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   431篇
  免费   6篇
  国内免费   22篇
安全科学   4篇
环保管理   1篇
综合类   295篇
基础理论   115篇
污染及防治   5篇
社会与环境   27篇
灾害及防治   12篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2014年   2篇
  2013年   12篇
  2012年   6篇
  2011年   18篇
  2010年   9篇
  2009年   17篇
  2008年   23篇
  2007年   27篇
  2006年   38篇
  2005年   34篇
  2004年   31篇
  2003年   25篇
  2002年   25篇
  2001年   34篇
  2000年   13篇
  1999年   5篇
  1998年   6篇
  1997年   3篇
  1996年   6篇
  1995年   20篇
  1994年   20篇
  1993年   11篇
  1992年   8篇
  1991年   5篇
  1990年   8篇
  1989年   9篇
  1988年   4篇
  1987年   6篇
  1986年   6篇
  1985年   3篇
  1984年   7篇
  1983年   3篇
  1982年   5篇
排序方式: 共有459条查询结果,搜索用时 15 毫秒
91.
从某避孕药生产厂污水处理站好氧池活性污泥中通过富集驯化,分离到一株降解甾体雌激素(3-甲氧基-17a羟基-1,3,5(10),8(9)-雌甾-4-烯,简称MHE)的细菌ZY3菌株.经形态及16SrDNA序列分析初步鉴定,该菌株属于Raoultella属(Raoultellasp.).经过对ZY3菌株以MHE为唯一碳源生长和降解特性的分析表明,ZY3菌株利用MHE生长的最适温度和pH值分别为35℃和10.0,72h内的最适降解浓度为10mg/L.加入营养物质麦芽糖和蛋白胨能促进菌株对底物的降解,在72h内降解率达到了87%和85%.  相似文献   
92.
The genotoxicity of lignin substances (LSs) isolated from biologically purified wastewaters of the pulp and paper industry was studied in experiments on Baikal endemic mollusks and corn. Both toxicity and mutagenic activity of LSs were revealed, with their levels depending on the physicochemical characteristics of LSs, the test organism, and experimental conditions. These results provide evidence that LSs discharged into water bodies create a genetic hazard to their ecosystems.  相似文献   
93.
本文介绍了区域岩屑地球化学异常Ⅲ级检查方法,并从单元素异常、多元素组合异常、岩层元素丰度及背景分布理论、元素点异常概率、特殊样品的地球化学特征等方面对区域化探异常进行综合解释评价,取得了较好效果。  相似文献   
94.
While the fetus and placenta have a common ancestry, chorionic villus tissue does not always reflect fetal genotype. Data are presented from 15 CVS subjects in whom cytogenetic inconsistencies were observed when comparing (1) cultured chorionic villi, (2) direct chromosome preparations of intact villi, and (3) cultured fetal tissue. Embryogenic models are presented to explain these discrepancies. Mosaicism confined to direct chromosome preparations was the most commonly observed inconsistency. This can be explained by postzygotic non-disjunction limited to cytotrophoblast. In all but one instance, the abnormal cell line was limited to the placenta, with the normal cell line reflecting fetal genotype. Analysis of direct chromosome preparations from multiple individually processed villus fragments may be helpful in recognizing mosaicism confined to the placenta. While both direct chromosome preparations and villus cultures can be misleading, the latter are more likely to reflect fetal genetic status since they are derived from the extraembryonic mesoderm.  相似文献   
95.
The autoradiographic labelling of different cell types in chorionic villi and decidual tissue was investigated after [3H]-thymidine incorporation in vitro. Although the extent of labelling was found to be lower in decidual than in villus tissue the possibility that direct chromosome preparations may contain maternal metaphases should be considered. The need for careful selection of villi for direct cytogenetic analysis was stressed.  相似文献   
96.
