. 相似文献