全文获取类型
收费全文 | 297篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 29篇 |
废物处理 | 2篇 |
环保管理 | 90篇 |
综合类 | 33篇 |
基础理论 | 63篇 |
污染及防治 | 52篇 |
评价与监测 | 19篇 |
社会与环境 | 16篇 |
灾害及防治 | 1篇 |
出版年
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 19篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有305条查询结果,搜索用时 31 毫秒
291.
Gerald Padmore 《Natural resources forum》1992,16(2):132-140
Governments of developing countries may obtain ownership participation in national mining projects in the hope of receiving greater policy control over, financial rewards from, and information about such projects. These objectives could be achieved by using their sovereign authority to tax, regulate and monitor projects more effectively. The principal problem is likely to be the administrative inability fully to enjoy rights that they lawfully possess. As such projects are nearly always controlled by foreign entities, and involve the exploitation of irreplaceable mineral wealth, they may engender feelings of suspicion and hostility. Government participation may sometimes be necessary to mitigate those feelings and to lead to more stable and successful projects. If these political objectives are fully recognized, then government participation may be structured so as to minimize any detrimental effect it might have on the fiscal and financial structure of the project. It may also prove to be a vehicle for future participation by private local interests, thereby eliminating the alien enclave feature generally characteristic of such projects. 相似文献
292.
The dimensionality of the concept organizational commitment, formulated by Porter, Steers, Mowday and Boulian in 1974 and later by Cook and Wall in 1980, is explored by metric and non-metric methods among industrial workers in Israel. A distinction is established between loyalty to the employing organization and identification with and readiness to exert effort on its behalf. This is a distinction between passive and active organizational commitment, hidden in the original additive scales, that could prove useful in understanding the behavior of different populations of industrial workers. 相似文献
293.
Nitrate reduction in the presence of wüstite 总被引:1,自引:0,他引:1
Recent strategies to reduce elevated nitrate concentrations employ metallic Fe0 as a reductant. Secondary products of Fe0 corrosion include magnetite (Fe3O4), green rust [Fe6(OH)12SO4], and wüstite [FeO(s)]. To our knowledge, no studies have been reported on the reactivity of NO3- with FeO(s). This project was initiated to evaluate the reactivity of FeO(s) with NO3- under abiotic conditions. Stirred batch reactions were performed in an anaerobic chamber over a range of pH values (5.45, 6.45, and 7.45), initial FeO(s) concentrations (1, 5, and 10 g L(-1)), initial NO3- concentrations (1, 10, and 15 mM), and temperatures (3, 21, 31, and 41 degrees C) for kinetic and thermodynamic determinations. Suspensions were periodically removed and filtered to measure dissolved nitrogen and iron species. Solid phases were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nitrate reduction by FeO was rapid and characterized by nearly stoichiometric conversion of NO3- to NH4+. Transient NO2- formation also occurred. The XRD and SEM results indicated the formation of Fe3O4 as a reaction product of the heterogeneous redox reaction. Kinetics of NO3- reduction suggested a rate equation of the type: -d[NO3-]/dt = k[FeO]0.57[H]0.22[NO3-]1.12 where k = 3.46 x 10(-3) +/- 0.38 x 10(-3) M(-1) s(-1), at 25 degrees C. Arrhenius and Eyring plots indicate that the reaction is surface chemical-controlled and proceeds by an associative mechanism involving a step where both NO3- and FeO(s) bind together in an intermediate complex. 相似文献
294.
A water quality index expressed as a single number is developed to describe overall water quality conditions using multiple water quality variables. The index consists of water quality variables: dissolved oxygen, specific conductivity, turbidity, total phosphorus, and fecal coliform. The objectives of this study were to describe the preexisting indices and to define a new water quality index that has advantages over these indices. The new index was applied to the Big Lost River Watershed in Idaho, and the results gave a quantitative picture for the water quality situation. If the new water quality index for the impaired water is less than a certain number, remediation—likely in the form of total maximum daily loads or changing the management practices—may be needed. The index can be used to assess water quality for general beneficial uses. Nevertheless, the index cannot be used in making regulatory decisions, indicate water quality for specific beneficial uses, or indicate contamination from trace metals, organic contaminants, and toxic substances. 相似文献
295.
We report on the oldest European songbird (Passeriformes), from the early Oligocene (30–34 million years ago) of Frauenweiler in Germany. The specimen represents the earliest associated remains of an early Tertiary passerine described so far. It ties the first appearance of Passeriformes in Europe to a minimum age of 30 million years. Passeriform birds are absent in Eocene deposits that yielded abundant remains of small land birds and apparently dispersed into Europe around the Eocene/Oligocene boundary (about 34 million years ago), not at the Oligocene/Miocene boundary (about 24 mya) as hitherto thought. This possibly relates the appearance of songbirds in Europe to a well-known major faunistic break at the Eocene/Oligocene boundary, called the grande coupure. The Frauenweiler songbird most notably differs from extant Passeriformes in having a larger processus procoracoideus on the coracoid and appears to be outside Eupasseres, the taxon which includes Oscines (all modern European and most Old World songbirds) and Suboscines (most South and Central American songbirds). It shows that there were earlier dispersal events of non-oscine songbirds into Europe before the arrival of Oscines from the Australian continental plate towards the late Oligocene. 相似文献
296.
