全文获取类型
收费全文 | 66676篇 |
免费 | 698篇 |
国内免费 | 589篇 |
专业分类
安全科学 | 2059篇 |
废物处理 | 2835篇 |
环保管理 | 8931篇 |
综合类 | 11460篇 |
基础理论 | 17718篇 |
环境理论 | 37篇 |
污染及防治 | 16412篇 |
评价与监测 | 4326篇 |
社会与环境 | 3744篇 |
灾害及防治 | 441篇 |
出版年
2022年 | 548篇 |
2021年 | 564篇 |
2020年 | 387篇 |
2019年 | 519篇 |
2018年 | 953篇 |
2017年 | 967篇 |
2016年 | 1450篇 |
2015年 | 1127篇 |
2014年 | 1664篇 |
2013年 | 5232篇 |
2012年 | 2059篇 |
2011年 | 2839篇 |
2010年 | 2331篇 |
2009年 | 2436篇 |
2008年 | 2826篇 |
2007年 | 2887篇 |
2006年 | 2635篇 |
2005年 | 2217篇 |
2004年 | 2164篇 |
2003年 | 2094篇 |
2002年 | 2009篇 |
2001年 | 2461篇 |
2000年 | 1727篇 |
1999年 | 1127篇 |
1998年 | 836篇 |
1997年 | 871篇 |
1996年 | 919篇 |
1995年 | 1009篇 |
1994年 | 905篇 |
1993年 | 821篇 |
1992年 | 828篇 |
1991年 | 814篇 |
1990年 | 781篇 |
1989年 | 804篇 |
1988年 | 695篇 |
1987年 | 615篇 |
1986年 | 595篇 |
1985年 | 617篇 |
1984年 | 665篇 |
1983年 | 667篇 |
1982年 | 673篇 |
1981年 | 582篇 |
1980年 | 509篇 |
1979年 | 538篇 |
1978年 | 466篇 |
1977年 | 417篇 |
1975年 | 398篇 |
1974年 | 381篇 |
1973年 | 412篇 |
1972年 | 403篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
132.
Per Angelstam o-Bronge Grzegorz Mikusiski Ulf Sporrong Anders Wstfelt 《Ambio-人类环境杂志》2003,32(8):587-596
土地由中心到边缘呈现不同分布利用方式的村庄,构成了欧洲文化景观的基本单元.然而在许多的乡村景观中,那些拥有细致结构的耕地和有树木的草场的真正前工业时代的村庄正在不断失去其原有的结构,这种遗失威胁着文化的继承和生物多样性.因此,监测景观中这样的村庄真实形态的变化范围和速度是非常重要的.随着废弃时间的增加,村庄的真实形态不断丢失,我们所要研究的是怎样的丢失程度才能够通过卫星图像定量分析和目视解译进行评价.1999年,我们在波兰东南部的Bieszczady山脉开展本研究.使用1998年的陆地卫星TM数据,利用景观元素的粒度(田地大小)和土地覆盖组成(灌木和森林的扩侵)对代表真实村庄结构形态退化不同阶段的6种类型村庄进行定量描述.我们利用历史地图勾勒出村庄的边界,并测量从前森林和空地的范围.利用卫星数据,将当前的土地利用和表示成粒度及森林的扩侵状况的土地废弃程度绘制成图.退化沿着2条变化路径发生:被废弃并且最终变成森林,或者形成集约农业.为了验证这样的结果,我们通过对原始卫星影像的目视解译,将1000km2范围内的22个其他村庄分成了4类.而后,我们收集了过去60年人口变化的历史数据.村庄真实形态的分类与人口下降速度明显相关.我们希望验证和应用这种快速评估文化景观真实形态的方法能够得到重视,尤其是在随着欧盟的扩大正在经历或者将要发生巨大变化的欧洲区域.最后,我们论证了村庄具有成为一个融合自然与社会科学的景观尺度的可能性. 相似文献
133.
Observations of air temperature changes in a steppe marmot burrow were performed from late July to mid-October. Until early September, temperature in the burrow remained relatively constant, but then it began to decrease rapidly. This occurred after air temperature above the ground became equal to the temperature in the burrow. Supposedly, it is in this particular period that marmots begin to plug the entrance to the burrow with earth, thus reducing heat exchange between the increasingly cold aboveground air and the air in the burrow. 相似文献
134.
V. I. Kolmakov N. A. Gaevskii E. A. Ivanova O. P. Dubovskaya I. V. Gribovskaya E. S. Kravchuk 《Russian Journal of Ecology》2002,33(2):97-103
In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (EPhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis. 相似文献
135.
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
136.
137.
138.
139.
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
140.
Methodological Basis of Ecological Safety Standards for the Technogenic Impact of Mineral Resource Exploitation 总被引:1,自引:0,他引:1
A new methodological approach to the development of biological and technological safety standards for the impact of underground mining on the natural biota is proposed. 相似文献