全文获取类型
收费全文 | 623篇 |
免费 | 3篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 10篇 |
废物处理 | 10篇 |
环保管理 | 38篇 |
综合类 | 229篇 |
基础理论 | 174篇 |
污染及防治 | 148篇 |
评价与监测 | 19篇 |
社会与环境 | 18篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 7篇 |
2013年 | 30篇 |
2012年 | 22篇 |
2011年 | 29篇 |
2010年 | 15篇 |
2009年 | 25篇 |
2008年 | 29篇 |
2007年 | 27篇 |
2006年 | 34篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 23篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1991年 | 7篇 |
1989年 | 6篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1978年 | 5篇 |
1974年 | 4篇 |
1966年 | 8篇 |
1965年 | 7篇 |
1964年 | 8篇 |
1963年 | 9篇 |
1962年 | 4篇 |
1961年 | 7篇 |
1960年 | 7篇 |
1959年 | 4篇 |
1958年 | 7篇 |
1957年 | 10篇 |
1956年 | 6篇 |
1955年 | 9篇 |
1954年 | 4篇 |
1953年 | 8篇 |
排序方式: 共有646条查询结果,搜索用时 15 毫秒
201.
202.
Klaus Keil Benton C. Clark A. K. Baird Priestley Toulmin III Harry J. Rose Jr. 《Die Naturwissenschaften》1978,65(5):231-238
Analyses of 13 samples of Martian surface materials with the Viking X-ray fluorescence spectrometers show SiO2 similar to that of terrestrial mafic rocks, whereas Fe2O3, Cl, and S are higher and Al2O3, K2O, Rb, Sr, Y, and Zr are lower. Low totals suggest presence of CO2, H2O, and Na2O. Duricrust fragments are higher in S than fines, but samples from both landing sites are surprisingly similar. We suggest that Martian surface materials are aeolian deposits of complex mixtures of weathering products of maficultramafic rocks, possibly consisting of iron-rich clays, sulfates, iron oxides, carbonates, and chlorides. 相似文献
203.
204.
205.
206.
207.
Philipp Balzer Klaus Peter Rippe Peter Schaber 《Journal of Agricultural and Environmental Ethics》2000,13(1):7-27
The 1992 incorporation of an article by referendum in the SwissConstitution mandating that the federal government issue regulations onthe use of genetic material that take into account the dignity ofnonhuman organism raises philosophical questions about how we shouldunderstand what is meant by ``the dignity of nonhuman animals,' andabout what sort of moral demands arise from recognizing this dignitywith respect to their genetic engineering. The first step in determiningwhat is meant is to clarify the difference between dignity when appliedto humans and when applied to nonhumans. Several conceptions of humandignity should be rejected in favor of a fourth conception: the rightnot to be degraded. This right implies that those who have it have thecognitive capacities that are prerequisite for self-respect. In the caseof nonhuman organisms that lack this capacity, respecting their dignityrequires the recognition that their inherent value, which is tied totheir abilities to pursue their own good, be respected. This value isnot absolute, as it is in the case of humans, so it does not prohibitbreeding manipulations that make organisms more useful to humans. But itdoes restrict morally how sentient animals can be used. In regard togenetic engineering, this conception requires that animals be allowedthe uninhibited development of species specific functions, a positionshared by Holland and Attfield, as opposed to the Original Purposeconception proposed by Fox and the Integrity of the Genetic Make-upposition proposed by Rolston. The inherent value conception of dignity,as here defended, is what is meant in the Swiss Constitution article. 相似文献
208.
209.
210.
Four-decade responses of soil trace elements to an aggrading old-field forest: B, Mn, Zn, Cu, and Fe 总被引:3,自引:0,他引:3
In the ancient and acidic Ultisol soils of the Southern Piedmont, USA, we studied changes in trace element biogeochemistry over four decades, a period during which formerly cultivated cotton fields were planted with pine seedlings that grew into mature forest stands. In 16 permanent plots, we estimated 40-year accumulations of trace elements in forest biomass and O horizons (between 1957 and 1997), and changes in bioavailable soil fractions indexed by extractions of 0.05 mol/L HCl and 0.2 mol/L acid ammonium oxalate (AAO). Element accumulations in 40-year tree biomass plus O horizons totaled 0.9, 2.9, 4.8, 49.6, and 501.3 kg/ha for Cu, B, Zn, Mn, and Fe, respectively. In response to this forest development, samples of the upper 0.6-m of mineral soil archived in 1962 and 1997 followed one of three patterns. (1) Extractable B and Mn were significantly depleted, by -4.1 and -57.7 kg/ha with AAO, depletions comparable to accumulations in biomass plus O horizons, 2.9 and 49.6 kg/ha, respectively. Tree uptake of B and Mn from mineral soil greatly outpaced resupplies from atmospheric deposition, mineral weathering, and deep-root uptake. (2) Extractable Zn and Cu changed little during forest growth, indicating that nutrient resupplies kept pace with accumulations by the aggrading forest. (3) Oxalate-extractable Fe increased substantially during forest growth, by 275.8 kg/ha, about 10-fold more than accumulations in tree biomass (28.7 kg/ha). The large increases in AAO-extractable Fe in surficial 0.35-m mineral soils were accompanied by substantial accretions of Fe in the forest's O horizon, by 473 kg/ha, amounts that dwarfed inputs via litterfall and canopy throughfall, indicating that forest Fe cycling is qualitatively different from that of other macro- and micronutrients. Bioturbation of surficial forest soil layers cannot account for these fractions and transformations of Fe, and we hypothesize that the secondary forest's large inputs of organic additions over four decades has fundamentally altered soil Fe oxides, potentially altering the bioavailability and retention of macro- and micronutrients, contaminants, and organic matter itself. The wide range of responses among the ecosystem's trace elements illustrates the great dynamics of the soil system over time scales of decades. 相似文献