全文获取类型
收费全文 | 1771篇 |
免费 | 6篇 |
专业分类
安全科学 | 461篇 |
废物处理 | 2篇 |
环保管理 | 106篇 |
综合类 | 1039篇 |
基础理论 | 102篇 |
污染及防治 | 52篇 |
评价与监测 | 8篇 |
社会与环境 | 4篇 |
灾害及防治 | 3篇 |
出版年
2015年 | 8篇 |
2013年 | 52篇 |
2011年 | 8篇 |
2010年 | 13篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 13篇 |
2005年 | 10篇 |
2004年 | 161篇 |
2003年 | 162篇 |
2002年 | 73篇 |
2001年 | 40篇 |
1998年 | 47篇 |
1997年 | 15篇 |
1995年 | 58篇 |
1994年 | 56篇 |
1993年 | 41篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 34篇 |
1989年 | 26篇 |
1988年 | 36篇 |
1987年 | 31篇 |
1986年 | 27篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1975年 | 12篇 |
1973年 | 10篇 |
1963年 | 9篇 |
1961年 | 9篇 |
1957年 | 9篇 |
1956年 | 8篇 |
1954年 | 8篇 |
1940年 | 10篇 |
1939年 | 10篇 |
1931年 | 12篇 |
1930年 | 10篇 |
1925年 | 7篇 |
1923年 | 9篇 |
1921年 | 9篇 |
1920年 | 7篇 |
1919年 | 50篇 |
1918年 | 45篇 |
1917年 | 36篇 |
1916年 | 55篇 |
1915年 | 38篇 |
1914年 | 74篇 |
1913年 | 106篇 |
排序方式: 共有1777条查询结果,搜索用时 875 毫秒
31.
32.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
33.
We report the first prenatal diagnosis of an affected fetus with Chediak-Higashi syndrome (CHS). Diagnosis was accomplished via fetal blood sampling at 17 menstrual weeks and was confirmed after birth. Retrospective measurement of the largest acid phosphatase-positive lysosomes in cultured amniotic fluid cells and chorionic villus cells showed that in CHS these lysosomes are significantly larger than those in normal cells. This method may be used for prenatal diagnosis of CHS by amniocentesis and chorionic villus sampling (CVS). 相似文献
34.
Dr Gertrude Kohn 《黑龙江环境通报》1987,7(4):303-305
Malformations of the upper distal extremities were noted in an otherwise healthy infant whose mother underwent diagnostic amniocentesis. A causal relationship is postulated. 相似文献
35.
Prenatal diagnosis of trisomy 20 mosaicism was made in two pregnancies by chromosome analysis of cultured amniotic fluid cells. In both cases, the pregnancy continued to term and a healthy male infant was delivered. Regular assessments up to the age of 6-5 years revealed normal physical and intellectual development in both children. 相似文献
36.
The first mammals were small, nocturnal, and presumably had low metabolic rates and were therefore probably unable to maintain a constant high body temperature throughout cool nights. How these animals, without sufficient heat production for endogenous rewarming, were able to become warm and active again before the next activity period remains unresolved. However, we discovered that, similar to reptiles, the carnivorous marsupial mammal Pseudantechinus macdonnellensis (body mass 30.8LJ.0 g) uses the morning sun to rewarm from low (26.3dž.5°C) body temperatures during torpor. Our findings provide the first evidence of basking during rewarming from torpor in mammals and may provide an alternative explanation as to how ancestral mammals could have become nocturnal to avoid diurnal predators despite their small size and a low endogenous heat production. 相似文献
37.
38.
39.
Amniocentesis and subsequent tests are reported on a fetus conceived of a rare mating type: its mother has an intermediate level of β hexosaminidase A (HEX A), characteristic of carriers of Tay-Sachs disease (TSD), while the father suffers from an adult-onset GM2 ganglio-sidosis (AOG) with severe HEX A deficiency. Activity of HEX A in the cultured fetal cells was very low when measured by the heat-inactivation method, thus showing the typical biochemical phenotype of TSD fetuses. However, upon separation of HEX isozymes by ion exchange chromatography, residual HEX A (17 per cent of total HEX) was demonstrated. Also in contrast to TSD fetuses, this fetus' fibroblasts were able to synthesize the precursor of a chains of HEX, and ultrastructural examination of its brain revealed few atypical lamellar bodies, unlike those found in TSD fetuses of the same gestational age. It is therefore concluded that the fetus was not affected with TSD, but rather with AOG. 相似文献
40.