全文获取类型
收费全文 | 676篇 |
免费 | 2篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 9篇 |
环保管理 | 4篇 |
综合类 | 651篇 |
基础理论 | 8篇 |
污染及防治 | 3篇 |
评价与监测 | 2篇 |
社会与环境 | 3篇 |
灾害及防治 | 2篇 |
出版年
2021年 | 6篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2013年 | 4篇 |
2012年 | 5篇 |
2011年 | 34篇 |
2010年 | 35篇 |
2009年 | 34篇 |
2008年 | 28篇 |
2007年 | 38篇 |
2006年 | 40篇 |
2005年 | 55篇 |
2004年 | 44篇 |
2003年 | 43篇 |
2002年 | 59篇 |
2001年 | 28篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1996年 | 1篇 |
1995年 | 27篇 |
1994年 | 44篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 25篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
排序方式: 共有682条查询结果,搜索用时 437 毫秒
621.
Iduronate sulphatase activity was determined in uncultured chorionic villi from four fetuses at risk for Hunter syndrome. AH fetuses were shown to be female by chromosome analysis. Biopsy material from three fetuses showed iduronate sulphatase activity within normal limits whilst the fourth fetus showed activity reduced to 7 per cent of our control mean. The importance of fetal sexing in prenatal diagnosis of this condition is emphasized as female carrier fetuses may show iduronate sulphatase activity reduced to levels observed in affected males. 相似文献
622.
Prenatal morphology of Meckel's syndrome was studied in five fetuses of different gestational age, that had been aborted because ultrasonography and elevated amniotic AFP-levels indicated neural tube defect. Histologically, the enlarged polycystic kidneys were completely alike with respect to the type of involvement and differed only in the severity of changes. They could be identified as type III cystic kidneys according to the classification of Potter. Proliferation of hepatic bile ducts and slight cystic dilatation of pancreatic ducts is already evident in the youngest fetus. Additional cyst formation in the epididymis was found in one of the cases. Occipital encephalocele, located within an apical occipital bone defect was always associated with a second mostly occult encephalocele protruding through a separate defect of the basal occipital squame and of the first and second vertebral arch. It is assumed that double encephalocele represents a constant finding in Meckel's syndrome, indicating a specific pattern within the disturbance of neural tube closure. 相似文献
623.
Amniotic band syndrome is a rare cause of fetal head deformity. We report a case in which antenatal ultrasound in the first half of pregnancy indicated the presence of a fetal cranial deformity, reported as either anencephaly or encephalocele. At assessment autopsy, disruption of the fetal skull was associated with amniotic band formation. Appropriate genetic counselling can be offered to such patients only when detailed pathological examination of the aborted fetus is made. The recurrence rate of amniotic band syndrome does not warrant amniocentesis in a subsequent pregnancy. 相似文献
624.
Markku Heikinheimo Pertti Aula Juhani Rapola Torsten Wahlström Hannu Jalanko Markku Seppälä 《黑龙江环境通报》1982,2(2):103-108
Amniotic fluid levels of pregnancy-specific β1-glycoprotein (SP1) were elevated in four pregnancies with Meckel's syndrome at 16 and 26 weeks, and the levels of hCG were also elevated in three out of four cases. These findings suggest a potential new application of SP1 measurement for prenatal diagnosis. 相似文献
625.
