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   971篇
  免费   1篇
安全科学   18篇
废物处理   1篇
环保管理   84篇
综合类   779篇
基础理论   53篇
污染及防治   29篇
评价与监测   5篇
灾害及防治   3篇
  2022年   2篇
  2016年   3篇
  2015年   3篇
  2014年   2篇
  2013年   37篇
  2010年   5篇
  2009年   4篇
  2008年   5篇
  2007年   4篇
  2005年   3篇
  2004年   3篇
  2003年   12篇
  2002年   8篇
  1998年   11篇
  1997年   4篇
  1995年   56篇
  1994年   50篇
  1993年   38篇
  1992年   32篇
  1991年   26篇
  1990年   32篇
  1989年   25篇
  1988年   34篇
  1987年   29篇
  1986年   21篇
  1985年   14篇
  1984年   12篇
  1983年   14篇
  1982年   10篇
  1981年   4篇
  1979年   5篇
  1976年   6篇
  1975年   9篇
  1974年   4篇
  1973年   10篇
  1972年   2篇
  1971年   4篇
  1963年   3篇
  1962年   2篇
  1961年   3篇
  1959年   2篇
  1940年   2篇
  1920年   2篇
  1919年   47篇
  1918年   44篇
  1917年   36篇
  1916年   53篇
  1915年   37篇
  1914年   71篇
  1913年   106篇
排序方式: 共有972条查询结果,搜索用时 703 毫秒
691.
692.
The article presents the results of a 4-month-period survey by questionnaire among all women attending the Marseille Centre for Prenatal Diagnosis for amniocentesis. Socio-cultural status of women getting access to amniocentesis is significantly higher than in the general population of pregnant women in the same geographic area of south-eastern France. Sociocultural status is also higher among women who have to cover costs of procedure to get access to amniocentesis than among those who benefit from it free-of-charge according to French Social Security regulations. In contrast, risk perception and attitudes toward termination of pregnancy are similar in these two groups. A total of 24·4 per cent of respondents declared that they got access to amniocentesis ‘on their own initiative’, the remaining 75·6 per cent declaring that they ‘were following medical advice’. Multidimensional analysis shows that the women who do not benefit from free-of-charge amniocentesis, and who have a high level of education and no antecedents of fetal and perinatal deaths, are more likely to perceive themselves as ‘self-referring’. The study indicates that institutional coverage may be effective in reducing socio-cultural inequities in access to prenatal diagnosis. But such a policy may conflict with the respect of women' s individual autonomy in the amniocentesis decision.  相似文献   
693.
Short- and long-term cultures of chorionic villi obtained in the 11th week of pregnancy revealed trisomy 14. After induced abortion trisomy 14 mosaicism was established in fetal skin and umbilical cord tissue while a second long-term culture of chorionic villi exhibited a normal karyotype. The results of the pathological investigations are discussed with respect to the cytogenetic findings.  相似文献   
694.
695.
Ten years ago in the United States, per capita water use for all purposes was about 1500 gallons a day. By the year 2000, our population will have grown from 200 to 350 million, and each person, in effect, will be using 2500 gallons per day, This could result in our using as much as 75 percent of the total average runoff from US. Rivers
Perhaps as much as 40,000 cubic miles of saline water are stored in rocks at various depths underlying extensive areas of the United States, according to the U.S. Geological Survey. This water, once considered of no value and even a nuisance, now represents a vast potential source of water, either as replacement of fresh water for certain uses or as the raw material for desalting techniques which have been studied intensively in recent years. Desalination creates new water in the sense that saline water, never before used, becomes part of our water economy.  相似文献   
696.
This paper describes three relatively recent innovations in the Dutch agri-environment programme which have helped nature management to be contiguous with natural features allowing the landscape to be managed whole rather than piecemeal—and thus generate higher quality and greater scope in environmental management. The first two, joint submissions by neighbouring farmers and payments related to the level of environmental output delivered, are scheme innovations. The third, Environmental Co-operatives (EC)—clubs of neighbouring farmers that inter alia co-ordinate and help manage the scheme innovations—is an institutional innovation. None has an equivalent in the UK. Evidence from interviews with farmer and non-farmer members, policy makers, academics and other interested parties show the role EC play in overcoming some of the postulated problems of the two scheme innovations. Not all the problems have been overcome, and cost-benefit analyses have not been conducted, nevertheless there is sufficient evidence to suggest that these innovations have benefited all actors involved: farmers, the government, the environment and the rural economy. Analysis of UK agri-environment policy using actor network theory (ANT) suggests the UK government will need to show similar levels of trust in and commitment to the farming community before these innovations could be introduced in the UK.  相似文献   
697.
Studies on the effects of various salinities on the uptake and catabolism of glucose in Vibrio marinus MP-1 revealed several significant shifts in total uptake and respiration as the cells were subjected to increasingly greater concentrations of NaCl. As the salinity increased from 0.30 to 1.0 M NaCl, there was a decrease in the C6/C1 (CO2) ratio. The resulting patterns suggests that the relative participation of the hexose monophosphate pathway in glucose catabolism was altered. This pathway is apparently shut down in the region of the minimum-growth salinity, and may be related to growth limitation at rower salinities. The shift in C6/C1 ratio was not affected by changing the incubation temperature, nor was it dependent specifically on the presence of Na+ or Cl-. As the salinity increased from 0.15 to 0.30 M NaCl, there was a shift in the total uptake patterns which suggests the formation and loss of metabolic by-products derived from the first, second, sixth, and presumably fifth carbons of glucose.This paper was taken in part from a dissertation by the senior author, submitted in partial fulfillment of the requirement for the Ph.D. degree, Oregon State University, Corvallis. Published as technical paper No. 3647, Oregon Agricultural Experiment Station.  相似文献   
698.
跨世纪安全科学技术人才培养模式的探讨   总被引:1,自引:2,他引:1  
针对二十一世纪对安全科技人才的素质需求及我国现行安全科技人才培养模式的状况,从安全工程专业教学方法和课程体系两方面对我国跨世纪安全科技人才培养模式进行探讨  相似文献   
699.
综采放顶煤是一种高产、高效的采煤工艺,通过对煤矿现场的调研及有关资料的研究,对其所伴随的自燃发火、瓦斯和粉尘等的危害问题及其相应的防治措施进行了系统的分析与总结,可作现场安全技术管理工作的参考  相似文献   
700.
Three cases of intra-abdominal extralobar pulmonary sequestration detected antenatally by ultrasound are reported. One case was associated with a large left diaphragmatic hernia. Sonographically, all the cases were found in the left supra-renal region presenting as a well-defined echogenic mass with cystic hypoechoic areas. The condition should be considered in the differential diagnosis of all antenatally detected upper abdominal echogenic masses, particularly when associated with a diaphragmatic hernia. Postnatal ultrasound-guided fine needle aspiration biopsy in one case yielded respiratory type epithelium and this procedure could provide a reasonably confident diagnosis of the lesion.  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