全文获取类型
收费全文 | 45655篇 |
免费 | 557篇 |
国内免费 | 1534篇 |
专业分类
安全科学 | 1458篇 |
废物处理 | 2013篇 |
环保管理 | 5321篇 |
综合类 | 10969篇 |
基础理论 | 10915篇 |
环境理论 | 20篇 |
污染及防治 | 11642篇 |
评价与监测 | 2794篇 |
社会与环境 | 2261篇 |
灾害及防治 | 353篇 |
出版年
2022年 | 520篇 |
2021年 | 477篇 |
2020年 | 365篇 |
2019年 | 428篇 |
2018年 | 708篇 |
2017年 | 743篇 |
2016年 | 1042篇 |
2015年 | 844篇 |
2014年 | 1296篇 |
2013年 | 3505篇 |
2012年 | 1517篇 |
2011年 | 2010篇 |
2010年 | 1689篇 |
2009年 | 1742篇 |
2008年 | 2002篇 |
2007年 | 2040篇 |
2006年 | 1763篇 |
2005年 | 1526篇 |
2004年 | 1411篇 |
2003年 | 1479篇 |
2002年 | 1345篇 |
2001年 | 1698篇 |
2000年 | 1217篇 |
1999年 | 787篇 |
1998年 | 562篇 |
1997年 | 574篇 |
1996年 | 583篇 |
1995年 | 667篇 |
1994年 | 661篇 |
1993年 | 554篇 |
1992年 | 565篇 |
1991年 | 530篇 |
1990年 | 583篇 |
1989年 | 524篇 |
1988年 | 424篇 |
1987年 | 408篇 |
1986年 | 370篇 |
1985年 | 391篇 |
1984年 | 419篇 |
1983年 | 407篇 |
1982年 | 396篇 |
1981年 | 389篇 |
1980年 | 309篇 |
1979年 | 336篇 |
1978年 | 289篇 |
1977年 | 235篇 |
1974年 | 239篇 |
1972年 | 248篇 |
1971年 | 241篇 |
1967年 | 259篇 |
排序方式: 共有10000条查询结果,搜索用时 852 毫秒
881.
Although amphibians are highly vocal, they generally emit only a limited number of acoustic communication signals. We report here the extraordinarily rich vocal repertoire of Amolops tormotus, a ranid species in China. These frogs produce countless vocalizations, some of which share features of birdsong or primate calls, e.g., ultrasonic frequency components, multiple upward and downward FM sweeps, and sudden onset and offset of selective harmonic components within a call note. Frame-by-frame video analysis of the frog's calling behavior suggests the presence of two pairs of vocal sacs that may contribute to the remarkable call-note complexity in this species. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-002-0335-x. 相似文献
882.
R.H. Field S. Benke K. Bdonyi R.B. Bradbury 《Agriculture, ecosystems & environment》2007,120(2-4):399-404
Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution. 相似文献
883.
884.
Aysen Müezzinoğlu Tolga Elbir Abdurrahman Bayram 《Environmental Engineering and Policy》1998,1(2):109-116
In this study, an inventory of air pollutant emission estimates from major air polluting sources in Turkey for period between 1985 and 2005 with 5-year intervals were estimated. Inventory covers anthropogenic sources of five major air pollutants of particulate matter, sulfur dioxide, carbon monoxide, nitrogen oxides and non-methane volatile organic compounds. Their break-down with respect to main activity sectors were shown and their distribution by the largest industrial source categories were worked out as annual estimates. This inventory and its analysis point to serious environmental implications of air pollutants and a need to develop a policy plan for reducing these emissions. 相似文献
885.
886.
Robert M. Wolcott Marco Antonio González 《Mitigation and Adaptation Strategies for Global Change》1997,2(2-3):vii-viii
Mitigation and Adaptation Strategies for Global Change - 相似文献
887.
深凹露天矿流场与污染物散布的模拟研究 总被引:1,自引:0,他引:1
利用高阶矩湍流闭合方案建立了一个三维非静力高分辨率PBL数值模式,并用此模式模拟了中性层结条件下一个深凹露天矿区实际地形的流场结构与湍流特性,分析并揭示露天矿自然通风特性,为进一步研究露天矿污染扩散规律提供背景流场。数值模拟的一些结果与同样试验条件下的风洞试验结果吻合甚好。 相似文献
888.
889.
In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous
component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can
be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency
vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned,
the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced
bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with
minimal energy input.
Received: 7 July 2000 / Accepted in revised form: 28 August 2000 相似文献
890.
The groundwater regime in Upper Palar basin, Tamilnadu has been highly contaminated in several locations due to discharge of effluents from a large number of tanneries. At some places total dissolved solids (TDS) concentration in groundwater was found as high as 8000 mg/l. Transmissivity and storativity of the regional aquifer were estimated at a few locations. The porosity and dispersivity values were not determined in the field. These parameters were assumed based on data available for similar geological formations elsewhere. The aquifer conceptualization thus arrived at formed the basis of a numerical groundwater flow model which was constructed using the finite difference method. The flow model was calibrated for steady state and then for transient condition for the period of 1984-92. The computed heads and calibrated parameters of the flow model were used to compute groundwater velocities. The migration of contaminants for a 20 year period was computed using the hydraulic heads and effective porosity value in a pathline model using FLOWPATH software. Mass transport model was constructed using Method of Characteristics (MOC) computer code in a separate model. The seepage rate of effluent is assumed at a rate of 30% of that discharged on the surface. The mass concentration of solute in the effluent reaching the water table was assumed as 40%, the same as in the surface effluent. The mass transport model was calibrated for a 20 year period. Prediction of contaminant migration from different clusters in the basin was analyzed. The prediction results indicated elevated TDS concentration of more than 4000 mg/l from most clusters. Also the area of the contaminated zone is likely to double in 20 years from contaminated zone of 1992. 相似文献