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   39066篇
  免费   1104篇
  国内免费   5621篇
安全科学   1907篇
废物处理   1738篇
环保管理   4700篇
综合类   14348篇
基础理论   8237篇
环境理论   13篇
污染及防治   10549篇
评价与监测   1973篇
社会与环境   1507篇
灾害及防治   819篇
  2023年   352篇
  2022年   918篇
  2021年   862篇
  2020年   680篇
  2019年   646篇
  2018年   874篇
  2017年   968篇
  2016年   1063篇
  2015年   1208篇
  2014年   1707篇
  2013年   3339篇
  2012年   1990篇
  2011年   2265篇
  2010年   1831篇
  2009年   1966篇
  2008年   2115篇
  2007年   1933篇
  2006年   1839篇
  2005年   1329篇
  2004年   1114篇
  2003年   1221篇
  2002年   1119篇
  2001年   1219篇
  2000年   1055篇
  1999年   783篇
  1998年   576篇
  1997年   613篇
  1996年   600篇
  1995年   567篇
  1994年   533篇
  1993年   452篇
  1992年   425篇
  1991年   402篇
  1990年   412篇
  1989年   350篇
  1988年   296篇
  1987年   285篇
  1986年   273篇
  1985年   257篇
  1984年   247篇
  1983年   266篇
  1982年   269篇
  1981年   258篇
  1980年   228篇
  1979年   237篇
  1978年   197篇
  1977年   191篇
  1976年   183篇
  1974年   189篇
  1973年   180篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
层燃—流化床焚烧城市垃圾技术   总被引:1,自引:0,他引:1  
首次提出的层燃-流化床燃烧技术是适合我国国情的城市垃圾处理技术,可使预处理过程达到最简化并保证燃烧过程的稳定必和彻底性,给出了层燃-流化床双床焚烧炉的结构和工作原理。  相似文献   
962.
在兰州炼油化工添加剂厂烷基酚装置过滤工序改造设计中 ,通过优化流程、更新设备、改善计量等措施 ,达到了消除装置瓶颈、提高生产能力、节能降耗、保证安全及解决环境污染的目的 ,取得了良好的效果。  相似文献   
963.
针对炼油厂蒸汽疏水器、锅炉排污、除氧器造成的能源浪费问题进行分析,并提出控制和解决的办法。  相似文献   
964.
Eco county construction in China   总被引:1,自引:0,他引:1  
1 IntroductionInChina,countyisthemostelementaryunitinadministration.Ithastherelativelyindependentauthorizationinpolicymakingandadministrativemanagement.Ingeneral,acountyhasalandareaof1000—4000km2withapopulationof0-2—0-8million.Sincethe1990s,countyisr…  相似文献   
965.
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited disease with a carrier frequency of approximately 1:100 in most Caucasian populations. The disease is implicated in sudden unexpected death in childhood. A prevalent disease-causing point mutation (A985G) in the MCAD gene has been characterized, thus rendering diagnosis easy in the majority of cases. Since the clinical spectrum of MCAD deficiency ranges from death in the first days of life to an asymptomatic life, there are probably other genetic factors—in addition to MCAD mutations—involved in the expression of the disease. Thus, families who have experienced the death of a child from MCAD deficiency might have an increased risk of a seriously affected subsequent child. In such a family we have therefore performed a prenatal diagnosis on a chorionic villus sample by a highly specific and sensitive polymerase chain reaction (PCR) assay for the G985 mutation. The analysis was positive and resulted in abortion. We verified the diagnosis by direct analysis on blood spots and other tissue material from the aborted fetus and from family members.  相似文献   
966.
A case of body stalk anomaly diagnosed prenatally by ultrasound during the 24th week of pregnancy in a cocaine abusing mother is presented. Accurate visualization of the fetal organs was difficult due to the severe oligohydramnios caused by premature rupture of membranes, probably related to the cocaine use. The sonographic findings were an omphalocoele, fetal attachment to the placenta, kyphoscoliosis, and absence of a floating umbilical cord. The prenatal diagnosis of the syndrome and the possible relationship with cocaine abuse are discussed.  相似文献   
967.
本文利用我国东部亚热带地区315个站点的资料,采用农业气候带分界指标,分析了北亚热带北界、中亚热带北界、南亚热带北界3个界限近百年的动态变化以及农业气候带界限波动变化对农业生产的影响。  相似文献   
968.
969.
970.
Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks.  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