全文获取类型
收费全文 | 364篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
404篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 16篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 25篇 |
2011年 | 15篇 |
2010年 | 18篇 |
2009年 | 10篇 |
2008年 | 18篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1968年 | 5篇 |
1932年 | 3篇 |
1929年 | 3篇 |
1923年 | 2篇 |
排序方式: 共有404条查询结果,搜索用时 15 毫秒
371.
372.
Genetic Control of Alkaline Phosphatase Synthesis in Neurospora: The Use of Partial Diploids in Dominance Studies 总被引:9,自引:5,他引:4 下载免费PDF全文
In wild-type Neurospora, alkaline phosphatase is made under conditions of phosphate limitation, but not conditions of phosphate sufficiency. Mutants at two unlinked loci, nuc-1 and nuc-2, do not make alkaline phosphatase under any conditions, while mutants at two quite closely linked loci, pcon and preg, make alkaline phosphatase even under conditions of phosphate sufficiency. pcon is extremely closely linked to nuc-2. nuc-2 and preg(c) (constitutive) mutants are recessive to their wild-type alleles in partial diploids as well as in heterokaryons, while pcon(c) mutants are dominant or co-dominant. nuc-1 is epistatic to both pcon(c) and preg(c) mutants. The implications of these findings for theories of metabolic control in eukaryotes are briefly discussed. 相似文献
373.
374.
Siân SE Cox Mark van der Giezen Sarah J Tarr Mark R Crompton Jorge Tovar 《BMC microbiology》2006,6(1):45-16
Background
Giardia intestinalis is a parasitic protozoan and major cause of diarrhoeal disease. Disease transmission is dependent on the ability of the parasite to differentiate back and forth between an intestine-colonising trophozoite and an environmentally-resistant infective cyst. Our current understanding of the intracellular signalling mechanisms that regulate parasite replication and differentiation is limited, yet such information could suggest new methods of disease control. Phosphoinositide-3 kinase (PI3K) signalling pathways have a central involvement in many vital eukaryotic processes, such as regulation of cell growth, intracellular membrane trafficking and cell motility. Here we present evidence for the existence of functional PI3K intracellular signalling pathways in G. intestinalis. 相似文献375.
Henry A. Gleason 《Brittonia》1996,48(3):318-321
At the May 1950 annual meeting of the Corporation of The New York Botanical Garden, the late H. A. Gleason (Fig. 1), then Head Curator, who first arrived at NYBG in 1919, gave an account of the scientific activity during the early years of the institution. The text of his presentation is here reproducedm with some slight modification. 相似文献
376.
Courtship behaviours may provide a more reliable means of identifying reproductively isolated taxa than traits such as morphology or many genetic markers. Here we describe the courtship songs of the Drosophila willistoni sibling species group, which consists of several species and subspecies. We find that song pattern is species-specific, despite significant differences among strains within species. D. paulistorum has the most variable song pattern, which reflects this species' traditional subdivision into semispecies. All the other species could be unambiguously identified by song. The major differences among these species was in the interpulse interval, as has been found in other studies of fly song. However, the interpulse intervals of the species studied here were often multimodal. This was partly due to the presence of multiple song types within the courtship repertoire, but it also reflected changes in interpulse interval within a song type by some males. Unusually, some species had distinctively patterned variation in interpulse interval. Song must have evolved rapidly within the species complex, probably due to sexual selection. 相似文献
377.
J G Gleason T W Ku M E McCarthy B M Weichman D Holden R R Osborn B Zabko-Potapovich B Berkowitz M A Wasserman 《Biochemical and biophysical research communications》1983,117(3):732-739
A structural analog of LTD4, 4R-hydroxy-5S-cysteinylglycyl-6Z-nonadecenoic acid (4R, 5S, 6Z-2-nor-LTD1) has been synthesized and pharmacologically characterized. It significantly antagonized the contractile action of LTD4, LTC4 and LTE4 in guinea pig airways. In addition, this compound antagonized the in vitro vasoconstrictive effects of LTD4 in the guinea pig pulmonary artery. The study of a series of structural analogs of 4R, 5S, 6Z-2-nor-LTD1 suggests that the spatial separation of the C-1 (eicosanoid) carboxyl relative to the hydroxyl is a critical determinant in LTD4 agonist/antagonist activity. 相似文献
378.
379.
380.