全文获取类型
收费全文 | 4378篇 |
免费 | 30篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 43篇 |
废物处理 | 168篇 |
环保管理 | 141篇 |
综合类 | 2009篇 |
基础理论 | 779篇 |
环境理论 | 7篇 |
污染及防治 | 876篇 |
评价与监测 | 243篇 |
社会与环境 | 151篇 |
灾害及防治 | 15篇 |
出版年
2022年 | 52篇 |
2021年 | 39篇 |
2019年 | 33篇 |
2018年 | 69篇 |
2017年 | 57篇 |
2016年 | 76篇 |
2015年 | 65篇 |
2014年 | 99篇 |
2013年 | 192篇 |
2012年 | 127篇 |
2011年 | 95篇 |
2010年 | 118篇 |
2009年 | 127篇 |
2008年 | 147篇 |
2007年 | 167篇 |
2006年 | 115篇 |
2005年 | 107篇 |
2004年 | 93篇 |
2003年 | 114篇 |
2002年 | 87篇 |
2001年 | 87篇 |
2000年 | 84篇 |
1999年 | 86篇 |
1998年 | 58篇 |
1997年 | 54篇 |
1996年 | 36篇 |
1995年 | 52篇 |
1994年 | 53篇 |
1991年 | 38篇 |
1990年 | 42篇 |
1985年 | 36篇 |
1979年 | 38篇 |
1978年 | 33篇 |
1973年 | 32篇 |
1969年 | 36篇 |
1968年 | 33篇 |
1967年 | 56篇 |
1966年 | 48篇 |
1965年 | 54篇 |
1964年 | 62篇 |
1963年 | 64篇 |
1962年 | 59篇 |
1961年 | 63篇 |
1960年 | 55篇 |
1959年 | 64篇 |
1958年 | 62篇 |
1957年 | 70篇 |
1956年 | 52篇 |
1955年 | 50篇 |
1954年 | 48篇 |
排序方式: 共有4432条查询结果,搜索用时 31 毫秒
861.
A curious feature of the honeybee's waggle dance is the imprecision in the direction indication for nearby food sources.
One hypothesis for the function of this imprecision is that it serves to spread recruits over a certain area and thus is an
adaptation to the typical spatial configuration of the bees' food sources, i.e., flowers in sizable patches. We report an
experiment that tests this tuned-error hypothesis. We measured the precision of direction indication in waggle dances advertising
a nest site (typically a tree cavity, hence a target that is almost a point) and compared it with that of dances advertising
a food source (typically a flower patch, hence a target that covers an area). The precision of dances for a nearby nest site
was significantly higher than that of dances for an equidistant feeder. This was demonstrated four times with four colonies.
Our evidence therefore supports the hypothesis that the level of precision in the direction indication for nearby food sources
is tuned to its optimum without being at its maximum.
Received: 9 December 1998 / Received in revised form: 24 February 1999 / Accepted 12 March 1999 相似文献
862.
863.
An evaluation of the degradation of soils can be performed in several ways. Here, one way will be demonstrated beginning with the definition of the objects which are to be evaluated, continued with the definition of protection aims and the derivation of indicators. Objects together with indicators provide the frame within which a multicriteria assessment, has to be performed. Often no deterministic quality function is available, so that the concept of partially ordered sets is suggested. This concept is demonstrated by an example of an evaluation exercise performed for the environmental protection agency in Baden Württemberg. A result is that the use of arbitrarily defined quality functions may lead to erroneous statements. 相似文献
864.
Tobias Türcke Stefan Norra Doris Stüben Zsolt Berner Markus Leosson 《Environmental Sciences Europe》1999,11(3):127-133
Different sources of traffic immissions (tyres, soot, oil, asphalt, plastic, paint) were analysed for stable carbon and sulphur isotope ratios. The aim of this study is to investigate whether these isotope ratios can be used to evaluate the environmental impact of traffic immitted harmful substances in roadside soils. The δ13C values of technical materials are between -30‰ and -18‰ (PDB). They can be distinguished by their δ13C value because of specific production methods. The δ13C value of asphalt is between -23 and -18‰, soot shows values from -27 to-22‰ Moreover, soot of different fuel have different carbon isotope ratios. Plastic, paint and oil have similar δ13C from -30 to -27‰ Carbon isotope ratios of automobile tyres are around -26‰ Traffic impact on the carbon isotope composition is reflected in δ13C values of various carbon spezies found in street sediments and road side soils. These δ13C values correlate to concentrations of lead and platinum. Although δ34S values of technical materials are between -6 and +8‰ it was not possible to characterise samples according to their Sulphur isotopic compostion. 相似文献
865.
