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   16060篇
  免费   149篇
  国内免费   118篇
安全科学   337篇
废物处理   650篇
环保管理   1889篇
综合类   3671篇
基础理论   3677篇
环境理论   7篇
污染及防治   4004篇
评价与监测   1021篇
社会与环境   1024篇
灾害及防治   47篇
  2022年   112篇
  2021年   130篇
  2019年   106篇
  2018年   204篇
  2017年   194篇
  2016年   316篇
  2015年   246篇
  2014年   363篇
  2013年   1099篇
  2012年   414篇
  2011年   626篇
  2010年   478篇
  2009年   555篇
  2008年   642篇
  2007年   682篇
  2006年   611篇
  2005年   505篇
  2004年   530篇
  2003年   522篇
  2002年   489篇
  2001年   623篇
  2000年   394篇
  1999年   296篇
  1998年   187篇
  1997年   206篇
  1996年   223篇
  1995年   234篇
  1994年   234篇
  1993年   218篇
  1992年   196篇
  1991年   209篇
  1990年   199篇
  1989年   171篇
  1988年   169篇
  1987年   154篇
  1986年   154篇
  1985年   149篇
  1984年   171篇
  1983年   168篇
  1982年   172篇
  1981年   145篇
  1980年   132篇
  1979年   123篇
  1978年   134篇
  1977年   115篇
  1976年   103篇
  1975年   107篇
  1974年   118篇
  1971年   98篇
  1967年   101篇
排序方式: 共有10000条查询结果,搜索用时 966 毫秒
431.
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   
432.
In this study, we describe a simple strategy to detect β-thalassaemia mutations in prospective parents and to make prenatal diagnosis in pregnancies at risk in the Mediterranean population. Screening of prospective parents is carried out by dot blot analysis on enzymatically amplified DNA with a set of oligonucleotide probes complementary to the most common mutations in this population. Prenatal diagnosis is accomplished by the same procedure on enzymatically amplified amniocyte or trophoblast DNA. The main advantages of this procedure are the simplicity, sensitivity (0.05 μg of DNA), and rapidity (12–24 h). Further simplification is obtained by amplification of the DNA from crude amniotic cell lysate. The very low amount of fetal material necessary for this analysis eliminates the need to culture amniotic fluid cells and may decrease the fetal loss rate associated with trophoblast sampling. The number of specific DNA sequences obtained by the amplification procedure allowed us to use non-radioactive labelled oligonucleotide probes, which have several advantages compared to radioactive probes.  相似文献   
433.
Prenatal diagnosis in a pregnancy at risk for a juvenile B1 variant of GM2-gangliosidosis was carried out. The biochemical study of the cultured amniocytes and the affected fetal brain is reported. The results obtained show that the sulphated artificial substrate can be used in the diagnosis of B1 variant, but not the neutral one. The accumulation of GM2-ganglioside in the fetal brain of the B1 juvenile form and an infantile form of GM2-gangliosidosis (0 variant) was compared.  相似文献   
434.
Prenatal diagnosis on chorionic villous tissue was performed for a woman with the karyotype 46,XX,t(2;18)(q32;q12)—a subtle ‘difficult’ translocation. The case illustrates the necessity of good quality cytogenetics for accurate prenatal diagnosis. For chorionic villi this can be obtained only with long-term culture.  相似文献   
435.
436.
437.
438.
Serum PAPP-A measurements taken from 254 women in the first trimester are reported. Eleven chromosomal abnormalities were detected. The mean serum PAPP-A levels in cases of Down syndrome were 0.44 MOM at 9 weeks gestation, 0.15 MOM at 10 weeks, and 0.29 MOM at 11 weeks. The PAPP-A level at 10 weeks was below those of pregnancies which aborted spontaneously. At 11 weeks, the pregnancies with Down syndrome recorded the lowest PAPP-A levels at that gestation. On this small sample, offering chorionic villus sampling to women with singleton pregnancies and a PAPP-A level below 0.3 MOM (approximately 6.5 per cent of this at-risk group) would have detected all the Down syndrome fetuses at 10 weeks and 50 per cent at 11 weeks without selecting those cases destined to abort. This suggests that serum PAPP-A should continue to be investigated as a potential first-trimester screening test for Down syndrome.  相似文献   
439.
440.
An efficient, reproducible and rapid fused silica capillary column gas chromatographic method, in splitless mode, for analysing of the three chloroanthracene isomers is described. The method affords efficient separation and good linearity for each isomer in the range of 0.2 -200 μg/ml. The method can also be used in separation and determination of another thirty three aromatic and their halosubstituted compounds. This paper also presents the applications of the method in analysing of complex products mixture from reaction of the selected aromatic compounds with hydrogen chloride on fly ash surface from municipal incinerator.  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