全文获取类型
收费全文 | 19567篇 |
免费 | 764篇 |
国内免费 | 3531篇 |
专业分类
安全科学 | 991篇 |
废物处理 | 1321篇 |
环保管理 | 2004篇 |
综合类 | 6923篇 |
基础理论 | 4639篇 |
环境理论 | 2篇 |
污染及防治 | 4673篇 |
评价与监测 | 1489篇 |
社会与环境 | 1340篇 |
灾害及防治 | 480篇 |
出版年
2024年 | 31篇 |
2023年 | 199篇 |
2022年 | 589篇 |
2021年 | 580篇 |
2020年 | 562篇 |
2019年 | 418篇 |
2018年 | 1891篇 |
2017年 | 1873篇 |
2016年 | 1648篇 |
2015年 | 747篇 |
2014年 | 803篇 |
2013年 | 1091篇 |
2012年 | 1387篇 |
2011年 | 2255篇 |
2010年 | 1390篇 |
2009年 | 1225篇 |
2008年 | 1561篇 |
2007年 | 1842篇 |
2006年 | 507篇 |
2005年 | 396篇 |
2004年 | 316篇 |
2003年 | 365篇 |
2002年 | 346篇 |
2001年 | 223篇 |
2000年 | 235篇 |
1999年 | 239篇 |
1998年 | 223篇 |
1997年 | 189篇 |
1996年 | 161篇 |
1995年 | 124篇 |
1994年 | 122篇 |
1993年 | 85篇 |
1992年 | 59篇 |
1991年 | 44篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1957年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
991.
Ecological footprint (EF) has received considerable attention as a useful indicator in the context of sustainable development. So far, EF has been used in numerous studies by academies, organizations and government authorities. However, the results of these studies failed to be comparable directly with each other due to imprecise data sets, unmodified accounting methods of pasture and fossil energy, ignored secondary products, undefined process Of calculating yield factors and improper biocapacity for biodiversity. In this paper, we elaborated on EF estimating methods from six categories of consumption in order to overcome the limitations above. We adopted precise data and revised methods, calculated EF of some secondary products, introduced weighted factor to calculate yield factors and adjusted biocapacity by an appropriate amount. Meanwhile, we investigated the resource consumption of Liaoning Province in 2006 to assess EF. Its results showed that Liaoning Province overused its natural capital and was in an unsustainable state. We concluded that two specific problems that had arisen in EF assessment and gave some suggestions for Liaoning Province to improve its unsustainable state. 相似文献
992.
杨文玉 《安全.健康和环境》2017,17(6)
运用大数据技术,对硫黄回收装置的工艺运行参数数据及SO_2排放数据进行挖掘与分析,提取与SO_2排放浓度强相关的关键性操作变量,完成硫黄回收装置环保大数据建模,从而实现硫黄回收装置SO_2排放浓度的预测和预警,并自动生成当前工况下硫黄回收装置尾气SO_2达标优化方案。 相似文献
993.
Rapid urbanization in the developing world calls for attention to address the issue of urban sustainability, especially in emerging countries such as China, where social equity and environmental conditions have been marginalized by the rapid economic development. In this paper, we addressed the above issue with an attempt to answer the following questions: (1) How did the sustainability of Chinese cities evolve over time? (2) What are the driving forces for the evolution? By constructing a composite index that incorporates three major aspects of sustainability, economy, environment, and social equity, we characterized the recent evolution of Chinese cities and assessed the disparity among regions in terms of the sustainability measures. Further, we analyzed the driving forces for the change of sustainability indices through a driving force-pressure-state-effect model. We substantiate our numerical analysis of Chinese cities with a detailed case study of Urumqi, the capital of Xinjiang Autonomous Region, which has experienced significant change over the past 3 decades in every aspect of sustainability. We highlight some fundamental socioeconomic driving forces that have caused spatial restructuring, reflected by land-use change, and consequently impacted the urban environment of Urumqi. A brief case analysis of Guangzhou is also provided. 相似文献
994.
Richard C. Foltz 《Journal of Agricultural and Environmental Ethics》2007,20(6):533-542
995.
Quantification and reduction of erroneous differences between images in remote sensing 总被引:1,自引:0,他引:1
The reliability of image data, along with the difficulty of accurately comparing images acquired at different times or from
different sensors, is a generic problem in remote sensing. Measurement repeatability errors occur frequently and can substantially
reduce the system’s ability to reliably quantify real spectral and spatial change in a target. This paper outlines methodologies
for quantifying and reducing erroneous differences between monochrome and multispectral or hyperspectral images. [Each of
these image types is acquired by an instrument that collects light photons across a variable range of the electromagnetic
spectrum (often referred to as an image band). The hyperspectral image is often referred to as a hyperspectral cube with XY
spatial dimensions and many Z bands (spectral demotions)]. In this paper, we specifically discuss the Pixel Block Transform
(PBT), the Spectral Averaging Transform (SAT), and the Wavelet Transform (WAVEL). We briefly address sensor fusion. Results
indicate that the PBT is a powerful cross-noise and repeatability error reducing tool, applicable to monochrome, multispectral,
and hyperspectral images. The SAT is as powerful as the PBT in reducing error but is suitable only for hyperspectral imagery.