Water samples were collected between 1999 and 2000 from wetlands in Minnesota that contained malformed frogs. The water samples were analyzed for 14 minerals/ions and screened for the presence of biologically active compounds using Xenopus laevis. Results indicated that water from two sites, CWB and ROI2, induced severe retardation with embryo lengths reduced 20% after 96 hr of development. The developmental delay observed with water from ROI2 was alleviated by supplementation with sodium, while both sodium and potassium alleviated the developmental delay observed with water whose mineral content mimicked that of CWB. Seasonal fluctuations in the sodium and potassium content at ROI2 and NEY correlated with changes in the rates of Xenopus development. Xenopus embryos reared on water from ROI2 for 120 hr displayed gut malformations not present in embryos reared on a synthetic media designed to mimic the mineral content of the water from ROI2. Embryos reared on water from ROI2 supplemented with minerals at levels comparable to that routinely employed in the rearing of Xenopus were neither retarded nor malformed. It is proposed that climate driven hydrology may influence the mineral composition at selected wetlands and delay development which may alter window(s) of susceptibility towards biologically active agents and the occurrence of malformed frogs. 相似文献
297.
Correlations between Human Collecting and Intertidal Mollusc Populations on Rocky Shores 总被引:3,自引:0,他引:3
We tested whether the population structures of intertidal molluscs varied with the activity of human collectors in northern Port Phillip Bay, Victora, Australia. We examined eight sites, two of which had been protected for around 70 years by the area being used as a rifle range with the other six being visited frequently by human. The shores were examined in two different years, and in 1991 we counted humans and recorded their activities. At heavily visited shores, almost half of the people seen were simply walking, while 25% were actively collecting, despite regulations prohibiting the collection of intertidal gastritis. The remaining people were fishing or skydiving. At the protected shores, we observed only one collector and a handful of walkers over more than 20 observation periods, including weekdays, normal weekends, and holiday weekends. In 1989 and 1991, we compared size distributions of seven intertidal species between sites in the two categories. Four mollify species are taken for food and bait; the remaining three served as “controls”. The size distributions and abundance of noncarbonated species (alicized napalm, Leaderless viola, and emization ebonies) did not differ between visited and protected sites in either year, although most species did vary between individual sites. In contrast, three of the four collected species, alicize trampoliners, Austrocochlea constricta, and Nerita atramentosa, were significantly larger at the protected sites, and N. atramentosa was markedly less abundant at heavily visited sites. The fourth collected species, Turbo undulatus, has a distribution extending into the subtidal zone, and it is possible that intertidal populations ate replenished from deeper water. The changes in mean size of molluscs are well within the range reported from South America and South Africa under subsistence fishing, and they demonstrate that at least close to major urban centers, human recreational activities can have substantial effects in developed countries. 相似文献
298.
Though it appears intuitively appealing that individual differences should be related to a person's decision to perform citizenship behaviors, the search for such individual differences has yet to yield clear results. In this study, data were collected to assess the extent of a relationship between individualism–collectivism as a within culture individual difference and self-reports of organizational citizenship behaviors. Results suggest that if an individual holds collectivistic values or norms, he/she would be more likely to perform citizenship behaviors. In addition, this relationship was found to be robust to common method effects and to the effect of the relationship between procedural justice and OCB. Implications for the way collectivistic tendencies within cultures may be used in organizations are discussed. 相似文献
299.
300.
Gwangseob Kim Juan B. Valdés Gerald R. North Hong Tae Kim 《Journal of the American Water Resources Association》2006,42(1):213-224
A spectral formalism was developed and applied to quantify the sampling errors due to spatial and/or temporal gaps in soil moisture measurements. A design filter was developed to compute the sampling errors for discrete measurements in space and time. This filter has as its advantage a general form applicable to various types of sampling design. The lack of temporal measurements of the two‐dimensional soil moisture field made it difficult to compute the spectra directly from observed records. Therefore, the wave number frequency spectra of soil moisture data derived from stochastic models of rainfall and soil moisture were used. Parameters for both models were estimated using data from the Southern Great Plains Hydrology Experiment (SGP97) and the Oklahoma Mesonet. The estimated sampling error of the spatial average soil moisture measurement by airborne L‐band microwave remote sensing during the SGP97 hydrology experiment is estimated to be 2.4 percent. Under the same climate conditions and soil properties as the SGP97 experiment, equally spaced ground probe networks at intervals of 25 and 50 km are expected to have about 16 percent and 27 percent sampling error, respectively. Satellite designs with temporal gaps of two and three days are expected to have about 6 percent and 9 percent sampling errors, respectively. 相似文献