全文获取类型
收费全文 | 17893篇 |
免费 | 1263篇 |
国内免费 | 2829篇 |
专业分类
安全科学 | 2409篇 |
废物处理 | 170篇 |
环保管理 | 2546篇 |
综合类 | 9968篇 |
基础理论 | 1949篇 |
环境理论 | 12篇 |
污染及防治 | 1024篇 |
评价与监测 | 1126篇 |
社会与环境 | 1728篇 |
灾害及防治 | 1053篇 |
出版年
2024年 | 51篇 |
2023年 | 188篇 |
2022年 | 413篇 |
2021年 | 530篇 |
2020年 | 518篇 |
2019年 | 446篇 |
2018年 | 403篇 |
2017年 | 546篇 |
2016年 | 681篇 |
2015年 | 750篇 |
2014年 | 786篇 |
2013年 | 1031篇 |
2012年 | 1290篇 |
2011年 | 1416篇 |
2010年 | 1034篇 |
2009年 | 998篇 |
2008年 | 813篇 |
2007年 | 1193篇 |
2006年 | 1216篇 |
2005年 | 976篇 |
2004年 | 819篇 |
2003年 | 902篇 |
2002年 | 740篇 |
2001年 | 629篇 |
2000年 | 576篇 |
1999年 | 580篇 |
1998年 | 428篇 |
1997年 | 349篇 |
1996年 | 284篇 |
1995年 | 246篇 |
1994年 | 247篇 |
1993年 | 208篇 |
1992年 | 165篇 |
1991年 | 122篇 |
1990年 | 83篇 |
1989年 | 55篇 |
1988年 | 46篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1977年 | 14篇 |
1974年 | 7篇 |
1973年 | 12篇 |
1971年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Kraigher H Al Sayegh Petkovsek S Grebenc T Simoncic P 《Environmental monitoring and assessment》2007,128(1-3):31-45
Mycorrhiza is the main spatial and temporal linkage between different constituents in a forest ecosystem. The functional compatibility
and stress tolerance of ectomycorrhizal types is species specific, and therefore the information on the ectomycorrhizal community
structure can add to the understanding of processes in forest ecosystems and can also be applied as tools for bioindication
of pollution stress in forest soils. We have studied the effects of pollution (N and S) on trees and forest soils by: (1)
quantification of ECM types diversity as in situ indicators in forest stands, (2) determination and quantification of pollution-sensitive or -insensitive ECM types as passive
monitors, (3) root growth and development of ECM on nonmycorrhizal spruce seedlings, planted at the studied sites (active
monitors), and (4) ECM infection (a bioassay based on mycorrhizal inoculum potential) of seedlings in an experimental set-up
as ex situ testers. ECM species richness for Norway spruce trees (Picea abies) showed higher values in unpolluted sites than in polluted ones, while the differences were not significant for European
beech trees (Fagus sylvatica). As pollution-sensitive or -insensitive ECM species in spruce forests, we suggest Hydnum rufescens (sensitive) and Paxillus involutus (unsensitive). Mycorrhizal potential in Norway spruce seedlings as a bioassay for soil N and S pollution was effective, and
is suggested as an additional, standardized and widely comparable system in bioindication of soil pollution. 相似文献
942.
Water is key element in human life. All forms of life upon the earth depend upon water for their mere existence. Life & water
may be aptly said to be two facets of the same coin. Most of the water bodies are getting polluted due to domestic waste,
sewage, industrial waste and agricultural effluent. The present study is designed to ascertain the effectiveness of artificial
aeration cum Ozonizer unit installed at Lower Lake, Bhopal for assessment of water quality. Various physico- chemical parameters
like pH, Dissolved oxygen, Biochemical Oxygen demand, Chemical oxygen demand, nitrate, phosphate and bacteriological status
were studied to assess the extent of deterioration in water quality of Lower lake and at the same time to assess the performance
of the dual aeration system in improvement of water quality. 相似文献
943.
The methodology of materials accounting is presented and applied to developing nutrient balance (nitrogen and phosphorus)
in a river basin. The method is based on the balance principle: inputs and outputs of each nitrogen and phosphorus related
sub-systems were balanced. The application of the methodology strategies was illustrated by means of a case study of the Krka
river, Slovenia. Different pathways of emission to surface waters were taken into account: WWTP discharges, direct discharges,
erosion/runoff and baseflow. Total annual emission into the river Krka was estimated to be 362 tonnes N/year and 73.3 tonnes
P/year. The main sources of nitrogen are diffuse sources, emitted via baseflow (52%). Other important sources are effluents
from WWTP, which account for 36% of total emissions. Other sources like erosion and direct discharges to surface water (animal
manure, industry, households) are of lower magnitude. Erosion is main source of phosphorus emission (55% of total emission),
WWTP effluents account for 37% of total emission, while other sources are less important. Besides reduction of point sources
by means of wastewater collection and implementation of nutrient removal technology, managing agricultural nitrogen and phosphorus
to protect water quality should become a major challenge in the Krka river basin. 相似文献
944.
Eutrophication conditions and ecological status in typical bays of Lake Taihu in China 总被引:4,自引:0,他引:4
Sampling was conducted at three site groups, group E (in East Taihu Bay), G (in Gonghu Bay) and M (in Meiliang Bay) in Lake
Taihu. TN and TP concentrations among site groups was in the increasing order of E < G < M. TP level at G sites is at the
critical threshold for loss of submersed macrophytes. Mean values of DO and Transparence showed different trend, i.e., E >
G > M. The mean phytoplankton fresh-weight biomass at M sites was 5.81 mg/l, higher than that at E sites (4.96 mg/l) and G
sites (5.18 mg/l). Mean zooplankton fresh-weight biomass was in the decreasing order of M (6.4 mg/l) > G (4.9 mg/l) > E (2.7 mg/l).
