全文获取类型
收费全文 | 29732篇 |
免费 | 335篇 |
国内免费 | 247篇 |
专业分类
安全科学 | 999篇 |
废物处理 | 1453篇 |
环保管理 | 3941篇 |
综合类 | 4469篇 |
基础理论 | 7748篇 |
环境理论 | 8篇 |
污染及防治 | 7348篇 |
评价与监测 | 2125篇 |
社会与环境 | 2043篇 |
灾害及防治 | 180篇 |
出版年
2023年 | 140篇 |
2022年 | 261篇 |
2021年 | 319篇 |
2020年 | 195篇 |
2019年 | 243篇 |
2018年 | 435篇 |
2017年 | 460篇 |
2016年 | 719篇 |
2015年 | 531篇 |
2014年 | 854篇 |
2013年 | 2463篇 |
2012年 | 1015篇 |
2011年 | 1349篇 |
2010年 | 1102篇 |
2009年 | 1144篇 |
2008年 | 1410篇 |
2007年 | 1329篇 |
2006年 | 1207篇 |
2005年 | 1079篇 |
2004年 | 1037篇 |
2003年 | 990篇 |
2002年 | 933篇 |
2001年 | 1091篇 |
2000年 | 768篇 |
1999年 | 482篇 |
1998年 | 363篇 |
1997年 | 383篇 |
1996年 | 397篇 |
1995年 | 465篇 |
1994年 | 394篇 |
1993年 | 343篇 |
1992年 | 376篇 |
1991年 | 355篇 |
1990年 | 326篇 |
1989年 | 322篇 |
1988年 | 295篇 |
1987年 | 241篇 |
1986年 | 247篇 |
1985年 | 247篇 |
1984年 | 267篇 |
1983年 | 254篇 |
1982年 | 268篇 |
1981年 | 221篇 |
1980年 | 165篇 |
1979年 | 181篇 |
1978年 | 162篇 |
1977年 | 133篇 |
1975年 | 137篇 |
1973年 | 167篇 |
1972年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
791.
Chukwujindu M. A. Iwegbue Godwin E. Nwajei Jude E. Ogala Chukwudumebi L. Overah 《Environmental geochemistry and health》2010,32(5):415-430
The concentrations of trace metals (Cd, Pb, Cu, Cr, Fe, Ni, Zn and Co) were studied in soil profiles of eight municipal waste
dump sites in Warri metropolis. The results indicate that concentrations of trace metals varied widely among the different
dumpsites and decreased with depths in a studied soil profile. The accumulation pattern for the heavy metals in the soil profiles
follows the order: Fe > Pb > Mn > Co > Cr > Zn > Ni > Cu > Cd. The concentrations of metals found in these sites was below
the Canadian remediation criteria for land for agricultural, residential and commercial/industrial purposes except for the
cadmium levels in some sites that exceeded criterion values for agricultural and residential. In such sites, remedial actions
are required before any form of chosen development can take place. The levels of heavy metals found in these dump sites were
higher than that of the control site. The examined metals showed no significant correlation with soil physicochemical properties
at the surface horizon, which is suggestive evidence that these metals arise from anthropogenic input. 相似文献
792.
The composition and structure of tree stands near the timberline have been studied on different slopes and at different elevations
in the Tylaisko-Konzhakovsko-Serebryanskii Massif, the North Urals. It has been found that the upper limits of tree stands
with different degrees of canopy closure have risen considerably (by about 100 m of elevation) since the mid-19th century,
although the formation of these stands started as early as the late 18th century. Woodless areas in the eastern part of the
massif started to be colonized by Larix sibirica in the late 18th to early 19th centuries; those in the western part, by Picea obovata in the mid-19th century; and in the southern part, by Betula tortuosa in the late 19th century. Analysis of meteorological data provides evidence for warming and increasing humidity of the climate
since the late 19th century. Favorable climatic changes that facilitated the expansion of the forest have taken place both
in the summer (prolongation of the growing period) and in winter seasons (increase of air temperature and precipitation).
The observed differences in the composition and dynamics of tree stands between the studied areas of the mountain range are
most probably explained by different requirements of tree species for the depth of snow cover and the degree of soil freezing. 相似文献
793.
794.
