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   89953篇
  免费   1230篇
  国内免费   1107篇
安全科学   3761篇
废物处理   3211篇
环保管理   14016篇
综合类   21083篇
基础理论   26220篇
环境理论   73篇
污染及防治   14418篇
评价与监测   5371篇
社会与环境   3597篇
灾害及防治   540篇
  2022年   771篇
  2021年   808篇
  2020年   650篇
  2019年   876篇
  2018年   1127篇
  2017年   1160篇
  2016年   2164篇
  2015年   1824篇
  2014年   2581篇
  2013年   9249篇
  2012年   2150篇
  2011年   2391篇
  2010年   3259篇
  2009年   3367篇
  2008年   1955篇
  2007年   1808篇
  2006年   2250篇
  2005年   2188篇
  2004年   2573篇
  2003年   2362篇
  2002年   1905篇
  2001年   2248篇
  2000年   1973篇
  1999年   1478篇
  1998年   1366篇
  1997年   1354篇
  1996年   1474篇
  1995年   1577篇
  1994年   1480篇
  1993年   1329篇
  1992年   1328篇
  1991年   1292篇
  1990年   1243篇
  1989年   1191篇
  1988年   1046篇
  1987年   981篇
  1986年   990篇
  1985年   1064篇
  1984年   1156篇
  1983年   1169篇
  1982年   1177篇
  1981年   1096篇
  1980年   941篇
  1979年   923篇
  1978年   826篇
  1977年   718篇
  1976年   639篇
  1975年   611篇
  1973年   641篇
  1972年   646篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Male phenotype associated with a 45,X karyotype is an infrequent finding. We present a case diagnosed prenatally on amniocentesis performed for maternal age. The male phenotype was associated with a translocation of a distal part of Yp including the pseudoautosomal SHOX gene and SRY gene on the short arm of a chromosome 21. By DNA analysis we could show that the X chromosome was of maternal origin and that the breakpoint was in interval 3 of the Y chromosome. Mechanisms and genetic counselling are discussed based on a review of published cases of 45,X and XX males. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
162.
Two de novo cases with Apert Syndrome detected prenatally are presented herein. In the first, fetal ultrasound findings of syndactyly of the hands, craniosynostosis and proptosis resulted in a prenatal diagnosis in the nineteenth week of gestation. This is the earliest prenatal diagnosis of this syndrome in a not-at-risk case. Following counseling, this pregnancy was terminated and subsequent pathological examination and DNA analysis confirmed the diagnosis of Apert Syndrome and coarctation of the aorta. In the second case, fetal ultrasound at 21 weeks' gestation revealed a hypoplastic left heart and clover-leaf skull. Following counseling, this pregnancy was also terminated. Further examination of the fetus and DNA analysis led to a diagnosis of Apert Syndrome. These cases emphasize the need to complete a thorough fetal ultrasound in cases with potentially lethal cardiac abnormality and the importance of incorporating a fetal pathologist, as well as a medical geneticist, in the investigations performed after delivery or pregnancy termination when a fetal abnormality is detected on ultrasound. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
163.
164.
165.
Energy efficiency is often stated to be the most cost-effective measure for satisfying our energy demand with minimal environmental damage. However, the potential energy savings attainable in 'the real world' are frequently overestimated, as is shown in an industrial case study of the glass industry. Nevertheless, there are significant energy savings to be realized, and the role of new technologies in this is important. However, the key to the effective use of new technology for improved energy efficiency is good management and. for best effect, it must be integrated into the normal resource management activities of a company.  相似文献   
166.
After briefly reviewing some conceptual underpinnings of sustainable cities, this paper analyses and compares sustainable cities initiatives in 24 US cities. The central question addressed in the paper is why some cities seem to take sustainability more seriously than others. Numerous demographic, socioeconomic and other characteristics of the cities are correlated with an Index of Taking Sustainability Seriously, which is a composite of some 34 different variables indicating whether each city engages in specific sustainability programmes, policies or activities. Many of the standard explanations, such as the income and wealth of the community, the liberalness of the city and the growth pressures placed on the city, are found to exhibit no correlation with the seriousness of the sustainability effort. What do correlate with the Index are: reliance on manufacturing, where having more residents employed in manufacturing industries is associated with less seriousness; and, the age of the population, where cities with older populations take sustainability more seriously. This has three implications for the future development of sustainable cities. First, some of the cities that might be said to need sustainability programmes the most--cities with heavy manufacturing that are more prone to pollution production--are the least likely to take such programmes seriously. Secondly, as cities' manufacturing bases decline, they should find it increasingly feasible to engage in sustainability initiatives. And, thirdly, as the populations of cities age, policy-makers should also find it easier to support, develop and take seriously sustainability programmes.  相似文献   
167.
168.
全球粮食生产的预测问题   总被引:1,自引:0,他引:1  
本文讨论了全球粮食生产体系能力预测模型的研发问题,文章特别对影响粮食生产的各种因素进行了鉴定和分析,并且对它们的相对影响和可预测性进行了估计。  相似文献   
169.
Quick fix. Putting out firs. Do it over. Fix it again. Bottlenecks. Come back to it later. Out of stock. Back order. Not what we ordered. Is that the best you can do? It's the contractor's fault. Not within specs. Defective. Nobody's perfect. Lost in the system. Over budget. Delayed. Late penalities. Fines.  相似文献   
170.
The purpose of this investigation was to monitor airborne dipersion of particulates in connection with exploration activities at a niobium-mineralization in the Sarfartoq area, SW Greenland, during the summer of 1989, and to provide a basis for monitoring strategies in later phases of the development of the mining site. During three periods moss bags were exposed at 9 stations close to the outcrop and at 3 background stations, and indigenous lichens and mosses were sampled before and after the exploration work.Analyses of element concentrations showed that the natural enrichment of elements in the indigenous vegetation is restricted to areas immediately at or on the outcrop. The elements found in elevated concentrations were Nb, La, Ce, Th and U.The moss bags and the indigenous monitor organisms showed rises in concentrations of the elements Nb, Ce, Cd, Pb and Zn after the exploration activities during the summer. This shows that some dispersion of dust has occurred in the area.  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