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   286篇
  免费   1篇
  国内免费   4篇
安全科学   2篇
环保管理   2篇
综合类   263篇
基础理论   17篇
污染及防治   3篇
评价与监测   4篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2019年   1篇
  2016年   1篇
  2014年   2篇
  2013年   2篇
  2012年   4篇
  2011年   3篇
  2010年   2篇
  2009年   4篇
  2008年   5篇
  2007年   4篇
  2006年   7篇
  2005年   2篇
  2004年   7篇
  2001年   1篇
  2000年   2篇
  1999年   3篇
  1995年   5篇
  1994年   13篇
  1993年   27篇
  1992年   20篇
  1991年   21篇
  1990年   21篇
  1989年   21篇
  1988年   16篇
  1987年   20篇
  1986年   12篇
  1985年   14篇
  1984年   11篇
  1983年   15篇
  1982年   10篇
  1981年   10篇
排序方式: 共有291条查询结果,搜索用时 15 毫秒
261.
In a retrospective analysis of 28 cases of fetal diaphragmatic hernia, overall mortality was 86 per cent, but fell to 70 per cent when multiple anomalies were excluded. Congenital heart disease constituted the majority of associated anomalies. The incidence of an abnormal karyotype was 10·5 per cent, but rose to 20 per cent when only fetuses with multiple anomalies were included. Polyhydramnios, which occurred in 75 per cent, was a poor predictor of fetal outcome. The same applied to the intrathoracic position of the fetal stomach. In all four survivors, diaphragmatic hernia was diagnosed beyond 32 weeks of gestation.  相似文献   
262.
A prenatal diagnosis of right atrial isomerism is often inferred through the recognition of a constellation of cardiac anomalies on the four-chamber view or by the detection of visceral heterotaxy and asplenia. However, the actual occurrence of discordance between the arrangement of the atria and thoracic and abdominal organs makes the identification of the morphology of both atrial appendages the only reliable way to make a final diagnosis of atrial isomerism. Three cases of right atrial isomerism with visceral heterotaxy and a complex cardiac defect, diagnosed in utero by cross-sectional and colour flow Doppler echocardiography, are reported. In all the patients, the right atrial isomerism was associated with an atrioventricular septal defect, a single aortic outlet from the right ventricle, and total anomalous venous return. The diagnosis of right atrial isomerism, always confirmed by neonatal re-evaluation and/or by post-mortem examination, was made through identifying two pyramidal atrial appendages in an echocardiographic transverse plane at the level of the atria and of the origin of the great arteries. This report demonstrates that a final intrauterine diagnosis of atrial isomerism is possible, whatever the visceral situs is.  相似文献   
263.
Cytomegalovirus is the most common cause of congenital viral infection. In utero infection is usually suspected in patients with growth-retarded fetuses or when maternal illness precipitates serological investigations. A case is presented where routine ultrasound examination at 30 weeks' gestation in an asymptomatic patient demonstrated mild fetal ventriculomegaly. Transvaginal ultrasound enabled the visualization of intraventricular adhesions and small periventricular cysts. The suspected diagnosis of in utero cytomegalovirus infection was confirmed by the presence of IgM antibodies in fetal blood and subsequently by isolation of the virus from the infant's urine. The presence of mild fetal ventriculomegaly should prompt transvaginal brain imaging.  相似文献   
264.
通过温室盆栽试验,研究亚铵法造纸废液干粉对绿豆(Vigna radiate)苗根系的AM真菌侵染及其地上部生物量的影响。结果发现,添加适量造纸废液干粉可以加速AM真菌对绿豆苗根系的侵染;添加质量分数0.1%造纸废液干粉,出苗4周时绿豆苗根系的AM真菌侵染率比对照提高80%,出苗7周时地上部生物量比对照提高20%;添加质量分数0.2%~0.5%造纸废液干粉,绿豆苗根系的AM真菌侵染率和地上部生物量在出苗4周之后均不同程度低于对照。结果表明,添加质量分数0.1%左右亚铵法造纸废液干粉对AM真菌侵染绿豆苗根系和植株生长具有较好促进作用。  相似文献   
265.
