全文获取类型
收费全文 | 8817篇 |
免费 | 5篇 |
国内免费 | 37篇 |
专业分类
安全科学 | 34篇 |
废物处理 | 653篇 |
环保管理 | 1066篇 |
综合类 | 949篇 |
基础理论 | 2761篇 |
环境理论 | 1篇 |
污染及防治 | 1684篇 |
评价与监测 | 870篇 |
社会与环境 | 837篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 10篇 |
2022年 | 32篇 |
2021年 | 8篇 |
2019年 | 18篇 |
2018年 | 1204篇 |
2017年 | 1128篇 |
2016年 | 991篇 |
2015年 | 148篇 |
2014年 | 44篇 |
2013年 | 93篇 |
2012年 | 382篇 |
2011年 | 1108篇 |
2010年 | 603篇 |
2009年 | 526篇 |
2008年 | 741篇 |
2007年 | 1034篇 |
2006年 | 37篇 |
2005年 | 52篇 |
2004年 | 88篇 |
2003年 | 88篇 |
2002年 | 106篇 |
2001年 | 94篇 |
2000年 | 41篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1985年 | 8篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1972年 | 10篇 |
1971年 | 4篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1959年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有8859条查询结果,搜索用时 484 毫秒
141.
Information on the forms of P present in animal manure may improve our ability to manage manure P. In most investigations of manure P composition, only inorganic and total P are determined, and the difference between them is assigned as organic P. In this study, we explored the possibility of identifying and quantifying more specific organic P forms in animal manure with orthophosphate-releasing enzymes. Pig (Sus scrofa) manure and cattle (Bos taurus) manure were first sequentially fractionated into water-soluble P, NaHCO3-soluble P, NaOH-soluble P, HCl-soluble P, and residual P. The fractions were separately incubated with wheat phytase, alkaline phosphatase, nuclease P1, nucleotide pyrophosphatase, or their combinations. The released orthophosphate was determined by a molybdate blue method. Part of the organic P in those fractions could be identified by the enzymatic treatments as phytate (i.e., 39% for pig manure and 17% for cattle manure in water-soluble organic P), simple phosphomonoesters (i.e., 43% for pig manure and 15% for cattle manure in NaOH-soluble organic P), nucleotide-like phosphodiesters (2-12%), and nucleotide pyrophosphate (0-4%). Our data indicate that the enzymatic treatment is an effective approach to identify and quantify the organic P forms present in animal manures. 相似文献
142.
Odland JØ Nieboer E Romanova N Thomassen Y Hofoss D Lund E 《Journal of environmental monitoring : JEM》2001,3(2):177-184
Concentrations in human placenta of 11 essential elements (P, Ca, Mg, Cu, S, Na, Fe, Zn, K, Se, Mn) and 5 toxic elements (Ba, Sr, Pb, Ni, Cd) are compared for each of two arctic communities in eastern Norway and western Russia, and for another in each country located at more southerly latitudes. All but Mg, Fe, P and K were present in higher concentrations in the Russian study group. The observed inter-element correlations are reflected by the four major factors identified in a principal component analysis. The total variation explained was 67.3%, of which more than half (35.3%) was contributed by Factor 1. P, Ca, Mg, Ba, Sr, Pb, and Ni were major contributors to this factor. The placental concentrations of these elements depended strongly on gestational age, increasing from about week 35 and peaking near weeks 39 and 40, and exhibited skewed frequency distributions and a dependence on maternal smoking. The gestational-dependent mineralization of the placenta is interpreted to reflect the deposition of metal phosphates coinciding with smoking-induced tissue damage. The loadings of the remaining three factors are reviewed in the context of common uptake mechanisms, similar biochemistries and unique transport pathways. The inter-element relationships and grouping of the elements observed should constitute a scientific base for the use of placenta composition in environmental monitoring and epidemiological studies. 相似文献
143.
