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   146篇
  免费   1篇
  国内免费   8篇
安全科学   4篇
废物处理   17篇
环保管理   11篇
综合类   34篇
基础理论   26篇
环境理论   3篇
污染及防治   45篇
评价与监测   4篇
社会与环境   11篇
  2023年   4篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2018年   1篇
  2017年   2篇
  2016年   5篇
  2015年   5篇
  2014年   4篇
  2013年   14篇
  2012年   11篇
  2011年   8篇
  2010年   8篇
  2009年   9篇
  2008年   9篇
  2007年   13篇
  2006年   8篇
  2005年   6篇
  2004年   6篇
  2003年   5篇
  2002年   5篇
  1998年   2篇
  1996年   2篇
  1994年   2篇
  1992年   2篇
  1990年   1篇
  1989年   1篇
  1986年   1篇
  1984年   1篇
  1981年   1篇
  1979年   5篇
  1977年   1篇
  1970年   1篇
  1967年   1篇
  1964年   1篇
  1963年   1篇
  1962年   3篇
  1959年   1篇
排序方式: 共有155条查询结果,搜索用时 31 毫秒
1.
A case of type III congenital cystic adenomatoid malformation of the lung was successfully diagnosed prenatally by fetal lung biopsy. We performed this procedure at 22 weeks of gestation, using a biopsy gun system under ultrasound guidance. The pregnancy was undisturbed by the procedure but as the condition was incompatible with life, an abortion was performed. The diagnosis was confirmed at post-mortem examination. Fetal lung biopsy appears to be a useful method for prenatal diagnosis of fetal lung disorders.  相似文献   
2.
3.
Environmental Economics and Policy Studies - We construct a two-stage Stackelberg model in which suppliers produce marginal cost-intensive green products and compare the diffusion of green products...  相似文献   
4.
Accumulation, transformation and toxicity of arsenic compounds to Japanese Medaka, Oryzias latipes were investigated. For sodium arsenite [As(II)] and disodium arsenate [As(V)], the mean value for 7-day lethal concentration LC50 for O. latipes were 14.6 and 30.3 mg As/l, respectively. Direct accumulation of arsenic in O. latipes increased as a function of As(III) concentration in water. A small proportion of accumulated arsenic was transformed to methylated arsenic. As much as 70% of the total arsenic accumulated in tissue was depurated. Accumulation and transformation of As(III) by O. latipes in a simple freshwater food chain were also investigated. The transformation of As(III) to As(V) by organisms was more prevalent than biomethylation of accumulated arsenic in organisms of the three steps of the food chain.  相似文献   
5.
Removal of Cr(VI) from contaminated soil by electrokinetic remediation   总被引:2,自引:0,他引:2  
A new process for the removal of hexavalent chromium [Cr(VI)] contaminated soil is described. The process provides for an efficient removal of anionic chemicals from contaminated soils. Chromate anions were removed from the soil to the anodic reservoir by the moving force of electromigration. In this process, the chromate anions that accumulate in the anodic reservoir are simultaneously eliminated by using a column packed adsorbent. The adsorbent (immobilized tannin) used was chemically incorporated into cellulose. Cr(VI) was found to be adsorbed to this adsorbent efficiently. In the electrokinetic process, the pH of the aqueous solution in the anodic reservoir was decreased by the electrolysis of water. In the present study, the pH of the solution in the anodic reservoir is maintained at pH 6 by the addition of an aqueous alkaline solution during the electrokinetic process. The advantage of pH control is that it promotes the release of Cr(VI) from the soil by electromigration, thus permitting the maximum adsorption of Cr(VI) on the immobilized tannin. Simultaneous collection of Cr(VI) from the anodic reservoir leads to the protection from secondary contamination with Cr(VI).  相似文献   
6.
To examine whether tree rings can be used to detect or assess local historical 90Sr or 137Cs fallout, such as that resulting from the Hiroshima atomic bomb, radial distribution of 90Sr and 137Cs in trees was examined. We studied a gymnosperm [Japanese cedar, Cryptomeria japonica (L. f.) D. Don] and an angiosperm (Japanese persimmon, Diospyros kaki Thunb.) tree species from the vicinity of the atomic bomb hypocenter, and from other locations in Japan. A significant amount of 137Cs was detected in tree rings formed before 1945, indicating lateral migration of Cs. In contrast, the specific activity of 90Sr in the Hiroshima Japanese cedar showed the highest level in 1945, due to relatively immobile characteristics of Sr compared with Cs. Strontium-90 and Sr analyses in tree rings helped identify and distinguish between residual 90Sr activity from the Hiroshima atomic bomb and the atmospheric nuclear testing. This indicates the possibility of detecting or assessing previous local 90Sr pollution through with treering analysis.  相似文献   
7.
8.
This study presents the laboratory scale results of an extra step in Poly (ethylene terephthalate) – PET mechanical recycling (grinding, washing, drying and reprocessing): a chemical washing after the conventional one. Cooking oil PET bottle flakes were washed in water and then subjected to a reaction with an aqueous solution of sodium hydroxide 5 M at 90 °C for 10 min (chemical washing). After rinsing and drying, the flakes were characterized by thermogravimetry, gas chromatography and elemental analysis tests. The results indicated that the chemically washed material had higher purity than PET washed only with water: 99.3% and 96.7%, respectively, which undoubtedly implies properties, applications and prices closer to those of virgin resin. The production of purified terephthalic acid (TPA) from the chemical washing residue was optimized and reached a purity of 99.6%. Despite the results, the use of chemically washed PET and of TPA obtained is not recommended for direct contact with food, since they still contain some impurities.  相似文献   
9.
10.
This study deals with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose. Softwood and hardwood pulp fibers were suspended in water and oxidized to various extents at pH 10 and 22 °C using sodium hypochlorite in the presence of TEMPO radical and sodium bromide. This reaction system is known to be the most efficient one for the introduction of both surface carboxyl and aldehyde groups. Important relationships between formation of these functional groups and the fibrillation yield, light transmittance of the water dispersions and degree of polymerization of the oxidized softwood and hardwood pulps were established in the present study. A birefringence test confirmed the presence of nanofibers which according to atomic force microscopy analyses had diameters in the 1.6–3.8 nm range.  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