Dr David A. Aitken Gary McCaw Jennifer A. Crossley Esther Berry J. Michael Connor Kevin Spencer James N. Macri 《黑龙江环境通报》1993,13(8):681-689
Alpha-fetoprotein (AFP), unconjugated oestriol (UE3), intact human chorionic gonado-trophin (intHCG), and the free β subunit of chorionic gonadotrophin (FβHCG) were investigated in a series of 21 chromosomally abnormal and 14 open neural tube defect pregnancies ascertained from a series of 14 000 prospectively collected maternal serum samples at 6–14 weeks' gestation. In 16 cases of Down's syndrome, significant reductions were found for AFP (0.65 multiples of the normal median) and UE3 (0.67 MOM). IntHCG levels were unaltered (0.97 MOM) but a significant increase was found for FβHCG (1.96 MOM). Significant correlations were found for AFP and UE3 in the controls and for int HCG and FβHCG in both the control and the Down's syndrome pregnancies. In a group of five trisomy 18 pregnancies, median MOMs were for AFP 0. 71 , for UE3 0. 34 , for intHCG 0. 27 , and for FβHCG 0.15. None of 13 pregnancies with open neural tube defects at 8-13 weeks gestation had elevated maternal serum AFP levels, whereas matched second-trimester samples from the same pregnancies at 16-18 weeks gestation all had significantly elevated AFP levels. Thus, biochemical screening for chromosome abnormalities may be practicable in the first trimester using free β human chorionic gonadotrophin in combination with AFP and maternal age. However, a separate screening protocol using AFP at 15-18 weeks gestation would still be required for effective detection of neural tube defects. 相似文献
626.
For the last 6 years, sonographic signs for excessive fluid accumulation in the backs of 10- to 12-week-old fetuses have been looked for prior to transabdominal chorionic biopsy. In 1400 pregnancies, subsequent karyotype analyses revealed 28 cases of Down syndrome. In 15 ( = 54 per cent), a large fluid cushion over most of the back had been documented at the time of biopsy. Only a few chromosomally normal fetuses with the same peculiarity were observed. The cushion was also present in fetuses with trisomies 18 and 13 , and in Turner syndrome. Systematic first-trimester screening for nuchal fluid accumulation seems to be a recommended method for the detection of Down syndrome and other chromosome anomalies in young pregnant women at low risk. It compares favourably with current methods of maternal serum screening performed at 16–18 weeks which require a higher number of invasive procedures. 相似文献
627.
David P. Bick MD Daniel F. Schorderet Paul A. Price Leslie Campbell Robert W. Huff Larry J. Shapiro Charleen M. Moore 《黑龙江环境通报》1992,12(1):19-29
We report the prenatal diagnosis of a male fetus with X-linked recessive chondrodysplasia punctata (CDPX), steroid sulphatase (STS) deficiency, X-linked Kallmann syndrome (KAL), and a chromosome deletion at Xp22.31. Biochemical analysis of bone from this case indicates that CDPX is not a defect of vitamin K metabolism. Immunocytochemical study of the brain suggests that KAL is a defect in neuronal migration. 相似文献
628.
A 20-year-old woman with Beckwith-Wiedemann syndrome (BWS) was ultrasonographically appraised at intervals during her pregnancy. Unequivocal evidence for a diagnosis of BWS was obtained in the fetus and this was confirmed postnatally. Early ultrasound diagnosis enabled appropriate genetic counselling to be given; neonatal complications, such as hypoglycaemic episodes, were prevented. 相似文献
629.
Barbara F. Crandall Mitchell S. Golbus James D. Goldberg Myles Matsumoto 《黑龙江环境通报》1991,11(6):377-380
Maternal sera (MS) taken from 1396 women prior to chorionic villus sampling at 9–12 menstrual weeks were assayed for unconjugated oestriol (uE3) and alpha-fetoprotein (AFP). Median levels increased by 41 and 26 per cent per week respectively in normal pregnancies. There were 32 pregnancies with a chromosome abnormality. The median MS uE3 and AFP were 0.73 and 0.75 multiples of the median (MoM) respectively in the ten cases of Down's syndrome (DS) but not decreased in the other abnormalities. These results suggest that both uE3 and AFP may be useful in identifying DS in the first trimester. Additional prospective studies are needed to confirm these findings. 相似文献
630.
Dr. Georg Keckstein Sonja Tschurtz Volker Schneider Wolfgang Mütter Rainer Terinde Wolf-Dietrich Jonatha 《黑龙江环境通报》1990,10(1):59-65
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