全文获取类型
收费全文 | 11853篇 |
免费 | 191篇 |
国内免费 | 1580篇 |
专业分类
安全科学 | 368篇 |
废物处理 | 608篇 |
环保管理 | 1220篇 |
综合类 | 3212篇 |
基础理论 | 2654篇 |
环境理论 | 1篇 |
污染及防治 | 3527篇 |
评价与监测 | 752篇 |
社会与环境 | 1073篇 |
灾害及防治 | 209篇 |
出版年
2023年 | 121篇 |
2022年 | 312篇 |
2021年 | 228篇 |
2020年 | 161篇 |
2019年 | 186篇 |
2018年 | 290篇 |
2017年 | 314篇 |
2016年 | 375篇 |
2015年 | 364篇 |
2014年 | 557篇 |
2013年 | 1058篇 |
2012年 | 602篇 |
2011年 | 676篇 |
2010年 | 542篇 |
2009年 | 612篇 |
2008年 | 656篇 |
2007年 | 621篇 |
2006年 | 517篇 |
2005年 | 441篇 |
2004年 | 402篇 |
2003年 | 422篇 |
2002年 | 395篇 |
2001年 | 446篇 |
2000年 | 336篇 |
1999年 | 245篇 |
1998年 | 228篇 |
1997年 | 168篇 |
1996年 | 184篇 |
1995年 | 200篇 |
1994年 | 155篇 |
1993年 | 140篇 |
1992年 | 138篇 |
1991年 | 107篇 |
1990年 | 98篇 |
1989年 | 82篇 |
1988年 | 81篇 |
1987年 | 80篇 |
1986年 | 58篇 |
1985年 | 65篇 |
1984年 | 65篇 |
1983年 | 61篇 |
1982年 | 60篇 |
1981年 | 71篇 |
1980年 | 47篇 |
1979年 | 48篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1974年 | 35篇 |
1973年 | 43篇 |
1972年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
31.
Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD. 相似文献
32.
A. Migné D. Davoult N. Spilmont D. Menu G. Boucher J.-P. Gattuso H. Rybarczyk 《Marine Biology》2002,140(4):865-869
This paper describes a closed-chamber method for measuring CO2 fluxes in intertidal soft sediments during periods of emersion. The method relies on closed-circuit incubations of undisturbed sediment and measurement of CO2 exchanges using an infrared gas analyser. The method was assessed during field experiments, both in light and dark conditions, on an exposed sandy beach and in an estuary. The rates of gross community production measured under moderate irradiance (4.2 mg C m-2 h-1 on the exposed sandy beach and 35 mg C m-2 h-1 in the estuary) are in good agreement with rates reported in the literature. In conjunction with appropriate sampling strategies, this method can be useful for estimating and comparing production of intertidal areas or for assessing factors that influence production. 相似文献
33.
Wastewater disinfection by peracetic acid: assessment of models for tracking residual measurements and inactivation. 总被引:1,自引:0,他引:1
Domenico Santoro Ronald Gehr Timothy A Bartrand Lorenzo Liberti Michele Notarnicola Adele Dell'Erba Dario Falsanisi Charles N Haas 《Water environment research》2007,79(7):775-787
With its potential for low (if any) disinfection byproduct formation and easy retrofit for chlorine contactors, peracetic acid (PAA) or use of PAA in combination with other disinfectant technologies may be an attractive alternative to chlorine-based disinfection. Examples of systems that might benefit from use of PAA are water reuse schemes or plants discharging to sensitive receiving water bodies. Though PAA is in use in numerous wastewater treatment plants in Europe, its chemical kinetics, microbial inactivation rates, and mode of action against microorganisms are not thoroughly understood. This paper presents results from experimental studies of PAA demand, PAA decay, and microbial inactivation, with a complementary modeling analysis. Model results are used to evaluate techniques for measurement of PAA concentration and to develop hypotheses regarding the mode of action of PAA in bacterial inactivation. Kinetic and microbial inactivation rate data were collected for typical wastewaters and may be useful for engineers in evaluating whether to convert from chlorine to PAA disinfection. 相似文献
34.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
35.
36.
37.
38.
本文对用硫化亚铁处理含砷废水时,在气相、液相和固相中砷的形态进行了研究结果表明,在气相中无AaH3,但在As(V)废水的液相中有As(V)和As(Ⅲ)共同存在,在固相中有As(0),FeAsO4(FeAsO3),As2S3(As2S5)和吸附砷,砷的形态变化表明,硫化亚铁处理含砷废水能取得良好的效果,是沉淀、沉淀转化、氧化还原、吸附共沉淀和中和五种反应共同作用的结果。 相似文献
39.
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices. 相似文献
40.
Winer N 《Disasters》1989,13(1):1-8
Food security in Ethiopia is discussed in the context of the repeated famines and the international responses both to them and to the socialist agricultural policies being pursued by Ethiopia. Increasing concern has been expressed by the international donor community regarding the ability of Ethiopia to absorb development funds without a major shift in emphasis in agricultural policy-making. The background to Ethiopia's present vulnerability is shown both in terms of the size of the vulnerable population and in terms of the poor performance of the agricultural sector in the last decade. The author looks at the present agricultural and marketing policy reforms and questions whether they are sufficient to generate the sort of international response needed to create the level of food security that would be required to avert future famines. 相似文献