全文获取类型
收费全文 | 2997篇 |
免费 | 184篇 |
国内免费 | 425篇 |
专业分类
安全科学 | 282篇 |
废物处理 | 50篇 |
环保管理 | 594篇 |
综合类 | 1217篇 |
基础理论 | 814篇 |
环境理论 | 2篇 |
污染及防治 | 123篇 |
评价与监测 | 119篇 |
社会与环境 | 315篇 |
灾害及防治 | 90篇 |
出版年
2024年 | 10篇 |
2023年 | 62篇 |
2022年 | 122篇 |
2021年 | 93篇 |
2020年 | 112篇 |
2019年 | 93篇 |
2018年 | 69篇 |
2017年 | 110篇 |
2016年 | 141篇 |
2015年 | 124篇 |
2014年 | 138篇 |
2013年 | 197篇 |
2012年 | 173篇 |
2011年 | 203篇 |
2010年 | 170篇 |
2009年 | 157篇 |
2008年 | 130篇 |
2007年 | 169篇 |
2006年 | 165篇 |
2005年 | 143篇 |
2004年 | 156篇 |
2003年 | 114篇 |
2002年 | 104篇 |
2001年 | 114篇 |
2000年 | 65篇 |
1999年 | 65篇 |
1998年 | 65篇 |
1997年 | 44篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 21篇 |
1993年 | 30篇 |
1992年 | 14篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 5篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 33篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有3606条查询结果,搜索用时 15 毫秒
31.
H酸综合废水治理工艺试验研究及工程应用 总被引:2,自引:0,他引:2
针对H酸母液及T酸一次洗水高含盐量有机废水进行系统的实验研究,结果表明:废水经冷却、结晶、过滤后,用铁屑过滤,石灰乳、PAM处理.使废水COD去除率为50%,脱色率为7O%,BOD/CODcr提高到0.2以上,预期COD去除率达60%以上,BOD去除率达85%以上,NH3—N去除率达80%以上. 相似文献
32.
Dr. Michael J. McCormack Margaret E. Rylance William E. Mackenzie John Newton 《黑龙江环境通报》1990,10(4):253-255
The attitudes of 190 patients who had undergone chorionic villus sampling (CVS) were assessed by means of a questionnaire. One hundred and fifty-two patients replied of whom 68 (45 per cent) were referred because of increased maternal age and in the other 84 cases the indications included previous chromosomal abnormalities, fetal sexing, DNA analysis, and biochemical analysis. One hundred and twenty-two patients had a transcervical procedure, 24 had a transabdominal, and six patients required both procedures. One hundred and forty-one patients (93 per cent) reported CVS to be a satisfactory procedure, and the same percentage thought earlier diagnosis was beneficial. Thirty-nine patients (81 per cent) reported a better experience with CVS than with a previous amniocentesis. A majority of patients (93 per cent) wished a CVS in a future pregnancy and 137 patients (97 per cent) would accept a risk of miscarriage from the procedure of twice that quoted for amniocentesis (1 per cent). 相似文献
33.
The density of red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), necessary to limit boll weevil abundance, Anthonomus grandis Boheman (Coleoptera: Curculionidae), below the action level was determined. An inaction level of 0.4 fire ants per shake bucket sample (i.e., four ants per 10 plant terminals) will provide boll weevil control approximately 90% of the time. A dynamic inaction level is also provided. Total mortality of boll weevil developmental stages including eggs through teneral adults averaged 97.9%. Of 100 boll weevil eggs deposited in cotton squares (flower buds), an average of two adults survive of which about half are female. Thus, the net replacement rate per generation (Ro is 1.0 which, in this case, indicates a stable boll weevil population. 相似文献
34.
A Simulation of Temporal and Spatial Variations in Carbon at Landscape Level: A Case Study for Lake Abitibi Model Forest in Ontario,Canada 总被引:2,自引:0,他引:2
Xiaolu Zhou Changhui Peng Qing-Lai Dang Jiaxin Chen Sue Parton 《Mitigation and Adaptation Strategies for Global Change》2007,12(4):525-543
Using a case study of the Lake Abitibi Model Forest (LAMF), this study aims to assess the temporal and spatial variability
in carbon storage during 1990–2000, and to present a comprehensive estimation of the carbon budget for LAMF's ecosystems.
As well, it provided the information needed by local forest managers to develop ecological and carbon-based indicators and
monitor the sustainability of forest ecosystems. Temporal and spatial carbon dynamics were simulated at the landscape level
using ecosystem model TRIPLEX1.0 and Geographical Information System (GIS). The simulated net primary productivity (NPP) and
carbon storage in forest biomass and soil were compared with field data and results from other studies for Canada's boreal
forests. The results show that simulated NPP ranged from 3.26 to 3.34 tC ha−1 yr−1 in the 1990s and was consistent with the range measured during the Boreal Ecosystem-Atmosphere Studies (BOREAS) in central
Canada. Modeled NPP was also compared with the estimation from remote sensing data. The density of total above-and belowground
biomass was 125.3, 111.8, and 106.5 tC ha−1 for black spruce, trembling aspen, and jack pine in the LAMF ecosystem, respectively. The total carbon density of forested
land was estimated at 154.4 tC ha−1 with the proportion of 4:6 for total biomass and soil. The analysis of net carbon balance of ecosystem suggested that the
LAMF forest ecosystem was acting as a carbon sink with an allowable harvest in the 1990s. 相似文献
35.
