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   3063篇
  免费   43篇
  国内免费   26篇
安全科学   164篇
废物处理   156篇
环保管理   623篇
综合类   337篇
基础理论   745篇
环境理论   5篇
污染及防治   762篇
评价与监测   215篇
社会与环境   106篇
灾害及防治   19篇
  2023年   22篇
  2022年   38篇
  2021年   26篇
  2020年   22篇
  2019年   32篇
  2018年   67篇
  2017年   68篇
  2016年   90篇
  2015年   58篇
  2014年   85篇
  2013年   283篇
  2012年   144篇
  2011年   180篇
  2010年   123篇
  2009年   124篇
  2008年   155篇
  2007年   190篇
  2006年   153篇
  2005年   108篇
  2004年   105篇
  2003年   116篇
  2002年   91篇
  2001年   69篇
  2000年   47篇
  1999年   53篇
  1998年   38篇
  1997年   43篇
  1996年   46篇
  1995年   40篇
  1994年   42篇
  1993年   36篇
  1992年   39篇
  1991年   28篇
  1990年   29篇
  1989年   19篇
  1988年   14篇
  1987年   20篇
  1986年   25篇
  1985年   17篇
  1984年   18篇
  1983年   28篇
  1982年   29篇
  1981年   25篇
  1980年   19篇
  1979年   16篇
  1977年   11篇
  1976年   9篇
  1975年   9篇
  1974年   10篇
  1971年   11篇
排序方式: 共有3132条查询结果,搜索用时 31 毫秒
991.
ABSTRACT: A bacterial transport model, developed to analyze bacterial translocation in coarse-grained soils, is presented. The complex governing equation is presented first, followed by analyses of each of the major processes influencing bacterial transport. These analyses suggest simplification of the governing equation is feasible when input data on specific processes are limited or unavailable. Model parameters, including bacterial die-off, bacterial distribution, input bacterial concentration, and saturated hydraulic conductivity, were randomly generated using a procedure known to produce either a normal or log-normal distribution of random numbers. Monte Carlo simulations were completed, and the resulting output was used to generate cumulative frequency distributions showing the probability of bacterial transport beyond various soil depths. Results from these simulations indicate that bacteria have a high probability of traveling through coarse-grained soils when low clay content and soil water temperatures limit bacterial retention and die-off.  相似文献   
992.
Lemurs are the most olfactory-oriented of primates, yet there is still only a basic level of understanding of what their scent marks communicate. We analyzed scent secretions from Milne-Edwards' sifakas (Propithecus edwardsi) collected in their natural habitat of Ranomafana National Park, Madagascar. We sought to test whether the scent mark could signal genetic relatedness in addition to species, sex, season, and individuality. We not only found correlations (r 2?=?0.38, P?=?0.017) between the total olfactory fingerprint and genetic relatedness but also between relatedness and specific components of the odor, despite the complex environmental signals from differences in diet and behavior in a natural setting. To the best of our knowledge, this is the first demonstration of an association between genetic relatedness and chemical communication in a wild primate population. Furthermore, we found a variety of compounds that were specific to each sex and each sampling period. This research shows that scent marks could act as a remote signal to avoid inbreeding, optimize mating opportunities, and potentially aid kin selection.  相似文献   
993.
Industrial ecology is a systemic organizing framework for the many facets of environmental management. It views the industrial world as a natural system, embedded in local ecosystems and the global biosphere. It provides a fundamental understanding of the value of modeling the industrial system on ecosystems to achieve sustainable environmental performance. In this article, the author shows how it offers powerful tools of analysis that complement and enhance those offered by such approaches as Total Quality Environmental Management or pollution prevention.  相似文献   
994.
995.
996.
997.
A model for life-cycle assessment of waste incinerators is described and applied to a case study for illustrative purposes. As life-cycle thinking becomes more integrated into waste management, quantitative tools for assessing waste management technologies are needed. The presented model is a module in the life-cycle assessment model EASEWASTE. The module accounts for all uses of materials and energy and credits the incinerator for electricity and heat recovered. The energy recovered is defined by the user as a percentage of the energy produced, calculated on the lower heating value of the wet waste incinerated. Emissions are either process-specific (related to the amount of waste incinerated) or input-specific (related to the composition of the waste incinerated), while mass transfer to solid outputs are governed by transfer coefficients specified by the user. The waste input is defined by 48 material fractions and their chemical composition. The model was used to quantify the environmental performance of the incineration plant in Aarhus, Denmark before and after its upgrading in terms of improved flue gas cleaning and energy recovery. It demonstrated its usefulness in identifying the various processes and substances that contributed to environmental loadings as well as to environmental savings. The model was instrumental in demonstrating the importance of the energy recovery system not only for electricity but also heat from the incinerator.  相似文献   
998.
Bravoceratops polyphemus gen. et sp. nov. is a large chasmosaurine ceratopsid from the lowermost part of the Javelina Formation (early Maastrichtian) of Big Bend National Park, TX, USA. B. polyphemus has a distinctive narrow snout, a long fenestrate frill, and a fan-shaped median parietal bar with a midline epiparietal on its posterior margin, as well as a symmetrical depression on its dorsal surface at the nexus of the parietal rami. This depression is interpreted to be the attachment point for a second midline epiparietal. This parietal morphology is distinct from that exhibited by Anchiceratops or Pentaceratops. The posterior midline epiparietal in B. polyphemus and its bifurcated quadratojugal–squamosal joint are features shared with the most derived chasmosaurines, Torosaurus and Triceratops. The combination of primitive and derived traits exhibited by B. polyphemus, and its stratigraphic position, is compatible with the gradual transition from basal, to intermediate, to derived chasmosaurines observed throughout the western interior of North America, and with phylogenetic analysis, which suggests that Bravoceratops may be closely related to Coahuilaceratops.  相似文献   
999.
The chemical composition of Danish household waste was determined by two approaches: a direct method where the chemical composition (61 substances) of 48 material fractions was determined after hand sorting of about 20 tonnes of waste collected from 2200 households; and an indirect method where batches of 80–1200 tonnes of unsorted household waste was incinerated and the content of the waste determined from the content of the outputs from the incinerator. The indirect method is believed to better represent the small but highly contaminated material fractions (e.g., batteries) than the direct method, because of the larger quantities included and the more homogenous material to sample from. Differences between the direct and the direct methods led to corrections in the of heavy metal concentration of a few fractions.The majority of the energy content of the waste originates from organic waste like paper, cardboard and organic fractions. The single fraction contributing most to the total energy content is the non-recyclable plastic fraction, contributing 21% of the energy content and 60% of the chlorine content, although this fraction comprises less than 7% by weight. Heavy metals originate mainly from inert fractions, primarily batteries.  相似文献   
1000.
Character (ethos) refers to those interpenetrable habitual qualities within individuals, and applicable to organizations that both constrain and lead them to desire and pursue personal and societal good. In our Incubator article, we undertake two objectives. First, we provide our conceptualization of character; briefly specifying what character is and is not. Second, we introduce several promising directions for organizationally based research on character. Copyright © 2008 John Wiley & Sons, Ltd.  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