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   16811篇
  免费   213篇
  国内免费   140篇
安全科学   486篇
废物处理   615篇
环保管理   2352篇
综合类   3196篇
基础理论   4252篇
环境理论   11篇
污染及防治   4113篇
评价与监测   1029篇
社会与环境   980篇
灾害及防治   130篇
  2022年   151篇
  2021年   138篇
  2020年   120篇
  2019年   163篇
  2018年   222篇
  2017年   272篇
  2016年   366篇
  2015年   299篇
  2014年   412篇
  2013年   1401篇
  2012年   507篇
  2011年   702篇
  2010年   552篇
  2009年   607篇
  2008年   676篇
  2007年   714篇
  2006年   675篇
  2005年   532篇
  2004年   520篇
  2003年   527篇
  2002年   463篇
  2001年   561篇
  2000年   429篇
  1999年   246篇
  1998年   209篇
  1997年   202篇
  1996年   221篇
  1995年   221篇
  1994年   218篇
  1993年   210篇
  1992年   220篇
  1991年   205篇
  1990年   209篇
  1989年   177篇
  1988年   159篇
  1987年   135篇
  1986年   161篇
  1985年   160篇
  1984年   163篇
  1983年   166篇
  1982年   160篇
  1981年   165篇
  1980年   154篇
  1979年   146篇
  1978年   108篇
  1977年   122篇
  1974年   109篇
  1973年   91篇
  1972年   107篇
  1971年   88篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
171.
The attitudes of 190 patients who had undergone chorionic villus sampling (CVS) were assessed by means of a questionnaire. One hundred and fifty-two patients replied of whom 68 (45 per cent) were referred because of increased maternal age and in the other 84 cases the indications included previous chromosomal abnormalities, fetal sexing, DNA analysis, and biochemical analysis. One hundred and twenty-two patients had a transcervical procedure, 24 had a transabdominal, and six patients required both procedures. One hundred and forty-one patients (93 per cent) reported CVS to be a satisfactory procedure, and the same percentage thought earlier diagnosis was beneficial. Thirty-nine patients (81 per cent) reported a better experience with CVS than with a previous amniocentesis. A majority of patients (93 per cent) wished a CVS in a future pregnancy and 137 patients (97 per cent) would accept a risk of miscarriage from the procedure of twice that quoted for amniocentesis (1 per cent).  相似文献   
172.
Selective termination by intracardiac potassium chloride injection was performed in twins discordant for hydrocephaly at 20 weeks' gestation. Because of the potential for vascular anastomoses to exist between the twins, fetal angiography was performed prior to the selective termination procedure. Determination of vascular connections between the fetuses was hindered by fetal bradycardia following intracardiac administration of contrast material. Selective termination was performed without difficulty using intracardiac potassium chloride (KCl) to produce asystole in the twin with hydrocephaly. The unaffected fetus appeared active and had a normal heart rate during and immediately after the procedure. However, both twins were found to have died the following day. Pathologic examination documented several vascular anastomoses between the monochorionic, diamniotic fetuses. A likely cause of death was exsanguination of the normal twin into the abnormal one. This case illustrates the difficulties encountered in selective termination of monozygotic twins and, to our knowledge, represents the first reported use of intrauterine fetal angiography.  相似文献   
173.
Cytogenetic study of chorionic villi sampled because of advanced maternal age revealed, after overnight culture, an apparently non-mosaic trisomy 7. Amniocentesis showed exclusively normal mitoses, and the pregnancy continued normally. One hundred mitoses from cord blood of the normal newborn revealed a non-mosaic 46,XX complement. No cells with a proven trisomy 7 were found in cultures from either of two biopsies of the morphologically normal placenta, but the peripheral biopsy showed in multiple cultures an abnormal clone: 47,XX, + 20,-2,-21, + t(2;21)(p13;q22). To our knowledge, this is the first case of non-mosaic trisomy 7 detected on CVS which has had follow-up studies of amniotic fluid, cord blood, and term placenta.  相似文献   
174.
The prenatal diagnosis of The Turner Syndrome is described at a menstrual age of 12 weeks. Detection of cystic hygroma was followed by vaginal chorionic villous sampling (CVS) which revealed a 45,X karyotype. Early documentation of fetal karyotype in the presence of a cystic hygroma is essential for accurate diagnosis and genetic counselling.  相似文献   
175.
Prenatal real-time ultrasonographic diagnosis of microphthalmia is presented. Diagnosis was made at 18 weeks' gestation in a fetus of a patient with a previous infant affected with the syndrome of cryptophthalmia with absence of septum nasi and ambiguous genitalia (Fraser syndrome). Recognition of microphthalmia as a part of Fraser syndrome and the easy visualization of fetal facial bones and orbits in the second trimester made the diagnosis possible.  相似文献   
176.
177.
178.
179.
180.
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