全文获取类型
收费全文 | 23986篇 |
免费 | 215篇 |
国内免费 | 177篇 |
专业分类
安全科学 | 522篇 |
废物处理 | 950篇 |
环保管理 | 3227篇 |
综合类 | 4356篇 |
基础理论 | 6465篇 |
环境理论 | 13篇 |
污染及防治 | 5207篇 |
评价与监测 | 1575篇 |
社会与环境 | 1929篇 |
灾害及防治 | 134篇 |
出版年
2022年 | 145篇 |
2021年 | 174篇 |
2020年 | 134篇 |
2019年 | 165篇 |
2018年 | 762篇 |
2017年 | 754篇 |
2016年 | 821篇 |
2015年 | 368篇 |
2014年 | 472篇 |
2013年 | 1589篇 |
2012年 | 770篇 |
2011年 | 1442篇 |
2010年 | 978篇 |
2009年 | 1082篇 |
2008年 | 1306篇 |
2007年 | 1555篇 |
2006年 | 741篇 |
2005年 | 664篇 |
2004年 | 606篇 |
2003年 | 696篇 |
2002年 | 652篇 |
2001年 | 669篇 |
2000年 | 516篇 |
1999年 | 303篇 |
1998年 | 250篇 |
1997年 | 222篇 |
1996年 | 228篇 |
1995年 | 262篇 |
1994年 | 236篇 |
1993年 | 241篇 |
1992年 | 245篇 |
1991年 | 235篇 |
1990年 | 250篇 |
1989年 | 208篇 |
1988年 | 178篇 |
1987年 | 158篇 |
1986年 | 179篇 |
1985年 | 185篇 |
1984年 | 192篇 |
1983年 | 198篇 |
1982年 | 178篇 |
1981年 | 198篇 |
1980年 | 178篇 |
1979年 | 169篇 |
1978年 | 128篇 |
1977年 | 142篇 |
1974年 | 122篇 |
1973年 | 107篇 |
1972年 | 127篇 |
1970年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Tanay B. Yıldırım Tutku Ak Zuhal Ölmez 《Environment, Development and Sustainability》2008,10(6):871-881
While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined. 相似文献
52.
Babay PA Romero Ale EE Itria RF Becquart ET Thiele B Batistoni DA 《Journal of environmental monitoring : JEM》2008,10(4):443-452
In the present work we have developed an analytical methodology for the determination of nonylphenol (NP) and nonylphenol mono- and di-ethoxylates (NP1EO and NP2EO) in water samples. The applicability of this methodology was proved by means of the analysis of environmentally relevant aqueous samples from Buenos Aires. This constitutes a starting point for a rigorous assessment of the incidence of NPnEO surfactants in Argentina, as only very few, qualitative or semi-quantitative data on the occurrence of these compounds in local systems were available up to this time. Enrichment of the analytes was carried out by solid-phase extraction on a C-18 sorbent, followed by elution with ethyl acetate. Normal-phase high performance liquid chromatography on an amino-silica column and fluorescence detection at excitation-emission wavelengths of 230-300 nm were employed for separation and quantification of the analytes. Confirmation of peak assignment in selected real samples was performed by off-line coupling HPLC with GC-MS analysis. A non-polar GC capillary column was used, and a characteristic peak pattern was obtained for the alkyl chain isomers of each ethoxylated homologue and NP. GC-MS analyses yielded in all cases purity levels higher than 80% for the HPLC collected fractions. The elevated concentrations found for the estrogenic metabolites of NPnEO are in accordance with an unrestricted use of this class of non-ionic surfactants in the country. 相似文献
53.
54.
55.
Collections made in the course of long-term field studies on ecology of the northern mole vole Ellobius talpinus Pall. in the Ural Region and neighboring areas (more than 2000 individuals from 24 points of the species range) were used
to analyze geographic variation in its coat color (color morphs). On the basis of long-term observations (1985–1999) on marked
animals from a polymorphic population (Kurtamyshskii raion, Kurgan oblast), the life spans of males and females and the dependence
of life span on population density and structure were estimated in animals of different color morphs. Each color morph of
E. talpinus was shown to have specific features of the seasonal dynamics of age structure and migrations. 相似文献
56.
57.
Schaefer CE do Amaral EF de Mendonça BA Oliveira H Lani JL Costa LM Fernandes Filho EI 《Environmental monitoring and assessment》2008,140(1-3):279-289
The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even
at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL
project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of
intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones:
Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The
highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the
high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed
to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus
lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow
soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector
is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of
sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable
capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high
C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed
to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need
for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting
C stocks in Amazonia when such great pedological variability is not taken into account. 相似文献
58.
Current demand analysis methods do not formally cover the case of chronic deficits in quantity or quality of water and sanitation
services. These services include drinking water supply (DWS), wastewater and sewage treatment (WST), and municipal solid waste
management (MSW). Formal analysis of this case would, at minimum, define the deficit state and evaluate appropriate options
for reducing it. This paper proposes for a formal analytical model for municipal sanitation systems (MSS) that operate with
deficits in at least one of the constituent services of DWS, WST, or MSW. The model introduces definitions and notation for
describing the deficit state for conducting demand analysis on municipal sanitation systems. This model of demand analysis
for systems with chronic deficits will hereinafter be referred to as deficit analysis. A case study for Bacoor, Philippines is presented as an example. 相似文献
59.
60.