全文获取类型
收费全文 | 34854篇 |
免费 | 392篇 |
国内免费 | 418篇 |
专业分类
安全科学 | 889篇 |
废物处理 | 1493篇 |
环保管理 | 4769篇 |
综合类 | 6407篇 |
基础理论 | 9074篇 |
环境理论 | 13篇 |
污染及防治 | 8218篇 |
评价与监测 | 2155篇 |
社会与环境 | 2479篇 |
灾害及防治 | 167篇 |
出版年
2022年 | 254篇 |
2021年 | 261篇 |
2020年 | 232篇 |
2019年 | 229篇 |
2018年 | 911篇 |
2017年 | 854篇 |
2016年 | 996篇 |
2015年 | 551篇 |
2014年 | 736篇 |
2013年 | 2299篇 |
2012年 | 1120篇 |
2011年 | 1981篇 |
2010年 | 1371篇 |
2009年 | 1562篇 |
2008年 | 1844篇 |
2007年 | 2068篇 |
2006年 | 1189篇 |
2005年 | 1063篇 |
2004年 | 1056篇 |
2003年 | 1058篇 |
2002年 | 1028篇 |
2001年 | 1156篇 |
2000年 | 828篇 |
1999年 | 552篇 |
1998年 | 368篇 |
1997年 | 401篇 |
1996年 | 412篇 |
1995年 | 460篇 |
1994年 | 404篇 |
1993年 | 385篇 |
1992年 | 345篇 |
1991年 | 369篇 |
1990年 | 344篇 |
1989年 | 314篇 |
1988年 | 301篇 |
1987年 | 266篇 |
1986年 | 273篇 |
1985年 | 270篇 |
1984年 | 340篇 |
1983年 | 291篇 |
1982年 | 315篇 |
1981年 | 282篇 |
1980年 | 236篇 |
1979年 | 252篇 |
1978年 | 212篇 |
1977年 | 199篇 |
1976年 | 167篇 |
1975年 | 183篇 |
1974年 | 192篇 |
1972年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
New data on the composition of surface assemblages of plant macroremains from soil and swamp samples have been obtained in the study of geomorphologically different localities in the middle reaches of the Nizhnyaya Tunguska River. The results of paleocarpological analysis of forest soil sections supported by relevant palynological and geochronological data are presented. Natural changes of the forest cover over the past 2400 years and quantitative characteristics of the paleoclimate during each stage are described.Translated from Ekologiya, No. 1, 2005, pp. 3–10.Original Russian Text Copyright © 2005 by Koshkarova, Koshkarov. 相似文献
82.
83.
A. Coulomb L'Herminé A. Aboura S. Brisset L. Cuisset V. Castaigne P. Labrune R. Frydman Dr G. Tachdjian 《黑龙江环境通报》2003,23(11):938-943
Prader–Willi syndrome (PWS) results from either paternal deletion of 15q11–q13, or maternal uniparental disomy (UPD) of chromosome 15 or imprinting center mutation. Prenatal diagnosis of PWS is currently indicated for chromosomal parental translocation involving chromosome 15 and for decreased fetal movements during the third trimester of gestation. Here we present the prenatal diagnosis of PWS during the first trimester of gestation and autopsy findings. Chorionic villus sampling (CVS) was performed for advanced maternal age at 13 weeks' gestation. CVS showed mosaicism including cells with a normal karyotype and cells with trisomy 15. Amniocentesis showed cells with a normal karyotype. Molecular analysis demonstrated that the fetus had a typical PWS abnormal methylation profile and maternal disomy for chromosome 15. Fetal ultrasound examination showed slightly enlarged lateral ventricles and hypoplasic male external genitalia without intra-uterine growth retardation. The autopsy showed a eutrophic male fetus with facial dysmorphy, hypoplasic genitalia, abnormal position of both feet and posterior hypoplasia of the corpus callosum. This report points out that in a karyotypically normal fetus with ambiguous male external genitalia and cerebral anomalies, extensive cytogenetic and molecular biology studies are strongly recommended because of risk of PWS. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
84.
85.
86.
87.
Spilt notochord syndrome is an extremely rare form of spinal dysraphism characterized by a complete cleft of the spine and a persistent communication between endoderm and ectoderm. A variant of split notochord syndrome was diagnosed in a 25-week-old fetus showing a prolapsed congenital colostomy and a spinal cystic lesion. The final diagnosis included protruding colon segment, imperforate anus with a rectourethral fistula and lipomyelomeningocele. The ultrasound features of the condition and the post-natal management are discussed. The neonate was successfully treated with a posterior sagittal anorectoplasty, while the lipomyelomeningocele was resected at a later stage. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
88.
89.
90.
Offshore oil and gas production platforms can be a source of chronic stress that could lead to sublethal impacts on resident benthic organisms. In June 1993 and January 1994, genetic diversity of Harpacticoida (Copepoda) living proximal to operating, offshore platforms in the Gulf of Mexico was estimated to test if platforms are associated with strong selective pressures. Because harpacticoids have short generation times and direct benthic development, they are suitable organisms for examining population responses. Genetic diversity was estimated by comparing restriction fragment length polymorphisms generated from mitochondrial DNA amplified by the polymerase chain reaction on individuals of five species (Cletodes sp., Enhydrosoma pericoense, Normanella sp., Robertsonia sp., and Tachidiella sp.). Populations living at Near regions (stations<50 m from a platform) had significantly less haplotype diversity than populations of the same species living at Far regions (stations>3 km from a platform). The levels of haplotype diversity exhibited by the Far populations were similar at three different platforms located hundreds of kilometers apart. The differences in haplotype diversity between Near and Far regions were the result of a higher proportion of dominant haplotypes, and a loss of less common haplotypes. Haplotypic diversity was inversely correlated with a multivariate measurement of levels of sediment contaminants. The pattern of haplotype diversity on the Gulf of Mexico continental shelf seems to consist of a uniform level of haplotype diversity, punctuated by islands of lower diversity around oil and gas platforms. The selective pressures that lead to a loss of genetic diversity may be the result of contaminants, other differences in the physico-chemical environment, or disturbance in general. 相似文献