At a rice-wheat rotational free-air CO2 enrichment(FACE) platform, the effect of elevated atmospheric CO2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmospheric CO2 (ambient 370 μl/L 200 μl/L).32 families and 40 genera of nematode were observed in soil suspensions during the study period. Under FACE treatment, the numbers of total nematodes, bacterivores and fungivores exhibited an increasing trend. Because of the seasonal variation of soil temperature and moisture, the effect of elevated atmospheric CO2 on soil nematodes was only observed under favorable conditions. The response of nematode communities to elevated atmospheric CO2 may indicate the change of soil food web. 相似文献
36.
在分析中国耕地总量动态平衡政策产生背景及区域耕地数量变化驱动因素的基础上,通过建立耕地总量动态平衡政策运行效果评价的社会经济影响因素分析模型,根据当前长江三角洲地区社会经济发展的趋势,认为2005年这一地区是有可能实现耕地总量动态平衡这一政策目标的。但是,2010年该地区耕地拥有量将与耕地总量动态平衡目标相差9.12%,因而实现耕地总量动态平衡的难度较大。同时,研究区域所属的11个城市耕地总量动态平衡政策目标实现的可能性也不一样,具体有4种类型:一是可以实现平衡的,为江苏省泰州市和浙江省湖州市;二是较难实现平衡的,有江苏省南通市、镇江市、常州市和浙江省嘉兴市;三是难以实现平衡的,有江苏省南京市、苏州市、无锡市和扬州市;四是实现平衡可能性不大的,为上海市。同时,文章还认为耕地质量的改善对于区域耕地保护具有实质性的积极意义。 相似文献
37.
Effects of acid deposition on forests in south China 总被引:1,自引:0,他引:1
1IntroductionWiththefastgrowingofmodernindustryandsharplyincreasingofenergyconsumptionprimarilycoal,airpolutionandaciddeposit... 相似文献
38.
Carbon Dioxide Balance of Wood Substitution: Comparing Concrete- and Wood-Framed Buildings 总被引:3,自引:0,他引:3
Leif Gustavsson Kim Pingoud Roger Sathre 《Mitigation and Adaptation Strategies for Global Change》2006,11(3):667-691
In this study a method is suggested to compare the net carbon dioxide (CO2) emission from the construction of concrete- and wood-framed buildings. The method is then applied to two buildings in Sweden
and Finland constructed with wood frames, compared with functionally equivalent buildings constructed with concrete frames.
Carbon accounting includes: emissions due to fossil fuel use in the production of building materials; the replacement of fossil
fuels by biomass residues from logging, wood processing, construction and demolition; carbon stock changes in forests and
buildings; and cement process reactions. The results show that wood-framed construction requires less energy, and emits less
CO2 to the atmosphere, than concrete-framed construction. The lifecycle emission difference between the wood- and concrete-framed
buildings ranges from 30 to 130 kg C per m2 of floor area. Hence, a net reduction of CO2 emission can be obtained by increasing the proportion of wood-based building materials, relative to concrete materials. The
benefits would be greatest if the biomass residues resulting from the production of the wood building materials were fully
used in energy supply systems. The carbon mitigation efficiency, expressed in terms of biomass used per unit of reduced carbon
emission, is considerably better if the wood is used to replace concrete building material than if the wood is used directly
as biofuel. 相似文献
39.
Debra Straussfogel 《Mitigation and Adaptation Strategies for Global Change》2006,11(4):911-931
This paper addresses the combined effects of two sources of disturbance on the boreal forest – climate change and the economic
relations of industrial forestry. It describes a theoretical blueprint constructed of concepts from the theory of dissipative
structures (derived from the discipline of physical chemistry) and world-systems theory (derived from the discipline of sociology)
into a proposed integrated theory pivoting on the concept of social vulnerability. The goal is to examine the key concepts
of this theory – vulnerability, resilience and adaptive capacity – as elements of the complex systems perspective provided
by dissipative structure principles. The focus on social vulnerability provides the means to establish the role of external
economic linkages relevant to industrial forestry – the core/periphery relations of the world-system – as they influence the
social vulnerability of the boreal forest SESs. These systems are posited as embedded peripheries, following world-system
criteria, and as the focal scale of analysis within a larger hierarchically organized dissipative structure. The goal is to
suggest and stimulate ideas for further discussion and exploration, motivated by the premise that any successful climate change
mitigation efforts depend on having sound theoretical foundations on which to stand. 相似文献
40.
铜铁矿井下采掘工程的环境影响及生态保护 总被引:2,自引:0,他引:2
对铜铁矿井下采掘工程产生的环境影响进行了分析,外排井下涌水下的铜可对鱼类养殖业水体的地表水质带来不利影响,采用帷幕注浆堵水工艺可防止大面积地表塌陷的发生,对难以避免的局部,小规模塌陷提出了生态安全的预警措施。 相似文献