全文获取类型
收费全文 | 31024篇 |
免费 | 336篇 |
国内免费 | 225篇 |
专业分类
安全科学 | 833篇 |
废物处理 | 1155篇 |
环保管理 | 4328篇 |
综合类 | 6097篇 |
基础理论 | 8269篇 |
环境理论 | 13篇 |
污染及防治 | 7813篇 |
评价与监测 | 1751篇 |
社会与环境 | 1140篇 |
灾害及防治 | 186篇 |
出版年
2018年 | 329篇 |
2017年 | 348篇 |
2016年 | 545篇 |
2015年 | 431篇 |
2014年 | 628篇 |
2013年 | 2366篇 |
2012年 | 826篇 |
2011年 | 1176篇 |
2010年 | 915篇 |
2009年 | 987篇 |
2008年 | 1183篇 |
2007年 | 1243篇 |
2006年 | 1120篇 |
2005年 | 921篇 |
2004年 | 911篇 |
2003年 | 929篇 |
2002年 | 865篇 |
2001年 | 1113篇 |
2000年 | 807篇 |
1999年 | 492篇 |
1998年 | 377篇 |
1997年 | 397篇 |
1996年 | 416篇 |
1995年 | 467篇 |
1994年 | 451篇 |
1993年 | 418篇 |
1992年 | 414篇 |
1991年 | 422篇 |
1990年 | 438篇 |
1989年 | 428篇 |
1988年 | 379篇 |
1987年 | 363篇 |
1986年 | 340篇 |
1985年 | 331篇 |
1984年 | 375篇 |
1983年 | 349篇 |
1982年 | 394篇 |
1981年 | 349篇 |
1980年 | 306篇 |
1979年 | 312篇 |
1978年 | 298篇 |
1977年 | 258篇 |
1976年 | 243篇 |
1975年 | 231篇 |
1974年 | 276篇 |
1973年 | 261篇 |
1972年 | 248篇 |
1971年 | 221篇 |
1970年 | 196篇 |
1967年 | 195篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
71.
72.
73.
74.
The typical parameters of acid precipitation are evaluated in the forest of Vallombrosa (Tuscan Appennines) during the dry period 1988-89. Individual rain events (dry and wet deposition) were sampled in a clearing of the forest and below the canopy of an evergreen tree as well as a deciduous broadleaf tree.
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献
75.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
76.
77.
78.
Henrietta Nittby Bengt Widegren Morten Krogh Gustav Grafström Henrik Berlin Gustav Rehn Jacob L. Eberhardt Lars Malmgren Bertil R. R. Persson Leif G. Salford 《The Environmentalist》2008,28(4):458-465
We have earlier shown that radio frequency electromagnetic fields can cause significant leakage of albumin through the blood–brain
barrier of exposed rats as compared to non-exposed rats, and also significant neuronal damage in rat brains several weeks
after a 2 h exposure to a mobile phone, at 915 MHz with a global system for mobile communications (GSM) frequency modulation,
at whole-body specific absorption rate values (SAR) of 200, 20, 2, and 0.2 mW/kg. We have now studied whether 6 h of exposure
to the radiation from a GSM mobile test phone at 1,800 MHz (at a whole-body SAR-value of 13 mW/kg, corresponding to a brain
SAR-value of 30 mW/kg) has an effect upon the gene expression pattern in rat brain cortex and hippocampus—areas where we have
observed albumin leakage from capillaries into neurons and neuronal damage. Microarray analysis of 31,099 rat genes, including
splicing variants, was performed in cortex and hippocampus of 8 Fischer 344 rats, 4 animals exposed to global system for mobile
communications electromagnetic fields for 6 h in an anechoic chamber, one rat at a time, and 4 controls kept as long in the
same anechoic chamber without exposure, also in this case one rat at a time. Gene ontology analysis (using the gene ontology
categories biological processes, molecular functions, and cell components) of the differentially expressed genes of the exposed
animals versus the control group revealed the following highly significant altered gene categories in both cortex and hippocampus:
extracellular region, signal transducer activity, intrinsic to membrane, and integral to membrane. The fact that most of these
categories are connected with membrane functions may have a relation to our earlier observation of albumin transport through
brain capillaries. 相似文献
79.
Nutrient removal by constructed wetlands can decline over time due to the accumulation of organic matter. A prescribed burn is one of many management strategies used to remove detritus in macrophyte-dominated systems. We quantified the short-term effects on effluent water quality and the amount of aboveground detritus removed from a prescribed burn event. Surface water outflow concentrations were approximately three times higher for P and 1.5 times higher for total Kjeldhal nitrogen (TKN) following the burn event when compared to the control. The length of time over which the fire effect was significant (P < 0.05), 3 d for TKN and up to 23 d for P fractions. Over time, the concentration of soluble reactive phosphorus (SRP) in the effluent decreased, but was compensated with increases in dissolved organic phosphorus (DOP) and particulate phosphorus (PP), such that net total P remained the same. Total aboveground biomass decreased by 68.5% as a result of the burn, however, much of the live vegetation was converted to standing dead material. These results demonstrate that a prescribed burn can significantly decrease the amount of senescent organic matter in a constructed wetland. However, short-term nutrient releases following the burn could increase effluent nutrient concentrations. Therefore, management strategies should include hydraulically isolating the burned area immediately following the burn event to prevent nutrient export. 相似文献
80.
Damianovic MH Saia FT Moraes EM Landgraf D Rezende MO Vazoller RF Foresti E 《Journal of environmental science and health. Part. B》2007,42(1):45-52
Wastewater samples from an anaerobic reactor were extracted with hexane and derivatized with diazomethane (method 1) and with acetic anidride (method 2). Gas chromatography with electron-capture detection (ECD) was employed for separating the parent compound and intermediates trichlorophenols (TCP) and dichlorophenols (DCP) which originated from the penta chlorophenol (PCP) degradation process. The relations between concentrations of PCP, TCP and DCP areas were linear in the range of concentrations of 0.2 to 8 mg/L and 0.025 mg/L to 5 mg/L for methods 1 and 2, respectively. The repeatability of the extraction methods was satisfactory, with variation coefficients lower than 11%. For method 1, at the fortification level of 0.2 mg/L, recovery of PCP, TCP, and DCP was 112%, 74% and 45%, respectively. For method 2, the corresponding recovery values at the fortification level of 0.1 mg/L were 91%, 93% and 103%, respectively. Storage of the frozen samples did not alter their PCP determination properties. The chromatographic methods adapted for chlorophenol determination in wastewater were suitable with relatively simple manipulation techniques. The obtained results were reproducible and allowed identification of intermediates formed during the PCP degradation process. 相似文献