全文获取类型
收费全文 | 18560篇 |
免费 | 409篇 |
国内免费 | 3107篇 |
专业分类
安全科学 | 616篇 |
废物处理 | 1297篇 |
环保管理 | 1886篇 |
综合类 | 5686篇 |
基础理论 | 4570篇 |
污染及防治 | 5035篇 |
评价与监测 | 1354篇 |
社会与环境 | 1271篇 |
灾害及防治 | 361篇 |
出版年
2024年 | 13篇 |
2023年 | 165篇 |
2022年 | 461篇 |
2021年 | 385篇 |
2020年 | 295篇 |
2019年 | 307篇 |
2018年 | 1740篇 |
2017年 | 1713篇 |
2016年 | 1572篇 |
2015年 | 562篇 |
2014年 | 677篇 |
2013年 | 923篇 |
2012年 | 1196篇 |
2011年 | 2092篇 |
2010年 | 1279篇 |
2009年 | 1131篇 |
2008年 | 1524篇 |
2007年 | 1727篇 |
2006年 | 523篇 |
2005年 | 379篇 |
2004年 | 312篇 |
2003年 | 394篇 |
2002年 | 408篇 |
2001年 | 252篇 |
2000年 | 299篇 |
1999年 | 301篇 |
1998年 | 245篇 |
1997年 | 223篇 |
1996年 | 193篇 |
1995年 | 158篇 |
1994年 | 120篇 |
1993年 | 118篇 |
1992年 | 107篇 |
1991年 | 87篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1979年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
Dinh Hieu Vu Kuen-Sheng Wang Jung-Hsing Chen Bui Xuan Nam Bui Hoang Bac 《Waste management (New York, N.Y.)》2012,32(12):2306-2314
Along with the gradually increasing yield of the residues, appropriate management and treatment of the residues have become an urgent environmental protection problem. This work investigated the preparation of a glass–ceramic from a mixture of bottom ash and fly ash by petrurgic method. The nucleation and crystallization kinetics of the new glass–ceramic can be obtained by melting the mixture of 80% bottom ash and 20% fly ash at 950 °C, which was then cooled in the furnace for 1 h. Major minerals forming in the glass–ceramics mainly are gehlenite (Ca2Al2SiO7) & akermanite (Ca2MgSiO7) and wollastonite (CaSiO3). In addition, regarding chemical/mechanical properties, the chemical resistance showing durability, and the leaching concentration of heavy metals confirmed the possibility of engineering and construction applications of the most superior glass–ceramic product. Finally, petrurgic method of a mixture of bottom ash and fly ash at 950 °C represents a simple, inexpensive, and energy saving method compared with the conventional heat treatment. 相似文献
872.
873.
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
874.
Richard C. Foltz 《Journal of Agricultural and Environmental Ethics》2007,20(6):533-542
875.
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
876.
877.
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
878.
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
879.
The discovery of cell-free DNA (cfDNA) in maternal plasma has opened up new promises for the development of non-invasive prenatal testing (NIPT). Application of cfDNA in NIPT of fetus diseases and abnormalities is restricted by the low amount of fetal DNA molecules in maternal plasma. Fetus-derived cfDNA in maternal plasma are shorter than maternal DNA, thus leveraging the maternal and fetus-derived cfDNA molecules size difference has become a novel and more accurate method for NIPT. However, multiple biological properties such as size distribution of plasma DNA, proportion of fetal-derived DNA and methylation levels in maternal plasma across different gestational ages still remain largely unknown. Further insights into the size distribution and fragmentation pattern of circulating plasma cfDNA will shed light on the origin and fragmentation mechanisms of cfDNA during physiological and pathological processes in prenatal diseases and enhance our ability to take the advantage of plasma cfDNA as a molecular diagnostic tool. In the review, we start by summarizing the research techniques for the determination of the fragmentation profiles of cfDNA in maternal plasma. We then summarize the main progress and findings in size profiles of maternal plasma cfDNA and cffDNA. Finally, we discuss the potential diagnostic applications of plasma cfDNA size profiling. 相似文献
880.
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