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   15316篇
  免费   162篇
  国内免费   126篇
安全科学   525篇
废物处理   607篇
环保管理   2324篇
综合类   2529篇
基础理论   3952篇
环境理论   14篇
污染及防治   3804篇
评价与监测   1003篇
社会与环境   738篇
灾害及防治   108篇
  2023年   82篇
  2022年   139篇
  2021年   131篇
  2020年   104篇
  2019年   128篇
  2018年   236篇
  2017年   213篇
  2016年   326篇
  2015年   261篇
  2014年   359篇
  2013年   1187篇
  2012年   521篇
  2011年   707篇
  2010年   558篇
  2009年   628篇
  2008年   709篇
  2007年   737篇
  2006年   633篇
  2005年   561篇
  2004年   485篇
  2003年   507篇
  2002年   455篇
  2001年   549篇
  2000年   396篇
  1999年   267篇
  1998年   181篇
  1997年   198篇
  1996年   214篇
  1995年   233篇
  1994年   237篇
  1993年   198篇
  1992年   172篇
  1991年   192篇
  1990年   197篇
  1989年   174篇
  1988年   127篇
  1987年   137篇
  1986年   145篇
  1985年   110篇
  1984年   127篇
  1983年   138篇
  1982年   147篇
  1981年   134篇
  1980年   111篇
  1979年   126篇
  1978年   77篇
  1977年   84篇
  1975年   85篇
  1974年   71篇
  1973年   73篇
排序方式: 共有10000条查询结果,搜索用时 921 毫秒
211.
212.
213.
214.
A fetus with multiple structural defects was seen at prenatal ultrasound examination. After termination of the pregnancy a bilateral cleft lip, alveolus, and palate; micrognathia; and webbed joints were seen. Fetal tissues showed indications of infection, intranuclear inclusion bodies, chronic stress, haemolysis, arterial wall damage, and profuse haemorrhage. Parvovirus B19 DNA was detected in fetal tissues by dot hybridization after polymerase chain reaction. The possibility of parvovirus B19 infection leading to congenital malformations is discussed.  相似文献   
215.
1977~1998年间,在苏格兰西部的艾尔萨克雷格对收集到的塘鹅蛋中的多氯联苯(PCB)同类物进行了回顾性分析.对一些年份所收集的塘鹅蛋中每年选择8~10个对其PCB同类物浓度范围分别进行了分析.所有的同类物在几年之内浓度都降在低,但不同的同类物降解速率不同.  相似文献   
216.
We present a remarkable chain of events in which percutaneous umbilical cord sampling was performed in an attempt to clarify a situation of possible fetal sex chromosome mosaicism in an amniotic fluid culture and led to the discovery that the mother herself had a 45,X/46,XX/ 47.XXX chromosome constitution. This may have simply represented the chance concurrence of pseudo-mosaicism in the amniotic fluid culture of a woman with an abnormal sex chromosome constitution, but it is also possible that the 45,X colony was maternal in origin. Although clearly a most unusual circumstance, the possibility should be kept in mind when termination of a pregnancy is being considered because of apparent mosaicism in a prenatal diagnostic study.  相似文献   
217.
218.
219.
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   
220.
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