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   28425篇
  免费   283篇
  国内免费   276篇
安全科学   816篇
废物处理   1354篇
环保管理   3533篇
综合类   3649篇
基础理论   7515篇
环境理论   7篇
污染及防治   7808篇
评价与监测   2202篇
社会与环境   1936篇
灾害及防治   164篇
  2022年   284篇
  2021年   277篇
  2020年   192篇
  2019年   234篇
  2018年   446篇
  2017年   440篇
  2016年   710篇
  2015年   492篇
  2014年   764篇
  2013年   2388篇
  2012年   916篇
  2011年   1234篇
  2010年   1084篇
  2009年   1101篇
  2008年   1271篇
  2007年   1354篇
  2006年   1224篇
  2005年   1013篇
  2004年   974篇
  2003年   1003篇
  2002年   931篇
  2001年   1277篇
  2000年   893篇
  1999年   544篇
  1998年   384篇
  1997年   355篇
  1996年   397篇
  1995年   414篇
  1994年   356篇
  1993年   316篇
  1992年   333篇
  1991年   304篇
  1990年   325篇
  1989年   324篇
  1988年   278篇
  1987年   238篇
  1986年   187篇
  1985年   217篇
  1984年   248篇
  1983年   234篇
  1982年   267篇
  1981年   204篇
  1980年   180篇
  1979年   211篇
  1978年   158篇
  1977年   158篇
  1976年   141篇
  1975年   129篇
  1974年   133篇
  1973年   129篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
681.
Biogenic volatile organic compounds (BVOCs) play an important role in atmospheric chemistry and the carbon cycle. Isoprene is quantitatively the most important of the non-methane BVOCs (NMBVOCs), with an annual emission of about 400–600 TgC; about 90% of this is emitted by terrestrial plants. Incorporating a mechanistic treatment of isoprene emissions within land-surface schemes has recently become a focus for the modelling community, the aim being to quantify the potential magnitude of associated climate feedbacks. However, these efforts are hampered by major uncertainties about why plants emit isoprene and the relative importance of different environmental controls on isoprene emission. The availability and reliability of observations of isoprene fluxes from different types of vegetation is limited, and this also imposes constraints on model development. Nevertheless, progress is being made towards the development of mechanistic models of isoprene emission which, in conjunction with atmospheric chemistry models, will ultimately allow improved quantification of the feedbacks between the terrestrial biosphere and climate under past and future climate states.  相似文献   
682.
683.
Air pollutants in exhaust gas produced from LP-gas (propane) were studied using both laboratory engines and vehicles. The objective of the study was both to evaluate propane as a low-pollution fuel and to provide information on adjustment of engine parameters for advantageous use of propane as a low-pollution fuel. Variables in the study were air-fuel ratio (A/F), ignition timing schedule, and ambient temperature. Data comparable to that for propane relating A/F and ambient temperature to emissions are shown for natural gas and for gasoline.  相似文献   
684.
Chlorotic dwarf is a serious disorder of eastern white pine (Pinus strobus L) in young plantations. Diseased trees are stunted and possess only current mottled foliage. Investigations into this problem were to define its symptomatology and etiology and to develop measures for control. Previous work had shown that susceptibility to chlorotic dwarf is genetically controlled and that the disease results from an aerological agent acting directly upon the foliage. By controlling the atmospheres around chlorotic dwarf field trees, evidence was obtained to prove that chlorotic dwarf is effected by the injury of gaseous dispersoids on the foliage of susceptible individuals.  相似文献   
685.
Abstract: Most protected areas are too small to sustain populations of wide‐ranging mammals; thus, identification and conservation of high‐quality habitat for those animals outside parks is often a high priority, particularly for regions where extensive land conversion is occurring. This is the case in the vicinity of Emas National Park, a small protected area in the Brazilian Cerrado. Over the last 40 years the native vegetation surrounding the park has been converted to agriculture, but the region still supports virtually all of the animals native to the area. We determined the effectiveness of scat‐detection dogs in detecting presence of five species of mammals threatened with extinction by habitat loss: maned wolf (Chrysocyon brachyurus), puma (Puma concolor), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), and giant armadillo (Priodontes maximus). The probability of scat detection varied among the five species and among survey quadrats of different size, but was consistent across team, season, and year. The probability of occurrence, determined from the presence of scat, in a randomly selected site within the study area ranged from 0.14 for jaguars, which occur primarily in the forested areas of the park, to 0.91 for maned wolves, the most widely distributed species in our study area. Most occurrences of giant armadillos in the park were in open grasslands, but in the agricultural matrix they tended to occur in riparian woodlands. At least one target species occurred in every survey quadrat, and giant armadillos, jaguars, and maned wolves were more likely to be present in quadrats located inside than outside the park. The effort required for detection of scats was highest for the two felids. We were able to detect the presence for each of five wide‐ranging species inside and outside the park and to assign occurrence probabilities to specific survey sites. Thus, scat dogs provide an effective survey tool for rare species even when accurate detection likelihoods are required. We believe the way we used scat‐detection dogs to determine the presence of species can be applied to the detection of other mammalian species in other ecosystems.  相似文献   
686.
Abstract: As zebra mussels (Dreissena polymorpha) continue to spread among inland lakes of the United States and Canada, there is growing interest from professionals, citizens, and other stakeholders to know which lakes are likely to be colonized by zebra mussels. Thus, we developed a classification of lake suitability for zebra mussels on the basis of measured or estimated concentrations of dissolved calcium in lake water and applied the classification to >11,500 lakes in Wisconsin and the Upper Peninsula of Michigan. The majority of lakes (58%) were classified as unsuitable (<10 mg/L Ca) for survival and reproduction of zebra mussels, 27% were identified as suitable (≥21 mg/L Ca), and 15% were classified as borderline suitable (≥10 and <21 mg/L Ca). Of the 77 inland lakes with confirmed zebra mussel records for which data on dissolved calcium were available, our method classified 74 as suitable and 3 as borderline suitable. To communicate this lake‐specific suitability information and to help prioritize regional efforts to monitor and prevent the expansion of zebra mussels and other invasive species, we developed a web‐based interface (available from http://www.aissmartprevention.wisc.edu/ ). Although we are still uncertain of how access to suitability information ultimately affects decision making, we believe this is a useful case study of building communication channels among researchers, practitioners, and the public.  相似文献   
687.
Environmental Science and Pollution Research - Traditional medicine (TM) also known as folk medicine consists of medical knowledge systems that were developed over generations in various countries...  相似文献   
688.
Environmental Science and Pollution Research - In this work, the activated persulfate oxidation of ciprofloxacin (CIP) using a low-grade titanium ore under sunlight or simulated sunlight were...  相似文献   
689.
Environmental Science and Pollution Research - Formation of oil-suspended sediment aggregates (OSAs) is believed to be one of the natural cleaning processes in the marine environment. In this...  相似文献   
690.
Environmental Science and Pollution Research - This paper presents the synthesis of a hybrid material through the use of natural pozzolan and titanium(IV) isopropoxide using the sol-gel method and...  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