首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   29959篇
  免费   330篇
  国内免费   227篇
安全科学   863篇
废物处理   1072篇
环保管理   4170篇
综合类   4712篇
基础理论   8673篇
环境理论   22篇
污染及防治   7767篇
评价与监测   1776篇
社会与环境   1260篇
灾害及防治   201篇
  2022年   179篇
  2021年   181篇
  2019年   222篇
  2018年   399篇
  2017年   388篇
  2016年   573篇
  2015年   498篇
  2014年   691篇
  2013年   2158篇
  2012年   856篇
  2011年   1282篇
  2010年   1038篇
  2009年   1059篇
  2008年   1272篇
  2007年   1356篇
  2006年   1199篇
  2005年   1024篇
  2004年   1017篇
  2003年   951篇
  2002年   950篇
  2001年   1250篇
  2000年   871篇
  1999年   558篇
  1998年   436篇
  1997年   441篇
  1996年   455篇
  1995年   492篇
  1994年   449篇
  1993年   405篇
  1992年   419篇
  1991年   378篇
  1990年   383篇
  1989年   415篇
  1988年   354篇
  1987年   304篇
  1986年   277篇
  1985年   312篇
  1984年   294篇
  1983年   333篇
  1982年   327篇
  1981年   275篇
  1980年   246篇
  1979年   274篇
  1978年   231篇
  1977年   196篇
  1976年   202篇
  1975年   194篇
  1974年   173篇
  1973年   172篇
  1972年   202篇
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
601.
The discussion on the possible increase of solar UV on earth due to the destruction of the stratospheric ozone has led to a renewed interest in the action of ultraviolet radiation on biological systems. The paper deals with changes at the cellular level stressing particularly molecular alterations in deoxyribonucleic acid, the carrier of genetic information. The most important repair processes by which lesions are removed or bypassed are described. It is also discussed whether the effectivity of a complex spectrum can be predicted on the basis of measurements with monochromatic radiation. Furthermore, possible consequences on human health are outlined which may be derived from cellular studies.  相似文献   
602.
Gross scoliosis of the fetal thoracic spine was diagnosed at 18 weeks gestation. The pregnancy was terminated and the fetus found to have webbing of the neck and an imperforate anus in addition to vertebral defects.  相似文献   
603.
604.
605.
606.
各种环境因素的协同作用已经导致保护运动在解释保护运动的基本信念时尤其缺乏信心。“反对派”行动主义者以为他们的论据是得到证实的,而“制度派”战术主义者倾向于采取他们并不赞同的功利主义的或经济的观点。根据现有的证据,在几百年以后,这个星球上主要的自然区域将基本消失,人类的生活质量将会受到极大的威胁。一种更可靠的观点认为:自然界是人类体验自由(这也是一种精神环境)的能力中不可或缺的一部分。这一观点将改变我们对待自然环境的方式,也关乎今后生物多样性长期生存的前景。  相似文献   
607.
In a case of fetal heart failure caused by endocardial fibroelastosis, prenatal echocardiography clearly demonstrated; a thickened endocardium. We therefore suggest that an abnormal endocardium may be detected in utero by ultrasound, thus representing an important clue in the differential diagnosis of fetal nonimmune hydrops and in the evaluation of pregnancies at risk for endocardial fibroelastosis.  相似文献   
608.
The polymerase chain reaction has been used to detect an abundant class of short repeat DNA families of the form (dC-dA)n.(dG-dT)n, known as microsatellites. These units are found throughout the human genome and have been characterized for several loci including APOC2 on chromosome 19ql2-ql3.2. The locus APOC2 is linked to the gene for dystrophia myotonica and a microsatellite within this locus was used to derive polymorphisms in a family to predict the inheritance of the disease. Chorionic villus sampling (CVS) was performed at 151/2 weeks' gestation. Following DNA extraction from the CVS material and parental blood samples, microsatellite analysis was carried out by the polymerase chain reaction.  相似文献   
609.
Prenatal diagnosis in a kindred with the Opitz (BBB) syndrome is presented. The inheritance is consistent with either autosomal dominant inheritance with sex limited expression or X-linked inheritance. The abnormalities in the kindred consist of hypertelorism, hypospadias, ambiguous genitalia, urocolic fistula, imperforate anus, mental retardation, diaphragmatic hernia, and malrotation with volvulus. A male fetus at 19 weeks was found by ultrasound to have hypertelorism and hypospadias with a small phallus consistent with the syndrome. The diagnosis was confirmed by pathologic examination after pregnancy termination. This is the first report of prenatal diagnosis of Opitz syndrome by ultrasonographic demonstration of hypertelorism and hypospadias in the second trimester.  相似文献   
610.
Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 μmol/1 at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat ≤ μmol/1. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18 159 ± 9083 pg/ml; 2657 ± 669 ng/ml) and 2 (1574 ± 847 pg/ml; 176 ± 50 ng/ml) in comparison with group 3 (35 ± 6 pg/ml; 21 ± 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (>50 μmol/1). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号