全文获取类型
收费全文 | 2745篇 |
免费 | 378篇 |
国内免费 | 814篇 |
专业分类
安全科学 | 499篇 |
废物处理 | 48篇 |
环保管理 | 283篇 |
综合类 | 1985篇 |
基础理论 | 366篇 |
环境理论 | 2篇 |
污染及防治 | 178篇 |
评价与监测 | 210篇 |
社会与环境 | 197篇 |
灾害及防治 | 169篇 |
出版年
2024年 | 21篇 |
2023年 | 77篇 |
2022年 | 152篇 |
2021年 | 163篇 |
2020年 | 203篇 |
2019年 | 130篇 |
2018年 | 160篇 |
2017年 | 176篇 |
2016年 | 186篇 |
2015年 | 170篇 |
2014年 | 160篇 |
2013年 | 227篇 |
2012年 | 254篇 |
2011年 | 258篇 |
2010年 | 206篇 |
2009年 | 183篇 |
2008年 | 106篇 |
2007年 | 172篇 |
2006年 | 163篇 |
2005年 | 127篇 |
2004年 | 101篇 |
2003年 | 113篇 |
2002年 | 83篇 |
2001年 | 58篇 |
2000年 | 61篇 |
1999年 | 31篇 |
1998年 | 39篇 |
1997年 | 25篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 27篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有3937条查询结果,搜索用时 15 毫秒
841.
Woodlands of the Mediterranean speciesJuniperus oxycedrus ssp.macrocarpa (maritime juniper) are both vulnerable and ecologically important. Their ecology and biological status along the SW coast
of Spain are not well known; this, the first major study of these juniper populations is a basis for future research and restoration
policies. These communities are subject to harsh conditions, the plant composition being controlled by several factors at
different scales. On a large scale, climate and soil texture play an important role in controlling the soil water availability
to plants, and in separating xerophytic from mesic communities. On a small scale, coastal physiography, and substrate composition
are related to differences in the floristic composition. Coastal plantations modify environmental conditions, such as sand
mobility and salt spray deposition, inducing important changes in plant communities. The population of maritime juniper on
this coast was estimated in ca. 25 000 individuals, of which 93.6% are concentrated in three locations. Large proportions
of young individuals were found in extensive and protected populations. Howerver, adult individuals dominated the smaller
populations located under pine plantations. This limitation of recruitment may be imposed by several factors. A male biased
ratio was detected on the southern coast of Cádiz, which I hypothesize is due to the lower cost of pollen production in a
stressful habitat. Preservation of suitable habitats, the recovery of abandoned pine plantations, and the connection between
juniper populations, seem to be important requisites for the conservation of maritime juniper in the southwestern coast of
Spain. 相似文献
842.
本文采用产生柱法测定取代苯乙酮类有机物的水溶解度和正辛醇-水分配系数,与静态法和振荡法测定的水溶解度、摇瓶法测定的正辛醇-水分配系数相比较,证明此方法是可行的,并和分子连接性指数呈良好的相关性。 相似文献
843.
844.
P. A. Findlater W. D. Scott S. E. Greenhill J. M. Hopwood 《Environmental Fluid Mechanics》2005,4(4):367-383
A method is developed to estimate the stress at the surface in a portable wind tunnel for wind erosion studies. The boundary layer height and the pressure gradient are used in a simple expression from the Kármán Integral Momentum Equation. Values of friction velocity u
* are within 10% of experimental values obtained through correlation techniques, including measurements of differential pressures with the Murdoch Turbulence Probe MTP and the X-wire, hot-wire anemometer XWA. Wind velocity and stress profiles reveal logarithmic trends and a constant stress layer near the surface in the DAWA portable wind tunnel. Realignment of the statistics with the mean wind is essential. 相似文献
845.
Green-Ruiz C Ruelas-Inzunza J Páez-Osuna F 《Environmental geochemistry and health》2005,27(4):321-329
In order to know the concentration of mercury in surface sediments, macroalgae and clams from Guaymas Bay, Mexico, 20 surface
sediment samples and several individuals of Codium amplivesciculatum (3), Enteromorpha clathrata (4), Gracilaria subsecundata (2), Ulva lactuca (2), Chione subrugosa (80) and Crassostrea gigas (40) were collected and their Hg concentration was measured by a cold vapor Hg analyzer, after acid digestion. In addition,
granulometric analysis and quantification of total organic carbon, aluminum, iron and manganese contents in sediments were
performed. A Pearsons correlation matrix was determined and, the enrichment factor, the geoaccumulation index and the biota-sediment
accumulation factor were calculated. Mercury concentrations in sediments ranged from 0.3 to 2.3 μg g−1, with the central and northern portions showing the highest values. Macroalgae had a content of Hg that oscillated from 0.058
to 0.134 μg g−1, while the average concentrations of this metal for clams and oysters were 0.063 and 0.230 μg g−1, respectively. A clear effect of Guaymas City and the anthropogenic activities carried out around the Guaymas Bay has been
observed and the enrichment factor and the geochemical index suggest that sediments from this coastal ecosystem are moderately
to strongly contaminated with Hg. However, according to the figure of the maximum human consumption of Hg per week recommended
by the World Health Organization, people can ingest clams without risk to their health. 相似文献
846.
富营养化水体中藻类生长限制因素的确定及其应用 总被引:10,自引:1,他引:10
在富化营养化的巢湖,围隔实验结果表明磷和其它营养元素不是水体藻类的生长限制因素、藻类生长的正磷酸盐阈值浓度为0.019mg/l,它低于巢湖实际浓度。湖水的矿物性浊度很高,净生产力在一米水深以下呈现负值,数据表明学强在大数时间是藻类生长的限制因素。在巢湖治理过程中,需大幅降低流域内的磷负荷,使湖水平均溶解态总磷浓度从目前的0.049ml/l降到0.019mg/l以下。因此巢湖在治理和恢复是一个缓慢的 相似文献
847.
在市场经济条件下,环境污染治理的形式、手段、效果、发展方向除了受社会的、政策的、法律的因素影响决定外,也受到经济效益因素的制约和影响.经济效益因素不仅决定环境污染治理的方式方法和发展趋势,还影响环境政策、法规的制定.文中作者从四个大的方面来分析阐述了经济效益因素对环境污染治理行为的决定和影响 相似文献
848.
气象条件对可吸入颗粒物浓度的影响 总被引:3,自引:0,他引:3
气象条件对可吸入颗粒物浓度有较大的影响,通过对鞍山市二年来的监测数据进行分析,得出了结论并提出建议. 相似文献
849.
室内废气污染的计算与分析 总被引:4,自引:0,他引:4
通过对吸油烟机抽吸风场有效强度矢量图的测量 ,给出了吸油烟机质量技术检验方法和油烟废气、燃气废气污染泄漏量的计算方法 ;对油烟、燃气废气在厨房的扩散与循环作了详细分析 ,并对国标提出几点建议。 相似文献
850.
Distribution of heavy metals in the Grand Canal (Hangzhou section) and its contributing factors 总被引:1,自引:0,他引:1
DistributionofheavymetalsintheGrandCanal(Hangzhousection)anditscontributingfactorsWengHuanxin,ZhangDengrongDepartmentofEarth... 相似文献