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   17435篇
  免费   261篇
  国内免费   167篇
安全科学   607篇
废物处理   489篇
环保管理   3073篇
综合类   3767篇
基础理论   4220篇
环境理论   14篇
污染及防治   4185篇
评价与监测   860篇
社会与环境   530篇
灾害及防治   118篇
  2021年   119篇
  2019年   133篇
  2018年   234篇
  2017年   254篇
  2016年   348篇
  2015年   267篇
  2014年   344篇
  2013年   1313篇
  2012年   502篇
  2011年   704篇
  2010年   493篇
  2009年   613篇
  2008年   672篇
  2007年   706篇
  2006年   632篇
  2005年   498篇
  2004年   509篇
  2003年   512篇
  2002年   446篇
  2001年   536篇
  2000年   403篇
  1999年   280篇
  1998年   222篇
  1997年   196篇
  1996年   236篇
  1995年   248篇
  1994年   266篇
  1993年   236篇
  1992年   234篇
  1991年   217篇
  1990年   239篇
  1989年   225篇
  1988年   190篇
  1987年   198篇
  1986年   185篇
  1985年   200篇
  1984年   187篇
  1983年   195篇
  1982年   207篇
  1981年   201篇
  1980年   173篇
  1979年   160篇
  1978年   168篇
  1977年   140篇
  1976年   148篇
  1975年   120篇
  1974年   146篇
  1973年   128篇
  1972年   133篇
  1967年   116篇
排序方式: 共有10000条查询结果,搜索用时 672 毫秒
151.
The female silkmoth Bombyx mori L. emits a second pheromone component bombykal (E-10, Z-12-hexade-cadien-1-al) in addition to the well-known sexual attractant bombykol (E-10, Z-12-hexadecadien-1-ol). Bombykal stimulates its own specialized and highly sensitive olfactory cells of the male moth. Surprisingly, the aldehyde inhibits the release of the male's wing-fluttering response to bombykol.  相似文献   
152.
153.
In recent years, an increasing number of inherited diseases in man have been recognized in which there is an impairment in the peroxisomal β-oxidation of very-long-chain fatty acids. In general, these disorders are associated with severe neurological and physical abnormalities and death within the first years of life. In this paper we describe our experience with regard to the prenatal diagnosis of a number of different inborn errors of peroxisomal β-oxidation. Eleven pregnancies at risk were monitored by measuring very-long-chain fatty acid levels as well as very-long-chain fatty acid β-oxidation in cultured chorionic villous fibroblasts and/or amniotic fluid cells. Five affected fetuses were identified. It is concluded that prenatal diagnosis in this group of diseases can be done reliably using cultured chorionic villous fibroblasts or amniotic fluid cells.  相似文献   
154.
This paper reports results of an exploratory study of prenatal diagnosis patients who experienced voluntary terminations of pregnancy following the detection of an abnormality or spontaneous miscarriages. The 121 participants were part of the national collaborative Chorionic Villus Sampling and Amniocentesis Study. They completed semi-structured telephone interviews and mailed questionnaires at 1 month and 6 months after the pregnancy losses. Scores on the Profile of Mood States showed that mood levels improved significantly over time. However, there were some declines in loss-related support from partners and others. The persisting distress and difficulties of a minority highlight the variability in women's responses to pregnancy losses. Women who lost pregnancies later in gestation, showed the greatest mood disturbances at initial assessments, used professional mental health assistance after the loss, or reported less satisfactory loss-related support from significant others showed the greatest levels of mood disturbance at the six-month assessment. Follow-up contacts with patients who lose pregnancies should be used to inform women about the variation in possible grief reactions, to assess the extent of support the women are receiving from their partners and significant others, and to provide additional follow-up or referral of those experiencing the greatest distress.  相似文献   
155.
Cytogenetic study of chorionic villi sampled because of advanced maternal age revealed, after overnight culture, an apparently non-mosaic trisomy 7. Amniocentesis showed exclusively normal mitoses, and the pregnancy continued normally. One hundred mitoses from cord blood of the normal newborn revealed a non-mosaic 46,XX complement. No cells with a proven trisomy 7 were found in cultures from either of two biopsies of the morphologically normal placenta, but the peripheral biopsy showed in multiple cultures an abnormal clone: 47,XX, + 20,-2,-21, + t(2;21)(p13;q22). To our knowledge, this is the first case of non-mosaic trisomy 7 detected on CVS which has had follow-up studies of amniotic fluid, cord blood, and term placenta.  相似文献   
156.
157.
The prenatal diagnosis of The Turner Syndrome is described at a menstrual age of 12 weeks. Detection of cystic hygroma was followed by vaginal chorionic villous sampling (CVS) which revealed a 45,X karyotype. Early documentation of fetal karyotype in the presence of a cystic hygroma is essential for accurate diagnosis and genetic counselling.  相似文献   
158.
Plasticity of honeybee castes   总被引:1,自引:0,他引:1  
  相似文献   
159.
160.
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