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   33475篇
  免费   420篇
  国内免费   278篇
安全科学   1068篇
废物处理   1206篇
环保管理   5069篇
综合类   5110篇
基础理论   9607篇
环境理论   28篇
污染及防治   8490篇
评价与监测   1970篇
社会与环境   1380篇
灾害及防治   245篇
  2022年   211篇
  2021年   223篇
  2020年   203篇
  2019年   270篇
  2018年   482篇
  2017年   486篇
  2016年   714篇
  2015年   588篇
  2014年   809篇
  2013年   2490篇
  2012年   1017篇
  2011年   1479篇
  2010年   1183篇
  2009年   1222篇
  2008年   1453篇
  2007年   1538篇
  2006年   1359篇
  2005年   1155篇
  2004年   1150篇
  2003年   1063篇
  2002年   1050篇
  2001年   1309篇
  2000年   933篇
  1999年   600篇
  1998年   487篇
  1997年   481篇
  1996年   495篇
  1995年   547篇
  1994年   499篇
  1993年   446篇
  1992年   455篇
  1991年   405篇
  1990年   405篇
  1989年   446篇
  1988年   374篇
  1987年   335篇
  1986年   305篇
  1985年   336篇
  1984年   326篇
  1983年   363篇
  1982年   369篇
  1981年   309篇
  1980年   269篇
  1979年   285篇
  1978年   253篇
  1977年   209篇
  1976年   214篇
  1975年   200篇
  1974年   177篇
  1972年   207篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
491.
492.
493.
494.
495.
The sinusoidal fetal heart rate pattern has been described in association with severe fetal anaemia, with fetal hypoxaemia, and with the administration of parenteral narcotics. Here, we report a case of decreased fetal movement in which a sinusoidal tracing was recorded. The sonographic diagnosis of a massive fetal intracranial haemorrhage was made. A non-interventive approach was taken and the fetus died soon after in utero. We review 28 previous cases in which the prenatal sonographic diagnosis of fetal intracranial haemorrhage was made, including the underlying maternal and fetal factors and neonatal outcomes. We propose that the sinusoidal tracing in this case was due to the intracranial bleed and suggest that fetal intracranial haemorrhage be considered in the sonographic evaluation of the fetus with a sinusoidal pattern.  相似文献   
496.
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   
497.
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   
498.
In a case of hydrops fetalis, serological examination showed a recent maternal human parvovirus B19 infection. Amniocentesis revealed a unique unbalanced translocation between chromosomes 3 and 11 of the fetus. The mother proved to have a balanced reciprocal translocation between chromosomes 3 and 11. A grossly macerated hydropic male fetus was delivered with a flat nose and low implanted deformed ears. Histopathological examination revealed nuclear inclusion bodies in fetal erythroid cells, confirming human parvovirus B19 infection. Parvovirus B19 DNA was demonstrated by in situ hybridization in the nuclei of heart muscle cells. Our finding of two different disorders in one case illustrates the importance of a complete evaluation of every case of hydrops fetalis, especially concerning counselling on the outcome of future pregnancies. The human parvovirus B19 infection will not recur due to the acquired immunity of the mother, whereas the balanced reciprocal translocation will endanger future pregnancies.  相似文献   
499.
A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features.  相似文献   
500.
A simplified method is described for processing both direct preparations and long-term cultures from the same fragment of chorionic villi. Enzyme separation of the outer trophoblast layers (used for direct preparations) from the inner mesenchymal core (used to initiate long-term cultures) facilitates the utilization of the same fragments for the two procedures, without jeopardizing the success of either method. This has proved useful in cases where the sample was so small that only one method of chromosome preparation may have been possible using other techniques.  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