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   752篇
  免费   8篇
  国内免费   7篇
安全科学   18篇
废物处理   54篇
环保管理   100篇
综合类   104篇
基础理论   137篇
环境理论   2篇
污染及防治   252篇
评价与监测   58篇
社会与环境   39篇
灾害及防治   3篇
  2023年   10篇
  2022年   30篇
  2021年   24篇
  2020年   19篇
  2019年   19篇
  2018年   29篇
  2017年   31篇
  2016年   35篇
  2015年   27篇
  2014年   28篇
  2013年   66篇
  2012年   43篇
  2011年   62篇
  2010年   33篇
  2009年   28篇
  2008年   46篇
  2007年   42篇
  2006年   43篇
  2005年   33篇
  2004年   21篇
  2003年   21篇
  2002年   25篇
  2001年   6篇
  2000年   5篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1996年   3篇
  1995年   4篇
  1994年   6篇
  1993年   3篇
  1990年   3篇
  1989年   4篇
  1988年   1篇
  1986年   3篇
  1985年   1篇
  1979年   1篇
  1971年   1篇
  1968年   1篇
  1964年   1篇
  1958年   1篇
排序方式: 共有767条查询结果,搜索用时 31 毫秒
101.
102.
The decline in the supply of natural resources is a cause for concern, especially given continued worldwide population growth. New habits and attitudes toward resource use are slowly being introduced into the everyday lives of persons residing in a number of countries. The term “ecological behavior” refers to acting in favor of the environment, whether these actions are voluntarily or not, or learned or not (Pato & Tamayo, 2006 ). The general objective of this study is to identify the environmental behavior—one of several terms used interchangeably with ecological behavior—of graduate students from a Brazilian federal institution of higher education. We chose this particular group because many of them already act, or will act, as professors. Thus, by virtue of their positions, they will function as opinion leaders who will influence the education of future professionals, establishing a chain through which shared values can gradually change the environmental behavior of society.  相似文献   
103.
104.
105.
Abstract: To assess the genetic consequences for a Neotropical tree of the loss of its main seed disperser, we compared the genetic structure of Inga ingoides in a site where the spider monkey (Ateles paniscus) was abundant and a site where it had been eliminated by subsistence hunting. Gene flow should be reduced in the site where the spider monkey is absent, and there should be a corresponding subpopulation differentiation of seedlings within the spatial range of the movements of these primates in the absence of between-site differences in allelic frequencies. At the microhabitat (  family) scale, seedlings growing under parent plants should be genetically more related in the absence of the spider monkey than in its presence. Subpopulation differentiation was smaller where the spider monkey was present (  four loci, FST = 0.011) than where it was absent (  four loci, FST = 0.053) for the first year of study, but not for the second year (three loci, FST = 0.005 vs. 0.003). The number of alleles in common among seedlings growing under parent plants was smaller in the presence of the spider monkey than in its absence, showing family genetic structure in the first generation for both years of study ( Mann-Whitney, z = −2.17, p = 0.03 and z = −2.72, p = 0.006 for 1996 and 1997, respectively). This family genetic structure in the first generation should accelerate the development of population genetic structure. Development of genetic structure might result in demographic changes, one of which would be a fitness reduction if the species were self-incompatible, as suggested for Inga by available evidence. Large birds and mammals are the main targets of subsistence hunting in the Neotropics. Extinction of seed-dispersing frugivores may result in pronounced changes in the demographic and genetic structure of tree species in Neotropical forests.  相似文献   
106.
为这片世界最南端的森林提出的一个主要森林管理和家具木材生产方案的可能影响,已经引起广泛关注.对这些原始森林的未来所给予的注意,突出说明了环境保护/生物多样性保护与经济效益之间的冲突.火地岛的公共当局和居民处在一个能指定他们合意的生活方式与环境质量的地位,而且能参与旨在以适合于其社会、经济和生态的条件和期望的方式确保可持续性的决策.  相似文献   
107.
