全文获取类型
收费全文 | 1616篇 |
免费 | 76篇 |
国内免费 | 193篇 |
专业分类
安全科学 | 110篇 |
废物处理 | 4篇 |
环保管理 | 173篇 |
综合类 | 984篇 |
基础理论 | 354篇 |
污染及防治 | 23篇 |
评价与监测 | 45篇 |
社会与环境 | 155篇 |
灾害及防治 | 37篇 |
出版年
2024年 | 20篇 |
2023年 | 61篇 |
2022年 | 76篇 |
2021年 | 73篇 |
2020年 | 46篇 |
2019年 | 50篇 |
2018年 | 41篇 |
2017年 | 45篇 |
2016年 | 41篇 |
2015年 | 60篇 |
2014年 | 110篇 |
2013年 | 78篇 |
2012年 | 81篇 |
2011年 | 96篇 |
2010年 | 104篇 |
2009年 | 100篇 |
2008年 | 108篇 |
2007年 | 73篇 |
2006年 | 71篇 |
2005年 | 71篇 |
2004年 | 54篇 |
2003年 | 62篇 |
2002年 | 61篇 |
2001年 | 51篇 |
2000年 | 42篇 |
1999年 | 28篇 |
1998年 | 26篇 |
1997年 | 33篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
排序方式: 共有1885条查询结果,搜索用时 31 毫秒
21.
干旱与半干旱地区土地生产潜力的测定──以新疆阜康县为例 总被引:1,自引:0,他引:1
本文探讨了一个通过土壤有效水分含量来确定土地等级和土地生产力的方法。这个方法采用倍增参量形式来确定土壤有效水分。其变量包括潜水位、土层厚度、土壤质地、坡度和盐分。此项研究证明用这种方法获得的土地初级生产力与实测值比较一致。因此,我们可以在类似环境下用这种方法估测土地生产潜力。 相似文献
22.
23.
我国淡水水域光合产物的气候生产力探讨 总被引:1,自引:0,他引:1
根据太阳辐射在水体中的有效分布、生长季水温和浮游植物光合生态特性等因子,模拟计算了我国大陆东部淡水水域的光合生产力、气候生产力及其季节变化的地理规律。从中得知,这些水域初级产物的年气候生产力主要呈纬向分布,由南向北递减,各地范围在 1.6-24.4gC/m2·a之间,长江以南是>15.0gC/m2·a的高值区,长城以北和四川盆地为<10.0gC/m2·a的低值区,因此,在气候生产力高值区有可能充分利用气候资源优势,开发低成本的自然淡水水域渔业;而在低生产力区,受自然资源的局限其自然捕鱼量需适量控制,因地制宜。 相似文献
24.
广州市荔湾区环保局"保护发展、保护环境"的工作思路,"以人为本,民生为重"的工作原则,以及"环境兴区"思想和"环境就是生产力"的理念,在推进荔湾区经济社会和环境协调发展方面,正发挥着越来越重要的作用. 相似文献
25.
Given the key role of biogenic volatile organic compounds(VOCs) to tropospheric chemistry and regional air quality, it is important to generate accurateVOCs emission inventories. However, only a less fraction of plant species, in temperate grassland of Inner Mongolia, has been characterized by quantitative measurements. A taxonomic methodology, which assigns VOCs measurements to unmeasured species, is an applicable and inexpensive alternation for extensive VOCs emission survey, although data are needed for additional plant families and genera to further validate the taxonomic approach in grassland vegetation. In this experiment, VOCs emission rates of 178 plant species were measured with a portable photoionization detector( PID). The results showed the most of genera and some families have consistent feature of their VOCs emission, especially for isoprene, and provide the basic premise of taxonomic methodology to develop VOCs emission inventories for temperate grassland. Then, the taxonomic methodology was introduced into assigning emission rate to other 96 species, which no measured emission rates available here. A systematical emission inventory of temperate grassland vegetation in Inner Mongolia was provided and further evidence that taxonomy relationship can serve as a useful guide for generalizing the emissions behavior of many, but not all, plant families and genera to grassland vegetation. 相似文献
26.
In this paper,the relationship among land productivity,population pressure and the fluctuation mechanism of ecotone is analyzed,taking coumties and banners of southeast Inner Mongolia plateau as an example,which is the most fragile part in the farming and husbandry interleaving belt of north China due to its severe desertification degree and low level of economic development.The Cv for the total output value of agriculture decreases from southeast to northwest,with the same rule as which the overloading population cumulated distributes,and both indicators have close relation with the high linear coefficient of 0.83.These reveal the fluctuation mechanism for ecotone:fluctuation of the level of economic development is a scientific and practical measure both to weakness degree and to instability of ecotone,because it is a synthesized response to the variation of climate as well as irrational land uses,which reinforce and magnify the fluctuation.In detail,the heavier the population overloading,the severer the grassland reclamation,the stronger the dependence of regional productivity on rainfall,the lower the level of economic development,the rougher the fluctuation of ecotone,but the weaker the PRED system. 相似文献
27.
Vegetation patterns and nature reserve construction in an extremely-arid desert in Anxi,NW China's Gansu Province 总被引:2,自引:0,他引:2
Anxi County is located in the northwestern part of the Hexi Corridor in gansu Province and has the sole national level nature reserve of extremely-arid desert in China.Phytosociological methods (Braun-Blanquet,1964) are used to classify plant community types in this area.Eleven are disting uished,including six of deserts,four of oases and one transitional type between deserts and oases.Direct gradient analysis (DCA) is employed to correlate the distribution of plant communities to physiogeographic conditions.This study makes clear that water is the most important ecological factor for the distribution of plant species and communities in this area.The effects of water have been demonstrated in different ways.A vegetation gradient from lower altitude to higher altitude in the southern part of the reserve is driven by a precipitation gradient.The effects of the depth of ground water table contribute to the differentiation of vegetation from desert to oasis in the flat area.In a finer scale,the washed gullies have obviously higher species richness and also higher vegetation cover than the surround gobi surfaces,possibly caused by the effects of floods.The vegetation patterns demonstrate that the area of Anxi County is a complete landscape unit.The range of the current nature reserve is not large enough for the purpose of conserving the unique biodiversity in this area. 相似文献
28.
科技是第一生产力,但是如果科技不向生产应用转化,将永远是躺在纸上的数字和符号。科学技术的不断发展,它必将推动经济建设的不断发展,不断迈向新的阶段。从大港油田公司的发展历史来看,科学技术对提高劳动生产率、提高经济效益和社会效益,加速油田的经济发展起着至关重要的作用。大港油田公司要想在今后的激烈竞争中站稳脚跟,求取发展,就必须继续走依靠科技求发展的路。 相似文献
29.
30.
应用香根草对垃圾场进行植被恢复及净化垃圾污水的研究 总被引:10,自引:0,他引:10
扼要报道了香根草技术用于垃圾堆放场覆盖改造效果及对垃圾渗滤液的净化效果。结果表明,香根草在这2方面都了良好效益,对垃圾场的生态恢复效果好,对污水的净化效果明显。因此,香根草技术是一种值得在我国南方都市推广的生态环保技术。 相似文献