However, Rotifera density was in the sequence of E > G > M. Both zooplankton biomass and phytoplankton biomass increased with the rise of TN
and TP concentrations. Relationships between zooplankton biomass and phytoplankton biomass showed that zooplankton played
a limited role in the control of algae in eutrophic lakes. Nutrient availability is much more important than zooplankton grazing
pressure in controlling phytoplankton growth in lakes. For most sites in Lake Taihu, reduction of nutrient loading, as well
as macrophyte conservation, zappears to be especially important in maintaining high water quality and regulating lake biological
structure, but for M sites, it’s urgent to control nutrient inputs rather than to restore macrophyte community. 相似文献
945.
Yu FC Chen CY Lin SC Lin YC Wu SY Cheung KW 《Environmental monitoring and assessment》2007,132(1-3):419-428
As the embodiment of human activities, the change of regional industrial structure is an essential driving factor of global
environmental change. Consequently, the research on the change of regional industrial structure and associated effects on
the environment is one of the key issues of researches on sustainable development, human–environment relationship, and regional
response to global environment change. However, compared to the flourish of researches on environmental impact assessment
of industrial departments, few studies have been conducted to assess the environmental impact of regional industrial structure.
In this study, based on a synthetic analysis of environmental disturbances of different industrial departments, the environmental
impact coefficient of industrial department associated with the index of environmental impact of industrial structure was
constructed, so as to make a quantitative assessment of environmental impact of the change of regional industrial structure.
And the results of the case study in Lijiang City, a rural region of China, have showed that there are two obvious changes
of industrial structure in the study area from 1992 to 2003, associated with a continuous decreasing of the index of environmental
impact of industrial structure, which indicated a positive environmental effects of the change of regional industrial structure. 相似文献
946.
947.
Characteristics that influence male reproductive success on a lek of Lethrinops c.f. parvidens (Teleostei: Cichlidae) 总被引:1,自引:1,他引:0
Sexual selection has long been proposed as a mechanism leading to the diverse cichlid (Teleostei: Cichlidae) fauna of Lake
Malawi, Africa. Many of the shallow-water, sand-dwelling, bower-building cichlid species are particularly well suited for
studies of sexual selection because they participate in leks. Since females in lekking systems appear to acquire only genetic
material from their mates, it has been suggested that leks are ideal systems to study female mate choice. The objectives of
the investigation were to examine Lethrinops c.f. parvidens male bower characteristics (i.e., bower size and location) as well as other male characteristics (i.e., length, gular color,
and duration on the lek) for their influence on male mating success as measured by the number of visits, circles, and eggs
laid by females. These measures are nested in that a visit by a female may or may not lead to circling, and circling by a
female may or may not lead to egg-laying. We found increased bower height and higher numbers of conspecific neighbors (analogous
to shallow-water, near-shore bower positions) to be positively, significantly associated with the number of visits by females.
The only significant correlate with the number of circles was visits, and similarly circles was the only significant correlate
with the number of eggs laid. The R
2 value for the egg-laying regression was quite low (19.8%) compared with visits (54.3%) and circling (78.9%), suggesting that
females may be using additional cues, that we failed to measure, when in close proximity to males or simply that a small proportion
of the females were ready to spawn. Both indirect selection and direct selection pressure due to egg predation may have influenced
female choice on the lek.
Received: 10 April 1999 / Received in revised form: 26 July 1999 / Accepted: 18 September 1999 相似文献
948.
Most studies of social polygyny in birds have examined male provisioning on the basis of the number of feeding visits. This
may be misleading if males compensate for infrequent visits by bringing larger prey at each visit. We investigated nestling
provisioning in the socially polygynous great reed warbler, Acrocephalus arundinaceus, in south Central Sweden in 1996–1997. We collected data on rate of feeding visits, prey size and the amount of biomass delivered
by males and females. Males had lower rates of feeding visits and provided smaller prey to nestlings in secondary than in
monogamous and primary nests. Secondary females had higher rates of feeding visits and brought larger prey than monogamous
and primary females. These results confirm that secondary females face a potential cost of polygyny through a lower rate of
male feeding, and that this cost was reinforced by the significantly lower male provisioning rate (biomass h–1) at secondary nests. Secondary females compensated for the lack of male assistance by increasing their rate of feeding and
bringing larger prey. As a result, offspring in nests of secondary females received as much food as did those in nests of
primary females. Prey load size increased with the parent’s proportion of feeding visits, suggesting that parents use different
feeding strategies depending on their amount of responsibility for nestling provisioning. We suggest that parents which take
the main responsibility for nestling feeding have to forage further away from the nest, and based on optimal-foraging theory,
they should then on average bring larger prey to their nest.
Received: 4 April 1999 / Received in revised form: 12 October 1999 / Accepted: 23 October 1999 相似文献
949.
战略环境评价系统及工作程序 总被引:26,自引:0,他引:26
介绍了战略环境评价系统组成的五个要素 ,即评价者、评价对象、评价目的、评价标准和评价方法 ,分析了其相互关系及各要素与战略环境评价系统的关系 ,并提出了战略环境评价工作程序。 相似文献
950.
成都市城市环境与经济协调发展分析 总被引:17,自引:2,他引:15
从城市环境与经济发展的协调度方面分析了成都市1990-1997年间协调度的变化趋势,评估了成都市城市环境与经济协调发展的类型,得出了成都市属于总体协调发展类环境滞后型的结论。 相似文献