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   24705篇
  免费   359篇
  国内免费   561篇
安全科学   753篇
废物处理   1071篇
环保管理   3394篇
综合类   4361篇
基础理论   6252篇
环境理论   7篇
污染及防治   6300篇
评价与监测   1539篇
社会与环境   1781篇
灾害及防治   167篇
  2023年   129篇
  2022年   277篇
  2021年   249篇
  2020年   235篇
  2019年   228篇
  2018年   401篇
  2017年   393篇
  2016年   582篇
  2015年   460篇
  2014年   660篇
  2013年   2028篇
  2012年   842篇
  2011年   1221篇
  2010年   949篇
  2009年   1042篇
  2008年   1160篇
  2007年   1225篇
  2006年   983篇
  2005年   850篇
  2004年   873篇
  2003年   819篇
  2002年   771篇
  2001年   932篇
  2000年   699篇
  1999年   419篇
  1998年   293篇
  1997年   308篇
  1996年   315篇
  1995年   380篇
  1994年   294篇
  1993年   278篇
  1992年   252篇
  1991年   266篇
  1990年   252篇
  1989年   243篇
  1988年   211篇
  1987年   201篇
  1986年   199篇
  1985年   205篇
  1984年   244篇
  1983年   199篇
  1982年   223篇
  1981年   217篇
  1980年   172篇
  1979年   195篇
  1978年   122篇
  1977年   130篇
  1974年   127篇
  1973年   129篇
  1972年   141篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
371.
372.
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   
373.
374.
375.
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   
376.
A prenatally detected case of a rare mosaic tetrasomy 12p/trisomy 12p is reported, presenting as the well-known accessory isochromosome 12p and a supernumerary single 12p marker in 17/24 and 6/24 clones of cultured amniotic fluid cells, respectively. The chromosomal nature of both marker chromosomes was investigated in cultured amniotic fluid cells by fluorescent in situ hybridization with various probes: the 12-centromeric probes pa12H8 and D12Z3, a whole chromosome 12 paint, and the chromosome 12p-specific paint M28. DNA analysis revealed a maternal origin of the extra 12p material. After counselling, the parents requested termination of pregnancy. Inspection and autopsy of the fetus revealed many of the dysmorphisms and internal structural abnormalities of the Pallister–Killian syndrome.  相似文献   
377.
378.
The polymerase chain reaction (PCR) was used on material from a blighted ovum to confirm indirectly the carrier status of a woman with a family history of Becker muscular dystrophy. Conventional testing including creatine kinase levels, muscle biopsy, and EMG had been inconclusive, and on the basis of one elevated creatine kinase level, the woman had been designated a possible carrier. Ultrasound examination at 10 weeks of pregnancy indicated a blighted ovum, from which DNA was subsequently extracted and subjected to PCR testing for determination of sex and genotypic status with respect to the known familial deletion of the dystrophin gene. The blighted ovum was found to have a Y chromosome and also to be deleted for at least exon 6 of the dystrophin gene, indirectly indicating that the mother most likely carried the family mutation for Becker muscular dystrophy.  相似文献   
379.
380.
IntroductionFertilizationisessentialforagriculturalproduction ,butunreasonablyapplyingfertilizerscouldresultinseriesofproblemssuchascropqualitydecline,fertilizeruseefficiencydecrease,residualfertilizerspollution groundwaterandriversandnitrogencontented …  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