Styro D Bumeliene Z Lukinskiene M Morkuniene R 《Journal of environmental radioactivity》2001,53(1):27-39
Variations in 137Cs concentrations were investigated over the period 1986-1997 in the southeastern part of the Baltic Sea, following the Chernobyl power plant accident. The rate of "self-cleaning" was demonstrated to be very slow, the average concentration of 137Cs in 1996 being almost the same as that measured directly after the accident, in 1986. Measurements of both 137Cs and 90Sr concentrations generally revealed homogeneous distributions in this region of the Baltic Sea, though patchy distributions did develop under some hydrometeorological conditions. Specifically, the 137Cs concentration distribution became heterogeneous with values varying in the range 60-92 Bq/m3 under south-southwesterly wind conditions whilst the 90Sr concentration distribution developed similar characteristics with values ranging from 15 to 64 Bq/m3 under east-southeasterly wind conditions. In addition, in coastal waters, over extensive periods of north-northwesterly winds in 1995, 137Cs concentrations increased to values 1.5-2 times the overall average concentration, which was registered in 1986 and 1996. These data therefore reveal a continuing significant pollution of the waters of the Baltic Sea resulting from the Chernobyl power plant accident, a pollution compounded by the slow rate of radionuclide self-cleaning and significant probability of sudden regional concentration increase. 相似文献
144.
Lemons J 《Environmental management》2011,48(3):379-391
I review the status of scientific, political, and moral problems of global climate change (GCC) and, based on lessons from
environmental and sustainability programs in universities, demonstrate that universities have had a lethargic response to
urgent needs to mitigate the problems. I explore reasons for the response, and conclude that there is an urgent need for comprehensive
and wide–ranging change in universities to help mitigate GCC. My discussion is focused on those within universities as well
as those in environmental professions regardless of their areas of specialization. 相似文献
145.
Measuring the Social Recreation Per-Day Net Benefit of the Wildlife Amenities of a National Park: A Count-Data Travel-Cost Approach 总被引:2,自引:0,他引:2
In this article, we apply count-data travel-cost methods to a truncated sample of visitors to estimate the Peneda-Gerês National
Park (PGNP) average consumer surplus (CS) for each day of visit. The measurement of recreation demand is highly specific because
it is calculated by number of days of stay per visit. We therefore propose the application of altered truncated count-data
models or truncated count-data models on grouped data to estimate a single, on-site individual recreation demand function,
with the price (cost) of each recreation day per trip equal to out-of-pocket and time travel plus out-of-pocket and on-site
time costs. We further check the sensitivity of coefficient estimations to alternative models and analyse the welfare measure
precision by using the delta and simulation methods by Creel and Loomis. With simulated limits, CS is estimated to be €194
(range €116 to €448). This information is of use in the quest to improve government policy and PNPG management and conservation
as well as promote nature-based tourism. To our knowledge, this is the first attempt to measure the average recreation net
benefits of each day of stay generated by a national park by using truncated altered and truncated grouped count-data travel-cost
models based on observing the individual number of days of stay. 相似文献
146.
People receive information about visiting places from a variety of sources, and it is important to understand how information
affects recreation experiences. This study examines how different information treatments describing a recreation place influence
perceived crowding and encounter norms. The study location was the Jungmoeri area of Mudeungsan Provincial Park (MPP) in Korea.
Data were collected from 50 college students utilizing a series of simulated moving pictures in a laboratory setting. Respondents
were given information describing three different types of conditions and experiences (nature preserve, transition/buffer,
and developed area), plus a no information control. Results showed that information influenced perceived crowding and encounter
norms. For the range of encounter numbers depicted in the photos, the nature preserve treatment produced higher crowding ratings
and lower tolerances for encounters, the developed area treatment produced lower crowding ratings and higher tolerances, and
the transition/buffer and the control were in between. Information treatments also influence the perceived importance of encounter
numbers, and importance was highest for the nature preserve. Management implications are discussed. 相似文献
147.
