首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   32786篇
  免费   664篇
  国内免费   5962篇
安全科学   1218篇
废物处理   2149篇
环保管理   3944篇
综合类   10032篇
基础理论   7639篇
环境理论   9篇
污染及防治   9373篇
评价与监测   2090篇
社会与环境   2281篇
灾害及防治   677篇
  2023年   260篇
  2022年   752篇
  2021年   625篇
  2020年   457篇
  2019年   523篇
  2018年   2155篇
  2017年   2165篇
  2016年   2141篇
  2015年   1305篇
  2014年   1355篇
  2013年   2390篇
  2012年   1970篇
  2011年   3112篇
  2010年   2055篇
  2009年   1950篇
  2008年   2413篇
  2007年   2728篇
  2006年   1181篇
  2005年   968篇
  2004年   763篇
  2003年   992篇
  2002年   933篇
  2001年   718篇
  2000年   676篇
  1999年   634篇
  1998年   557篇
  1997年   459篇
  1996年   437篇
  1995年   390篇
  1994年   336篇
  1993年   289篇
  1992年   251篇
  1991年   165篇
  1990年   146篇
  1989年   127篇
  1988年   96篇
  1987年   84篇
  1986年   86篇
  1985年   68篇
  1984年   95篇
  1983年   97篇
  1982年   70篇
  1981年   81篇
  1980年   56篇
  1979年   37篇
  1978年   39篇
  1977年   26篇
  1976年   20篇
  1975年   28篇
  1971年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga subzone over the past five years are presented. The relationship between net primary production and the stock of live phytomass is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass and net primary production decrease.  相似文献   
63.
Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the respondents identified Federal groups and the DOE as potential stewards. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue  相似文献   
64.
65.
Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD.  相似文献   
66.
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   
67.
With China's rapid economic growth, ecological construction and environmental protection become increasingly important. The regenerated resources industry is an effective way to solve problems, such as resources depletion, energy shortage, and pollution, and it also has strategic importance for the construction of a resource-conserving and environment-friendly society. The regenerated resources industry has been established in Miluo for long time, which includes a recycling system, a processing and utilization system, and a refuse decontamination system. An industrial cluster is in its early stage of development. In order to solve current problems, such as short industrial chain, low processing rate, and low added value, the industrial cluster should be dynamically upgraded by means of technology innovation, chain nucleus creation, and chain extension. We think the industrial cluster of regenerated resources will become a local brand for Miluo, from which other regions or cities will gain valuable experiences and inspirations.  相似文献   
68.
Environmental factors have long been shown to influence species distributions, with range limits often resulting from environmental stressors exceeding organism tolerances. However, these abiotic factors may differentially affect species with multiple life-history stages. Between September 2004 and January 2006, the roles of temperature and nutrient availability in explaining the southern distributions of two understory kelps, Pterygophora californica and Eisenia arborea (Phaeophyceae, Laminariales), were investigated along the coast of California, USA and the Baja California Peninsula, Mexico, by limiting either: (a) tissue nitrogen uptake and storage by adult sporophytes during periods of elevated temperature, and/or (b) production of embryonic sporophytes by microscopic gametophytes. Results suggest that while adult sporophytes of both species are tolerant of high temperatures and low nutrients, reproduction by their microscopic stages is not. Specifically, while E. arborea produced embryonic sporophytes at both 12 and 18°C, temperatures commonly observed throughout the southern portion of its range, P. californica produced sporophytes at 12 but not at 18°C. As a result, it appears that the southern distribution of P. californica, which ends in northern Baja California, Mexico, may be limited by temperature acting on its microscopic stages. In contrast, the ability of E. arborea’s microscopic and adult stages to tolerate elevated temperatures allows it to persist in the warmer southern waters of Baja California, as well as to the north along the California coast where both species co-occur.  相似文献   
69.
70.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号