全文获取类型
收费全文 | 2106篇 |
免费 | 186篇 |
国内免费 | 1篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 44篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 33篇 |
2017年 | 24篇 |
2016年 | 64篇 |
2015年 | 105篇 |
2014年 | 93篇 |
2013年 | 146篇 |
2012年 | 158篇 |
2011年 | 171篇 |
2010年 | 86篇 |
2009年 | 77篇 |
2008年 | 132篇 |
2007年 | 136篇 |
2006年 | 137篇 |
2005年 | 96篇 |
2004年 | 99篇 |
2003年 | 118篇 |
2002年 | 92篇 |
2001年 | 24篇 |
2000年 | 13篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 21篇 |
1992年 | 11篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 23篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1971年 | 5篇 |
1970年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有2293条查询结果,搜索用时 15 毫秒
41.
Clare A. Hasenkampf 《Chromosoma》1984,90(4):285-288
The whole-mount spreading technique was used to examine the chromosome complement in ten zygotene nuclei of Tradescantia ohiensis var. paludosa. Spread preparations have normal synaptonemal complex (SC) morphology. Neither kinetochores nor recombination nodules were regularly visible. Cloudlike structures (LFSs) 2–6 m in diameter were sometimes associated with SC and with unsynapsed lateral components (LCs). They differed in number and location in different nuclei. Thickenings of the lateral elements and LCs were observed in mid through late zygotene nuclei. These longitudinal axis thickenings (LATS) were distributed fairly uniformly amongst the chromosomes and occurred in both synapsed and unsynapsed regions. There was a stage-dependent increase in the number and size of LATS. They were nonrandomly distributed along the length of a chromosome, being more frequent in synapsed areas, especially near junctions with unsynapsed regions. 相似文献
42.
C S Easmon M J Hastings A J Clare B Bloxham R Marwood R P Rivers J Stringer 《BMJ (Clinical research ed.)》1981,283(6289):459-461
The acquisition of group B streptococci by babies in a special-care baby unit and two postnatal wards was investigated over a six-month period using serology and phage typing. Sixty-three culture-positive babies were identified in the postnatal wards, one-third of whom had been born to mothers who were not carrying the organism in the genital tract or anorectal area during labour. A non-maternal source was identified for 14 of these 21 infants: either colonised mothers and babies in the same ward or, on one occasion, a member of the hospital staff. In the special-care baby unit, however, only one instance of nosocomial acquisition of group B streptococci was recorded despite a high prevalence of colonisation in the staff on the unit and the presence of heavily colonised babies. The results of this survey suggest that although sepsis caused by group B streptococci may be the result of nosocomial transmission, this may be prevented by careful attention to hygiene. 相似文献
43.
44.
45.
46.
The molecular mechanisms by which meiotic events are regulated are at present unknown. To approach this problem, we have exploited the natural synchrony of Lilium meiocytes to compare the nuclear protein profiles of a variety of stages of meiosis. This approach has facilitated the identification of a number of nuclear proteins that appear and disappear in a stagespecific fashion. Here we report the presence of an abundant nuclear protein that first appears during premeiotic interphase, a period during which the irreversible commitment to meiosis occurs. Antibodies directed against this protein demonstrate its meiosis specificity as well as conservation of the epitope(s) in both mono-and dicotyledonous plant species. Chromatin fractionation studies indicate that this protein, which we have termed meiotin-1, is associated with strings of nucleosomes. Implications for meiotic chromatin packaging and chromosome structure are discussed.by J.H. Taylor 相似文献
47.
48.
49.
A 569 bp probe against the β-chain of hepatotropin was used to examine expression of RNA for this growth factor in human adult and foetal liver, foetal kidney and pancreas, and rat liver after partial hepatectomy. Low level expression of a 6kb RNA occurred in human adult and normal rat liver. 70% hepatectomy increased expression, peaking at 10 h and returning to near normal levels 24 h after resection. The 6 kb band was strongly expressed in human foetal liver, as compared with adult, but not in foetal kidney or pancreas, suggesting a major role for hepatotropin in both foetal development and regeneration of the liver. 相似文献
50.
Four patients developed massive pulmonary embolism after jejuno-ileal bypass for morbid obesity. All patients were in Greenfield's Class IV and were in shock. Severe hypoxia was evidenced in their blood gases. The patients were managed with digitalis, diuretics, Solu-Medrol (methylprednisolone sodium succinate), oxygen, and heparin therapy. Each patient underwent partial vena cava interruption with Mobin Uddin's umbrella, and all four survived without residual complications. 相似文献