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   516篇
  免费   11篇
  国内免费   10篇
安全科学   23篇
废物处理   15篇
环保管理   141篇
综合类   51篇
基础理论   93篇
污染及防治   134篇
评价与监测   47篇
社会与环境   22篇
灾害及防治   11篇
  2023年   2篇
  2021年   6篇
  2019年   5篇
  2018年   4篇
  2017年   6篇
  2016年   8篇
  2015年   14篇
  2014年   15篇
  2013年   69篇
  2012年   20篇
  2011年   23篇
  2010年   20篇
  2009年   17篇
  2008年   21篇
  2007年   27篇
  2006年   24篇
  2005年   21篇
  2004年   13篇
  2003年   19篇
  2002年   16篇
  2001年   10篇
  2000年   12篇
  1999年   10篇
  1998年   6篇
  1997年   6篇
  1996年   4篇
  1995年   9篇
  1994年   12篇
  1993年   9篇
  1992年   7篇
  1991年   9篇
  1990年   7篇
  1989年   4篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1980年   11篇
  1979年   8篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1973年   2篇
  1971年   1篇
  1968年   1篇
排序方式: 共有537条查询结果,搜索用时 15 毫秒
201.
Conservation Biology and Scientific Method   总被引:1,自引:0,他引:1  
  相似文献   
202.
Coping with variability and change: Floods and droughts   总被引:3,自引:0,他引:3  
Floods and droughts are natural phenomena for which the risks of occurrence are likely to continue to grow. Increasing levels of exposure and insufficient adaptive capacity are among the factors responsible for the rising vulnerability. The former is conditioned by anthropopressure (e.g., economic development of flood–prone areas) and adverse effects of climate change; scenarios for future climates indicate the possibility of amplified water–related extremes. This article presents the current situation of coping with extreme hydrological events within the pressure–state–response framework. Among promising response strategies, the role of forecast and warning, and of watershed management are reviewed. Sample success stories and lessons learnt related to hydrological extremes are given and policy implications discussed.  相似文献   
203.
204.
Endangered Species Left Homeless in Sweet Home   总被引:1,自引:0,他引:1  
  相似文献   
205.
ABSTRACT: Autochthonous energy input, in the form of periphyton production and growth, was studied before and after partial logging of the watershed surrounding School Brook, a small tributary of the Aroostook River, Maine. Due to infection by the spruce budworm (Chiristoneura fumiferana), the buffer strip on one bank of the stream was logged and only limited riparian vegetation was left. Though impacts in subsequent years are unknown, the effect of the logging on the periphyton community was insignificant during the nine months following cutting, seemingly due to several factors. Because only 5 percent of the canopy was actually removed, the intensity of available light changed little. Small springs in the area helped maintain a stable thermal regime, and only a small portion of the low gradient watershed was actually logged. Consequently, the nutrients reaching the stream did not change. The relatively low concentrations of nitrates (< 0.3 mg/l) and phosphates (< 10 μg/l), both before and in the first nine months after logging, reflect the limited autochthonous input, thereby reducing the effect of this limited cutting on the stream community.  相似文献   
206.
207.
Contents of Cd and Zn in the blue mussel, Mytilus edulis, collected on the coast of the southern Bothnian Sea and the northern Baltic proper, were determined using flame AAS. The observed concentrations ranged from 4.7 to 10.8 mg kg(-1) dw for Cd and from 121 to 215 mg kg(-1) dw for Zn. The Zn/Cd ratio was around 20 at a majority of the investigated locations. Cd exhibited an approximate two-fold gradual increase from south to north in the study area. It is likely that this increase was due largely to enhanced bioavailability for Cd at lower salinity. However, it is not possible to eliminate the influence from a generally elevated overall concentration of cadmium in the southern Bothnian Sea caused by natural and anthropogenic input. Compared to mussels from marine waters on the west coast of Sweden, Cd concentrations were 5-10 times higher, similarity indicating an influence of low salinity. Zn did not show these salinity correlated differences. The high Zn content found south of the outlet of the river Dal?lven and gradually decreasing southwards was possibly caused by the high riverine input.  相似文献   
208.
