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53.
前沿技术进步、技术效率和区域经济差距 总被引:1,自引:0,他引:1
采用1998-2009年中国30个省市的人均GDP与当年全国人均GDP的差值作为区域经济差距指标,运用核密度估计方法观察了我国区域经济差距的变动状况。从核密度图可知,我国区域经济呈现出收敛的态势;通过随机前沿模型从全要素生产率中分解出前沿技术进步和技术效率,利用1998-2009年28个省市的面板数据,检验了全要素生产率对区域经济差距的影响。实证结果显示,前沿技术进步能够显著的缩小区域经济差距,其中对于东部地区的效果较为显著,技术效率则能够扩大东部地区的经济差距,对于中部和西部地区的影响不显著。政策含义是缩小东部地区经济差距的主要途径是加大对科技创新领域的投入,加强对欠发达地区的技术支持;对于中部地区和西部地区而言,则应该是加大市场化水平、对外开放水平和地方支出比重。 相似文献
54.
The main focus of this study was to evaluate long term effects of cadmium on forearm bone mineral density after stopping ingestion of cadmium-polluted rice for 10 years in a Chinese population. A total of 532 persons (338 women and 194 men), living in control, moderately and heavily polluted areas, were included in this study. The residents living in the polluted area ceased ingesting cadmium-polluted rice in 1996. All participants were require to answer a questionnaire and the bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA) at the proximal radius and ulna. Samples of urine and blood were collected for determination of cadmium in urine (UCd) and blood (BCd).The BMD of subjects living in the heavily polluted area was significantly lower than that of those living in control area in both men and women (p < 0.01). For the people living in the moderately polluted area, only the women's BMD was greatly lower compared to that in the control area (p < 0.05). The BMD declined with the increasing BCd and UCd in both sexes, especially in the highest level (BCd > 5 µg/L, UCd > 10 µg/g crea) groups (p < 0.01). It was found that there were significant differences in the prevalence of osteoporosis among the different areas (χ2 = 13.046, p = 0.0003) and different UCd groups (χ2 = 4.511, p = 0.0337) in women, but not in men (χ2 = 0.962, p = 0.3268; χ2 = 1.906, p = 0.1675). But a significant difference exists in the prevalence of osteoporosis among different BCd groups in both genders (χ2 = 9.304, p = 0.00229, in women; χ2 = 4603, p = 0.0319, in men). This study suggested that cadmium could play a long-term role on bone and more attention should be paid to cadmium effects on bone metabolism after reduction of exposure. 相似文献
55.
长江中上游防护林体系森林植被碳贮量及固碳潜力估算 总被引:6,自引:0,他引:6
基于“八五”期间长江中上游流域各省的森林资源调查资料,结合经典的材积源生物量法估算了长江中上游防护林体系生物量碳密度和碳贮量,并根据不同树种生物量-生产力回归关系推算了该地区当前的固碳潜力。结果表明:长江中上游地区森林平均碳密度为2575 t/hm2;碳贮量为1 39459 Tg (1 Tg = 1012 g),其中林分(包括经济林)碳贮量为1 20430 Tg,灌木林为13437 Tg,竹林为5592 Tg,三者分别占总碳贮量的8636%、963%和401%。整个防护林体系森林植被的固碳潜力为36856 Tg/a。位于本区西部的四川盆地嘉陵江流域和西部高山峡谷区,其森林碳密度、碳贮量和固碳潜力较高,而东部地区的川鄂山地长江干流、鄱阳湖水系以及洞庭湖水系相对较低,因此,长江中上游森林碳密度、碳贮量和固碳潜力总体上呈现自西向东逐渐降低的趋势。 相似文献
56.
This study has indicated that there is close relationship between development density and environmental quality; therefore,
it is necessary to decide the form of development carefully beforehand. The form of development is shaped either by new development
or urban renewal which is a major tactic nowadays adopted by the Hong Kong Government to improve the living condition of the
citizens and the quality of the built environment. This study is limited to urban renewal and aims to find out the major urban
design considerations for sustaining the environment. Through a questionnaire survey carried out in Hong Kong, the opinions
of architects, planners, property development managers, and local citizens were sought and evaluated, and critical design
factors for enhancing environmental sustainability of urban renewal projects are highlighted. The results derived from factor
analysis indicated that certain design considerations should be incorporated for sustaining the urban environment. “Land Use
Planning”, “Quality of Life”, “Conservation & Preservation”, “Integrated Design”, “Provision of Welfare Facilities”, and “Conservation
of Existing Properties” were believed to be the significant underlying factors for achieving environmental sustainability
of local urban renewal projects.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
57.
