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   846篇
  免费   2篇
  国内免费   12篇
安全科学   18篇
废物处理   10篇
环保管理   42篇
综合类   440篇
基础理论   142篇
环境理论   2篇
污染及防治   156篇
评价与监测   26篇
社会与环境   20篇
灾害及防治   4篇
  2018年   12篇
  2017年   12篇
  2015年   10篇
  2014年   11篇
  2013年   34篇
  2012年   21篇
  2011年   19篇
  2010年   22篇
  2009年   30篇
  2008年   26篇
  2007年   32篇
  2006年   19篇
  2004年   34篇
  2003年   15篇
  2002年   16篇
  2001年   16篇
  2000年   13篇
  1999年   24篇
  1998年   8篇
  1997年   7篇
  1996年   9篇
  1995年   7篇
  1994年   7篇
  1992年   7篇
  1990年   8篇
  1989年   7篇
  1979年   8篇
  1978年   7篇
  1967年   9篇
  1966年   12篇
  1965年   11篇
  1964年   9篇
  1962年   7篇
  1961年   10篇
  1960年   8篇
  1957年   12篇
  1955年   8篇
  1954年   7篇
  1952年   8篇
  1941年   8篇
  1940年   9篇
  1937年   12篇
  1936年   10篇
  1935年   9篇
  1934年   11篇
  1933年   7篇
  1931年   8篇
  1929年   8篇
  1922年   6篇
  1921年   7篇
排序方式: 共有860条查询结果,搜索用时 31 毫秒
81.
Using the reproductive capacity of fish appears to be a suitable approach for risk assessment in the aquatic environment since fish are a typical representative thereof and in addition they are of considerable societal value. Generally the early embryonic stages are considered to be one of the most sensitive parts of a fish's life cycle. A method has been developed to use the state of health of live, naturally spawned fish embryos from plankton samples for biological effects monitoring. During the years 1985–1987 in the southern North Sea and in 1991–1992 in the whole of the North Sea fish eggs were sampled from surface waters and examined for developmental abnormalities. Elevated embryo malformation rates were detected in the plume of the major rivers Elbe and Rhine as well as along the eastern coast of England. Occurring malformations are thought to be pollution-related and may be used to define areas of environmental deterioration. The method is discussed in view of its suitability for biological effects monitoring using malformations in fish embryos as biomarkers.  相似文献   
82.
Objectives To validate the use of Real Time PCR, a widely used technique that can detect very low levels of Y chromosomal sequence, and to assess the use of a highly sensitive PCR technique, pyrophosphorolysis-activated polymerisation (PAP), for fetal sex determination using free fetal DNA (ffDNA). Methods The fetal sex was determined by Real Time PCR in 58 pregnancies using ffDNA isolated from maternal plasma. In parallel with the Real Time PCR experiments, the presence of Y chromosome sequence was also determined using PAP on 54 isolated ffDNA samples. Results Both techniques detected Y chromosome sequence at very low levels with 98% specificity and 100% sensitivity (Real Time n = 44, PAP n = 54). Furthermore, the PAP technique was shown to be more robust than the Real Time PCR as none of the samples tested failed to meet the acceptance criteria. Combining the two techniques for male fetal sex detection from maternal blood plasma increases the sensitivity and specificity to 100% in this series. Conclusions This study shows that both Real Time PCR and PAP can be used for Y chromosome detection on ffDNA. Furthermore, by using PAP in combination with Real Time PCR more reliable early prenatal sexing can be performed using ffDNA. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
83.
84.
85.
Trisomy 7 mosaicism was detected prenatally in cultured amniocytes but not in fetal lymphocytes. The child that was born had pigmentary changes of the skin and facial asymmetry suggestive of a chromosomal mosaicism. Skin fibroblasts were studied and trisomy 7 mosaicism was confirmed. At 3 years of age the boy had developed mentally within normal limits. However, dysmorphic findings include sparse hair, short leftpalpebral fissure, ptosis of the left eyelid, strabismus, enamel dysplasia, low-set and posteriorly rotated ears and undescended testes. These findings share some common features with previously reported cases of trisomy 7 mosaicism. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
86.
87.
Dissolved organic sulfur (DOS) is an important fraction for sulfur mobilization in ecosystem. In this work stream waters were sampled in 25 forested sites in southern China to study the dissolved sulfur fractions. Dissolved sulfur was fractionated into dissolved organic sulfur (DOS) and inorganic sulfate (SO42-) for 95 stream water samples. The results showed that the concentration of DOS ranged from 0 to 13.1 mg/L (average 1.3 mg/L) in all the streams. High concentrations of DOS in stream waters were found in the sites with high concentrations of sulfate. DOS constituted less than 60.1% of dissolved sulfur (average 17.9%). Statistical analysis showed that DOS concentration was correlated with SO42- in streams waters and total sulfur in surface layer soils. The results also showed that DOS concentration in stream waters had a seasonal variation, but no trends were found with it. The implication was that the long term sulfur deposition had led the increase of the concentration and fraction of DOS in stream waters in acid rain prevailing regions  相似文献   
88.
89.
The problems of reproduction of Octopus vulgaris and the seasonal distribution in the sea of planktonic larvae, benthonic juveniles and adults are discussed. The influence of environmental factors on growth is shown by experimental studies in the laboratory, and the difficulties of interpreting field data are emphazised.Dedicated to Professor Dr. Adolf Portmann on his 75th birthday, 27 May, 1972Laboratoire associé au C.N.R.S.  相似文献   
90.
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