A mechanically stirred anaerobic sequencing batch reactor (ASBR) containing granular biomass was applied to the treatment of a wastewater simulating the effluent from a personal care industry. The ASBR was operated with cycle lengths (tC) of 8, 12 and 24 h and applied volumetric organic loads (AVOL) of 0.75, 0.50 and 0.25 gCOD/L.d, treating 2.0 L liquid medium per cycle. Stirring frequency was 150 rpm and the reactor was kept in an isothermal chamber at 30 °C. Increase in tC resulted in efficiency increase at constant AVOL, reaching 77% at tC of 24 h versus 69% at tC of 8 h. However, efficiency decreased when AVOL decreased as a function of increasing tC, due to the lack of substrate in the reaction medium. Moreover, replacing part of the wastewater by a chemically balanced synthetic one did not yield the expected effect and system efficiency dropped.  相似文献   
108.
This is the first report showing that using honeybee (Apis mellifera) and wild pollinators complementary pollination can enhance soybean productivity (Glycine max). Current industrial production of soybean involves autopollination and high loads of pesticides. Therefore, growers have neglected possible biotic pollination despite suggestions that soybean benefit from insect pollinators. Reports advocating possible biotic pollination are based on experiments where bees are caged with flowering plants and the absence of pesticides, thus not in field conditions. Therefore, here we compared in field conditions soybean yield produced (1) independently of biotic pollinators, (2) with wild pollinators and (3) with honeybee colonies. Results showed an increase of +6.34 % of soybean yield in areas where wild pollinators had free access to flowers. The introduction of honeybee colonies further raised the yield of +18.09 %. Our findings therefore show that, though soybean is autogamous, allowing pollination by wild pollinators leads to higher yields. Moreover, adding honeybee mitigates pollination deficits and improves yield compared to current practices.  相似文献   
109.
There is a general lack of information on the impact of forest plantations and the presence of urban settlements on populations of resource-demanding species such as large felids. To partially address this problem, a project study was conducted to find out whether mosaics of forest plantations and native vegetation can function as an adequate habitat for pumas (Puma concolor) in southern Brazil. The study was conducted within a 1255-km2 area, managed for planted stands of Pinus spp. and Eucalyptus spp. Individual identification of pumas was carried out using a combination of track-matching analysis (discriminant analysis) and camera-trapping. Both techniques recorded closely similar numbers of individual pumas, either total (9–10 individuals) or resident (5–6 individuals). A new approach, developed during this study, was used to individualize pumas by their markings around the muzzle. The estimated density varied from 6.2 to 6.9 individuals/100 km2, ranking among the highest across the entire puma range and indicating a potential total population of up to 87 individuals in the study site. In spite of the availability of extensive areas without human disturbance, a radio-tracked female used a core home range that included forest plantations, an urbanized village, and a two-lane paved road with regular vehicular traffic. The high density of pumas and the species’ intensive use of modified landscapes are interpreted here as deriving from conditions rarely found near human settlements: mutual tolerance by pumas and humans and an adequate habitat (regardless of plantations) largely due to the inhibition of invasions and hunting and maintenance of sizable extents of native forest patches. More widely, it suggests the potential of careful management in forestry operations to provide habitat conditions for resource-demanding species such as the puma. Furthermore, it highlights the importance of curbing invasions and hunting, in this case provided by the presence of company employees, for the maintenance of wildlife populations.  相似文献   
110.
The prenatal diagnosis of congenital transmission of Chagas' disease in a pregnant woman with the indeterminate form of the disease is reported. Sonography revealed fetal hydrops at 31 weeks' gestation. Anti-Trypanosoma cruzi IgM and IgG antibodies were negative in the fetal blood sampled by cordocentesis, but T. cruzi trypomastigotes were found in its buffy coat. Owing to anemia, in utero exchange transfusion was undertaken, but fetal demise ensued. Labor was induced and a stillborn infant weighing 2030 g was delivered. The pathological examination revealed placentitis and meningoencephalitis, myocarditis and splenitis in the stillborn fetus. Amastigotes were found in the myocardium, brain and placenta. Copyright © 2004 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