Agricultural Land Use Effects on Sediment Loading and Fish Assemblages in Two Minnesota (USA) Watersheds 总被引:1,自引:1,他引:0
We examined the relationship between water quality and fish communities within two agricultural areas using a computer simulation model. Our analyses focused on a coolwater stream, Wells Creek in southeastern Minnesota, and a warmwater stream, the Chippewa River in western Minnesota. We used the Agricultural Drainage and Pesticide Transport (ADAPT) model in relation to land use to calculate instream suspended sediment concentrations using estimates of sediment delivery, runoff, baseflow and streambank erosion, and quantified the effects of suspended sediment exposure on fish communities. We predicted the effects of agricultural practices on stream fish communities under several possible land use scenarios, with reference to current conditions. Land use changes led to reductions in sediment loading of up to 84% in Wells Creek and 49% in the Chippewa River. The reduction in sediment loading across scenarios may be directly related to a reduction in runoff by about 35% in both study areas. We found a 98% decrease in lethal concentrations of suspended sediment on fish in Wells Creek with an increase in conservation tillage, riparian buffers, and permanent vegetative cover. However, the effects of suspended sediment did not significantly decrease in the Chippewa River. This difference between study areas was likely due to differences in tolerance to suspended sediment between coolwater and warmwater fish communities and differences in topography, runoff and bank erosion between the two streams.
The Minnesota Cooperative Fish and Wildlife Research Unit is jointly sponsored by the US Geological Survey, the University of Minnesota, the Minnesota Department of Natural Resources, and the Wildlife Management Institute. 相似文献
148.
In this study, we analyzed the sustainability and determinant factors of waste reduction through variable charging schemes.
We drew three main conclusions from the study. (1) Waste reduction was achieved by variable charging and was sustained over
an average of at least 10 years. The results regarding the sustainability of the price effect were inconclusive. (2) The main
factors contributing to the combustible waste reduction achieved through variable charging were two-tier pricing and the price
of waste bags. The effect of two-tier pricing programs was positive. (3) Waste paper recycling and variable charging reinforce
each other to promote waste reduction.
Received: September 3, 2001 / Accepted: January 13, 2002 相似文献
149.
J. R. Crabtree N. A. Chalmers Z. E. D. Appleton 《Journal of Environmental Planning and Management》1994,37(4):415-429
This paper considers the external costs of public access on privately‐owned farm and estate land in Scotland. The increased costs and reductions in income associated with public access are found to be highly variable and site‐specific, with the main effects on land in areas of high population density or high scenic quality, or with recreational attributes. Although costs were on average higher for estates, reflecting their larger area and recreational potential, on a per‐hectare basis the costs of access were greater for the farm sector. Whilst much of the public access exists through de facto rights on open‐access land, there was evidence for an increasing commercialization of open‐air recreation, particularly with respect to more specialized activities. The discussion considers the extent to which the costs of access for land managers are reflected in policies determining the public provision of countryside access. 相似文献
150.
Sanjiang National Nature Reserve (NNR) is a state-owned natural wetland in China that has suffered severe degradation due
to cultivation and wetland reclamation by farmers. As a consequence, the conversion of cultivated land to wetlands (CCW) was
proposed by the government of Heilongjiang province and the United Nations Development Programme/Global Environment Facility
(UNDP/GEF) project team in 2007. We suggest that voluntary participation in the CCW could be an important tool for accomplishing
the integrated objectives of wetland conservation and local development. The purpose of this study was to examine the main
factors that influence farmers’ willingness to participate in the CCW through a field investigation and a questionnaire. Based
on the data from our questionnaire, which provided an effective sample of 310 households in 11 villages, the influencing factors
of farmers’ willingness to participate were analyzed through binary logistic regression analyses. It was concluded that age,
education, the amount of cultivated land, geographical location, and the perceived benefits and risks were important factors
for participation. Furthermore, suggestions for improving the wetland compensation system and providing alternative livelihoods
are proposed to strengthen participation. 相似文献