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   6761篇
  免费   47篇
  国内免费   930篇
安全科学   113篇
废物处理   209篇
环保管理   515篇
综合类   3405篇
基础理论   518篇
污染及防治   1948篇
评价与监测   552篇
社会与环境   383篇
灾害及防治   95篇
  2023年   25篇
  2022年   35篇
  2021年   23篇
  2020年   29篇
  2019年   31篇
  2018年   33篇
  2017年   53篇
  2016年   43篇
  2015年   99篇
  2014年   47篇
  2013年   46篇
  2012年   444篇
  2011年   481篇
  2010年   87篇
  2009年   158篇
  2008年   494篇
  2007年   507篇
  2006年   418篇
  2005年   389篇
  2004年   363篇
  2003年   370篇
  2002年   314篇
  2001年   260篇
  2000年   167篇
  1999年   87篇
  1998年   30篇
  1997年   27篇
  1996年   33篇
  1995年   67篇
  1994年   45篇
  1993年   93篇
  1992年   84篇
  1991年   105篇
  1990年   131篇
  1989年   88篇
  1988年   190篇
  1987年   240篇
  1986年   122篇
  1985年   234篇
  1984年   214篇
  1983年   197篇
  1982年   161篇
  1981年   145篇
  1980年   128篇
  1979年   75篇
  1978年   77篇
  1977年   35篇
  1976年   62篇
  1975年   47篇
  1974年   69篇
排序方式: 共有7738条查询结果,搜索用时 15 毫秒
1.
1 INTRODUCTIONIn the past, natural resources management initiatives havefocused on large but specific sector projects such as dams,reservoirs for water supply schemes, irrigation systems,crop production, at forestation, etc. Often these projectswere treated as technical and administrative issues ratherthan as a socio-economic and political one. However, thehigh social and environmental cost of such schemes haveled to a change of paradigm since the 1980s towards small-scale community projec…  相似文献   
2.
A sensitivity analysis of a proposed parameterization of the stomatal conductance (g(s)) module of the European ozone deposition model (DO(3)SE) for Quercus ilex was performed. The performance of the model was tested against measured g(s) in the field at three sites in Spain. The best fit of the model was found for those sites, or during those periods, facing no or mild stress conditions, but a worse performance was found under severe drought or temperature stress, mostly occurring at continental sites. The best performance was obtained when both f(phen) and f(SWP) were included. A local parameterization accounting for the lower temperatures recorded in winter and the higher water shortage at the continental sites resulted in a better performance of the model. The overall results indicate that two different parameterizations of the model are needed, one for marine-influenced sites and another one for continental sites.  相似文献   
3.
Macronutrients (P, S, K, Na, Mg, Ca), heavy metals (Fe, Zn, Mn, Cu, Pb, Cr, Ni, Cd,) and Al concentrations as well as values of Ca/Al in the tip, middle and base sections, and sheaths of current year and previous year needles of Pinus massoniana from Xiqiao Mountain were analyzed and the distribution patterns of those elements were compared. The results indicated that many elements were unevenly distributed among the different components of needles. Possible deficiency of P, K, Ca, Mn and Al toxicity occurred in needles under air pollution. Heavy metals may threaten the health of Masson pine. Needle sheaths were good places to look for particulate pollutants, in this case including Fe, Cu, Zn, Pb, Cr, Cd and Al.  相似文献   
4.
Seasonal variations in microcystin concentrations in Lake Taihu, China   总被引:1,自引:0,他引:1  
An enzyme-limited immunosorbent assay (ELISA) was used to monitor spatial and temporal variation of microcystins (MCs) in Lake Taihu. MC concentrations were higher in summer and autumn than in other seasons. Maximal MC concentration was 15.6 mug L(-1). Compared to central Lake Taihu and Wuli Bay, Meiliang Bay had higher MC concentrations due to high biomass of Microcystis.  相似文献   
5.
6.
<正> 关于金伯利岩中金刚石及超基性岩和榴辉岩捕虏体形成的地幔假说,近几年来几乎已成为定理。对此问题的一些不同的看法,或是因为不值得引起严重注意未被提及,或是因为缺乏足够的论据和实际分析资料而完全被忽视。  相似文献   
7.
In the high technology industry, small and medium sized technology enterprises (SMSTEs) play a pivotal role in advancing the whole industry. To achieve sustainable development, they need to extend their scope of business activities beyond a national view and exploit international market actively to meet international competitions that increase quickly in the form of allocating resources within the scope of the world. However, the SMSTEs are also facing risks associated with themselves during the process of exploiting international market owing to their own restrictions, so what they should do is to consider risk evaluations in exploiting the international market.  相似文献   
8.
当前市场上的各种报警系统种类繁多,各类制造商也是比比皆是,消费者可以随心所欲地选择他们喜欢的系统。各类系统之间的差别也非常有限,下面我们来介绍一套报警设备的DIY方案,供读者参考(由Alicia示范)。  相似文献   
9.
本文发展了一种对城市空气中多环芳烃(PAH)定量测定的方法。该方法可以用极少量溶剂,相当快地完成测定工作。  相似文献   
10.
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