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   6385篇
  免费   113篇
  国内免费   240篇
安全科学   210篇
废物处理   357篇
环保管理   501篇
综合类   1301篇
基础理论   1529篇
环境理论   2篇
污染及防治   1567篇
评价与监测   468篇
社会与环境   744篇
灾害及防治   59篇
  2023年   63篇
  2022年   140篇
  2021年   121篇
  2020年   87篇
  2019年   98篇
  2018年   115篇
  2017年   155篇
  2016年   160篇
  2015年   130篇
  2014年   203篇
  2013年   504篇
  2012年   236篇
  2011年   314篇
  2010年   270篇
  2009年   274篇
  2008年   306篇
  2007年   293篇
  2006年   277篇
  2005年   245篇
  2004年   223篇
  2003年   246篇
  2002年   203篇
  2001年   266篇
  2000年   170篇
  1999年   109篇
  1998年   46篇
  1997年   61篇
  1996年   54篇
  1995年   62篇
  1994年   67篇
  1993年   61篇
  1992年   61篇
  1991年   64篇
  1990年   67篇
  1989年   53篇
  1988年   58篇
  1987年   56篇
  1986年   58篇
  1985年   43篇
  1984年   47篇
  1983年   47篇
  1982年   48篇
  1980年   30篇
  1979年   32篇
  1978年   29篇
  1977年   28篇
  1976年   28篇
  1974年   31篇
  1973年   30篇
  1972年   28篇
排序方式: 共有6738条查询结果,搜索用时 375 毫秒
101.
102.
103.
104.
Duodenal stenosis associated with oesophageal atresia was diagnosed by ultrasound at 12 weeks' gestation. The diagnosis was made by recognition of a double bubble sign which was more pronounced when a vaginal transducer was used. Post-abortion autopsy confirmed the diagnosis. Oesophageal and duodenal obstruction in this case had no effect on the amount of amniotic fluid or the alpha-fetoprotein concentration since swallowing and subsequent utilization of amniotic fluid do not occur before 12 weeks of gestation.  相似文献   
105.
An analysis of the impacts on Mexican energy demand and associated carbon dioxide (CO2) emissions in the year 2005 due to efficient lighting in the commercial and residential sectors and cogeneration in the industrial sector is presented. Estimation of CO2 abatement costs and an incremental cost curve for CO2 mitigation options are considered. These technologies are cost effective opportunities, and together are projected to reduce CO2 emissions in 2005 by nearly 13 percent. Implementation of efficient lighting is already part of the demand side management (DSM) programs of the Mexican state-owned utility. However, there are important barriers that may hinder the implementation of large scale cogeneration plants.  相似文献   
106.
Ninety-two families with spinal muscular atrophy (SMA) applied for genetic counselling and further prenatal diagnosis. To minimize expenses, only one tightly linked informative marker was determined in the course of preliminary examination, and non-radioactive allele detection was preferably used. Four prenatal diagnoses of SMA type I, four of SMA type II, and one of SMA type III were made. This trial programme shows the considerable requirements, importance, and potential effectiveness of prenatal prediction of SMA in Russia.  相似文献   
107.
绿色设计方法——设计领域发展的新趋势   总被引:13,自引:0,他引:13       下载免费PDF全文
 简要地介绍了设计领域发展的新趋势—绿色设计的基本思想,综述了绿色设计各主要研究领域的现状和问题以及发展趋势,阐明了我国开展绿色设计的研究与应用的必要性与可行性.  相似文献   
108.
The diagnosis of Freeman–Sheldon syndrome was made by ultrasonographic evaluation of a 20-week fetus with a positive family history. The ultrasonographic features were abnormalities of the extremities and mouth.  相似文献   
109.
With the advent of more stringent controls on wastewater treatment, sewage sludge production in Europe and many parts of the world is increasing. With this increase comes the problem of sludge disposal, and recycling to land arguably offers an economically and environmentally sustainable option. However, a major limitation of sewage sludge reuse is the potential release of heavy metals from the sludge and heavy metal accumulation to toxic levels in topsoils. The properties of the sludge play a crucial role in determining the initial release and subsequent availability of heavy metals in amended soils. Bioavailable forms of heavy metals in recently amended soils are most likely to be those that are bioavailable in the sewage sludge. In this paper, published research on the importance of sewage sludge characteristics on metal release and bioavailability will be reviewed and contrasted with original research. A selection of sludges from around Australia has been collected for this purpose. Through the use of incubation studies, isotope dilution techniques, ion-selective electrode measurements and 13C-NMR spectroscopy, the importance of a range of sludge properties on heavy metal behaviour in sludges and sludge-amended soils is addressed.  相似文献   
110.
 In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned, the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with minimal energy input. Received: 7 July 2000 / Accepted in revised form: 28 August 2000  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