As it is practically impossible in an industrial society to reduce impacts into ecosystems to a level that would preclude any damages, the need for damage valuation arises. One of the available valuation tools is the economic approach. Subsequent publications present this approach using the example of soils. In the first part, soils as part of ecosystems are considered from an ecological and a conventional economic point of view. In the following so-called ecological-economic perspective, more recent developments in economic valuation research are introduced. It is shown how ecological and economic valuation can complement one another. It is emphasized that economic valuations should be restricted to a critical soil structure which, in economic terms, is determined by the non-substitutable services of the ecological asset. 相似文献
866.
867.
Gerald Spindler Konrad Müller Hartmut Herrmann 《Environmental science and pollution research international》1999,6(2):89-94
Aerosol filter samples have been collected nearby the industrialised basin of Leipzig in Saxony (Germany) at the research station Melpitz of the Institut für Troposphärenforschung e.V. (IfT). Time series (1992–1998) and a three year comparison (1995–1997) of two different aerosol filter sampling systems, the Sierra-Andersen-PM 10 high volume sampler (daily sample, PM 10 inlet) and the Rupprecht and Patashnik Co. Inc. Model Partisol 2000 (weekly sample, PM 10 and PM 2.5 inlet) are presented and discussed. The comparison of the different sampling systems and strategies yields small differences between the daily and weekly samples for mass and different ions, which may be influenced by sampling duration and flow rates. A general trend of change in aerosol composition was observed: Soot and Sulphate concentrations decreased whereas Nitrate and Ammonium concentrations increased. During summers the mass of coarse particles is higher than in other seasons. One reason could be found in the occurence of longer periods of dry ground surfaces enabling reemission of crustal and biological material. The time series have been integrated in a longer historical aerosol mass trend for Saxony and do show a good agreement. Since 1990 a significant downward trend in gravimetric mass concentration was found. 相似文献
868.
869.
For phosphorus recovery from wastewater, the present paper aims at understanding the crystallization of calcium phosphate by using calcites (Juraperle and Coccolith) as seeds from hard water. Synthetic hard water with 60 mgCl(-1) carbonate and 10 mgPl(-1) phosphate was prepared and used in the batch experiments of calcite-seeded crystallization. The solution composition was measured throughout the batch crystallization process, and the corresponding saturation indices with respect to the minerals were calculated with PHREEQC Program. The surface of the calcite seeds was observed and measured with environmental scanning electron microscopy (ESEM), Fourier transform infrared (FTIR) and BET method. The studies show that both calcites are effective seeds for the crystallization of calcium phosphate from hard water; the used calcites are more efficient than the original ones because newly formed crystals with calcium phosphate have covered their surfaces. The studies show that the calcite seeds can be used for phosphorus recovery from hard waters. 相似文献
870.
Rüdiger K.W. Wurzel Jeremy F.G. Moulton Winfried Osthorst Linda Mederake Pauline Deutz Andrew E.G. Jonas 《环境政策》2019,28(1):146-166
ABSTRACTInnovative climate governance in small-to-medium-sized structurally disadvantaged cities (SDCs) are assessed. Considering their deeply ingrained severe economic and social problems it would be reasonable to assume that SDCs act primarily as climate laggards or at best as followers. However, novel empirical findings show that SDCs are capable of acting as climate pioneers. Different types and styles of climate leadership and pioneership and how they operate within multi-level and polycentric governance structures are identified and assessed. SDCs seem relatively readily willing to adopt transformational climate pioneership styles to create ‘green’ jobs, for example, in the offshore wind energy sector and with the aim of improving their poor external image. However, in order to sustain transformational climate pioneership they often have to rely on support from ‘higher’ levels of governance. For SDCs, there is a tension between learning from each other’s best practice and fierce economic competition in climate innovation. 相似文献