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   27419篇
  免费   299篇
  国内免费   238篇
安全科学   769篇
废物处理   909篇
环保管理   3963篇
综合类   5439篇
基础理论   7094篇
环境理论   11篇
污染及防治   6963篇
评价与监测   1491篇
社会与环境   1147篇
灾害及防治   170篇
  2021年   187篇
  2019年   211篇
  2018年   337篇
  2017年   330篇
  2016年   525篇
  2015年   379篇
  2014年   541篇
  2013年   2072篇
  2012年   714篇
  2011年   1016篇
  2010年   803篇
  2009年   877篇
  2008年   1073篇
  2007年   1110篇
  2006年   1012篇
  2005年   774篇
  2004年   876篇
  2003年   834篇
  2002年   754篇
  2001年   1048篇
  2000年   722篇
  1999年   472篇
  1998年   370篇
  1997年   336篇
  1996年   377篇
  1995年   394篇
  1994年   432篇
  1993年   366篇
  1992年   400篇
  1991年   371篇
  1990年   413篇
  1989年   396篇
  1988年   317篇
  1987年   316篇
  1986年   280篇
  1985年   302篇
  1984年   314篇
  1983年   308篇
  1982年   306篇
  1981年   303篇
  1980年   256篇
  1979年   267篇
  1978年   241篇
  1977年   226篇
  1976年   200篇
  1975年   206篇
  1974年   238篇
  1973年   216篇
  1972年   233篇
  1971年   179篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
241.
242.
243.
Research in molecular neurobiology has recently entered a new phase of rapid development as a result of the application of the techniques of molecular genetics. This is illustrated by recent work on the electric ray (Torpedo marmorata and T. californica), whose electric organ is a rich source of cholinergic synapses. Other examples from recent literature of the application of the recombinant DNA technique to the mammalian central nervous system are given and possible future developments are discussed.  相似文献   
244.
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   
245.
246.
247.
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   
248.
Mosaicism for the Wolf-Hirschhorn syndrome, del(4)(p16), is extremely rare and has not been reported in association with a numerical chromosome abnormality. We report the prenatal diagnosis of mosaic del(4)(p16) and non-mosaic trisomy 21 in a 16-week female fetus. The pregnancy ended in spontaneous abortion at 34 weeks secondary to fetal demise. The fetus had features of both 4p – and trisomy 21.  相似文献   
249.
A case of gastric outlet obstruction diagnosed prenatally at 22 weeks' gestation is described. The differential diagnosis and the clinical management of this rare condition are discussed, and an updated literature review is presented.  相似文献   
250.
Cytomegalovirus (CMV) is the most common cause of intrauterine infection. Recent publications show amniocentesis to have an 81–100 per cent sensitivity in antenatal diagnosis after 21 weeks' gestation. Testing before 21 weeks' gestation is less well documented. We performed 36 amniocenteses between 14 and 20 weeks' gestation. The sensitivity was 45 per cent and the specificity 100 per cent. Implications and possible causes of this low sensitivity are discussed.  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