Complications arise when ratios are used to present environmental data because ratios are an unbounded, multiplicative scale that can lead to asymmetrical (skewed) data distributions. Enantiomeric ratios (ERs), historically used in discussions of chiral signatures, often are published as mean ER+/-single-value standard deviation. Application of statistical summaries, such as the widely used sample mean and standard deviation, to skewed ratio data is misleading and often inappropriate. Comparison of statistically summarized ER and enantiomer fraction (EF) data (which are based on a bounded, additive scale) for a range of hypothetical values reveals substantial discrepancies when conversion between ER and EF formats is used. These discrepancies are largest when the ratio data are greater than one and have large variability, because the data are more skewed. In many cases, the use of fractions instead of ratios can help to minimize misrepresentation of environmental data, including chiral data. The use of nonparametric statistical summaries, e.g., median and percentiles, provides a more robust indicator of the typical value and spread for both ER and EF data.  相似文献   
209.
Multinational corporations are facing increasing pressures and finding stronger incentives to integrate environmental management into their overall business strategies. National and local environmental regulations are becoming more stringent in Europe, Japan, East and Southeast Asia, Latin America, and many developing countries, and international voluntary standards of environmental management are being endorsed by a growing number of governments. Multinational firms are embracing these standards not only to assure the public of their concern for environmental protection, but also to enhance their competitiveness in international markets. The British Standard 7750, the European Eco-Management and Audit Scheme (EMAS), and the ISO 14000 series are setting new guidelines for effective corporate environmental management. Beyond complying with local and national laws, corporations now have wider latitude in how they adapt their business practices to these emerging environmental management standards. In order to capitalize on that creative latitude, companies must have corporate cultures and internal management systems that allow them to respond quickly and effectively to changing environmental requirements. Exemplary corporate environmental performance is usually related to strong and progressive leadership, a culture that recognizes the importance of environmental protection, and the willingness to operate by quality-based management principles. This article describes how one international corporation, Sonoco, in responding successfully to changing environmental pressures to reclaim and recycle its products in the wake of the solid waste crisis in the United States and more stringent environmental regulations in Europe, used its management competencies and corporate culture to turn what could have been serious barriers to expansion of its core businesses into new opportunities. By adopting a bold materials reclamation program, Sonoco was able to overcome potential limitations on its operations in the United States and abroad and to develop new business segments that benefited the company and the environment.  相似文献   
210.
More than 200 years ago, Adam Smith, the founder of modern economics, wrote in the Wealth of Nations that “…consumption is the sole end and purpose of all production; and the interest of the producer ought to be attention to…that of the consumer.” In recent years, the rapid growth of the world economy has given Adam Smith's maxim new meaning. The age-old desire for consumption grows unabated and increasing numbers of consumers around the world are attaching new value to the environmental quality of goods and services and expressing concern over the environmental impacts of industrialization. That concern is growing because more than 70 percent of the world's urban population live in areas where the air is seriously polluted and as many as 750,000 people—the majority in developing countries—die each year of ailments caused by air pollution.1 Over the past 25 years, corporations throughout the world have made dramatic changes in the way they do business as more people come to understand how the ecological system works and how polluted air and water endanger human health. The key to increasing industry's participation in the drive for higher standards of air quality is the growing realization that effective environmental management, technological development, and technology dissemination are cost-effective and profitable business strategies. Global competition is making firms around the world more customer-conscious and, to the extent that consumers demand products that minimize environmental degradation and enhance the quality of their lives, businesses in every industry must respond in order to survive.2 This article examines how changes in business practices, driven by a better understanding of how natural environments function, are converging to provide new opportunities for environmental management that go beyond regulatory compliance to reduce air pollution. Although sound and well-enforced environmental regulations are an essential foundation for improving air quality, command-and-control systems alone are unlikely to achieve the lower levels of pollution that will be necessary to achieve sustainable development in the 21st century. In cooperation with government, businesses in every industry can play crucial roles in achieving higher standards of air quality while at the same time maintaining acceptable levels of economic growth. We explore three ways in which corporations can contribute to environmentally sustainable development: (1) by adopting proactive environmental management systems that focus on air pollution prevention; (2) by developing new technologies for air pollution control and reduction; and (3) by transferring air pollution control and prevention technologies through international trade and investment.  相似文献   
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