全文获取类型
收费全文 | 22800篇 |
免费 | 219篇 |
国内免费 | 177篇 |
专业分类
安全科学 | 634篇 |
废物处理 | 980篇 |
环保管理 | 2911篇 |
综合类 | 3202篇 |
基础理论 | 5954篇 |
环境理论 | 10篇 |
污染及防治 | 6728篇 |
评价与监测 | 1548篇 |
社会与环境 | 1088篇 |
灾害及防治 | 141篇 |
出版年
2023年 | 127篇 |
2022年 | 244篇 |
2021年 | 286篇 |
2020年 | 168篇 |
2019年 | 218篇 |
2018年 | 415篇 |
2017年 | 423篇 |
2016年 | 628篇 |
2015年 | 516篇 |
2014年 | 741篇 |
2013年 | 1925篇 |
2012年 | 865篇 |
2011年 | 1090篇 |
2010年 | 808篇 |
2009年 | 876篇 |
2008年 | 1108篇 |
2007年 | 1136篇 |
2006年 | 970篇 |
2005年 | 804篇 |
2004年 | 814篇 |
2003年 | 736篇 |
2002年 | 724篇 |
2001年 | 817篇 |
2000年 | 594篇 |
1999年 | 352篇 |
1998年 | 263篇 |
1997年 | 243篇 |
1996年 | 286篇 |
1995年 | 295篇 |
1994年 | 286篇 |
1993年 | 238篇 |
1992年 | 227篇 |
1991年 | 206篇 |
1990年 | 225篇 |
1989年 | 202篇 |
1988年 | 199篇 |
1987年 | 187篇 |
1986年 | 170篇 |
1985年 | 158篇 |
1984年 | 189篇 |
1983年 | 190篇 |
1982年 | 183篇 |
1981年 | 178篇 |
1980年 | 149篇 |
1979年 | 168篇 |
1978年 | 118篇 |
1977年 | 107篇 |
1975年 | 101篇 |
1973年 | 96篇 |
1972年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
71.
Assessment of environmental changes in the Orinoco River delta 总被引:1,自引:0,他引:1
H. Echezuría J. Córdova M. González V. González J. Méndez C. Yanes 《Regional Environmental Change》2002,3(1-3):20-35
Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on
environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m3 s–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into
a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and
estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the
Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km
further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this
distributary, where successional colonization and species replacement by different species of grasses and mangroves take place.
Electronic Publication 相似文献
72.
In situ assessment of modification of sediment properties by burrowing invertebrates 总被引:4,自引:0,他引:4
Benthic organisms can significantly alter the physical properties of marine sediments, but it has hitherto been difficult to assess and quantify the effects of bioturbation. In situ geophysical techniques offer new methods for measuring these effects: measurement of acoustic shear-wave velocity and electrical resistivity allows nondestructive assessment of the properties of the grain framework and pore-fluid matrix, respectively, of the seabed sediment. The influence of burrowing invertebrates on the structural properties of sandy sediments at intertidal locations on the coast of Wales (UK) was investigated during the periol 1986–1987 using these techniques. Three species (Arenicola marina, Corophium arenarium and Lanice conchilega) were selected on the basis of their contrasting styles of burrow construction. All three species produced measurable and significant, although different, changes in bed properties. They modified shear-wave propagation through the bed by changing bed rigidity: while A. marina and C. arenarium decreased rigidity by creating open burrows, L. conchilega increased rigidity by building shell-lined tubes. All produced a decrease in electrical resistivity by altering porosity and/or tortuosity, which implies an increase in permeability; these changes were attributable not only to the presence of the burrows but also to modification of the between-burrow sediment texture and bed properties. 相似文献
73.
74.
P.P. Povinec H. Bokuniewicz W.C. Burnett J. Cable M. Charette J.-F. Comanducci E.A. Kontar W.S. Moore J.A. Oberdorfer J. de Oliveira R. Peterson T. Stieglitz M. Taniguchi 《Journal of environmental radioactivity》2008,99(10):1596
Results of groundwater and seawater analyses for radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, and 228Ra) and stable (D and 18O) isotopes are presented together with in situ spatial mapping and time series 222Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d−1 to 360 cm d−1; the unit represents cm3/cm2/day), as well as during a few hours (from 0 cm d−1 to 110 cm d−1), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous 222Rn measurements is 17 ± 10 cm d−1. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7 × 103 m3 d−1 per km of the coast. The isotopic composition (δD and δ18O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of 222Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1–2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region. 相似文献
75.
Thierry Rousseau Nicole Laurent Christel Thauvin-Robinet Stéphanie Lionnais Christine Durand Laurence Faivre Paul Sagot 《黑龙江环境通报》2002,22(8):692-696
Fraser syndrome (MIM 219000) is a rare disorder of autosomal recessive inheritance, characterized by the association of cryptophthalmos, syndactyly and genital abnormalities. Here we report on two cases of Fraser syndrome (cryptophthalmos syndrome) in a non-consanguineous couple, with variable expression in echographic, clinical and autopsy findings. Furthermore, we highlight the difficulties in prenatal diagnosis of Fraser syndrome. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
76.
77.
A. Migné D. Davoult N. Spilmont D. Menu G. Boucher J.-P. Gattuso H. Rybarczyk 《Marine Biology》2002,140(4):865-869
This paper describes a closed-chamber method for measuring CO2 fluxes in intertidal soft sediments during periods of emersion. The method relies on closed-circuit incubations of undisturbed sediment and measurement of CO2 exchanges using an infrared gas analyser. The method was assessed during field experiments, both in light and dark conditions, on an exposed sandy beach and in an estuary. The rates of gross community production measured under moderate irradiance (4.2 mg C m-2 h-1 on the exposed sandy beach and 35 mg C m-2 h-1 in the estuary) are in good agreement with rates reported in the literature. In conjunction with appropriate sampling strategies, this method can be useful for estimating and comparing production of intertidal areas or for assessing factors that influence production. 相似文献
78.
Branquinho C Serrano HC Pinto MJ Martins-Loução MA 《Environmental pollution (Barking, Essex : 1987)》2007,146(2):437-443
The several established criteria to define a hyperaccumulator plant were applied to a rare and endangered species, Plantago almogravensis, and to the 3rd most abundant element in the earth crust, Al. Using the most common criteria, P. almogravensis undoubtedly is an Al hyperaccumulator plant. If the recent proposed requirements were considered, most of them matching those for a plant to be used in phytoextraction, it can only be considered an unusual accumulator of Al. A discussion is made concerning the several criteria of a hyperaccumulator plant in order to include rare and endemic ones and abundant elements. In ecological terms, the enrichment in Al and Fe observed may account for the differences in the vegetation pattern. Due to the rarity and endangered nature of this plant, the contribution of this work is also relevant for the ecological understanding and the development of conservation options of this endemic species. 相似文献
79.
80.
Alletto L Benoit P Bergheaud V Coquet Y 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):678-688
Laboratory studies were conducted to evaluate the effects of temperature and water pressure head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T1/2) were measured in the seedbed samples under MT at 25 °C and −33 cm water pressure head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter. 相似文献