全文获取类型
收费全文 | 31021篇 |
免费 | 336篇 |
国内免费 | 225篇 |
专业分类
安全科学 | 870篇 |
废物处理 | 1170篇 |
环保管理 | 4142篇 |
综合类 | 4846篇 |
基础理论 | 8859篇 |
环境理论 | 22篇 |
污染及防治 | 8237篇 |
评价与监测 | 1890篇 |
社会与环境 | 1352篇 |
灾害及防治 | 194篇 |
出版年
2022年 | 229篇 |
2021年 | 233篇 |
2020年 | 179篇 |
2019年 | 244篇 |
2018年 | 439篇 |
2017年 | 443篇 |
2016年 | 641篇 |
2015年 | 539篇 |
2014年 | 763篇 |
2013年 | 2289篇 |
2012年 | 943篇 |
2011年 | 1374篇 |
2010年 | 1091篇 |
2009年 | 1076篇 |
2008年 | 1354篇 |
2007年 | 1438篇 |
2006年 | 1254篇 |
2005年 | 1052篇 |
2004年 | 1034篇 |
2003年 | 965篇 |
2002年 | 969篇 |
2001年 | 1256篇 |
2000年 | 868篇 |
1999年 | 557篇 |
1998年 | 429篇 |
1997年 | 441篇 |
1996年 | 445篇 |
1995年 | 490篇 |
1994年 | 440篇 |
1993年 | 403篇 |
1992年 | 414篇 |
1991年 | 378篇 |
1990年 | 379篇 |
1989年 | 412篇 |
1988年 | 348篇 |
1987年 | 301篇 |
1986年 | 276篇 |
1985年 | 305篇 |
1984年 | 286篇 |
1983年 | 323篇 |
1982年 | 322篇 |
1981年 | 273篇 |
1980年 | 243篇 |
1979年 | 270篇 |
1978年 | 229篇 |
1977年 | 195篇 |
1976年 | 202篇 |
1975年 | 193篇 |
1974年 | 173篇 |
1972年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
This paper documents the rapid expansion and changes in food aid flows to Sub-Saharan Africa up to mid-1985. Trends for Sub-Saharan Africa as a whole and for the more seriously affected countries are examined, as are the comparative experiences of food aid of individual countries in the region. Table 11 lists the Sub-Saharan African countries and indicates the most seriously affected food-short countries, as defined by the WFP/FAO task force. It should be borne in mind that some practical problems exist in compiling data on food aid. These include lack of availability of reliable data, especially of most recent data; lack of common terminology and definitions; and different accounting systems. These data problems are sometimes a source of confusion. However, the basic facts are clear: food aid gradually emerged during the early 1980s as a resource too often of considerable significance to many countries of Sub-Saharan Africa. These trends were only accelerated with the crisis of 1984-1985. These facts provide a point of reference for further analysis of the sources of the crisis, its actual dimensions and consequences. 相似文献
82.
Taylor AJ 《Disasters》1986,10(1):70-73
This paper was prepared in 1978 on the basis of a review of sociological and anthropological fieldwork conducted up to that time. Although theoretical in presentation its conclusions are formulated in accordance with the author's own extensive observations of organizational response to natural disasters in developing countries, especially those having sudden onset. Practical implications for co-ordination agencies and pre-disaster training are drawn. 相似文献
83.
Rate-temperature responses in scyphozoan medusae and polyps 总被引:1,自引:0,他引:1
The effects of temperature on oxygen consumption and spontaneous rhythmic activity have been investigated in various stages of the life histories of 3 species of jellyfish from the Chesapeake Bay, USA. All 3 species clearly show the ability to acclimate positively to temperature change. Thermal sensitivity of metabolism in the winter medusa Cyanea capillata fulva is fairly low at temperature intervals which are experienced in nature. Polyps of the two summer medusae, Chrysaora quinquecirrha and Aurelia aurita, show reduced metabolic sensitivity at temperatures normally accompanying high developmental activity and the onset of strobilation. 相似文献
84.
85.
86.
87.
88.
89.
90.