全文获取类型
收费全文 | 4057篇 |
免费 | 18篇 |
国内免费 | 51篇 |
专业分类
安全科学 | 77篇 |
废物处理 | 137篇 |
环保管理 | 453篇 |
综合类 | 998篇 |
基础理论 | 893篇 |
环境理论 | 3篇 |
污染及防治 | 909篇 |
评价与监测 | 287篇 |
社会与环境 | 360篇 |
灾害及防治 | 9篇 |
出版年
2022年 | 36篇 |
2021年 | 66篇 |
2020年 | 31篇 |
2019年 | 35篇 |
2018年 | 63篇 |
2017年 | 57篇 |
2016年 | 90篇 |
2015年 | 53篇 |
2014年 | 118篇 |
2013年 | 319篇 |
2012年 | 121篇 |
2011年 | 182篇 |
2010年 | 122篇 |
2009年 | 163篇 |
2008年 | 155篇 |
2007年 | 174篇 |
2006年 | 141篇 |
2005年 | 117篇 |
2004年 | 111篇 |
2003年 | 130篇 |
2002年 | 119篇 |
2001年 | 134篇 |
2000年 | 95篇 |
1999年 | 63篇 |
1998年 | 33篇 |
1997年 | 41篇 |
1996年 | 25篇 |
1995年 | 55篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 38篇 |
1991年 | 37篇 |
1990年 | 49篇 |
1989年 | 40篇 |
1988年 | 28篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 38篇 |
1982年 | 26篇 |
1981年 | 41篇 |
1980年 | 30篇 |
1979年 | 30篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1975年 | 25篇 |
1972年 | 23篇 |
1970年 | 23篇 |
1965年 | 23篇 |
排序方式: 共有4126条查询结果,搜索用时 0 毫秒
991.
Effects of Riparian Forest Removal on Fish Assemblages in Southern Appalachian Streams 总被引:12,自引:0,他引:12
E. B. Dale Jones III Gene S. Helfman ‡ Joshua O. Harper and Paul V. Bolstad† 《Conservation biology》1999,13(6):1454-1465
992.
Mario Schirmer John W. Molson Emil O. Frind James F. Barker 《Journal of contaminant hydrology》2000,46(3-4)
Biodegradation of organic contaminants in groundwater is a microscale process which is often observed on scales of 100s of metres or larger. Unfortunately, there are no known equivalent parameters for characterizing the biodegradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimated at the laboratory scale by model fitting generally overpredict the rate of biodegradation when applied to the field scale because limited electron acceptor availability and microbial growth are not considered. On the other hand, field-estimated zero- and first-order rates are often not suitable for predicting plume development because they may oversimplify or neglect several key field scale processes, phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by applying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Borden. All input parameters were derived from independent laboratory and field measurements or taken from the literature a priori to the simulations. The simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input parameters showed only a minor influence on the simulation results. Furthermore, it is shown that the flow field, the amount of electron acceptor (oxygen) available, and the Monod kinetic parameters have a significant influence on the simulated results. It is concluded that laboratory-derived Monod kinetic parameters can adequately describe field scale degradation, provided all controlling factors are incorporated in the field scale model. These factors include advective–dispersive transport of multiple contaminants and electron acceptors and large-scale spatial heterogeneities. 相似文献
993.
The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are reported. Chemical partition of the metals in the sediments reveals that 2–30% of the total metal load was contributed by the non-detrital (acid-soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70–98%). Using multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physio-chemical changes (dissolved oxygen, pH, salinity and conductivity) in the water column. Fe–Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and detrital trace metals in the sediments. On the basis of index of geoaccumulation (I-geo) and comparison with previous studies, the Calabar River surface sediments have been classified as unpolluted. 相似文献
994.
995.
996.
Skole D.L. Justice C. O. Townshend J.R.G. Janetos A. C. 《Mitigation and Adaptation Strategies for Global Change》1997,2(2-3):157-175
An international system for monitoring land cover change is needed to support a range of scientific and policy objectives. Although much of the technology and methods are readily available, such a program has yet to be implemented. This paper outlines the rationale, requirements, and strategy for implementing a land cover-monitoring program using satellite remote sensing, field and ground measurements, and models and assessments. The proposed program builds on existing activities throughout the world and is designed to simultaneously meet the needs of the international policy, global change research, and national resource management. Outputs from this program would provide support to the Framework Convention on Climate Change, lead to the development of consistent country-level emission inventories, and address important scientific problems in global change research such as closing the global carbon budget. 相似文献
997.
The spatial distribution of coarse woody debris in pine forests has been studied in the Transvolga region of the Marii El Republic. For this purpose, 30 test plots have been established in pine (Pinus sylvestris) stands of the study region. The results are indicative of a tendency toward the spatial grouping (clustering) of woody debris by fractions, decomposition classes, and stocks along with increase in stand age. 相似文献
998.
Chemical composition and liberation are critical attributes in characterizing a resource stock for beneficiation investigations. Though end-of-life printed circuit board is recognized as a valuable secondary resource stock, no procedural standard exists for the determination of its chemical composition, nor for the ?75 μm fines generated during its comminution. The effect of the digestion procedure on the final assays in wet spectroscopic analyses was assessed in this work. Liberation was also explored against literature background. Determination of assays of all constituent elements in printed circuit board comminution fines was found to require comparison of data from more than one digestion condition, while composite particles still persist at the fines sizes, though very few. The discussion reflects how these impact the beneficiation investigations. 相似文献
999.
1000.
Leaf-cutting ants exhibit an aggressive alarm response. Yet in most alarm reactions, not all of the ants encountering a disturbance will respond. This variability in behaviour was investigated using field colonies of Atta capiguara, a grass-cutting species. Crushed ant heads were applied near foraging trails to stimulate alarm reactions. We found that minor workers were disproportionately likely to respond. Only 34.7DŽ.8% of ants travelling along foraging trails were minor workers, but 82.1Lj.1% of ants that responded were minors. Workers transporting grass did not respond at all. The alarm response was strongest at the position and time where minors were most abundant. Ants were more likely to respond when they were travelling along trails with low rather than high traffic. Minor workers followed a meandering route along the trail, compared with the direct route taken by foragers. We argue that an important function of minor workers on foraging trails is to patrol the trail area for threats, and that they then play the key role in the alarm reaction. 相似文献