全文获取类型
收费全文 | 1844篇 |
免费 | 10篇 |
国内免费 | 7篇 |
专业分类
安全科学 | 35篇 |
废物处理 | 59篇 |
环保管理 | 107篇 |
综合类 | 648篇 |
基础理论 | 314篇 |
环境理论 | 7篇 |
污染及防治 | 535篇 |
评价与监测 | 83篇 |
社会与环境 | 71篇 |
灾害及防治 | 2篇 |
出版年
2021年 | 15篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 31篇 |
2017年 | 38篇 |
2016年 | 38篇 |
2015年 | 34篇 |
2014年 | 44篇 |
2013年 | 94篇 |
2012年 | 35篇 |
2011年 | 72篇 |
2010年 | 51篇 |
2009年 | 58篇 |
2008年 | 88篇 |
2007年 | 83篇 |
2006年 | 66篇 |
2005年 | 64篇 |
2004年 | 40篇 |
2003年 | 45篇 |
2002年 | 46篇 |
2001年 | 58篇 |
2000年 | 44篇 |
1999年 | 27篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 30篇 |
1993年 | 13篇 |
1991年 | 15篇 |
1989年 | 12篇 |
1984年 | 14篇 |
1981年 | 16篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1969年 | 13篇 |
1968年 | 13篇 |
1967年 | 15篇 |
1966年 | 23篇 |
1965年 | 29篇 |
1964年 | 16篇 |
1963年 | 25篇 |
1962年 | 22篇 |
1961年 | 30篇 |
1960年 | 20篇 |
1959年 | 21篇 |
1958年 | 13篇 |
1957年 | 24篇 |
1956年 | 16篇 |
1955年 | 16篇 |
排序方式: 共有1861条查询结果,搜索用时 128 毫秒
71.
72.
Dr. Yash P. Agrawal Päivi Ylikangas Markku T. Parviainen Ilkka M. Penttilä 《黑龙江环境通报》1994,14(12):1141-1149
The histochemical measurement of urea-resistant alkaline phosphatase from maternal blood neutrophils is known to have a high detection rate for the prenatal detection of Down's syndrome pregnancies. However, because the histochemical method is laborious and subjective to use, it has not gained widespread acceptance in prenatal screening programmes. We present a simple and objective method for the measurement of urea-resistant alkaline phosphatase by flow cytometry. The method should allow the design of larger studies aimed at evaluating the role of neutrophil urea-resistant alkaline phosphatase in the prenatal screening for Down's syndrome. 相似文献
73.
74.
Paula Muukkonen Helin Hartikainen Kirsti Lahti Asko Srkel Markku Puustinen Laura Alakukku 《Agriculture, ecosystems & environment》2007,120(2-4):299-306
No-tillage (NT) is a method adopted to reduce erosion and particulate phosphorus (P) load from arable land to watercourses. However, it has been found to increase the loss of dissolved P with surface runoff, but the reasons for that have rarely been examined in detail. The objective of the present study was to determine the chemical factors explaining this response by investigating the impact of NT on the type and distribution of P reserves as well as on organic carbon (C) in the 0–35 cm topsoil layer of clay soil profiles (Vertic Cambisols). Soil samples were taken from two experimental fields (Jokioinen and Aurajoki) at 0–5, 5–20 and 20–35 cm depths in conventionally tilled (CT) and non-tilled (for 4–5 years) plots. The plots had been cultivated and fertilized according to the common field practices in Finland (15–18 kg P and 100–128 kg N ha−1 year−1).Inorganic and organic P reserves characterized by a modified Chang and Jackson fractionation procedure were not significantly affected by the cultivation methods. However, in the uppermost soil layer (0–5 cm) in NT of the Jokioinen field, the labile P determined by water extraction (Pw) increased significantly, whereas the increase in P extracted with acid ammonium acetate (PAAC) remained statistically insignificant. The increase in labile P coincided with a significant increase in organic carbon (C), which supports the theory that competition between organic anions and phosphate for the same sorption sites on oxide surfaces will enhance the lability of soil P. In the Aurajoki field with distinct soil cracking, Pw and PAAC were not affected by NT in the uppermost soil layer, but they increased in the deepest soil layer (20–35 cm) concomitantly with an increase in Al-bound P and organic C. However, the increases were not statistically significant. In both fields, soil acidification due to the repeated application of N fertilizers at a shallow soil depth as well as the accumulation of organic C lowered pH of the uppermost soil layer in NT compared to the deeper soil layers. The results indicated that even short-term NT can increase the labile P in clay soil. However, further studies are needed to assess the long-term changes in lability of surface soil P and, consequently, the possible need for readjustment of the fertilization level in NT. 相似文献
75.
