全文获取类型
收费全文 | 1257篇 |
免费 | 46篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 128篇 |
废物处理 | 11篇 |
环保管理 | 267篇 |
综合类 | 777篇 |
基础理论 | 72篇 |
污染及防治 | 21篇 |
评价与监测 | 34篇 |
社会与环境 | 6篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 20篇 |
2018年 | 12篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 29篇 |
2013年 | 36篇 |
2012年 | 45篇 |
2011年 | 50篇 |
2010年 | 32篇 |
2009年 | 25篇 |
2008年 | 23篇 |
2007年 | 31篇 |
2006年 | 31篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 15篇 |
1994年 | 31篇 |
1993年 | 76篇 |
1992年 | 50篇 |
1991年 | 53篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 47篇 |
1987年 | 51篇 |
1986年 | 26篇 |
1985年 | 37篇 |
1984年 | 75篇 |
1983年 | 43篇 |
1982年 | 36篇 |
1981年 | 18篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1972年 | 50篇 |
1971年 | 56篇 |
1967年 | 1篇 |
排序方式: 共有1327条查询结果,搜索用时 20 毫秒
521.
Family studies including the proband are usually needed before a prenatal diagnosis may be performed for Duchenne muscular dystrophy. We report here on prenatal diagnosis in a family where the solitary index case was dead, and where the consultand and her mother were assumed to be carriers by independent evidence. DNA anaylsis revealed that both the consultand and her mother had an X chromosome deleted for DNA material in the Xp21 region. The female fetus also carried the deleted X chromosome. 相似文献
522.
Jeffrey S. Duncan Martha T. Fernandez Patricia L. Abbitt Siva Thiagarajah Stuart S. Howards W. Allen Hogge M.D. 《黑龙江环境通报》1990,10(3):175-182
To delineate the natural history of fetal multicystic dysplastic kidneys (MDKs), all cases that were prenatally detected in the Prenatal Diagnosis Center of the University of Virginia from September 1985 to 31 August 1988 were reviewed. All patients were followed through the Center with serial ultrasound evaluations at approximately 4-week intervals, and each liveborn infant was evaluated and followed by one of the authors (S.S.H.) Of the 14 cases detected, ten were detected in the second trimester, the earliest at 16·5 weeks' gestation. Of the nine fetuses with non-lethal disease, there were two cases in which the lesion remained unchanged during observation. Both had an initial diagnosis in the third trimester. In those cases diagnosed in the second trimester (7), all showed an initial increase in the size and number of cysts, followed by involutional changes either in utero (2) or in the neonatal period (3). Two infants had immediate surgical removal of the MDK, one because of respiratory compromise, and the other because of an uncertain diagnosis on renal scan. Abnormalities of the contralateral kidney were found in 7 of 14 fetuses. Five were lethal conditions. Associated non-renal abnormalities were common in bilateral MDK (80 per cent), but rare in unilateral MDK (11 per cent). 相似文献
523.
Two unrelated, apparently balanced, reciprocal translocations involving chromosomes 3 and 17, and 10 and 15 were found in cultured amniotic fluid cells from a 41-year-old 10-gravida. Chromosome analysis of peripheral blood lymphocytes of both parents revealed normal katryotypes. Post-partum examination of lymphocyte cultures from the proband confirmed the chromosome rearrangements. The child showed normal development during follow-up examinations up to the age of 4 years. 相似文献
524.
An ultrasound examination at 17 weeks gestation on a woman with a family history of spina bifida suggested that the fetus had a closed encephalocele. Amniotic fluid alphafetoprotein, rapidly adhering cells and acetylcholinesterase gel electrophoresis were normal. The pregnancy was terminated and the fetus was found to have a large cystic hygroma. It is suggested that in counselling parents of an infant or fetus with a cystic hygroma and with a normal chromosome constitution, ultrasound examination in future pregnancies is advisable, because of the possibility of autosomal recessive inheritance. 相似文献
525.
Mosaic trisomy 15 was prenatally diagnosed on amniotic fluid cells from two consecutive amniocenteses and was confirmed on cells from five different fetal tissues. The proportion of normal versus trisomic cells was consistently higher in the amniotic cell cultures and-with one exception-in the fetal tissues, while serial subcultures gave different results. The slightly atypical external features and internal malformations of the affected fetus as compared to the only clinical observation from the literature are not unusual enough to allow the delineation of a specific malformation pattern. 相似文献
526.
By means of questionnaires, 100 women were asked for their experiences concerning prenatal diagnosis. At four standardized stages of the pregnancy a questionnaire was filled in asking for: expectation, knowledge, attitude towards termination of the pregnancy in case of abnormal findings, reactions to the counselling and the obstetric treatment, interpretation of own risk, experiences since the normal test results were known and ideas to improve the treatment. With regard to the effect of pre-amniocentesis counselling it is concluded that the counselling had little impact on decision making; the counselling caused an increase of factual knowledge: somewhat more than half of the women who did not give a correct answer before counselling, indicated the right answer some time afterwards. Presumed differences in reaction patterns for a number of characteristics were not affirmed by the study; the reactions during the procedure of prenatal diagnosis seem to be highly individual and difficult to predict. In addition to the reactions of the 100 women described in this study, the responses to the first questionnaire of another 16 patients, declining amniocentesis after counselling, are presented. 相似文献
527.
528.
Prenatal diagnosis has been performed on umbilical cord blood of an 18 weeks fetus of heterozygous triosephosphate isomerase (TPI) deficient parents. After excluding maternal blood contamination, TPI activity was measured and found to be 60 per cent of the normal mean whereas the value of glucose-6-phosphate dehydrogenase activity was in the normal range of fetal blood. In addition, the analysis of the characteristics of fetal TPI, i.e. Km measurements for glyceraldehyde-3-phosphate, heat stability tests and electrophoretic studies, did not show any evidence of a special form of TPI in fetal blood. These results were consistent with the heterozygous state and were confirmed at birth. 相似文献
529.
The authors report a case of tuberous sclerosis (TS), diagnosed by prenatal ultrasound, which was suspected by the detection of intracardiac tumours and confirmed by the family investigation. Cardiac rhabdomyomata can be visualized early on echography and must suggest this diagnosis. The place of genetic counselling and prenatal diagnosis in TS is examined. 相似文献
530.
Two fetuses with extreme growth retardation (IUGR) of 31 and 34 weeks gestation were studied using a combination of two dimensional echocardiography (2DE), pulse wave Doppler (PWD) and differential measurement of the instantaneous vessel diameter techniques. The first fetus was diagnosed as having univentricular heart or possible double outlet right ventricle (DORV). Descending aorta blood flow was reduced as was indexing for weight. The second fetus was diagnosed as having univentricular heart with periodic bigeminal and trigeminal rhythm. Descending aorta blood flow was measured on two occasions and was reduced both times. Indexing for weight was within normal limits the first time and showed gross reduction on the second occasion prior to fetal demise. Fetal death occurred in both cases at 34 weeks gestation. Cardiovascular evaluation in fetuses with IUGR is useful as the detection of severe congenital cardiac abnormalities may substantially alter the management of these pregnancies, in particular caesarean section may be avoided when the prognosis for the fetus is considered hopeless. 相似文献