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   734篇
  免费   4篇
  国内免费   4篇
安全科学   16篇
废物处理   22篇
环保管理   74篇
综合类   426篇
基础理论   78篇
污染及防治   95篇
评价与监测   19篇
社会与环境   12篇
  2023年   7篇
  2018年   7篇
  2017年   8篇
  2015年   16篇
  2014年   12篇
  2013年   28篇
  2012年   14篇
  2011年   18篇
  2010年   17篇
  2009年   17篇
  2008年   16篇
  2007年   21篇
  2006年   25篇
  2005年   22篇
  2004年   12篇
  2003年   16篇
  2002年   14篇
  2001年   7篇
  2000年   9篇
  1999年   13篇
  1998年   7篇
  1995年   7篇
  1967年   10篇
  1966年   8篇
  1965年   9篇
  1963年   15篇
  1962年   8篇
  1961年   7篇
  1959年   12篇
  1958年   9篇
  1957年   7篇
  1956年   12篇
  1955年   18篇
  1954年   14篇
  1951年   9篇
  1950年   7篇
  1947年   6篇
  1941年   8篇
  1940年   8篇
  1939年   15篇
  1938年   10篇
  1937年   12篇
  1934年   6篇
  1933年   7篇
  1932年   10篇
  1929年   7篇
  1926年   6篇
  1920年   7篇
  1914年   6篇
  1913年   6篇
排序方式: 共有742条查询结果,搜索用时 15 毫秒
91.
We have determined the activity of alkaline phosphatase in chorionic villous tissue obtained in the first trimester of pregnancy, in order to obtain the normal range of values as a prerequisite for application to the prenatal diagnosis of the rare bone disease hypophosphatasia. The activities found were a combination of intestinal and liver/bone/kidney types; traces of placental type were present in only one sample.  相似文献   
92.
93.
Regional Environmental Change - Managing multiple ecosystem services (ES) in agricultural landscapes is a challenging task, especially in regions with complex topographical and agro-ecological...  相似文献   
94.
95.
96.
ABSTRACT: Ground water contamination by excess nitrate leaching in row‐crop fields is an important issue in intensive agricultural areas of the United States and abroad. Giant cane and forest riparian buffer zones were monitored to determine each cover type's ability to reduce ground water nitrate concentrations. Ground water was sampled at varying distances from the field edge to determine an effective width for maximum nitrate attenuation. Ground water samples were analyzed for nitrate concentrations as well as chloride concentrations, which were used as a conservative ion to assess dilution or concentration effects within the riparian zone. Significant nitrate reductions occurred in both the cane and the forest riparian buffer zones within the first 3.3 m, a relatively narrow width. In this first 3.3 m, the cane and forest buffer reduced ground water nitrate levels by 90 percent and 61 percent, respectively. Approximately 40 percent of the observed 99 percent nitrate reduction over the 10 m cane buffer could be attributed to dilution by upwelling ground water. Neither ground water dilution nor concentration was observed in the forest buffer. The ground water nitrate attenuation capabilities of the cane and forest riparian zones were not statistically different. During the spring, both plant assimilation and denitrification were probably important nitrate loss mechanisms, while in the summer nitrate was more likely lost via denitrification since the water table dropped below the rooting zone.  相似文献   
97.
Summary. Host plant odours are known to be important in long-range host location by the cabbage root fly, whereas at short distances orientation is mainly visual. We show that olfaction also plays a significant role after a fly lands on a plant and before it moves down onto the soil to oviposit. Host plant acceptance by the cabbage root fly seems to result from a synergistic response to simultaneously perceived olfactory and contact chemostimulation. Received 12 May 1999; accepted 24 July 1999  相似文献   
98.
99.
The socio-cultural assessment of ecosystem services has been proposed as a promising tool for eliciting people’s preferences towards ecosystem services. Despite an increasing integration of the socio-cultural perspective in ecosystem service research, little knowledge exists about linkages between landscape and the socio-cultural values people assign to ecosystem services. This paper combines a socio-cultural valuation approach with the use of landscape pictures to analyse and compare people’s perceived importance of the provisioning, regulating, and cultural ecosystem service categories across three landscape types (i.e. larch meadows, spruce forests, and hay meadow). A survey with 470 tourists visiting the region of South Tyrol (Italy) was conducted to link people’s perceived importance to their socio-demographic background and to the landscape types explored. The results show that regulating ecosystem services are preferred over provisioning and cultural services, whereby environmental awareness is found to be more influential than formal education levels regarding the perceived importance of regulating services. The results further demonstrate that cultural background is an important driver in determining people’s perceived importance of cultural services. The underlying landscape types, however, exert an even stronger influence on people’s socio-cultural valuation of ecosystem service categories. This finding suggests that the focus of most ecosystem services assessments on the study area as a whole risks mistakenly attributing differences in people’s socio-cultural values to socio-demographic characteristics only. A better knowledge of the spatial integration of socio-cultural values, however, could help with anticipating the consequences of changes in the landscape and provide better guidance for future landscape planning.  相似文献   
100.
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