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   302篇
  免费   2篇
  国内免费   5篇
安全科学   2篇
废物处理   1篇
环保管理   10篇
综合类   238篇
基础理论   26篇
污染及防治   22篇
评价与监测   6篇
社会与环境   1篇
灾害及防治   3篇
  2022年   2篇
  2021年   3篇
  2020年   5篇
  2019年   3篇
  2018年   2篇
  2017年   8篇
  2015年   2篇
  2014年   5篇
  2013年   10篇
  2012年   2篇
  2011年   9篇
  2010年   3篇
  2009年   4篇
  2008年   3篇
  2007年   2篇
  2006年   2篇
  2005年   9篇
  2003年   4篇
  2002年   3篇
  2001年   5篇
  2000年   2篇
  1995年   50篇
  1994年   27篇
  1993年   40篇
  1992年   44篇
  1991年   28篇
  1990年   17篇
  1989年   8篇
  1987年   1篇
  1986年   1篇
  1983年   2篇
  1981年   1篇
  1975年   1篇
  1964年   1篇
排序方式: 共有309条查询结果,搜索用时 15 毫秒
131.
We describe a previously unknown congenital abnormality of the lymphatic system, characterized by multiple cystic lesions of the lower extremities and thorax. Diagnosis was made by ultrasound in the second trimester. The ultrasound findings, pathology results, and differential diagnosis are presented.  相似文献   
132.
A case of X-linked hydrocephaly is presented. Early second trimester evaluation of the size of the lateral cerebral ventricles resulted in onemale fetus cfontinuing further normal developmentand one male fetus being abroted because of progressive hydrocephaly. The affected fetus was characterized by cerebral ventricular dilation without aqueductal stenosis. This case history shows the feasibility of early monitoring of pregnancies at risk of X-linked hydrocephaly. In some cases, ventricular enlargement rather than aqueductal stenosis may be the primary lesion.  相似文献   
133.
A prenatal diagnosis of campomelic dysplasia in a primigravida is described. First level fetal ultrasonography demonstrated bowing and shortening of lower limbs. Second level examination allowed the correct diagnosis by demonstrating several skeletal anomalies pathognomonic of campomelic dysplasia.  相似文献   
134.
We describe here the first case of neonatal death due to the hyperornithinaemia, hyperammonaemia, and homocitrullinuria (HHH) syndrome and the first prenatal diagnosis of this disorder in a subsequent pregnancy in this family.  相似文献   
135.
We report two cases of prenatal detection of lissencephaly by high-resolution ultrasound. The first case studied was referred for high-risk obstetrical management and serial antenatal ultrasounds because of a family history of lissencephaly in an unresolved chromosomal abnormality. Diagnosis of a smooth gyral pattern consistent with lissencephaly was made at 32 weeks' gestation. The second case was referred for prenatal ultrasound because of a size versus dates discrepancy. The ultrasound examination showed a smooth gyral pattern at 31.5 weeks. In light of this ultrasound finding, a fetal blood sample was obtained and a chromosomal abnormality reported, confirming the diagnosis. To our knowledge, these cases represent the first report of the sonographic prenatal diagnosis of cerebral agyria or lissencephaly.  相似文献   
136.
A case is presented in which chorionic villus direct preparation and cultured chorionic villus cells revealed a 47,XX, + mar karyotype. The marker was a small metacentric chromosome and appeared to be i(18p)—isochromosome 18p. Follow-up studies in both amniotic fluid and fetal fibroblasts confirmed the karyotype. In order to characterize the marker, a panel of biotinylated DNA probes was used, including a whole chromosome 18 probe, chromosome 18-specific alpha satellite DNA, Yac clones, and a pan-telomeric probe. These studies show that the marker is a monocentric i(18p) in which about 80 per cent of chromosome 18 alpha satellite DNA has been lost.  相似文献   
137.
The sonographic diagnosis of fetal neural tube defects (NTDs) has been enhanced by the recognition of associated brain and skull anomalies. Previous reports have found these anomalies to be accurate in predicting spina bifida after 16 weeks' gestation, and an inverse correlation was suggested between the presence of these sonographic markers and gestational age. Therefore, we assumed that early second-trimester sonography would be at least as accurate as that performed after 16 weeks' gestation. To examine this hypothesis, we looked for the presence of these cranial sonographic markers suggestive of open NTDs in 8011 low-risk cases, using transvaginal sonography (TVS), between the 12th and 17th week of gestation (menstrual age). Fetal NTDs were identified in ten cases (l.25%o). The NTDs were cervico-cranial in three, lumbo-sacral in six, and thoracal in one of the ten cases. None of the seven cases examined was dyskaryotic. Cerebellar dysmorphism, ‘banana’ sign, cerebellar absence, and hypoplasia were detected in all the low NTDs, usually before the detection of the spinal lesion. All the sonographically diagnosed malformations were confirmed by post-abortal examination except in one case, where the patient decided to continue the pregnancy and refused follow-up. We therefore conclude that transvaginal sonographic examination of the fetal skull before the 17th week of gestation is an accurate method for the detection of low NTDs.  相似文献   
138.
Intrauterine fetal movement plays a key role in normal embryonic and fetal development (Moessinger, 1983). When movement is absent or decreased, abnormal development takes place which can be appreciated in newborns and/or fetuses with the fetal akinesia/ hypokinesia sequence. This sequence is caused by a number of heterogeneous entities which result in decreased fetal movements by the action of intrinsic or extrinsic factors. Prenatal diagnosis of the akinesia/hypokinesia sequence may be possible during the second trimester through the use of real-time ultrasonographic evaluation of fetal movement. We report a family with three consecutive affected pregnancies in which the prenatal presentation of this sequence varied. Based on the phenotypic findings of the three affected fetuses, we believe that although they superficially resemble those features found in the New–Laxova syndrome, they are probably affected with a distinctly different lethal form of akinesia/ hypokinesia transmitted in an autosomal recessive fashion.  相似文献   
139.
Aplasia cutis congenita associated with epidermolysis bullosa and pyloric atresia is a rare congenital disease in which localized or widespread areas of skin are absent at birth. Alpha- fetoprotein (AFP) and skin biopsy have been used for prenatal diagnosis of this condition. A patient in whom normal levels of amniotic AFP at 16 weeks' gestation presumably excluded the disease and who was at risk for aplasia cutis congenita associated with epidermolysis bullosa and pyloric atresia is described. However, 10 weeks later, ultrasonographic examination revealed hydramnios, a dilated stomach, a deformed external ear, and a contracted fisted hand. All signs were confirmed postnatally. The role of ultrasonography and the value of other diagnostic methods in this congenital disease are discussed.  相似文献   
140.
The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 case samples—from women with MSAFP levels greater than 3·0 multiples of the median (MOM) and pregnancies that ended in fetal loss—and 44 matched control samples—from women with MSAFP levels greater than 0·4 and less than 2·2 MOM and live births at term—were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio=0·77, 95 per cent confidence interval 0·28–2·11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing.  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