全文获取类型
收费全文 | 4155篇 |
免费 | 158篇 |
国内免费 | 307篇 |
专业分类
安全科学 | 320篇 |
废物处理 | 221篇 |
环保管理 | 726篇 |
综合类 | 855篇 |
基础理论 | 795篇 |
环境理论 | 3篇 |
污染及防治 | 1186篇 |
评价与监测 | 285篇 |
社会与环境 | 166篇 |
灾害及防治 | 63篇 |
出版年
2023年 | 42篇 |
2022年 | 88篇 |
2021年 | 84篇 |
2020年 | 70篇 |
2019年 | 57篇 |
2018年 | 105篇 |
2017年 | 122篇 |
2016年 | 128篇 |
2015年 | 131篇 |
2014年 | 153篇 |
2013年 | 400篇 |
2012年 | 213篇 |
2011年 | 273篇 |
2010年 | 209篇 |
2009年 | 213篇 |
2008年 | 230篇 |
2007年 | 246篇 |
2006年 | 220篇 |
2005年 | 173篇 |
2004年 | 146篇 |
2003年 | 166篇 |
2002年 | 136篇 |
2001年 | 137篇 |
2000年 | 101篇 |
1999年 | 78篇 |
1998年 | 52篇 |
1997年 | 58篇 |
1996年 | 43篇 |
1995年 | 39篇 |
1994年 | 45篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 37篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 30篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1971年 | 6篇 |
1957年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有4620条查询结果,搜索用时 62 毫秒
31.
32.
33.
Material within the terrestrial environment is rarely homogeneously distributed, either spatially or temporally. One consequence of heterogeneity is that uncertainty is usually generated in measurements that are taken with the aim of characterising the environment. For example, a measurement of analyte concentration within soil taken from one sampling location on contaminated land can vary substantially when compared against another sample taken at effectively the same nominal location. The measurement uncertainty arising from the heterogeneity can substantially limit the reliability of the interpretations made upon environmental investigations. The sampling uncertainty usually outweighs the analytical uncertainty from the laboratory, often by a factor of 20 or more. One approach to reducing the uncertainty is to design a more suitable sampling strategy. This might be achieved by predicting the degree of heterogeneity prior to the investigation, but this is often difficult to achieve accurately. Another approach, which was investigated here, is to actually characterise the heterogeneity prior to the main investigation using rapid and inexpensive technology, such as in situ measurement techniques. In situ portable X-ray fluorescence (PXRF) and X-ray microprobe (XMP) techniques were employed to test the feasibility of this approach. Two contrasting contaminated land sites were chosen to characterise the two-dimensional spatial heterogeneity of heavy metal contamination in topsoil at a range of scales (50 m to 0.001 m). The spatial heterogeneity of contaminants, expressed as relative standard deviations, was found to differ between the two sites by a factor of two, largely due to the mode of deposition of pollution. The study also indicated that the heterogeneity did not change systematically with the scale of measurement between sampling locations at either site. 相似文献
34.
Land degradation is a consequence stemming from both natural processes and social economic activities. On the bases of analyzing general situation of agricultural land degradation in China, the monetary estimating methods such as market value method and shadow engineering method were used to quantitatively assess the economic loss resulting from land deterioration. Results showed that the economic loss in 1999 was 326.8l billion RMB Yuan, which accounted for 4.1% of GDP in the same year of China. If taking five items namely farmland conversion, soil erosion, salinization, decline in reservoir functions, and siltation in waterways and, comparing with that in 1992, the percentage of economic loss to GDP has increased by 1.5 in the only 7 years. 相似文献
35.
Paul Uvebrant Eva Björck Nils Conradi Klas-Henry Hökegård Tommy Martinsson Jan Wahlström 《黑龙江环境通报》1993,13(7):651-657
A family with two siblings, 10 and 8 years old, both with clinical and ultrastructural evidence of juvenile neuronal ceroid lipofuscinosis is described. The family was found to be informative for the restriction fragment length polymorphisms (RFLPs) detected by the probes pCJ52–95Ml (locus D16S148) and pCJ52-94Tl (locus D16S159) flanking the juvenile neuronal ceroid lipofuscinosis locus, CLN3. The parents were both heterozygous using these probes, while their two children with juvenile neuronal ceroid lipofuscinosis were both homozygous. Chorionic villi analysis showed that the fetus was heterozygous and had inherited the one allele of the mother which was not found in the two siblings. This suggested that the fetus had derived one healthy allele from the mother, the risk for a double crossing-over being less than 1 per cent. Electron microscopy showed no fingerprint inclusions in chorionic villi. The child was investigated at 6 months of age and found to be healthy, as new fingerprint inclusions were found at electron microscopy and no vacuolated lymphocytes were found in the blood smear. Due to the risk of heterogeneity, both DNA-based analysis and electron microscopy on chorionic villi are recommended for prenatal examination for juvenile neuronal ceroid lipofuscinosis. 相似文献
36.
37.
Effects of atmospheric mercury pollution on terrestrial ecosystem in Chongqing, China 总被引:1,自引:0,他引:1
1 IntroductionMercury(Hg)asaglobalpollutanthascausedconcernworldwidesincetheendof 1980s.Itisemittedtotheatmospherefrombothanthropogenicandnaturalsources.Importantsourceoftheformeristhedischargefrom productionanduseofHgaswellasthecombustionoffossilfuels(Nri… 相似文献
38.
G.L. Feng J. Letey A.C. Chang M. Campbell Mathews 《Agriculture, ecosystems & environment》2005,110(3-4):219-229
Large scale dairy operations are common. In many cases the manure is deposited on a paved surface and then removed with a flushing system, after which the solids are separated, the liquid stored in ponds, and eventually the liquid applied on adjacent crop land. Management of liquid manure to maximize the fertilizer value and minimize water quality degradation requires knowledge of the interactive effects of mineralization of organic N (ON) to NH4+, crop uptake of mineral N, and leaching of NO3− on a temporal basis. The purpose of the research was to use the ENVIRO-GRO model to simulate how the amount of applied N, timing of N application, ON mineralization rates, chemical form of N applied, and irrigation uniformity affected (1) yields of corn (Zea mays) in summer and a forage grass in winter in a Mediterranean climate and (2) the amount of NO3− leached below the root zone. This management practice is typical for dairies in the San Joaquin Valley of California. The simulations were conducted for a 10-year period. Steady state conditions, whereby an equivalent amount of N applied in the organic form will be mineralized in a given year, are achieved more rapidly for materials with high mineralization rates. Both timing and total quantity of N application are important in affecting crop yield and potential N leaching. Major conclusions from the simulations are as follows. Frequent low applications are preferred to less frequent higher applications. Increasing the amount of N application increased both the crop yield and the amount of NO3− leached. Increasing irrigation uniformity increased crop yields but had variable effects on the amount of NO3− leached. A winter forage crop following a summer corn crop effectively reduced the leaching of residual soil N following the corn crop. 相似文献
39.
本文以呼市发电厂废水、粉尘和灰场污染治理为例,研究制定发电厂粉煤灰综合治理与回收利用技术方案、旧灰场的生态工程建设和冲灰水的回收利用方案,通过污染物治理,废水的利用率达到85%,粉煤灰处理后的产草量和年利用率为98%,灰场的植被覆盖度达到97%,通过治理使发电厂的污染物排放量减少,废弃物资源得以利用,灰场变成环境优美的生态旅游区,为我国电厂的治理工作提供一个切实可行的科学依据。 相似文献
40.