全文获取类型
收费全文 | 43889篇 |
免费 | 860篇 |
国内免费 | 5663篇 |
专业分类
安全科学 | 1738篇 |
废物处理 | 1984篇 |
环保管理 | 5153篇 |
综合类 | 12750篇 |
基础理论 | 11052篇 |
环境理论 | 23篇 |
污染及防治 | 12918篇 |
评价与监测 | 2270篇 |
社会与环境 | 1718篇 |
灾害及防治 | 806篇 |
出版年
2023年 | 329篇 |
2022年 | 838篇 |
2021年 | 716篇 |
2020年 | 563篇 |
2019年 | 638篇 |
2018年 | 898篇 |
2017年 | 1028篇 |
2016年 | 1228篇 |
2015年 | 1334篇 |
2014年 | 1823篇 |
2013年 | 3715篇 |
2012年 | 2088篇 |
2011年 | 2563篇 |
2010年 | 1970篇 |
2009年 | 1975篇 |
2008年 | 2243篇 |
2007年 | 2221篇 |
2006年 | 1996篇 |
2005年 | 1599篇 |
2004年 | 1398篇 |
2003年 | 1476篇 |
2002年 | 1399篇 |
2001年 | 1628篇 |
2000年 | 1275篇 |
1999年 | 1014篇 |
1998年 | 846篇 |
1997年 | 784篇 |
1996年 | 774篇 |
1995年 | 762篇 |
1994年 | 671篇 |
1993年 | 581篇 |
1992年 | 562篇 |
1991年 | 460篇 |
1990年 | 444篇 |
1989年 | 465篇 |
1988年 | 392篇 |
1987年 | 329篇 |
1986年 | 301篇 |
1985年 | 318篇 |
1984年 | 301篇 |
1983年 | 338篇 |
1982年 | 333篇 |
1981年 | 283篇 |
1980年 | 244篇 |
1979年 | 270篇 |
1978年 | 231篇 |
1977年 | 195篇 |
1976年 | 202篇 |
1975年 | 196篇 |
1972年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
On-going population growth and resulting domestic demand for water require rapid and effective decision-making as regards groundwater management and control of the various sources of salinization and pollution in Coastal aquifers. Sustainability of water resources for utilization by future generations must therefore be a high priority, not only for the purpose of fulfilling needs for water usage but also for bringing people into harmony with their ambient natural environment.The objective of this paper is to propose an empirical approach for prioritization of the needs involved for sustainable aquifer management. The approach involves a schematic format to:(1) develop a global understanding of an aquifer's hydrological and environmental properties in order to delineate appropriate eco-hydrological scenarios and recommend corresponding operational management activities; and(2) emphasize the importance of educating and increasing the awareness of the population involved as to the need for and viability of socially acceptable measures for sustainable management of groundwater and other resources.The psychologist Abraham Maslow utilized a pyramid to illustrate that until people's most basic needs were fulfilled, higher levels of needs would remain irrelevant. This paper postulates a comparable pyramid prioritizing hydrological needs required for progressing towards sustainable groundwater resources. Two sub-regions of Israel's Coastal aquifer in the Sharon region have been presented as representative areas, each characterized by different stress of exploitation. In assessing these sub-regions situation, specific measures have been recommended for achieving and/or maintaining sustainable groundwater resources in light of the ambient environment, and the level of the population on the pyramidal hierarchy of groundwater needs. 相似文献
72.
73.
74.
文章从四个方面阐释学生文化体系的构成,即重在打基础,鼓励学生个性化发展;培植防灾学院自己的学生文化“精英”;创新与创业是学生文化的闪光点;培育一个好的学生文化的管理环境。做到此四点,就可办一个好的、有特点的、合格的高等学校。本文有的放矢,用事实来说话。 相似文献
75.
Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6. 相似文献
76.
77.
78.
Paul F. J. Eagles 《生态毒理学报》2002,(4):65-67
要保护公园的生态、社会、经济和文化价值 ,游客管理具有根本的重要性 . 政府要求公园进一 步在财政上自给自足 . 正在制定一个更加完善的管理方法代替单纯地限制游客的数量 . 这种 方法鼓励公众参与公园的目标设定和游客满意度评价 ,并奖励胜任的财务管理 . 相似文献
79.
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
80.
Xiao Yali Jiang Dahe Wang Dan 《中国人口.资源与环境(英文版)》2007,5(3):51-56
Urban agglomeration of the Yangtze Delta (UAYD), one of the most developed regions of China, has witnessed an increasing prevalence in building ecological cities when the ecological cities are pursued by many modem cities, and great achievements have been made in this regard. It is inevitable, however, that certain problems exist during the construction of ecological city, which include but not limited to non-harmonious development of urban complex ecosystem, and the difficulty in quantifying eco-city construction or incomplete quantification in assessing the construction of present and future eco-city. Based on the analysis on social-economic conditions and regional conditions of the UAYD, this paper attempts to set up an index system of eco-cities combining with local characteristics, and to adopt the indices of eco-city, urban harmony, and eco-city colligate to evaluate the ecological level, urban harmonious development and eco-city construction of cities within the UAYD. Results indicate that among 15 cities in UAYD, Suzhou City ranks the highest in terms of eco-city construction, whereas Nantong ranks relatively lower; sustainable eco-city construction is possible only when cities are developed in every respect of harmony. 相似文献