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   756篇
  免费   4篇
  国内免费   17篇
安全科学   12篇
环保管理   17篇
综合类   676篇
基础理论   30篇
环境理论   2篇
污染及防治   17篇
评价与监测   6篇
社会与环境   10篇
灾害及防治   7篇
  2023年   2篇
  2022年   2篇
  2021年   7篇
  2020年   8篇
  2018年   3篇
  2017年   4篇
  2016年   5篇
  2015年   2篇
  2014年   4篇
  2013年   19篇
  2012年   20篇
  2011年   80篇
  2010年   69篇
  2009年   53篇
  2008年   53篇
  2007年   59篇
  2006年   52篇
  2005年   53篇
  2004年   50篇
  2003年   52篇
  2002年   46篇
  2001年   30篇
  1999年   2篇
  1997年   1篇
  1996年   2篇
  1995年   36篇
  1994年   29篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1990年   4篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1984年   6篇
  1983年   4篇
  1982年   1篇
  1979年   1篇
排序方式: 共有777条查询结果,搜索用时 234 毫秒
601.
602.
603.
It is generally recognized that the sonographic findings of infantile polycystic kidney disease (IPKD) are bilaterally enlarged kidneys, oligohydramnios, an absent fetal bladder, and the typical kidney texture. Since there is a broad spectrum of renal compromise with IPKD, in utero diagnosis is thought to be limited to the severe forms. This paper reports a mild case of IPKD, where the in utero diagnosis was established by measuring fetal urine production and amniotic fluid volume serially during pregnancy, and by ultrasonographic examination of fetal kidneys.  相似文献   
604.
CA-125, alpha-fetoprotein (AFP), and human chorionic gonadotropin (HCG) were determined in maternal serum in the first trimester from 14 women with a Down's syndrome fetus and 61 women with a healthy fetus. In the second trimester, 15 and 60 serum samples were determined from women with a Down's syndrome and a healthy fetus respectively. In both trimesters, maternal serum CA-125 was found to be elevated in Down's syndrome pregnancies compared with controls. Using discrimination functions, our preliminary results indicate that CA-125 is a better marker than AFP and HCG respectively for a Down's syndrome fetus in the first trimester and improves the detection rate in the second trimester.  相似文献   
605.
The objective of the study was to evaluate the psychological reaction of two groups of parents to a pregnancy termination after they had undergone a prenatal diagnostic procedure. The analysis involved interviews with a study group of 76 patients who were at risk of giving birth to a child with a genetic disease or defect and a comparison group of 124 who had a pregnancy termination after a major anomaly had been detected by routine ultrasound and who were not at known risk for a genetic disease. Only patients in the study group had received counselling before the prenatal diagnosis and were aware that the fetus could be affected. The overall reaction of the comparison group was one of shock, denial of fetal abnormality, and guilt over ‘abandoning the fetus’. A feeling of guilt was expressed by patients in the comparison group (73 per cent versus 29 per cent) in the period immediately following the interruption. One-third of patients in both groups felt obliged to undergo a therapeutic abortion. More patients in the study group than in the comparison group expressed the need to see a psychiatrist at the time of the study (19 per cent versus 7 per cent) and viewed future pregnancies as a replacement for the lost pregnancy (63 per cent versus 19 per cent). The recommendations of the study focus on information sessions to personnel, nursing support, analgesia during the expulsion period, an atmosphere of respect that should be present at the time that the fetus is viewed, the anticipation of mourning, and the long-term follow-up of the couple to ensure that counselling for future pregnancies and psychological support are provided when needed.  相似文献   
606.
In our previous work we have isolated fetal cells from maternal blood and used fluorescent in situ hybridization (FISH) for chromosome-specific probes to detect aneuploidy. Current efforts in the Baylor College of Medicine programme are focusing on obtaining consistency in flow-sorting methodology and on determining sensitivity and specificity. To this end, systematic evaluation of five glycophorin A (gly A) antibodies all produced agglutination, leading us to abandon the use of gly A antibodies for positive selection of fetal cells. Conversely, we have found LDS-751 to be useful for nuclear selection. CD45 negative selection can best be accomplished by the use of flasks coated with goat antibodies against mouse antibodies. Positive selection by flow sorting for either CD71+ cells or gamma-globin-positive cells seems to be successful. Using these two approaches, we have recently detected male (fetal) cells in pregnancies in which the fetus was 46, XY in 10 of 18 and in 12 of 14 cases, respectively.  相似文献   
607.
