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   4301篇
  免费   30篇
  国内免费   10篇
安全科学   86篇
废物处理   162篇
环保管理   205篇
综合类   1542篇
基础理论   898篇
环境理论   8篇
污染及防治   1056篇
评价与监测   204篇
社会与环境   173篇
灾害及防治   7篇
  2022年   32篇
  2019年   41篇
  2018年   83篇
  2017年   92篇
  2016年   102篇
  2015年   95篇
  2014年   109篇
  2013年   200篇
  2012年   115篇
  2011年   197篇
  2010年   133篇
  2009年   129篇
  2008年   210篇
  2007年   177篇
  2006年   158篇
  2005年   127篇
  2004年   111篇
  2003年   106篇
  2002年   139篇
  2001年   82篇
  2000年   74篇
  1999年   50篇
  1998年   41篇
  1997年   38篇
  1996年   48篇
  1995年   49篇
  1994年   48篇
  1993年   32篇
  1992年   45篇
  1991年   39篇
  1990年   37篇
  1989年   32篇
  1981年   30篇
  1976年   32篇
  1973年   29篇
  1968年   29篇
  1967年   34篇
  1966年   30篇
  1965年   47篇
  1964年   37篇
  1963年   36篇
  1962年   31篇
  1961年   44篇
  1960年   39篇
  1959年   41篇
  1958年   45篇
  1957年   39篇
  1956年   40篇
  1955年   37篇
  1954年   40篇
排序方式: 共有4341条查询结果,搜索用时 15 毫秒
171.
172.
173.
174.
175.
176.
177.
178.
In 19 pregnancies at risk for 21-hydroxylase deficiency (21OHD) in 18 families with at lea one affected child, prenatal diagnosis was performed by RFLP analysis using the enzymi Taq I and EcoRI and the DNA probes specific for the 21 OH genes, the closely linke complement C4 genes and the highly polymorphic HLA class II genes DRB, DQB, and DPI For fetal DNA analysis either chorionic villi or cultivated amniotic cells were used. In all 1 cases, a clear prenatal diagnosis was possible either with the 21OH probe alone or in mo cases, by combining the results of the different closely linked loci.  相似文献   
179.
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   
180.
Panorpa vulgaris   has become a model insect for testing theories of sexual selection. This contribution summarizes that which has been learned in recent years and presents new data that clearly show that the mating system of P. vulgaris is not simply a resource-defense polygyny, as has previously been thought. In P. vulgaris neither the pattern in food exploitation nor the ratio of variance in the lifetime reproductive success of the two sexes is in accordance with that expected in resource defense polygynous mating systems. Lifetime mating duration is the most important proximate determinant of male fitness. Males employing alternative mating tactics obtain copulations of varying duration in relation to the following sequence: saliva secretion  1  food offering  1  no gift. The number of salivary masses which males provide to females during their lifetime is significantly correlated with the lifetime condition index. The condition index depends on the fighting prowess of males and their ability to find food items. Thus saliva secretion of Panorpa is considered a Zahavian handicap, which can serve as an honest quality indicator used by mating females. Our results confirm four main predictions of the indicator model of the theory of sexual selection: (a) the indicator signals high ecological quality of its bearer, (b) the indicator value increases with phenotypic quality, (c) the indicator value is positively correlated with the genetic quality affecting offspring fitness in a natural selection context, and (d) the quality indicator is more costly for low- than for high-quality individuals. The evolutionary consequences of the mating pattern and the sperm competition mechanism in P. vulgaris are discussed in the context the way in which sexual selection creates and maintains sperm mixing and the evolution of a promiscuous mating system.  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