The significant processes controlling the fate of particulates are convection an dispersion on one hand, and sedimentation on the other hand. Due to inteparticulated reactions, larger aggregates can be formed from smaller units thus changing the sedimentation characteristics. These phenomena are summarized in a mathematical model whereby hydrodynamic effects as well as the control mechanisms of the dissolved phase are included. A relationship was derived on the basis of energy considerations leading to the formulation of a critical sedimentation velocity of the suspensa, which determines the transport capacity of the flowing system. The sedimentation term is calculated from the above discussed transport capacity, hydro-dynamic parameters and suspending media properties. Aggregation effects are taken into account as an increase of sedimentation velocities of the particles. The equations are solved in a particular computational routine such that the horizontal distribution of suspended solids in a natural system can be describe as function of the above discussed phenomena. The model was tested with in situ-measurements. It was found that the observed processes are described satisfactorily by this model. 相似文献
76.
A pedagogic problem in forestry and landscape management is to visualize future landscape effects of forest growth and current management activities in the forest. This paper presents a method for forecasting digital image projections of forest landscape dynamics. Static nonlinear regression functions estimate the digital numbers in a Landsat Thematic Mapper image. Regressors used are forest stand variables. By estimating the future forest stand data, based on intermediate treatment and growth, future satellite digital images are created. In a case study example, the future landscape of a forest block in the province of Västernorrland, Sweden, is projected to demonstrate the application of this visualization technique. 相似文献
77.
Maie Bachmann Maksim Säkki Jaan Kalda Jaanus Lass Viiu Tuulik Hiie Hinrikus 《The Environmentalist》2005,25(2-4):165-171
Summary This study focuses on discrimination of changes, produced by low-level microwave exposure in intensity and time variability
of the human EEG at rest. The power spectral density (PSD) method and nonlinear scaling analysis of the length distribution
of low variability periods (LDLVP) were selected for analysis of the EEG signal. During the study, 19 healthy volunteers were
exposed to a microwave (450 MHz) of 217 Hz frequency on-off modulation. The field power density at the scalp was 0.16 mW/cm2. The experimental protocol consisted of ten cycles of repetitive microwave exposure. Signals from frontal, temporal, parietal
and occipital EEG channels on EEG theta, alpha and beta rhythms were analysed. Exposure to microwave causes average increase
of EEG activity. LDLVP analysis discriminated significant effect in time variability for 2 subjects (11%). PSD method detected
significant changes in intensity for 4 subjects (21%). The effect of low-level microwave exposure is stronger on EEG beta
rhythm in temporal and parietal regions of the human brain. 相似文献
78.
Simo Sarkki Jari Niemelä Rob Tinch Jukka-Pekka Jäppinen Matti Nummelin Heikki Toivonen 《Journal of Environmental Planning and Management》2016,59(8):1377-1396
The Convention on Biological Diversity's national biodiversity strategies and action plans (NBSAPs) are major mechanisms for mainstreaming biodiversity into national policies. This article examines whether and how the NBSAPs contribute to mainstreaming biodiversity across policy sectors in Finland in order to halt biodiversity loss. We have developed an innovative analytical framework where the concept of responsibility addresses how motivations for mainstreaming can be built, and the concept of social learning outcomes addresses the extent of institutional changes for biodiversity. The Finnish NBSAP processes have been able to build diverse forms of responsibility (liability, accountability, responsiveness and care) in different policy sectors by providing new knowledge, careful process design and developing institutional linkages. Despite pro-biodiversity outcomes in the targeted policy sectors, the responsibilities do not diffuse from the environmental administration to other policy sectors to a sufficient extent. Closing this ‘responsibility gap’ is a key challenge for building effective environmental policies. 相似文献
79.
80.
Micael Jonsson Ryan M. Burrows Johan Lidman Emma Fältström Hjalmar Laudon Ryan A. Sponseller 《Ambio》2017,46(3):311-323
Land use is known to alter the nature of land–water interactions, but the potential effects of widespread forest management on headwaters in boreal regions remain poorly understood. We evaluated the importance of catchment land use, land cover, and local stream variables for macroinvertebrate community and functional trait diversity in 18 boreal headwater streams. Variation in macroinvertebrate metrics was often best explained by in-stream variables, primarily water chemistry (e.g. pH). However, variation in stream variables was, in turn, significantly associated with catchment-scale forestry land use. More specifically, streams running through catchments that were dominated by young (11–50 years) forests had higher pH, greater organic matter standing stock, higher abundance of aquatic moss, and the highest macroinvertebrate diversity, compared to streams running through recently clear-cut and old forests. This indicates that catchment-scale forest management can modify in-stream habitat conditions with effects on stream macroinvertebrate communities and that characteristics of younger forests may promote conditions that benefit headwater biodiversity. 相似文献