IntroductionForlasttwodecades,awaveoftheexperimentalconsciousnessisbeingdevelopedindevelopingcountriesincludingIndia.Moderntechnologyhavebeencreatedenvironmentalpollutant,ofwhichnoiseisconsideredastheworstenemyofhumanhealthandacurseofoursociety .Noisei…  相似文献   
97.
The effects of different concentrations of Zn2+ion on root growth,cell division,and nucleoli of Allium cepa were studied. The test Zn2+ ion concentration was made up from zinc sulphate (ZnSO4. 7H2O) ranging from 10-7 to 10-2 mol/L. The solutions were prepared in tap water (pH =6. 5).The results indicated that Zn2+ could obviously inhibit root growth at concentrations from 10-4)to 10-2 mol/L.Roots treated with zinc sulphate showed the presence of c-mitosis, anaphase bridges,including sticky and fluidized bridges (at 10-3 to 10-2 mol/L) , chromosome stickiness, irregularly shaped nuclei, broken nuclei and micronuclei. A toxicity effect was also observed on the nucleoli using silver staining technique after 48h of treatment with 10-4to 10-2 mol/L Zn2+, e. g,the nucleolar particulate material scattered around the nucleoli in the nucleus of root tip cells.  相似文献   
98.
The purpose of this study was to examine the natural history and differential diagnosis of ultrasound-detected, isolated fetal ascites. Retrospective review of our patient data base, from 1989 to 1993, revealed 18 patients with fetal ascites diagnosed sonographically. Fetuses presenting with generalized hydrops were excluded. One of the 18 fetuses with ascites had a chromosomal abnormality (trisomy 21), four fetuses had intrauterine infections, seven had gastrointestinal processes, two had genitourinary tract abnormalities, and four were labelled as ‘idiopathic’ (all four resulting in normal neonates). Seventeen of 18 fetuses survived; there was one fetal demise secondary to active syphilis. One fetus with parvovirus infection required intrauterine transfusion and did well. Two infants are developmentally retarded, including one with trisomy 21 and one with microcephaly secondary to cytomegalovirus infection. Fourteen of 18 fetuses had documented in-utero resolution of the ascites. Eleven of the 18 were associated with polyhydramnios sometime during fetal life. None of the fetuses developed hydrops. In conclusion, fetal ascites can result from many different aetiologies, including gastrointestinal and genitourinary anomalies. Chromosomal abnormalities and viral aetiologies must also be considered. Fetuses who have isolated ascites can have a good outcome with resolution of the ascites antenatally.  相似文献   
99.
以黄鳝为试验材料,研究了艾割和使它隆二种除草剂对鱼类的致突变性。对经腹腔注射染毒上述二种除草剂的受试黄鳝,通过对其活体肾细胞染色体数目和形态的观察,分析其突变率。研究结果(经t检验)显示:艾割和使它隆二种除草剂分别在其试验最低受试剂量50mg/kg和8.0mg/kg即可引起黄鳝的染色体畸变。采用SOS/Umu显色试验研究,在SOS/Umu试验中,使它隆和艾割2个受试除草剂可以诱发SOS阳性反应,且呈明显的剂量-效应关系。试验表明这二种除草剂具有遗传毒性,应对这二种除草剂严加管控,避免其对环境的影响。  相似文献   
100.
A complex chromosome rearrangement, apparently a balanced translocation involving chromosomes 4,6, 15 and 16, was found in cultured cells of amniotic fluid from a 32–year-old primigravida who requested amniocentesis for prenatal diagnosis because of a family history of mental retardation. Chromosome analysis of peripheral blood from both parents were normal. The couple was counselled for the prenatal diagnosis of this de novo complex translocation and, subsequently, elected to terminate the pregnancy. Post-mortem examination revealed a 23–week fetus with intrauterine growth retardation. The identical chromosome rearrangement was subsequently confirmed in cultured fibroblasts from skin and cord obtained from the abortus. To our knowledge, this is the first report where routine prenatal diagnosis revealed a fetus with a balanced complex chromosomal rearrangement involving four chromosomes of de novo origin.  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