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   8256篇
  免费   91篇
  国内免费   244篇
安全科学   162篇
废物处理   394篇
环保管理   938篇
综合类   1368篇
基础理论   2109篇
污染及防治   2006篇
评价与监测   612篇
社会与环境   953篇
灾害及防治   49篇
  2023年   65篇
  2022年   134篇
  2021年   107篇
  2020年   69篇
  2019年   100篇
  2018年   147篇
  2017年   156篇
  2016年   216篇
  2015年   159篇
  2014年   278篇
  2013年   715篇
  2012年   286篇
  2011年   389篇
  2010年   327篇
  2009年   350篇
  2008年   405篇
  2007年   406篇
  2006年   317篇
  2005年   298篇
  2004年   294篇
  2003年   285篇
  2002年   273篇
  2001年   343篇
  2000年   216篇
  1999年   116篇
  1998年   91篇
  1997年   85篇
  1996年   109篇
  1995年   126篇
  1994年   96篇
  1993年   86篇
  1992年   91篇
  1991年   93篇
  1990年   81篇
  1989年   74篇
  1988年   70篇
  1987年   77篇
  1986年   55篇
  1985年   63篇
  1984年   64篇
  1983年   59篇
  1982年   58篇
  1981年   64篇
  1980年   47篇
  1979年   46篇
  1977年   38篇
  1976年   36篇
  1974年   34篇
  1973年   43篇
  1972年   51篇
排序方式: 共有8591条查询结果,搜索用时 0 毫秒
861.
862.
863.
864.
At 10 weeks' gestation, chorionic villus biopsy was obtained from a woman at risk for Sanfilippo type C disease. Acetyl-CoA: α-glucosaminide N-acetyltransferase activity was markedly deficient. The pregnancy was terminated at 12 weeks' gestation and follow-up study on fetal fibroblasts confirmed the diagnosis.  相似文献   
865.
Water hyacinth [Eichhorniacrassipes (Mart.) Solms] is an effective fertillizer, mulch, soil amendment and fodder for cattle and sheep. The consequences of the ability of the plant to accumulate heavy metals needs consideration. Small and large water hyacinth ecotypes collected from two “rural” rivers in Florida, the Peace and Withalachoochee respectively, were examined for an accumulation of cadmium from the natural environment. Less than trace amounts (below limits of detection, 2.5ppb) were present. Water hyacinths tested for cadmium accumulation under laboratory conditions exhibited a pronounced ability to absorb and accumulate the metal. The roots contained 0.982 mg of the 2.0 mg cadmium presented to the plant. The distribution of the metal within the plant was 76.7% in the roots, 22.4% in the stems with the remainder in the leaves. Of the total cadmium presented to the plant, 80.8 ± 3.0% was recovered by the plant after 7 days, the mean generation time of the plant. With increasing urbanization, accumulation of cadmium by water hyacinths exists. It is either an asset or a potential hazard and needs to be appreciated.  相似文献   
866.
Silver in the three species of pinnipeds [northern fur seal (Callorhinus ursinus), Steller sea lion (Eumetopias jubatus), and harbor seal (Phoca vitulina)] caught in the North Pacific Ocean were analyzed using inductively coupled plasma-mass spectrometry, in order to understand accumulation and distribution of silver in pinnipeds. In northern fur seals, relatively high concentrations of silver were observed in the liver and body hair. Some 70% of the silver burden was concentrated in the liver. Hepatic silver concentrations were significantly correlated to age in northern fur seals (r = 0.766, P < 0.001, n = 49) and Steller sea lions (r = 0.496, P < 0.01, n = 28). Levels of silver concentrations per wet weight (microgram g-1) in the three pinnipeds ranged from 0.04 to 0.55 for northern fur seals, from 0.1 to 1.04 for Steller sea lions and from 0.03 to 0.83 for harbor seals. Silver concentrations in liver for all pinnipeds were significantly correlated with mercury, and selenium (P < 0.001). Molar ratios between silver to selenium approximated 1:180 in northern fur seals, 1:120 in Steller sea lions, and 1:60 in harbor seals. The silver-mercury molar ratios were approximately 1:170 in northern fur seals, and 1:80 both in the other species. Increase in silver accumulation in the liver was caused by the retention in nuclei and mitochondria fraction together with mercury and selenium in the cells of northern fur seals.  相似文献   
867.
Environmental managers at U.S. Department of Defense (DoD) installations overseas are faced with the challenge of managing contaminated sites at these installations with little information on the extent of contamination or the risk posed by the site. In this regard, DoD managers overseas encounter a situation quite similar to the situation faced by decision makers in the U.S. who are managing brownfields. Innovative site characterization and risk-based decision-making methods, which are currently being developed for expeditious application at brownfield sites in the U.S., may also be appropriate for application at overseas DoD sites. In this paper, the analytic hierarchy process (AHP) is used by DoD decision makers to evaluate and rank innovative site characterization technologies and risk-based decision-making and management methods, for use at installations in Korea. Results indicate that for sites with high potential risk the decision makers preferred site characterization technologies that produce data of high quality and a method that can be used to establish credible risk-based remediation goals. This study provides a framework for applying characterization technologies and risk management to poorly characterized contaminated sites in developing countries, where resources for remedial actions may be limited.  相似文献   
868.
Intrauterine fetal growth restriction (IUGR) is an important pregnancy complication associated with significant adverse clinical outcome, stillbirth, perinatal morbidity and cerebral palsy. To date, no uniformly accepted management protocol of Doppler surveillance that reduces mortality and cognitive morbidity has emerged. Aortic isthmus (AoI) evaluation has been proposed as a potential monitoring tool for IUGR fetuses. In this review, the current knowledge of the relationship between AoI Doppler velocimetry and preterm fetal growth restriction is reviewed. Relevant technical aspects and reproducibility data are reviewed as we discuss AoI Doppler and its place within the existing repertoire of Doppler assessments in placental insufficiency. The AoI is a link between the right and left ventricles which perfuse the lower and upper body, respectively. The clinical use of AoI waveforms for monitoring fetal deterioration in IUGR has been limited, but preliminary work suggests that abnormal AoI impedance indices are an intermediate step between placental insufficiency-hypoxemia and cardiac decompensation. Further prospective studies correlating AoI indices with arterial and venous Doppler indices and perinatal outcome are required before encorporating this index into clinical practice. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
869.
870.
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