全文获取类型
收费全文 | 2069篇 |
免费 | 165篇 |
国内免费 | 247篇 |
专业分类
安全科学 | 341篇 |
废物处理 | 30篇 |
环保管理 | 450篇 |
综合类 | 683篇 |
基础理论 | 548篇 |
环境理论 | 8篇 |
污染及防治 | 108篇 |
评价与监测 | 66篇 |
社会与环境 | 190篇 |
灾害及防治 | 57篇 |
出版年
2024年 | 8篇 |
2023年 | 47篇 |
2022年 | 58篇 |
2021年 | 87篇 |
2020年 | 80篇 |
2019年 | 78篇 |
2018年 | 87篇 |
2017年 | 113篇 |
2016年 | 118篇 |
2015年 | 122篇 |
2014年 | 129篇 |
2013年 | 243篇 |
2012年 | 101篇 |
2011年 | 114篇 |
2010年 | 95篇 |
2009年 | 89篇 |
2008年 | 81篇 |
2007年 | 101篇 |
2006年 | 100篇 |
2005年 | 85篇 |
2004年 | 71篇 |
2003年 | 68篇 |
2002年 | 56篇 |
2001年 | 54篇 |
2000年 | 42篇 |
1999年 | 39篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 14篇 |
1995年 | 30篇 |
1994年 | 21篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有2481条查询结果,搜索用时 281 毫秒
991.
基于政府视角的人力资本投资分析 总被引:4,自引:0,他引:4
本文首先分析了政府在人力资本投资中的作用,然后从实现政府工作目标的角度探讨了人力资本投资的重要意义,最后提出增加人力资本投资的政策性建议. 相似文献
992.
Dr Jérôme Solassol Haíssam Rahil Vincent Sapin Didier Lemery Bernard Dastugue Odile Boespflug-Tanguy Isabelle Creveaux 《黑龙江环境通报》2003,23(4):287-291
Prenatal diagnosis of fetal trisomy 21 is usually performed by cytogenetic analysis. This requires lengthy laboratory procedures, high costs and is unsuitable for large-scale screening of pregnant women. Today, trisomy 21 can be rapidly diagnosed within 24 h by molecular analysis of uncultured fetal cells using the semi-quantification of fluorescent PCR products from short tandem repeat (STR) polymorphic markers. The aim of our study was to test a chromosome quantification method on the basis of the analysis of fluorescent PCR products derived from non-polymorphic target genes. Co-amplification of a portion of DSCR1 (Down syndrome Critical Region 1) and the reference gene, CFTR (cystic fibrosis transmembrane regulator) enabled molecular detection of trisomy 21. Our method was successfully tested on a total of 154 amniotic fluids in a blind prospective study. Calculation of the DSCR1/CFTR ratio allowed us to distinguish between 152 normal amniotic fluids (mean ratio 0.99) and 2 amniotic fluids presenting a trisomy 21 status (DSCR1/CFTR ratio of 1.53 and 1.61, respectively). The results obtained by conventional cytogenetic analysis and our quantitative PCR method were concordant in every case. Our gene-based fluorescent PCR approach represents an alternative molecular method for rapid and reliable detection of trisomy 21, which can be helpful in the prenatal diagnosis of women at high risk of fetal trisomy 21. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
993.
994.
Sincetheinternationalgeophysicalyear(IGY,1957—1958),Antarcticahasbeentheobjectofintensivescientificinvestigationbyteamsofscientists... 相似文献
995.
Sun Kee Hong 《环境科学学报(英文版)》1999,11(2):181-187
Throughthestatisticsandtheanalysisoflandscapemap,changesoflandsuseregimeandlandscapestructureduring20yearswereinvestigatedin... 相似文献
996.
