全文获取类型
收费全文 | 39801篇 |
免费 | 435篇 |
国内免费 | 339篇 |
专业分类
安全科学 | 1291篇 |
废物处理 | 1700篇 |
环保管理 | 5433篇 |
综合类 | 7133篇 |
基础理论 | 10113篇 |
环境理论 | 14篇 |
污染及防治 | 9829篇 |
评价与监测 | 2535篇 |
社会与环境 | 2293篇 |
灾害及防治 | 234篇 |
出版年
2022年 | 307篇 |
2021年 | 368篇 |
2019年 | 299篇 |
2018年 | 529篇 |
2017年 | 546篇 |
2016年 | 850篇 |
2015年 | 657篇 |
2014年 | 987篇 |
2013年 | 3211篇 |
2012年 | 1228篇 |
2011年 | 1671篇 |
2010年 | 1327篇 |
2009年 | 1438篇 |
2008年 | 1728篇 |
2007年 | 1679篇 |
2006年 | 1528篇 |
2005年 | 1311篇 |
2004年 | 1294篇 |
2003年 | 1272篇 |
2002年 | 1172篇 |
2001年 | 1428篇 |
2000年 | 1004篇 |
1999年 | 653篇 |
1998年 | 473篇 |
1997年 | 488篇 |
1996年 | 535篇 |
1995年 | 592篇 |
1994年 | 543篇 |
1993年 | 484篇 |
1992年 | 508篇 |
1991年 | 497篇 |
1990年 | 480篇 |
1989年 | 475篇 |
1988年 | 424篇 |
1987年 | 363篇 |
1986年 | 359篇 |
1985年 | 375篇 |
1984年 | 384篇 |
1983年 | 373篇 |
1982年 | 394篇 |
1981年 | 351篇 |
1980年 | 295篇 |
1979年 | 301篇 |
1978年 | 278篇 |
1977年 | 239篇 |
1976年 | 234篇 |
1975年 | 231篇 |
1974年 | 247篇 |
1973年 | 270篇 |
1972年 | 244篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
471.
Stuhlbacher A Bradley MC Naylor C Calow P 《Environmental pollution (Barking, Essex : 1987)》1993,80(2):153-158
The extent to which responses to toxicants can be modified by the environment and genotype of Daphnia magna is important for interpreting the results from ecotoxicity tests. Variation in the development of cadmium resistance and its relevance for survivorship has been investigated in two genetically distinct clones of D. magna. Cadmium resistance was induced by pre-exposing daphnids to a sublethal concentration of a Cd/Zn mixture and thereafter cadmium tolerance was assessed in standard acute tests. The results showed that the ability to develop cadmium resistance is affected by temperature, but there is no consistent pattern for maternal nutrition. The age of the daphnids had no apparent effect on the development of cadmium resistance. Differences in the induction of cadmium resistance between clones were seen only under resource depression. 相似文献
472.
Summary We hypothesise that foraging group size (FGS) and population group size (PGS) in primates and carnivores are related to quantifiable variables indexing the intensity of exploitative competition. Group size is predicted to increase with both food density and travel capabilities, as estimated by the constraint-free day-range (DRs), i.e. the day-range of a solitary individual uninfluenced by competition from conspecifics. We test this exploitation competition hypothesis among primates and carnivores, using data on populations, species and genera. Food density was indexed by population density. Where DRs could be estimated by regression it was found to be correlated with observed day-range (DRm). DRs was therefore indexed by DRm in all species. Population density and DRm were associated with each other, but in a multiple regression each variable contributed independently to explaining variation in group size. PGS was predicted better than FGS, but regressions involving either measure of group size were significant in all analyses. The multiple regression analyses were validated by the method of linear contrasts, which accounts for possible lack of independence among taxa. We conclude that species differences in group size are influenced by both food density and DRs. This suggests that variation in the intensity of exploitation competition is partly responsible for differences in group size.Correspondence to: R.W. Wrangham 相似文献
473.
This paper focuses on community-wide emergencies caused by war-related events in Lebanon at the beginning of June 1982. Mobilization for the "Peace for Galilee" campaign began on Friday, 4th June. Overnight, families were disrupted, husbands and sons were in danger, and within 24 hours there were notifications of casualities and deaths. Families in crisis became a widespread phenomenon. In Herzlia, as in many other communities, a new service - the Emergency Center - emerged under the auspices of the Ministry of Labor and Social Affairs and the Municipality. The authors describe this process of getting organized, the populations served, how the Center was staffed, the role of citizen volunteers, and the types of interventions used to help vulnerable families as well as soldiers home on leave. Stress is placed on the unique type of short-term co-operation achieved between social workers of the local Department of Social Welfare, the staff of the Department of Community Services (especially its Volunteer Bureau), the local liason officer of the Israel Defence Force, the municipal government, and public-spirited volunteers. Mention is made of conditions which made possible the activation of such a service within hours, of the Center's capacity to serve all segments of the population, and of how it was deactivated within a few weeks when the emergency ended. On the basis of lessons learned from this experience, the paper ends with a number of specific recommendations. The authors hope that such innovative forms of crisis-intervention will become part of the helping technology widely available at the community level in future years. 相似文献
474.
475.
Paul A. Rweyemamu 《Natural resources forum》1978,3(1):27-33
This article discusses the problems facing refinery operations in developing countries and possible solutions to them. The topics covered include security of crude oil supply to the developing countries; difficulties encountered in development of indigenous expertise in refinery operation; refinery capacity and the special problems of maintenance and repair facing refinery operators in the developing parts of the world; and the potential for improved refinery operation through increased international co-operation. 相似文献
476.
477.
Epidemiological procedures can be organised under disaster conditions by means of a simple surveillance system and with few personnel.
In the aftermath of the 4 February 1976 earthquake in Guatemala, an information system was organized by which the requisite information for decision-making was obtained with adequate speed and promptness.
The initial epidemiologic informution was based on reports collected during the early days on symptoms observed at hospitals and health centers and in localities and villages in the stricken area.
At a second, post-emergency stage a more elaborate surveillance system was instituted to provide guidance in the investigntwn of outbreaks, evaluate the health activities and establish basic criteria for preventive and control measures. 相似文献
In the aftermath of the 4 February 1976 earthquake in Guatemala, an information system was organized by which the requisite information for decision-making was obtained with adequate speed and promptness.
The initial epidemiologic informution was based on reports collected during the early days on symptoms observed at hospitals and health centers and in localities and villages in the stricken area.
At a second, post-emergency stage a more elaborate surveillance system was instituted to provide guidance in the investigntwn of outbreaks, evaluate the health activities and establish basic criteria for preventive and control measures. 相似文献
478.
The results of recent IAEA intercomparison programs are reviewed. 相似文献
479.
David J. Schaeffer Konanur G. Janardan Harold W. Kerster 《Environment international》1980,4(2):157-162
The “filter model” has been developed to explain the biologic effects of radiation and chemicals. We have examined nearly 300 sets of dose response data, of which 50 are presented here. Responses (induced by radiation and chemicals) which have been examined include in vitro survival studies on animal and plant tissues, induction of cellular aberrations and time to tumor or death. Similar data from in vivo studies has also been examined. All of the data appear to fit the model R = a lnD + b(lnD)2 + c, where R is the response, a and b are parameters fitted by regression to a particular set of data, and c is the response at zero (or lowest) dose. By writing this model in exponential form, it can be seen that the response R results from multistage filtering (by net amounts a and b) of the initial dose, D. The threshold is obtained from this model as the point, , at which the second derivative becomes zero. This is given by when a and b are oppositelt signed. 相似文献
480.