WAVEL can reduce some of the finer scale noise, but it is not as powerful in reducing cross-noise as PBT or SAT and it requires
some trial and error for selecting the appropriate wavelet function. It is important that those involved in developing statistically
sound relationships between remotely sensed imagery and other data sources understand the problems and their solutions to
prevent wasting time or developing relationships that are statistically insignificant or unstable, or that lead to faulty
conclusions. 相似文献
996.
The morphogenesis of ephyrae of Atorella vanhoeffeni Bigelow, 1909 (Werner, 1967) and of Nausithoe maculata Jarms, 1990 during strobilation is described. We found differences in the developmental pattern of marginal structures and structural
changes of longitudinal muscle tubes in particular. During strobilation the polyp’s tetraradiate symmetry is passed to the
ephyra of both taxa as a tetraradiate central symmetry that we consider a major plesiomorphic character. The present results
also indicate divergent patterns of ephyra development during strobilation that lead to variable marginal symmetries of ephyrae
and thus of medusae. Therefore, the marginal symmetry of medusae of N. maculata is octoradiate and of A. vanhoeffeni is hexaradiate. We conclude the latter is stated as derived pattern. These results lead us to maintain both families Nausithoidae
and Atorellidae. 相似文献
997.
我国安全生产的形势和任务 总被引:10,自引:0,他引:10
杨富 《中国安全科学学报》2000,10(2):1-6
论述了我国安全生产工作发展概况与安全的关系 ,分析了我国安全生产状况 ;指出了我国安全生产面临的主要难点 ;提出了我国安全生产工作的重任所在 ;笔者认为 ,只要从实际出发 ,坚持改革、标本兼治和技术创新 ,发挥政府、企业、劳动者三方协调机制的作用 ,借鉴和吸收国际成功经验 ,我国安全生产水平是会列于世界先进行列的。 相似文献
998.
Paulina Bolibok Marek Wiśniewski Katarzyna Roszek Artur P. Terzyk 《Die Naturwissenschaften》2017,104(3-4):36
In this study, graphene oxide (GO) has been applied as a matrix for enzyme immobilization. The protein adsorption capacity of GO is much higher than of other large surface area carbonaceous materials. Its structure and physicochemical properties are reported beneficial also for enzymatic activity modifications. The experimental proof was done here that GO-based biocatalytic systems with immobilized catalase are modifiable in terms of catalyzed reaction kinetic constants. It was found that activity and stability of catalase, considered here as model enzyme, closely depend on enzyme/GO ratio. The changes in kinetic parameters can be related to secondary structure alterations. The correlation between enzyme/GO ratio and kinetic and structure parameters is reported for the first time and enables the conscious control of biocatalytic processes and their extended applications. The biological activity of obtained biocatalytic systems was confirmed in vitro by the use of functional test. The addition of immobilized catalase improved the cells’ viability after they were exposed to hydrogen peroxide and tert-butyl-hydroperoxide used as source of reactive oxygen species. 相似文献
999.
Walter Q. Betancourt Sherif Abd-Elmaksoud Charles P. Gerba 《Food and environmental virology》2018,10(2):209-211
This study examined the efficacy of reovirus concentration from large volumes of water using two positively charged filters: Zeta Plus 1MDS and NanoCeram. The results indicated that an average of 61 and 81% of input reoviruses were effectively recovered, respectively, from recycled water and tap water using NanoCeram filtration. 相似文献
1000.
For biofilters treating waste gases containing volatile organic compounds(VOCs), biomass accumulation is a common problem which will induce bed clogging and significant decrease in VOCs removal efficiency during long-term operation. In this study, ozone injection was developed as a biomass control strategy, and its effects on the biofilter performance and the microbial community structure were investigated in long-term operation. Two biofilters,identified as BF1 and BF2, were operated continuously for 160 days treating gaseous toluene under the same conditions, except that 200 mg/m3 ozone was continuously injected into BF1 during days 45–160. During the operation period, ozone injection did not change the toluene removal efficiency, while the pressure drop of BF1 with ozone injection was significantly lowered compared with BF2. The wet biomass accumulation rate of BF1 was 11 g/m~3/hr, which was only46% of that in BF2. According to the carbon balance result, ozone injection also increased the toluene mineralization rate from 83% to 91%, which could be an important reason for the low biomass accumulation. The PMA-q PCR result indicated that ozone injection increased the microbial viability of the biofilm. The high-throughput sequencing result also revealed that the dominant phyla and genera were not changed significantly by ozone injection, but some ozonetolerant genera such as Rhodanobacter, Dokdonella and Rhodococcus were enhanced by ozone exposure. All the results verified that ozone injection is capable of sustaining the long-term performance of biofilters by lowering the biomass accumulation, increasing the microbial viability and changing the microbial community structure. 相似文献