全文获取类型
收费全文 | 20130篇 |
免费 | 182篇 |
国内免费 | 170篇 |
专业分类
安全科学 | 542篇 |
废物处理 | 909篇 |
环保管理 | 2585篇 |
综合类 | 3490篇 |
基础理论 | 4990篇 |
环境理论 | 7篇 |
污染及防治 | 5395篇 |
评价与监测 | 1303篇 |
社会与环境 | 1161篇 |
灾害及防治 | 100篇 |
出版年
2022年 | 179篇 |
2021年 | 160篇 |
2020年 | 110篇 |
2019年 | 131篇 |
2018年 | 276篇 |
2017年 | 255篇 |
2016年 | 423篇 |
2015年 | 314篇 |
2014年 | 456篇 |
2013年 | 1494篇 |
2012年 | 573篇 |
2011年 | 826篇 |
2010年 | 660篇 |
2009年 | 750篇 |
2008年 | 842篇 |
2007年 | 903篇 |
2006年 | 807篇 |
2005年 | 679篇 |
2004年 | 657篇 |
2003年 | 711篇 |
2002年 | 635篇 |
2001年 | 875篇 |
2000年 | 600篇 |
1999年 | 374篇 |
1998年 | 238篇 |
1997年 | 244篇 |
1996年 | 239篇 |
1995年 | 302篇 |
1994年 | 266篇 |
1993年 | 220篇 |
1992年 | 234篇 |
1991年 | 248篇 |
1990年 | 234篇 |
1989年 | 245篇 |
1988年 | 212篇 |
1987年 | 194篇 |
1986年 | 143篇 |
1985年 | 179篇 |
1984年 | 204篇 |
1983年 | 208篇 |
1982年 | 199篇 |
1981年 | 166篇 |
1980年 | 148篇 |
1979年 | 163篇 |
1978年 | 127篇 |
1977年 | 133篇 |
1976年 | 119篇 |
1975年 | 138篇 |
1974年 | 149篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
11.
12.
Abstract: Broadly conceived and considered in its many usages, sustainability has grave defects as a planning goal, particularly when used by conservationists: it confuses means and ends; it is vague about what is being sustained and who or what is doing the sustaining; it is uninspiring; it is little more than Pinchot-era conservation (and thus ignores the many lessons learned since then); it need not be linked to land, to the land's functioning, or to any ecological science; it need not include a moral component; it is consistent with the view of humans as all-powerful manipulators of the planet; and, in general, it is such a malleable term that its popularity provides only a facade of consensus. When sustainability is defined broadly to include the full range of economic and social aspirations, it poses the particular risk that ecological and biodiversity concerns will be cast aside in favor of more pressing human wants. Given these many defects, the conservation movement should discard the term in favor of a more alluring goal, attentive to nature and its ecological functioning. A sound goal would incorporate and distill the considerable ecological and moral wisdom accumulated since Pinchot's day while giving conservationists the rhetorical tools needed to defend the land against competing pressures. In our view, conservation would be well served by an updated variant of "land health," Aldo Leopold's ecologically grounded goal from the 1940s. Land health as an independent understanding should set the essential terms of how we live and enjoy the earth, providing the framework within which we pursue our many social and economic aims. 相似文献
13.
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices. 相似文献
14.
15.
Protein, lipid, phosphorus, and organic carbon contents, as well as electron transport system (ETS) activity, lactatedehydrogenase activity, and gut evacuation rate, were measured in four interzonal species of Pacific copepods:Calanus australis, C. pacificus, Eucalanus inermis, andE. elongatus f.hyalinus, collected at the upwelling areas off Peru (8°S) and California (27°N), and in the middle of the North Pacific (30°N), from February to April 1987. The two Eucalanidae species —E. inermis andE. elongatus — have distinctive biochemical and elemental body composition and rates of main physiological processes. Relative protein, lipid, phosphorus, and organic carbon contents (µg mg–1 wet weight) in these species were, respectively, ca. 1/7 to 1/10, 1/5 to 1/20, 1/5 to 1/10, and 1/5 those inCalanus spp. Likewise, oxygen uptake rate per unit of wet weight (based on ETS activity) inE. inermis andE. elongatus was 5 to 10% of that in calanids; a similar difference was found in phosphorus excretion rate. In addition, gut evacuation rates inE. inermis andE. elongatus were ca. one-fifth of those inCalanus spp. Based on these data, we considered the eucalanids as belonging to a distinctive physiological group, figuratively named jelly-body copepods. In contrast with calanids, active lactatedehydrogenase has been found in the bodies ofE. inermis andE. elongatus, apparently allowing them to survive for a long time in layers of extremely low oxygen content (<0.2 ml l–1). The adaptive value of physiological features in these eucalanids and typical calanids is compared. 相似文献
16.
M. E. Berlyand N. Sh. Volberg R. F. Lavrinenko E. N. Rusina 《Environmental monitoring and assessment》1982,2(4):393-402
- The Air Polluttion Monitoring System has got a significant development of late, which is in direct relation with a considerable extention and improvement of the observation network in cities and industrial areas, with creation of a new network for assessing regional and global background of the atmosphere pollution, as well as with the wide involvement of meteorologists to monitoring organization.
- While developing a new global monitoring system, it is necessary to take into account its relationship with the local monitoring within the region of air pollution sources, i.e. at the \lsimpact\rs level. The need in such an account is dictated first of all by the physics of pollutant spreading that states: changes in air pollution over large territories must be in a certain agreement with greater changes in the vicinity of emission sources. Methods applied in the global and local monitoring have also a number of common peculiarities. White organizing regional network for observations of the background pollution of the atmosphere twin stations (one of the pair of stations located outside the city boundaries in a small community, and the other, in the nearest city with the population of 200–400 thousand inhabitants) were established in the U.S.S.R. and in a number of socialist countries in Europe.
- Implementation of the twin-station principles in the U.S.S.R. has contributed to data interpretation and representativity assessment as well as to correction of the station location. Observation results from the Soviet background stations and those abroad have been compared by now according to a number of indices.
- The correlation of monitoring systems of various scales tells positively both on mutual improvement and completion of observational methods. The methods of obtaining integral characteristics of air pollution were used for the global monitoring, in particular spectral actinometric observations and chemical analysis of the precipitation composition. Now they find still wider employment. Thus methods of spectral actinometric measurements and data processing were used to estimate the degree of aerosol pollution of a number of industrial centres. The theory of solar radiation spreading and aerosol contents determination in urban atmosphere has also been developed. It is a generalization of an earlier developed theory, used to estimate global atmosphere pollution basing on actinometric data. The organization of precipitation collection and analysis on a network of stations around Leningrad and in Donbass area enables us to compare the admixture content in precipitations falling in industrial and agricultural areas.
- A considerable increase of possibilities to measure microconcentrations of sulphur dioxide, nitrogen oxides and of a number of other pollutants is connected with the use of solid solvents for sampling. Their use will allow to avoid establishment of special laboratories at background stations and only send samples by post for their analysis in centralized laboratories.
17.
18.
The Science of Nature - 相似文献
19.
F. Schaller 《Die Naturwissenschaften》1971,58(11):573-574
20.