全文获取类型
收费全文 | 15026篇 |
免费 | 163篇 |
国内免费 | 115篇 |
专业分类
安全科学 | 467篇 |
废物处理 | 653篇 |
环保管理 | 2366篇 |
综合类 | 2794篇 |
基础理论 | 3482篇 |
环境理论 | 8篇 |
污染及防治 | 3827篇 |
评价与监测 | 908篇 |
社会与环境 | 715篇 |
灾害及防治 | 84篇 |
出版年
2022年 | 117篇 |
2021年 | 129篇 |
2020年 | 94篇 |
2019年 | 116篇 |
2018年 | 223篇 |
2017年 | 194篇 |
2016年 | 340篇 |
2015年 | 251篇 |
2014年 | 331篇 |
2013年 | 1205篇 |
2012年 | 429篇 |
2011年 | 620篇 |
2010年 | 494篇 |
2009年 | 564篇 |
2008年 | 601篇 |
2007年 | 679篇 |
2006年 | 585篇 |
2005年 | 471篇 |
2004年 | 498篇 |
2003年 | 500篇 |
2002年 | 451篇 |
2001年 | 507篇 |
2000年 | 372篇 |
1999年 | 265篇 |
1998年 | 164篇 |
1997年 | 174篇 |
1996年 | 167篇 |
1995年 | 227篇 |
1994年 | 199篇 |
1993年 | 178篇 |
1992年 | 165篇 |
1991年 | 193篇 |
1990年 | 170篇 |
1989年 | 161篇 |
1988年 | 167篇 |
1987年 | 149篇 |
1986年 | 132篇 |
1985年 | 129篇 |
1984年 | 173篇 |
1983年 | 160篇 |
1982年 | 166篇 |
1981年 | 128篇 |
1980年 | 118篇 |
1979年 | 131篇 |
1978年 | 105篇 |
1977年 | 104篇 |
1976年 | 92篇 |
1975年 | 104篇 |
1974年 | 116篇 |
1972年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
131.
James Gitundu Kairo Farid Dahdouh-Guebas Patrick O.Gwada Catrick O.Gwada Nico Koedam 《Ambio-人类环境杂志》2002,31(8)
本文研究了米达河(南纬3°20',东经40°00')两个红树林森林地区(乌永博和基雷普维)带状横断面的红树林植被的结构和恢复型式. 相似文献
132.
133.
134.
135.
J. Heinze H. Remmert F. L. Boschke D. Reinen L. Jaenicke 《Die Naturwissenschaften》1983,70(11):575-576
136.
137.
138.
139.
Forty-two open neural tube defects (NTDs) were identified in our series of 7440 amniocenteses tested between 11 and 15 weeks of gestation. Using a cut-off of ≥2.0 MOM, the detection rate for open NTDs was 95 per cent; 100 per cent each for anencephaly and spina bifida; and 78 per cent for encephalocele. Two encephaloceles had AFP levels less than 2.0 MOM and negative AChEs. Thirty-four (81 per cent) of these NTDs were tested between 13 and 15 weeks and 8 (19 per cent) before 13 weeks. There were 0.6 per cent false positives by AFP (excluding serious abnormalities and fetal death) and 0.1 per cent after AChE. The likelihood of an open NTD after an elevated AFP (≥2.0 MOM) was 24 and 77 per cent for any serious abnormality. These results, when combined with an earlier study, indicate that amniotic fluid AFP appears to be as sensitive a test for open NTDs between 13 and 15 weeks as between 16 and 20 weeks. Additional experience is necessary to determine this before 13 weeks. 相似文献
140.
Dr Marianne Johansen Marian Knight Edward J. Maher Kim Smith Ian L. Sargent 《黑龙江环境通报》1995,15(10):921-931
Trophoblast deportation is known to occur in normal human pregnancy, but it is not yet clear whether these cells routinely enter the maternal peripheral circulation and are available as a source of fetal DNA for non-invasive prenatal diagnosis of genetic disorders. To resolve this issue requires an efficient method of enriching trophoblast from maternal blood combined with a means to confirm its identity. Five different techniques were tested on ten retroplacental blood samples to determine the most sensitive and operator-efficient method. Lysis of red cells alone gave the best recovery of trophoblast but had to be discounted, together with Ficoll density gradient centrifugation, due to the very low purity and the excessive time required. Fluorescence-activated cell sorting (FACS) of pre-enriched trophoblast resulted in the lowest recovery rate (8 per cent) despite a 3250-fold enrichment and a very high purity. Immunomagnetic beads (Dynabeads) coated with anti-CD 16 antibody proved to be the best method for the subsequent immunocytochemical characterization of deported trophoblast. However, IO beads coated with anti-CD45 antibody may be more useful for isolating trophoblast for prenatal diagnosis due to the high purity, enrichment (32-fold), and recovery rate (78 per cent) obtained with this method. 相似文献