全文获取类型
收费全文 | 50908篇 |
免费 | 549篇 |
国内免费 | 625篇 |
专业分类
安全科学 | 1568篇 |
废物处理 | 2094篇 |
环保管理 | 6684篇 |
综合类 | 8375篇 |
基础理论 | 14016篇 |
环境理论 | 36篇 |
污染及防治 | 13168篇 |
评价与监测 | 3232篇 |
社会与环境 | 2565篇 |
灾害及防治 | 344篇 |
出版年
2022年 | 439篇 |
2021年 | 439篇 |
2020年 | 349篇 |
2019年 | 437篇 |
2018年 | 757篇 |
2017年 | 728篇 |
2016年 | 1112篇 |
2015年 | 896篇 |
2014年 | 1306篇 |
2013年 | 3968篇 |
2012年 | 1621篇 |
2011年 | 2266篇 |
2010年 | 1834篇 |
2009年 | 1882篇 |
2008年 | 2248篇 |
2007年 | 2341篇 |
2006年 | 2050篇 |
2005年 | 1720篇 |
2004年 | 1668篇 |
2003年 | 1695篇 |
2002年 | 1568篇 |
2001年 | 2038篇 |
2000年 | 1419篇 |
1999年 | 889篇 |
1998年 | 666篇 |
1997年 | 670篇 |
1996年 | 679篇 |
1995年 | 752篇 |
1994年 | 748篇 |
1993年 | 636篇 |
1992年 | 656篇 |
1991年 | 615篇 |
1990年 | 653篇 |
1989年 | 641篇 |
1988年 | 559篇 |
1987年 | 495篇 |
1986年 | 423篇 |
1985年 | 478篇 |
1984年 | 478篇 |
1983年 | 495篇 |
1982年 | 482篇 |
1981年 | 440篇 |
1980年 | 360篇 |
1979年 | 407篇 |
1978年 | 358篇 |
1977年 | 278篇 |
1976年 | 285篇 |
1975年 | 290篇 |
1974年 | 257篇 |
1972年 | 288篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
681.
Fifty-three patients who elected to reduce their pregnancies to a twin gestation in our centre are known to have subsequently undergone genetic amniocentesis. Five of these patients lost their entire pregnancy following the genetic amniocentesis procedure. This is equivalent to a 9·4 per cent pregnancy loss rate for reduced twin gestations in comparison with an expected loss rate of 2 per cent for non-reduced twin gestations. 相似文献
682.
IntroductionTheprocessofmunicipalsolidwaste(MSW)isoneofthemostseriousissuesintermsofenvironmentalprotection.ProcessingofMSWwithoutfurtherdisastrouscontaminationcanbeachievedonlyinmodernizedmeasures,suchasincineratingandenergygeneratingconcurrently(Shen… 相似文献
683.
Chinese life cycle impact assessment factors 总被引:5,自引:0,他引:5
IntroductionLifecycleassessment(LCA)isanenvironmentalmanagementtoolthatisusedtoexamineandevaluatetheenvironmentalimpactsassociatedwiththeexistenceofproducts(Jensen,1998;Weidema,1997;Wenzel,1997).ThefocusofLCAisontheentirelifecycleoftheproduct,i.e.fromtheextracti… 相似文献
684.
IntroductionChengdu KunmingRailwayLineislocatedonthemountainregionofsouthwesternChina .Therearealotofdebrisflowgulliesspreadingbesidethisrailwayline .Onsummer,thedebrisflowoftenburstsandthreatensthesafetyoftherailwaytransportation.In 1981,alarge scaledebris… 相似文献
685.
Ten out of the 12 new EU members, used to belong to the so-called “former eastern block”, with a post WWII environmental policy radically different from the tendencies followed in Western Europe. The lack of conservation regulations has resulted in a rather harmful industrialization, regarding natural resources and environmental quality. While air pollution transfer is a phenomenon of transboundary level, there is a particular interest in examining the contribution of the new EU member states to the environmental pressure faced by the older member states and vice versa. The current study utilises the official data for almost 20 years published by the European Monitoring and Evaluation Program concerning the transboundary transfer of NOx and SO2 in order to analyse the situation and discuss the present and future environmental policy regarding air pollution. 相似文献
686.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
687.
A multiple pregnancy of high rank may occur in a couple at risk for a Mendelian disorder. Prenatal diagnosis is hampered by the difficulty of (1) obtaining chorionic villi from each zygote arid (2) unequivocally relating each sample to the corresponding embryo. The calculation of the genetic risk according to the number of zygotes led us to propose a diagnostic strategy based on embryo reduction, a technique initially designed to improve the perinatal outcome of multiple pregnancies with normal embryos. We report a case in which this approach allowed rational use of first-trimester chorionic villus sampling in a quintuplet pregnancy at risk for non-ketotic hyperglycinaemia, resulting in the selective birth of unaffected twins. 相似文献
688.
We describe a new method for the post-mortem examination of the fetal central nervous system. The brain is immobilized in gelatin prior to ultrasonic examination. Correlation with prenatal ultrasound is excellent and subsequent pathological examination is enhanced and facilitated. 相似文献
689.
A case is described of the prenatal diagnosis of choroid plexus cysts at 17 weeks' gestation which persisted beyond 36 weeks but could not be detected after delivery. At birth the child was found to have trisomy 18. 相似文献
690.
D. J. H. Brock 《黑龙江环境通报》1994,14(13):1243-1252
A number of different models of CF carrier screening have now been tested in pilot trials. Apart from opportunistic and cascade testing (which are strictly speaking not true forms of screening), the major programmes have been directed either to young adults in primary care or to pregnant women in antenatal clinics. Only in the latter form of screening has sufficient data been collected to allow conclusions to be reached on the optimum mode of delivery. It seems very probable that when CF carrier screening passes into routine service, it will be the antenatal couple model that is used. 相似文献