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   84556篇
  免费   1215篇
  国内免费   1081篇
安全科学   3632篇
废物处理   3013篇
环保管理   13196篇
综合类   20879篇
基础理论   25461篇
环境理论   71篇
污染及防治   11868篇
评价与监测   5071篇
社会与环境   3182篇
灾害及防治   479篇
  2022年   760篇
  2021年   776篇
  2020年   635篇
  2019年   850篇
  2018年   1043篇
  2017年   1068篇
  2016年   2076篇
  2015年   1811篇
  2014年   2557篇
  2013年   9206篇
  2012年   1920篇
  2011年   1965篇
  2010年   3132篇
  2009年   3257篇
  2008年   1471篇
  2007年   1267篇
  2006年   1831篇
  2005年   1916篇
  2004年   2265篇
  2003年   2087篇
  2002年   1637篇
  2001年   1862篇
  2000年   1763篇
  1999年   1396篇
  1998年   1341篇
  1997年   1322篇
  1996年   1443篇
  1995年   1533篇
  1994年   1436篇
  1993年   1290篇
  1992年   1272篇
  1991年   1249篇
  1990年   1192篇
  1989年   1167篇
  1988年   1007篇
  1987年   950篇
  1986年   981篇
  1985年   1047篇
  1984年   1141篇
  1983年   1157篇
  1982年   1166篇
  1981年   1087篇
  1980年   932篇
  1979年   902篇
  1978年   812篇
  1977年   705篇
  1976年   629篇
  1975年   589篇
  1973年   611篇
  1972年   615篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
252.
253.
254.
255.
Community evacuation following a chlorine release, Mississippi   总被引:1,自引:0,他引:1  
On 7th September 1986, four miles north of Collins, Mississippi, a train transporting chlorine derailed. Two cars ruptured and gas escaped. As a result, 100 families were evacuated. To study the evacuation process, we conducted person-to-person interviews with sixty-two families staying in the evacuation center. Only 52.5% of the families received their first directive to evacuate directly from police or other officials. Delays in evacuating tended to be shorter when people were warned by the police and were told the reason for evacuating. Lack of personal transportation and preexisting health problems resulted in delays in evacuation. Concerns about evacuation included fear of looting, lack of a place to go, lack of transportation, difficulty in moving with children and elderly persons, and the need to take care of pets. One third of the interviewees reported feeling panic. Community evacuation procedures would be improved if: (1) officials contact all households directly; (2) the warning message addresses people's concerns; and (3) transportation is provided.  相似文献   
256.
After several years of experimentation and demonstration, photovoltaic (PV) power is now firmly established for certain applications where reliable power is required in remote locations. The technology has recently matured to the point where PV is now an appropriate, cost-effective technology for village use. This paper reviews experience and presents economic comparisons between photovoltaic and conventional power systems. It is concluded that PV is cost-effective for individual home lighting and small loads such as radios, when compared with kerosene lamps and batteries. For mutiple uses PV is cost-effective compared with diesel generators for daily electricity demands up to around 20 kWh, depending on local conditions.  相似文献   
257.
ABSTRACT: This paper describes the formulation of an Index of Water Quality to evaluate the level of pollution in fresh water. A Four-Round Delphi equation, using a panel of seven nationally recognized water scientists, was performed to ascertain the pollutants to be included in the index, the relationship between the quantity of these pollutants in the water and the resulting quality of the water, and the importance of each pollution variable to each water use as well as to overall pollution. A multiplicative index was used to bring the pollutants together into one system.  相似文献   
258.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily.  相似文献   
259.
260.
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