Jeremy R. Brammer Nicolas D. Brunet A. Cole Burton Alain Cuerrier Finn Danielsen Kanwaljeet Dewan Thora Martina Herrmann Micha V. Jackson Rod Kennett Guillaume Larocque Monica Mulrennan Arun Kumar Pratihast Marie Saint‐Arnaud Colin Scott Murray M. Humphries 《Conservation biology》2016,30(6):1277-1287
Many argue that monitoring conducted exclusively by scientists is insufficient to address ongoing environmental challenges. One solution entails the use of mobile digital devices in participatory monitoring (PM) programs. But how digital data entry affects programs with varying levels of stakeholder participation, from nonscientists collecting field data to nonscientists administering every step of a monitoring program, remains unclear. We reviewed the successes, in terms of management interventions and sustainability, of 107 monitoring programs described in the literature (hereafter programs) and compared these with case studies from our PM experiences in Australia, Canada, Ethiopia, Ghana, Greenland, and Vietnam (hereafter cases). Our literature review showed that participatory programs were less likely to use digital devices, and 2 of our 3 more participatory cases were also slow to adopt digital data entry. Programs that were participatory and used digital devices were more likely to report management actions, which was consistent with cases in Ethiopia, Greenland, and Australia. Programs engaging volunteers were more frequently reported as ongoing, but those involving digital data entry were less often sustained when data collectors were volunteers. For the Vietnamese and Canadian cases, sustainability was undermined by a mismatch in stakeholder objectives. In the Ghanaian case, complex field protocols diminished monitoring sustainability. Innovative technologies attract interest, but the foundation of effective participatory adaptive monitoring depends more on collaboratively defined questions, objectives, conceptual models, and monitoring approaches. When this foundation is built through effective partnerships, digital data entry can enable the collection of more data of higher quality. Without this foundation, or when implemented ineffectively or unnecessarily, digital data entry can be an additional expense that distracts from core monitoring objectives and undermines project sustainability. The appropriate role of digital data entry in PM likely depends more on the context in which it is used and less on the technology itself. 相似文献
795.
M.A.S.S. Ravagnani M.H.M. Reis R. Maciel Filho M.R. Wolf-Maciel 《Process Safety and Environmental Protection》2010,88(1):67-73
Production of anhydrous ethanol in large scale has been made by extractive distillation using conventional solvents like ethylene-glycol. In the present paper, extractive distillation process is studied to obtain pure ethanol using ethylene-glycol and tetraethylene-glycol as solvents. Residue curve maps are used to analyse the proposed distillation processes in interpreting mixture behaviours and feasibility of distillation columns. The industrial process is simulated at steady state from residue curve map analysis. Simulation results for the ethanol/water mixture using ethylene-glycol, the conventional solvent, and tetraethylene-glycol, an alternative solvent, are presented. These results showed that the process using tetraethylene-glycol is reliable, although it requires more energy than the process with ethylene-glycol. However, ethylene-glycol has a considerable toxicity level while tetraethylene-glycol is non-toxic. 相似文献
796.
797.
A. Mirmohseni M. Rastgouy Houjaghan 《Journal of environmental science and health. Part. B》2013,48(4):278-284
A simple and cost-effective analysis method based on quartz crystal nanobalance (QCN) coated with a molecularly imprinted polymer (MIP) for measurement of methomyl was investigated. In the first part of this study, a sensitive, selective and reliable quartz crystal nanobalance (QCN) sensor was designed for the selective determination of methomyl in aqueous solutions. In the second part, in order to demonstrate the applicability and performance of the fabricated sensor in the real world situation, it was successfully applied for the determination of methomyl residual in photo catalytic degradation by ZnO powders in aqueous solutions. The fabricated sensor presents a high selectivity and sensitivity (4.56 Hz per mg L?1) for methomyl and it can be used for determination of methomyl concentration ranged between 1 to 45 mg L?1. Furthermore, good reproducibility, R.S.D. = 2.14% (n = 5) was observed. To investigate the performance of the sensor, the change in the insecticide concentration during the photocatalytic degradation of methomyl by ZnO was investigated by QCN and UV/Vis spectroscopy. Results obtained from QCN sensor and UV/Vis spectroscopy measurement are in good mutual agreement. So the fabricated sensor may provide an efficient, low cost, easy-to-use method for the in-field evaluation of specific targeted analytes in aqueous solutions which in turn may lead to improved food and water safety. 相似文献
798.
799.
A. P. Altshuller S. L. Kopczynski D. Wilson W. Lonneman F. D. Sutterfield 《Journal of the Air & Waste Management Association (1995)》2013,63(10):791-794
Effects associated with photochemical air pollution were measured during irradiation of n-butane-nitrogen oxide or n-butane-ethane-nitrogen oxide mixtures, with small amounts of propylene or toluene added. The effects measured including nitrogen dioxide and oxidant dosages, yields of formaldehyde and peroxy-acetyl nitrate, and eye irritation response. The results obtained clearly show that beneficial effects result from selective changes in hydrocarbon composition as well as from reduction of total hydrocarbon concenfration. Exclusion of olefins and alkylbenzenes was highly effective in reducing oxidant dosage, formaldehyde and peroxyacetyl nitrate concentrations, and eye irritation response. The only penalty was a modest increase in nitrogen dioxide dosage. A large reduction in nitrogen oxide concentration reduced nitrogen dioxide dosage and eye irritation response, but with the penalty of a large increase in oxidant dosage. The desirability of preferentially reducing olefins and alkylbenzenes rather than paraffinic hydrocarbons, acetylene, and benzene is strongly supported by this study. Research and development efforts should be directed toward preferential hydrocarbon control by mechanical or catalytic control 相似文献
800.