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   87165篇
  免费   1222篇
  国内免费   1072篇
安全科学   3677篇
废物处理   3143篇
环保管理   13404篇
综合类   21005篇
基础理论   25817篇
环境理论   73篇
污染及防治   12908篇
评价与监测   5230篇
社会与环境   3703篇
灾害及防治   499篇
  2022年   774篇
  2021年   793篇
  2020年   645篇
  2019年   861篇
  2018年   1131篇
  2017年   1180篇
  2016年   2148篇
  2015年   1849篇
  2014年   2595篇
  2013年   9272篇
  2012年   2053篇
  2011年   2198篇
  2010年   3228篇
  2009年   3361篇
  2008年   1711篇
  2007年   1539篇
  2006年   1989篇
  2005年   2102篇
  2004年   2363篇
  2003年   2180篇
  2002年   1746篇
  2001年   1923篇
  2000年   1812篇
  1999年   1428篇
  1998年   1357篇
  1997年   1335篇
  1996年   1459篇
  1995年   1556篇
  1994年   1446篇
  1993年   1301篇
  1992年   1284篇
  1991年   1266篇
  1990年   1213篇
  1989年   1179篇
  1988年   1018篇
  1987年   954篇
  1986年   983篇
  1985年   1050篇
  1984年   1143篇
  1983年   1158篇
  1982年   1168篇
  1981年   1093篇
  1980年   938篇
  1979年   909篇
  1978年   813篇
  1977年   711篇
  1976年   632篇
  1975年   592篇
  1973年   615篇
  1972年   619篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
20世纪70和80年代,"酸雨"成为一个主要公共政策问题.在加拿大和北欧的斯堪的纳维亚半岛的酸化水体中,生物群落及生境遭到频繁破坏,诸如土著鲑鱼和鳟鱼种群受损乃至灭绝的现象屡见不鲜.  相似文献   
202.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown.  相似文献   
203.
In recent years flows of foreign direct investment (FDI) to developing countries have rapidly been increasing. It is now an important contributor to the national economy and urban growth in scores of developing countries. Rapid urbanization in these countries is leading to many problems in the cities. Existing urban infrastructure and municipal services have been unable to cope with the increased demand arising from growing population and rapid economic growth. Consequently, the environment in these cities has deteriorated alarmingly. This paper assesses the role of FDI in urban environmental management (UEM) by analyzing the linkages between them for Hanoi City in Vietnam. The paper's analysis and findings are presented under three main themes: one, FDI, employment and income; two, FDI and environmental degradation; and three, potential of utilizing FDI for the provision of urban environmental infrastructure and services (UEI&S) in order to improve the urban environment. Both primary and secondary source data have been used. Policy implications of the research findings are drawn from the perspective of sustainable development.  相似文献   
204.
205.
Assessment of environmental changes in the Orinoco River delta   总被引:1,自引:0,他引:1  
Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m3 s–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this distributary, where successional colonization and species replacement by different species of grasses and mangroves take place. Electronic Publication  相似文献   
206.
Long-term stationary studies on the ecology of the northern mole vole (Ellobius talpinus Pall.), performed by the mark–recapture method from 1985 to 1997, have provided original data on population dynamics and structure. The analysis shows that, to reveal cyclic fluctuations of population size in this species, the period of three years should be taken as a unit of time for estimating the duration of one phase. The 12-year population cycle in E. talpinus has four distinct phases: an increase, a peak, a decline, and a minimum. At each phase, the population is characterized by certain features of family structure, age composition, birth and death rates, and the composition of migrants.  相似文献   
207.
We present a case of ultrasonographic prenatal diagnosis at 24 weeks of femur—fibula—ulna (FFU) complex. To our knowledge, this is the first report of an early prenatal diagnosis of FFU.  相似文献   
208.
209.
210.
Observations of air temperature changes in a steppe marmot burrow were performed from late July to mid-October. Until early September, temperature in the burrow remained relatively constant, but then it began to decrease rapidly. This occurred after air temperature above the ground became equal to the temperature in the burrow. Supposedly, it is in this particular period that marmots begin to plug the entrance to the burrow with earth, thus reducing heat exchange between the increasingly cold aboveground air and the air in the burrow.  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