Blood collected from 62 fetuses aged 20–38 weeks of gestation was studied. The values of ten lipid parameters were determined: cholesterol (TC), triglycerides (TGs), apolipoprotein Al (apo A1), apolipoprotein B (apo B), apolipoprotein E (apo E), total apolipoprotein CIII (apo CIII), apolipoprotein CIII present in particles containing apo B (apo CIII LpB) or not (apo CIII Lp non-B), lipoparticles A1 (LpA1), and lipoprotein a (Lp(a)). The results show that, except for apo E, all the studied parameters were present in lower concentrations than in adults and newborns, and that Lp(a) is not detectable at that stage in life.  相似文献   
608.
In the majority of congenital peroxisomal disorders, β-oxidation of very long chain fatty acids is deficient. We have investigated the appearance and localization of the three peroxisomal β-oxidation enzymes in normal fetal liver (fertilization age between 5 and 18 weeks) with protein A- gold immunocytochemistry and silver enhancement for light microscopic visualization. With specificity-tested polyclonal antibodies, acyl-CoA-oxidase, bifunctiooal enzyme, and 3-oxoacyl-CoA thiolase were localized in the peroxisomes of the parenchymal cells, which appear as brown or black granules. In the youngest specimen, no immunopositive reaction was obtained. A weak reaction with anti-thiolase was obtained at the age of 6–7 weeks. At a fertilization age of 8 weeks, peroxisomes could be distinctly visualized after immunostaining for all three enzymes. From a staining series with anti-thiolase on simultaneously treated slides, it appears that the amount of antigen per peroxisome and the organelle size increase between the seventh and eighteenth weeks. These data should enable a more specific diagnosis in fetal liver biopsies from pregnancies at risk and after termination of pregnancy.  相似文献   
609.
Isoelectric focusing (IEF) of amniotic fluid α-fetoprotein (AFP) in thin-layer polyacrylamide gels containing 8 M urea followed by immunoblotting reveals at least nine bands, band I lying next to the cathode. Compared with 298 amniotic fluid samples from normal pregnancies, we found that the density of band V was increased in seven cases of fetal death. In 16 amniotic fluid samples from pregnancies with open neural tube defects (ONTO), band V disappeared or was markedly decreased. In seven cases with elevated AFP and positive acetylcholines-terase (AChE) due to contamination with fetal blood, no difference in pattern was observed compared with samples from normal pregnancies. It is suggested that IEF of AFP and subsequent immunoblotting are an apparently diagnostic test for ONTD and intrauterine fetal death (IUFD).  相似文献   
610.
Antiphospholid antibodies are associated with fetal distress and fetal death. Although different therapeutic regimens have been used, the incidence of fetal growth retardation varies between 30 and 60 per cent of reported cases. We report the evolution of fetal growth in patients with antiphospholipid antibody syndrome treated with high-dose intravenous immunoglobulins (IVIG). Fourteen patients with a history of recurrent spontaneous abortion and immunological diagnosis of antiphospholipid syndrome were followed longitudinally. Intravenous immunoglobulin at a dose of 0.5 g/kg body weight for two consecutive days was started from the fifth week of pregnancy and repeated every 4 weeks until the 33rd week of gestation. Fetal biometry was evaluated longitudinally from the appearance of the gestational sac at 4 weekly intervals. In the period between 26 and 34 weeks, the frequency of evaluation was increased to every 14 days. Data obtained were compared with a control group of 70 fetuses with uneventful pregnancies matched for gestational age. Neonatal weight is shown in relation to the centiles for the normal population. One patient out of 14 (7.1 per cent) developed gestational hypertension and abruptio placentae. No other pregnancy complications were seen. No proteinuria was found. The mean maternal age was 31.2±3.8 years. Median birth weight was 3433 g±287. The median centile of the birth weight was 65.3±18.6. Mean gestational age at delivery was 1.3 weeks. No fetal or neonatal growth retardation was seen. No significant differences were found in the biometrical parameters investigated in the various gestational ages vs. the control group (Student's t-test not significant); a significant increase in head circumference (P< 0.001) and abdominal circumference (P< 0.05) was found at 36–37 weeks gestational age in the IVIG-treated fetuses. The presence of antiphospholipid antibodies is considered detrimental for pregnancy outcome because of their negative effects on placental vascular perfusion and fetal transfer of metabolites. The use of IVIG seems to avoid or inhibit the reduced availability of nutrients for the fetal anabolic functions, as the expected reduction in fetal growth was not seen in our series.  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