全文获取类型
收费全文 | 4075篇 |
免费 | 33篇 |
国内免费 | 16篇 |
专业分类
安全科学 | 48篇 |
废物处理 | 266篇 |
环保管理 | 250篇 |
综合类 | 648篇 |
基础理论 | 834篇 |
环境理论 | 4篇 |
污染及防治 | 1446篇 |
评价与监测 | 379篇 |
社会与环境 | 241篇 |
灾害及防治 | 8篇 |
出版年
2023年 | 44篇 |
2022年 | 128篇 |
2021年 | 123篇 |
2020年 | 48篇 |
2019年 | 51篇 |
2018年 | 149篇 |
2017年 | 107篇 |
2016年 | 207篇 |
2015年 | 111篇 |
2014年 | 230篇 |
2013年 | 389篇 |
2012年 | 248篇 |
2011年 | 244篇 |
2010年 | 187篇 |
2009年 | 144篇 |
2008年 | 230篇 |
2007年 | 232篇 |
2006年 | 213篇 |
2005年 | 146篇 |
2004年 | 123篇 |
2003年 | 110篇 |
2002年 | 93篇 |
2001年 | 63篇 |
2000年 | 47篇 |
1999年 | 36篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 26篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1985年 | 7篇 |
1970年 | 6篇 |
1967年 | 7篇 |
1966年 | 11篇 |
1965年 | 15篇 |
1964年 | 28篇 |
1963年 | 12篇 |
1962年 | 17篇 |
1961年 | 11篇 |
1960年 | 9篇 |
1959年 | 26篇 |
1958年 | 25篇 |
1957年 | 17篇 |
1956年 | 13篇 |
1955年 | 18篇 |
1954年 | 7篇 |
排序方式: 共有4124条查询结果,搜索用时 937 毫秒
481.
482.
Héctor M Poggi-Varaldo Liliana M Alzate-Gaviria Antonino Pérez-Hernández Virginia G Nevarez-Morillón Noemí Rinderknecht-Seijas 《Waste management & research》2005,23(3):270-280
The objective of this work was to compare the performance of two laboratory-scale, mesophilic systems aiming at the anaerobic digestion of the organic fraction of municipal solid wastes (OFMSW). The first system consisted of two coupled reactors packed with OFMSW (PBR1.1-PBR1.2) and the second system consisted of an upflow anaerobic sludge bed reactor (UASB) coupled to a packed reactor (UASB2.1-PBR2.2). For the start-up phase, both reactors PBR 1.1 and the UASB 2.1 (also called leading reactors) were inoculated with a mixture of non-anaerobic inocula and worked with leachate and effluent full recirculation, respectively. Once a full methanogenic regime was achieved in the leading reactors, their effluents were fed to the fresh-packed reactors PBR1.2 and PBR2.2, respectively. The leading PBR 1.1 reached its full methanogenic regime after 118 days (Tm, time to achieve methanogenesis) whereas the other leading UASB 2.1 reactor reached its full methanogenesis regime after only 34 days. After coupling the leading reactors to the corresponding packed reactors, it was found that both coupled anaerobic systems showed similar performances regarding the degradation of the OFMSW. Removal efficiencies of volatile solids and cellulose and the methane pseudo-yield were 85.95%, 80.88% and 0.109 NL CH4 g(-1) VS(fed) in the PBR-PBR system; and 88.75%, 82.61% and 0.115 NL CH4 g(-1) VS(fed0 in the UASB-PBR system [NL, normalized litre (273 degrees K, 1 ata basis)]. Yet, the second system UASB-PBR system showed a faster overall start-up. 相似文献
483.
484.
485.
Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for couples at risk of transmitting genetic disorders to their offspring. We present a fluorescence in situ hybridization (FISH) analysis of embryos obtained after seven PGD cycles in six couples with Robertsonian translocations and male factor infertility: 4 der(13;14), 1 der(14;21) and 1 der(15;21). Of 74 metaphase II (MII) injected oocytes, 61 (82.4%) fertilized normally and cleaved. Of these, 37/61 (60.7%) embryos were of high morphological quality with ≥6 blastomeres. After biopsy of 44 embryos at day 3 of development, seven degenerated, seven arrested in development and 30/44 (68.2%) evolved, of which 25/30 (83.3%) reached the morula/blastocyst stage. Analysis of biopsied blastomeres showed 23/44 (52.3%) of normal/balanced embryos, of which 15 (11 at the morula/blastocyst stage) were transferred in six cycles. One term pregnancy was achieved, which ended by cesarean section at 37 weeks of gestation, giving birth to two healthy newborn. Analysis of 49 embryos (excluding 12 inconclusive cases) showed a predominance of alternate segregation (38/49, 77.6%) over adjacent segregation (7/49, 14.3%), with one (2%) being a polyploid mosaic and three (6.1%) chaotic. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
486.
487.
488.
The Science of Nature - 相似文献
489.
490.
Prof. J. M. Gutiérrez-Vázquez 《The Environmentalist》1983,3(3):209-211
Summary This paper looks at the problems of science and technology education in Mexico, and proposes ways in which the quality of education at every level can be improved. It advocates an interdisciplinary approach, and from that approach to science education, the development of environmental education.Prof. Gutiérrez-Vázquez received his training in microbiology and biochemistry in the National Polytechnic Institute in his native Mexico City, receiving his degree in 1954. He went from instructor to assistant professor (1950–1960), becoming a full professor, deputy dean and then dean of the Faculty of Biology in the same Institute (1961–1969); he published two books and some 20 papers dealing with the physiology of tubercle bacillus and other mycobacteria, as well as with other topics on microbiology. More recently (1970 to date), he became a full professor in the Center for Advanced Studies of the same Institute, where he has been head of the Department of Educational Research (1972–1981) and carried out research and development projects on science education for children and adolescents. During this period he has published some 20 more books and 30 odd papers, and written more than 80 science programmes for commercial television. 相似文献