全文获取类型
收费全文 | 192篇 |
免费 | 32篇 |
国内免费 | 1篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
1.
Biotin and protein synthesis in rat liver 总被引:5,自引:0,他引:5
2.
A hierarchical breeding design was used to determine if winter flounder Pseudopleuronectes americanus embryos and yolk-sac larvae sired by Georges Bank males developed and grew larger than fish sired by Passamaquoddy Bay males, and to examine parental contributions to variations in fertilization success, time to 50% hatch, hatch success and larval morphological development. Significant stock effects were detected for time to hatch and larval development. Eggs fertilized by Passamaquoddy Bay males reached 50% hatch significantly earlier than eggs fertilized by Georges Bank males. Larvae sired by Georges Bank males were significantly larger during larval development for four of the six traits measured at 12 days post-hatch: head depth, jaw length, myotome height and body area. Embryo and larval development were strongly influenced by maternal contributions; there were significant maternal variance components for the majority of the variables measured. Paternal variance components were significant for fertilization success, time to hatch, larval jaw length and larval head depth, however, they acted principally through parental interactions. This information has important implications for the long-term sustainable development of winter flounder for aquaculture purposes as well as for understanding winter flounder genetic variation in the wild. 相似文献
3.
Human immunodeficiency virus reverse transcriptase expressed in transformed yeast cells. Biochemical properties and interactions with bovine tRNALys 总被引:11,自引:0,他引:11
4.
5.
6.
In vitro and in vivo studies of Trypanosoma cruzi DNA polymerase 总被引:1,自引:0,他引:1
A Solari D Tharaud Y Repetto J Aldunate A Morello S Litvak 《Biochemistry international》1983,7(2):147-157
One major DNA polymerase has been purified and characterized from Trypanosoma cruzi. The enzyme has a sedimentation coefficient of 6.8 S corresponding to an approximate molecular weight of 180,000 assuming a globular shape. The enzyme recognizes activated DNA very efficiently, as well as synthetic polydeoxynucleotides, whereas poly rA-dT12 is very poorly utilized. Trypanosoma cruzi DNA polymerase is not inhibited at all by aphidicolin, while araCTP inhibits the enzyme very slightly. The purified enzyme is strongly inhibited by N-ethyl maleimide, dideoxyTTP, ethidium bromide and berenil. All our attempts to find a DNA polymerase sensitive to aphidicolin in vitro have failed, nor have we been able to find a low molecular weight DNA polymerase in this organism. However, when DNA synthesis was studied in whole trypanosomes, aphidicolin was shown to inhibit DNA synthesis more efficiently than ethidium bromide and berenil. 相似文献
7.
The response of isoprene emission rate and photosynthetic rate to photon flux and nitrogen supply in aspen and white oak trees 总被引:4,自引:0,他引:4
M. E. Litvak F. Loreto P. C. Harley T. D. Sharkey R. K. Monson 《Plant, cell & environment》1996,19(5):549-559
Isoprene is the primary biogenic hydrocarbon emitted from temperate deciduous forest ecosystems. The effects of varying photon flux density (PFD) and nitrogen growth regimes on rates of isoprene emission and net photosynthesis in potted aspen and white oak trees are reported. In both aspen and oak trees, whether rates were expressed on a leaf area or dry mass basis, (1) growth at higher PFD resulted in significantly higher rates of isoprene emission, than growth at lower PFD, (2) there is a significant positive relationship between isoprene emission rate and leaf nitrogen concentration in both sun and shade trees, and (3) there is a significant positive correlation between isoprene emission rate and photosynthetic rate in both sun and shade trees. The greater capacity for isoprene emission in sun leaves was due to both higher leaf mass per unit area and differences in the biochemical and/or physiological properties that influence isoprene emission. Positive correlations between isoprene emission rate and leaf nitrogen concentration support the existence of mechanisms that link leaf nitrogen status to isoprene synthase activity. Positive correlations between isoprene emission rate and photosynthesis rate support previous hypotheses that isoprene emission plays a role in protecting photosynthetic mechanisms during stress. 相似文献
8.
9.
WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF
colonization factor
- CFA
Colonization Factor Antigen
- CS
coli-surface-associated antigen
- EAggEC
enteroaggregativeE. coli
- ECDD
E. coli diarrheal disease
- EHEC
enterohemorrhagicE. coli
- EIEC
enteroinvasiveE. coli
- EPEC
enteropathogenicE. coli
- ETEC
enterotoxigenicE. coli
- Gal
galactose
- GalNAc
N-acetyl galactosamine
- LT
heat-labile toxin
- NeuAc
N-acetyl neuraminic acid
- PCF
Putative colonization factor
- RBC
red blood cells
- SLT
Shiga-like toxin
- ST
heat-stable toxin 相似文献
10.
Matthew K. Litvak 《Environmental Biology of Fishes》1993,36(2):183-192
Synopsis Many species of shoaling fish are preyed upon by aerial predators. However, to date there has been no analysis of the evasive
response of a group of shoaling fish to an aerial threat or attack. The response of a shoal of fish encompasses a suite of
behaviors starting with a startle response. Shoals of golden shiner, Notemigonus crysoleucas, responded to the threat of aerial predation from a kingfisher model with a startle response, an increase in shoal depth,
an increase in polarity, swimming in the opposite direction under the model predator, shoal compression along the depth axis,
and shoal expansion on the plane perpendicular to the depth axis. It was hypothesized that shoal compression along the depth
axis serves to increase predator confusion by placing more fish in the predator's visual field. This compression was termed
the ‘plane of confusion’. 相似文献