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   36935篇
  免费   354篇
  国内免费   465篇
安全科学   876篇
废物处理   1365篇
环保管理   4436篇
综合类   9803篇
基础理论   8341篇
环境理论   10篇
污染及防治   8866篇
评价与监测   2011篇
社会与环境   1863篇
灾害及防治   183篇
  2022年   331篇
  2019年   269篇
  2018年   488篇
  2017年   462篇
  2016年   676篇
  2015年   524篇
  2014年   779篇
  2013年   2702篇
  2012年   951篇
  2011年   1286篇
  2010年   1084篇
  2009年   1240篇
  2008年   1365篇
  2007年   1423篇
  2006年   1221篇
  2005年   1036篇
  2004年   1070篇
  2003年   1089篇
  2002年   969篇
  2001年   1274篇
  2000年   896篇
  1999年   601篇
  1998年   433篇
  1997年   406篇
  1996年   459篇
  1995年   508篇
  1994年   497篇
  1993年   446篇
  1992年   455篇
  1991年   451篇
  1990年   485篇
  1989年   462篇
  1988年   380篇
  1987年   377篇
  1986年   337篇
  1985年   381篇
  1984年   375篇
  1983年   363篇
  1982年   377篇
  1981年   385篇
  1980年   336篇
  1979年   347篇
  1978年   295篇
  1977年   270篇
  1976年   280篇
  1974年   288篇
  1973年   283篇
  1972年   280篇
  1967年   311篇
  1966年   270篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
741.
Two types of fermented organic waste (trade and industry waste and fruit and vegetable waste) were successfully used as a sole carbon source to produce poly-3-hydroxybutyrate-co-valerate (PHBV) by Ralstonia eutrophus (formerly Alcaligenes eutrophus) via oxygen limitation.The production of PHBV could be optimized by optimizing the oxygen transfer through the fermentor. Thereby, a peak concentration of 1.1 g PHBV per liter cell suspension, 40 w% of cell dry weight, was obtained at an aeration rate of 0.24 mol O2/h·kg biomass. The yield of PHBV on the fatty acid concentration in the organic waste was 0.16 g polymer/g volatile organic matter. The process obtained, compares well with the commercial production process of PHBV based on glucose.  相似文献   
742.
743.
One hundred and fifty-one women of advanced maternal age who underwent genetic termination of pregnancy (TOP) were studied for their reproductive behaviour and the type of procedure for prenatal diagnosis in a subsequent pregnancy. A total of 59 women (39 per cent) had a further pregnancy. In all continuing pregnancies prenatal diagnosis was performed, of which 75 per cent consisted of chorionic villus sampling (CVS). Reproductive behaviour following a genetic termination was negatively correlated with maternal age and parity. Both reproductive behaviour and the choice to undergo a diagnostic procedure in the next pregnancy were independent of the type of diagnostic procedure in the previous affected pregnancy.  相似文献   
744.
745.
746.
747.
748.
749.
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   
750.
We report two cases of apparently balanced complex de novo chromosomal rearrangements (BCCR) detected prenatally at 17 weeks and 10 weeks of gestation, respectively. Chromosomes were studied using GTG-banding and fluorescent in situ hybridization (FISH). In one case four chromosomes and in the other case three chromosomes were involved in the rearrangements. One of the pregnancies was terminated and no external or internal abnormalities were detected at autopsy. The other pregnancy continued to term. Level III ultrasound examination showed no abnormalities. The child is now 3 years old and has neither congenital anomalies nor evidence of delayed psychomotor development.  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