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   16342篇
  免费   172篇
  国内免费   137篇
安全科学   448篇
废物处理   628篇
环保管理   2285篇
综合类   2567篇
基础理论   4459篇
环境理论   4篇
污染及防治   4301篇
评价与监测   1005篇
社会与环境   851篇
灾害及防治   103篇
  2022年   111篇
  2021年   129篇
  2020年   105篇
  2019年   148篇
  2018年   224篇
  2017年   220篇
  2016年   354篇
  2015年   239篇
  2014年   357篇
  2013年   1268篇
  2012年   441篇
  2011年   632篇
  2010年   536篇
  2009年   520篇
  2008年   691篇
  2007年   691篇
  2006年   659篇
  2005年   506篇
  2004年   587篇
  2003年   522篇
  2002年   482篇
  2001年   702篇
  2000年   471篇
  1999年   282篇
  1998年   241篇
  1997年   217篇
  1996年   227篇
  1995年   247篇
  1994年   271篇
  1993年   219篇
  1992年   247篇
  1991年   222篇
  1990年   254篇
  1989年   238篇
  1988年   193篇
  1987年   173篇
  1986年   158篇
  1985年   167篇
  1984年   192篇
  1983年   180篇
  1982年   185篇
  1981年   179篇
  1980年   137篇
  1979年   153篇
  1978年   131篇
  1977年   117篇
  1975年   118篇
  1974年   115篇
  1973年   110篇
  1972年   133篇
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
961.

Purpose  

The aims of this paper were to quantify the heavy metals (HM) in the air of different sites in Rio de Janeiro (RJ) and Salvador (SA) using Tillandsia usneoides (Bromeliaceae) as a biomonitor, and to study the morphology and elemental composition of the air particulate matter (PM) retained on the Tillandsia surface.  相似文献   
962.
A Finizio  A D Guardo 《Chemosphere》2001,45(6-7):1063-1070
Temperature dependence data for physical-chemical properties is increasingly required for modelling the fate of chemicals in the environment. Solubility and octanol-water partition coefficient (Kow) are among the most important parameters. A simple and fast method is presented to determine solubility and Kow of organic chemicals at different temperatures (5 degrees C, 15 degrees C, 25 degrees C, 35 degrees C) utilising a variable temperature RP-HPLC column. Correlations between capacity factors (k') and solubility and Kow were determined for some halogenated and methylated benzenes and showed that this approach could be used to predict acceptable results. New values for solubility and Kow as function of temperature for several compounds are presented.  相似文献   
963.
964.
Fetal magnetocardiography provides the requisite precision for diagnostic measurement of electrophysiological events in the fetal heart. Despite its significant benefits, this technique with current cryogenic based sensors has been limited to few centers, due to high cost of maintenance. In this study, we show that a less expensive non-cryogenic alternative, optically pumped magnetometers, can provide similar electrophysiological and quantitative characteristics when subjected to direct comparison with the current technology. Further research can potentially increase its clinical use for fetal magnetocardiography. © 2016 John Wiley & Sons, Ltd.  相似文献   
965.
966.
967.
Eucalyptus forest; and in the composition of understorey herbs, sedges, and grasslands. Pollen concentration and charcoal and organic content also exhibit post-European changes. Thus, pollen analysis provides a technique for determining changes in sediment budgets and identifying major vegetation changes in floodplains.  相似文献   
968.
Designing chemical processes for the environment requires consideration of several indexes of environmental impact including ozone depletion, global warming potentials, human and aquatic toxicity, photochemical oxidation, and acid rain potentials. Current methodologies, such as the generalized waste reduction algorithm (WAR), provide a first step towards evaluating these impacts. However, to address the issues of accuracy and the relative weights of these impact indexes, one must consider the problem of uncertainties. Environmental impacts must also be weighted and balanced against other concerns, such as their cost and long-term sustainability. These multiple, often conflicting, goals pose a challenging and complex optimization problem, requiring multi-objective optimization under uncertainty. This paper will address the problem of quantifying and analyzing the various objectives involved in process design for the environment. Towards this goal, we proposed a novel multi-objective optimization framework under uncertainty. This framework is based on new and efficient algorithms for multi-objective optimization and for uncertainty analysis. This approach finds a set of potentially optimal designs where trade-offs can be explicitly identified, unlike cost-benefit analysis, which deals with multiple objectives by identifying a single fundamental objective and then converting all the other objectives into this single currency. A benchmark process for hydrodealkylation (HDA) of toluene to produce benzene modeled in the ASPEN simulator is used to illustrate the usefulness of the approach in finding environmentally friendly and cost-effective designs under uncertainty.  相似文献   
969.
970.
Carbon monoxide (CO) in the surface sea waters is produced predominantly by photochemical processes, oxidized by micro-organisms and outgassed to the atmosphere. to assess carbon monoxide flux from the oceans to the atmosphere, the photochemical production and microbial oxidation of carbon monoxide in the oceanic mixed-layer was investigated during several oeanographic cruises and in the laboratory. the photoproduction rate of carbon monoxide was found to be well correlated to the concentration of dissolved organic carbon (DOC) in coastal and open ocean surface waters. Taking a global average carbon monoxide production rate of 10 ± 2 nmole litre-1 (mg DOC hr)-1 in the surface open ocean water, and 25 ± 7 nmole litre-1 (mg DOC hr)-1 in coastal sea water, at cloud-free summer solar noon, the photochemical production of carbon monoxide in the global oceans is estimated to be at a rate of 1200 ± 200 Tg CO y-1. the microbial carbon monoxide turnover time in the mixed-layer was observed to range from hours in a coastal estuary to 16 days in the Pacific along 1057deg; W in dark incubations. Natural sunlight can largely inhibit the microbial consumption of carbon monoxide in surface water. On a global scale, microbial consumption is responsible for the loss of less than 10% of photochemical produced carbon monoxide in the surface ocean. Field measurements have shown that the net transport of carbon monoxide from the euphotic zone to the underlying deeper ocean water is limited and that the overall life time in surface sea waters is less than 3-4 hours. When combined, these field measurements with the photoproduction and microbial consumption rates obtained, we estimate the oceanic flux to the atmosphere is about 1000 ± 200 Tg CO y-1, which represents the largest single source of atmospheric carbon monoxide.  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