266.
Between October 1985 and February 1989, 49 ultrasound-guided intravascular fetal blood transfusions were performed in 16 patients (14 with rhesus (Rh) isoimmunization, 2 with non-immunologic hydrops fetalis (NIHF)). As an intra-operative complication, perivascular haematoma of the cord occurred in three patients (7 per cent). In two cases, fetal bradycardia necessitated delivery by Caesarean section at 30 and 32 weeks' gestation, respectively. In the third case, fetal bradycardia developed during transfusion, at 31 weeks' gestation, but normalized within 3 min. The baby was delivered as planned at 36 weeks of gestation, after another transfusion at 34 weeks. Dislodgement of the needle tip into perivascular tissue, caused by sudden fetal or maternal movements, is the reason for this complication. The haematoma develops as a result of delayed recognition and continuous transfusion into Wharton' s jelly. Cord haematoma may be diagnosed in time by continuous ultrasound imaging, as illustrated in case 3. To minimize the risk of needle dislodgement during transfusion, sedation of the mother and complete immobilization of the fetus by injecting a short-acting muscle relaxant into the umbilical vessel are recommended.  相似文献   
267.
Five hundred cordocenteses were performed between 12 and 21 weeks. The indications were thalassaemia (386), rapid karyotyping (97), feto-maternal allo-immunization (10), rubella (6), and toxoplasmosis (1). One hundred and ten pregnancies underwent termination on the basis of the result, while 20 of the 370 pregnancies intended to continue were lost to follow-up. Amongst these were 16 fetal losses (4·3 per cent) and 22 premature deliveries (5·9 per cent); no other complications were reported. Four adverse prognostic factors were identified: (a) cord bleeding; (b) fetal bradycardia; (c) prolonged procedure time; and (d) anterior insertion of the placenta. There was no‘obvious’ difference in fetal loss rate with advancing gestation until 19–21 weeks, when the risk of fetal loss decreased to 2·5 per cent.  相似文献   
268.
Magnetic resonance (MR) imaging was performed on two women at the 33rd and 34th pregnancy week, respectively, after ultrasonographic detection of a brain malformation. Fetal neuromuscular blockade was induced by pancuronium bromide injected into the umbilical vein under continuous ultrasound (US) guidance. MR images supported the echotomographic diagnosis of holoprosencephaly, improving the image quality and offering additional information in such cases of difficult differential fetal diagnosis. Holoprosencephaly was finally confirmed by neonatal US and autopsy (case 1), US, CT and MR (case 2).  相似文献   
269.
A case of a prenatally recognized hepatic mesenchymal hamartoma is presented and the literature reviewed. These tumors are benign and usually present in early infancy with symptoms that are related to the mass effect on adjacent organs. Radiologic methods used in the past to image this tumor include angiography and ultrasound. However, there is no specific radiologic finding, and, therefore, the diagnosis is usually made during surgery. Once the tumor is removed, the prognosis is generally good. With the increasing use of high resolution ultrasound in prenatal diagnosis, this rare tumor should be considered in the differential diagnosis of any multicystic mass found in the fetal abdomen. The recognition of a mass should then alert the physician to the need for early neonatal intervention.  相似文献   
270.
Four cases of multiple gestation with second trimester death of one fetus and subsequent damage to a survivor are reported. Monochorionic placentation was documented in three of the cases. Central nervous system lesions occurred in all cases, and bowel injury was noted in two of the damaged fetuses. Although rare maternal clotting problems have been reported in similar situations, none was noted in any of these four cases. Prior reports have indicated that losses in the first half of gestation were of no consequence to the surviving fetuses. These four cases contradict this suggestion, and indicate that close sonographic observation of the survivors is important in any multiple gestation where one fetus has died.  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