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   23777篇
  免费   268篇
  国内免费   338篇
安全科学   610篇
废物处理   1068篇
环保管理   3045篇
综合类   3983篇
基础理论   6555篇
环境理论   12篇
污染及防治   6398篇
评价与监测   1538篇
社会与环境   1028篇
灾害及防治   146篇
  2022年   193篇
  2021年   184篇
  2019年   169篇
  2018年   344篇
  2017年   314篇
  2016年   484篇
  2015年   389篇
  2014年   562篇
  2013年   1875篇
  2012年   658篇
  2011年   967篇
  2010年   804篇
  2009年   796篇
  2008年   993篇
  2007年   1039篇
  2006年   900篇
  2005年   779篇
  2004年   774篇
  2003年   761篇
  2002年   721篇
  2001年   994篇
  2000年   701篇
  1999年   394篇
  1998年   299篇
  1997年   320篇
  1996年   310篇
  1995年   372篇
  1994年   342篇
  1993年   324篇
  1992年   305篇
  1991年   307篇
  1990年   317篇
  1989年   305篇
  1988年   270篇
  1987年   258篇
  1986年   240篇
  1985年   211篇
  1984年   267篇
  1983年   228篇
  1982年   291篇
  1981年   233篇
  1980年   193篇
  1979年   213篇
  1978年   193篇
  1977年   158篇
  1975年   156篇
  1974年   164篇
  1973年   170篇
  1972年   154篇
  1971年   154篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
201.
202.
203.
Defense Mechanisms of Arthropods, no. 96; no. 95: Eisner et al.: Chemoecology (in press)  相似文献   
204.
205.
206.
207.
208.
Behavioural ecologists attempt to predict fitness in birds from estimates of body condition and immune capacity. We investigated how the stresses associated with capture, confinement and captive-rearing of wild zebra finches (Taeniopygia guttata) affected different elements of the immune system and body condition. Wild birds had higher heterophil:lymphocyte ratios and total leucocyte counts than aviary birds, presumably an outcome of mounting specific resistance to pathogens, but this response diminished significantly within 10 days of confinement. Wild birds had lower phytohaemagglutinin-A (PHA) responses than their aviary-bred counterparts possibly because energetic costs limited a general resistance response. Wild birds were heavier and had higher haematocrits than their aviary counterparts, but had less fat, although just 10 days of captivity significantly increased fat levels. Measures of body condition were of limited use for predicting immune responsiveness. We conclude that the different elements of the immune system and body condition respond independently, and often unpredictably, to many ecological and behavioural stressors.  相似文献   
209.
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   
210.
Five cases of mosaicism for an isochromosome of 20q have been detected from a total of 50 000 cases analysed for prenatal diagnosis by amniocentesis. Karyotypes were designated mos 46,X_/46,X_,i(20q). In all cases, the abnormal cell line was detected in more than one primary culture, thus fulfilling the criterion for true (level III) mosaicism. Indications for prenatal diagnosis were parental anxiety (two cases), low maternal serum alpha-fetoprotein (AFP) (two cases), and high maternal serum AFP (one case). Level II ultrasounds on all five fetuses were normal, and the abnormal cell line was never detected in fetal blood and/or cord blood. All five pregnancies were continued and had normal outcomes, with birth weights ranging from 2.4 to 3.8 kg. The development of all five children has been normal, with the oldest child in the study now 4 years of age. We suggest that the abnormal cell line in each case was of extrafetal origin, and that this may be one of the more common examples of this phenomenon, occurring in approximately 1/10000 prenatal diagnoses. Mosaicism i(20q) may have been missed in the past because of the higher resolution necessary to detect this subtle change.  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