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   34630篇
  免费   340篇
  国内免费   341篇
安全科学   977篇
废物处理   1560篇
环保管理   4506篇
综合类   4631篇
基础理论   9164篇
环境理论   9篇
污染及防治   9642篇
评价与监测   2515篇
社会与环境   2056篇
灾害及防治   251篇
  2022年   312篇
  2021年   345篇
  2020年   221篇
  2019年   299篇
  2018年   531篇
  2017年   519篇
  2016年   827篇
  2015年   624篇
  2014年   949篇
  2013年   2981篇
  2012年   1149篇
  2011年   1484篇
  2010年   1255篇
  2009年   1334篇
  2008年   1537篇
  2007年   1668篇
  2006年   1465篇
  2005年   1212篇
  2004年   1223篇
  2003年   1186篇
  2002年   1135篇
  2001年   1461篇
  2000年   1040篇
  1999年   627篇
  1998年   462篇
  1997年   429篇
  1996年   504篇
  1995年   478篇
  1994年   456篇
  1993年   418篇
  1992年   389篇
  1991年   360篇
  1990年   375篇
  1989年   373篇
  1988年   348篇
  1987年   299篇
  1986年   246篇
  1985年   266篇
  1984年   318篇
  1983年   306篇
  1982年   324篇
  1981年   277篇
  1980年   240篇
  1979年   284篇
  1978年   213篇
  1977年   191篇
  1976年   174篇
  1975年   169篇
  1973年   163篇
  1972年   162篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
951.
Poor early-life nutrition could reduce adult reproductive success by negatively affecting traits linked to sexual attractiveness such as song complexity. If so, this might favor strategic mate choice, allowing males with less complex songs to tailor their mating tactics to maximize the reproductive benefits. However, this possibility has been ignored in theoretical and empirical studies. By manipulating the micronutrient content of the diet (e.g., low or high) during the postnatal period of male zebra finches, we show for the first time (1) that males reared on a poor (low) micronutrient diet had less complex songs as adults; (2) that these males, in contrast to the high micronutrient diet group, were more selective in their mating strategies, discriminating against those females most likely to reduce their clutch size when paired with males having less complex songs; and (3) that by following different mating strategies, males reared on the contrasting diets obtained similar reproductive benefits. These results suggest that early-life dietary conditions can induce multiple and long-lasting effects on male and female reproductive traits. Moreover, the results seem to reflect a previously unreported case of adaptive plasticity in mate choice in response to a nutritionally mediated reduction in sexual attractiveness.  相似文献   
952.
Journal of Material Cycles and Waste Management - The use of lignocellulosic fibers as fillers in polymer matrices has aroused the interest of the scientific community and industrial sectors. In...  相似文献   
953.
Journal of Material Cycles and Waste Management - Waste lubricating oil is considered to be a hazardous waste and has tremendous impact on human health and environment. The present review...  相似文献   
954.
Journal of Material Cycles and Waste Management - Leather production is a technology that boosts the economy because of its versatility and durability. However, the wastes generated throughout the...  相似文献   
955.
Journal of Material Cycles and Waste Management - The daily use of facemask to prevent virus transmission increases the negative effect on the environment because of improper waste disposal. Due to...  相似文献   
956.
Russian Journal of Ecology - Changes in the distribution of broadleaf tree species—Tilia cordata Mill., Quercus robur L., Acer platanoides L., and Ulmus glabra Huds.—in the central part...  相似文献   
957.
Russian Journal of Ecology - Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study,...  相似文献   
958.
Environment, Development and Sustainability - The COVID-19 pandemic has caused a global emergence, and the absence of a proven vaccine or medicine has led to the implementation of measures to...  相似文献   
959.
In the Ohio River (OR), backwater confluence sedimentation dynamics are understudied, however, these river features are expected to be influential on the system’s ecological and economic function when integrated along the river’s length. In the following paper, we test the efficacy of organic and inorganic tracers for sediment fingerprinting in backwater confluences; we use fingerprinting results to evidence sediment dynamics controlling deposition patterns in confluences used for wetland and marina functions; and we quantify the spatial extent of tributary drainages with wetland and marina features in OR confluences. Both organic and inorganic tracers statistically differentiate sediment from stream and river end‐members. Carbon and nitrogen stable isotopes produce greater uncertainty in fingerprinting results than inorganic elemental tracers. Uncertainty analysis of the nonconservative tracer term in the organic matter fingerprinting application estimates an apparent enrichment of the carbon stable isotopes during instream residence, and the nonconservativeness is quantified with a statistical approach unique to the fingerprinting literature. Wetland and marina features in OR confluences impact 42% and 11% of tributary drainage areas, respectively. Sediment dynamics show wetland and marina confluences experience deposition from river backwaters with longitudinally linear and nonlinear patterns, respectively, from sediment sources.  相似文献   
960.
A statistical procedure is developed to adjust natural streamflows simulated by dynamical models in downstream reaches, to account for anthropogenic impairments to flow that are not considered in the model. The resulting normalized downstream flows are appropriate for use in assessments of future anthropogenically impaired flows in downstream reaches. The normalization is applied to assess the potential effects of climate change on future water availability on the Rio Grande at a gage just above the major storage reservoir on the river. Model‐simulated streamflow values were normalized using a statistical parameterization based on two constants that relate observed and simulated flows over a 50‐year historical baseline period (1964–2013). The first normalization constant is a ratio of the means, and the second constant is the ratio of interannual standard deviations between annual gaged and simulated flows. This procedure forces the gaged and simulated flows to have the same mean and variance over the baseline period. The normalization constants can be kept fixed for future flows, which effectively assumes that upstream water management does not change in the future, or projected management changes can be parameterized by adjusting the constants. At the gage considered in this study, the effect of the normalization is to reduce simulated historical flow values by an average of 72% over an ensemble of simulations, indicative of the large fraction of natural flow diverted from the river upstream from the gage. A weak tendency for declining flow emerges upon averaging over a large ensemble, with tremendous variability among the simulations. By the end of the 21st Century the higher‐emission scenarios show more pronounced declines in streamflow.  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