采用电称冲击低压系统(ELPI)将无烟室和吸烟室内的空气颗粒物(0.03~10.00 μm)分成12级,对其粒子数和质量浓度进行测定.结果表明,吸烟室PM0.03~10.00的日平均粒子数和质量浓度分别是无烟室的1.50、1.13倍.烟草烟雾对室内颗粒物粒子数的影响集中在0.03~1.00 μm粒径段;对室内颗粒物质量浓度的影响表现为双模态结构,峰值分别在0.20~0.70、5.00~8.20 μm粒径段.烟草烟雾颗粒物的粒子数和质量浓度随烟雾消散时间的增加而减少,粒径越小,减小的越明显;烟草烟雾颗粒物在室内消散缓慢,会在长时间内造成影响,应引起足够关注. 相似文献
58.
Silvina Vargas Gil Analia Becker Claudio Oddino Mónica Zuza Adriana Marinelli Guillermo March 《Environmental management》2009,44(2):378-386
Soil microbial populations can fluctuate in response to environmental changes and, therefore, are often used as biological
indicators of soil quality. Soil chemical and physical parameters can also be used as indicators because they can vary in
response to different management strategies. A long-term field trial was conducted to study the effects of different tillage
systems (NT: no tillage, DH: disc harrow, and MP: moldboard plough), P fertilization (diammonium phosphate), and cattle grazing
(in terms of crop residue consumption) in maize (Zea mays L.), sunflower (Heliantus annuus L.), and soybean (Glycine max L.) on soil biological, chemical, and physical parameters. The field trial was conducted for four crop years (2000/2001,
2001/2002, 2002/2003, and 2003/2004). Soil populations of Actinomycetes, Trichoderma spp., and Gliocladium spp. were 49% higher under conservation tillage systems, in soil amended with diammonium phosphate (DAP) and not previously
grazed. Management practices also influenced soil chemical parameters, especially organic matter content and total N, which
were 10% and 55% higher under NT than under MP. Aggregate stability was 61% higher in NT than in MP, 15% higher in P-fertilized
soil, and also 9% higher in not grazed strips, bulk density being 12% lower in NT systems compared with MP. DAP application
and the absence of grazing also reduced bulk density (3%). Using conservation tillage systems, fertilizing crops with DAP,
and avoiding grazing contribute to soil health preservation and enhanced crop production. 相似文献
59.
J. Juri Ayub D.E. Di Gregorio H. Velasco H. Huck M. Rizzotto F. Lohaiza 《Journal of environmental radioactivity》2009
The 7Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the 7Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. 7Be activity concentration in rainwater ranged from 0.7 ± 0.3 Bq l−1 to 3.2 ± 0.7 Bq l−1, with a mean value of 1.7 Bq l−1 (sd = 0.53 Bq l−1). No relationship was found between 7Be content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. 7Be ground deposition was found to be well correlated with rainfall amount (R = 0.92). For the precipitation events considered, the 7Be depositional fluxes ranged from 1.1 to 120 Bq m−2, with a mean value of 32.7 Bq m−2 (sd = 29.9 Bq m−2). The annual depositional flux was estimated at 1140 ± 120 Bq m−2 y−1. Assuming the same monthly deposition pattern and that the 7Be content in soil decreases only through radioactive decay, the seasonal variation of 7Be areal activity density in soil was estimated. Results of this investigation may contribute to a valuable characterization of 7Be input in the explored semiarid ecosystem and its potential use as tracer of environmental processes. 相似文献
60.
E. L. Zheleznaya 《Russian Journal of Ecology》2009,40(1):39-43
The overgrowing of meadow-bog communities by shrubs and trees (age 5–40 years, crown closure 0.4–0.9) leads to a decrease in incident illumination. As a consequence, juvenile and generative plants disappear from D. incarnata population loci, their average ecological density decreases, and the loci enter the state of regression. The digging activity of wild boars disrupts phytocenotically closed groups of longirhizomatous herbs, thereby creating favorable conditions for seed reproduction of D. incarnata. The species begins to form population loci with a complete ontogenetic spectrum and high ecological density, eventually restoring the normal (definitive) population structure. 相似文献