Comparing Forecasts of the Global Impacts of Climate Change 总被引:2,自引:0,他引:2
Mendelsohn Robert Williams Larry 《Mitigation and Adaptation Strategies for Global Change》2004,9(4):315-333
This paper utilizes the predictions ofseveral Atmosphere-Ocean GeneralCirculation Models and the Global ImpactModel to create forecasts of the globalmarket impacts from climate change. Theforecasts of market impacts in 2100 varyconsiderably depending on climate scenariosand climate impact sensitivity. The modelsdo concur that tropical nations will behurt, temperate nations will be barelyaffected, and high latitude nations willbenefit. Although the size of theseeffects varies a great deal across models,the beneficial and harmful effects areoffsetting, so that the net impact on theglobe is relatively small in almost alloutcomes. Looking only at market impacts,the forecasts suggest that while the globalnet benefits of abatement are small, thedistribution of damages suggests a largeequity problem that could be addressedthrough a compensation program. The largeuncertainty surrounding these forecastsfurther suggests that continued monitoringof both the climate and impacts isworthwhile. 相似文献
997.
Influence of Llamas, Horses, and Hikers on Soil Erosion from Established Recreation Trails in Western Montana, USA 总被引:8,自引:1,他引:7
T. H. Deluca W. A. Patterson IV W. A. Freimund D. N. Cole 《Environmental management》1998,22(2):255-262
/ Various types of recreational traffic impact hiking trails uniquely and cause different levels of trail degradation; however, trail head restrictions are applied similarly across all types of packstock. The purpose of this study was to assess the relative physical impact of hikers, llamas, and horses on recreational trails. Horse, llama, and hiker traffic were applied to 56 separate plots on an existing trail at Lubrecht Experimental Forest in western Montana. The traffic was applied to plots at intensities of 250 and 1000 passes along with a no-traffic control under both prewetted and dry trail conditions. Soil erosion potential was assessed by sediment yield and runoff (using a Meeuwig type rainfall simulator), changes in soil bulk density, and changes in soil surface roughness. Soil moisture, slope, and rainfall intensity were recorded as independent variables in order to evaluate the extent that they were held constant by the experimental design. Horse traffic consistently made more sediment available for erosion from trails than llama, hiker, or no traffic when analyzed across wet and dry trail plots and high and low intensity traffic plots. Although total runoff was not significantly affected by trail user, wet trail traffic caused significantly greater runoff than dry trail traffic. Llama traffic caused a significant increase in sediment yield compared to the control, but caused erosion yields not significantly different than hiker traffic. Trail traffic did not increase soil compaction on wet trails. Traffic applied to dry trail plots generally resulted in a significant decrease in soil bulk density compared to the control. Decreased soil bulk density was negatively correlated with increased sediment yield and appeared to result in increased trail roughness for horse traffic compared to hiker or llama traffic. Differences described here between llama and horse traffic indicate that trail managers may want to consider managing packstock llamas independent of horses.KEY WORDS: Recreational impacts; Sediment yield; Trail degradation 相似文献
998.
999.
An ECO-optimized reuse of process liquors addresses the financial gain and the effective use of resources. In processes that have a potential for process liquor recovery, the minimization of both economic and environmental burdens can be realised by an ECO-optimal design of reuse and recycling network (RRN).In this paper, a procedure for synthesizing such an RRN for a metal finishing process is investigated. The simultaneous analysis of environmental impact sensitivity (SAEIS) based on a superstructure approach, combined with multi-objective optimization is performed by mixed-integer nonlinear programming (MINLP). This allows an “eco–eco” trade-off i.e. total annualized cost and environmental impacts are minimized simultaneously. By varying the weighting factor, different RRN alternatives were generated. A replacement of the standard and closed-loop system by these solutions, even for the environmentally friendliest case, yielded a reasonable cost saving on raw material's inputs. 相似文献
1000.
以南通市为例,探索宏观层面的城市人居环境生态评估方法.通过统计、整理南通市人居环境数据资料,建立城市人居环境宏观评估模型及其评估指标体系(共25项指标),进而分析并评价南通市人居环境整体现状. 相似文献