全文获取类型
收费全文 | 1053篇 |
免费 | 101篇 |
出版年
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 36篇 |
2014年 | 48篇 |
2013年 | 48篇 |
2012年 | 67篇 |
2011年 | 65篇 |
2010年 | 51篇 |
2009年 | 51篇 |
2008年 | 62篇 |
2007年 | 75篇 |
2006年 | 69篇 |
2005年 | 74篇 |
2004年 | 54篇 |
2003年 | 69篇 |
2002年 | 63篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 18篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有1154条查询结果,搜索用时 78 毫秒
1.
It has been suggested that Locusta migratoria amplifies its ribosomal RNA genes in the growing oocytes (Kunz (1967) Chromosoma20, 332–370). Cloned ribosomal DNA of L. migratoria was used to analyze rDNA structure and number. The rDNA is localized on three chromosome pairs in six nucleolus organizers. It was found that all structural variants of the rRNA genes which have been described previously are represented in the same relative amounts in DNA from isolated oocytes as in somatic cells. Furthermore, the rRNA gene number is not increased in oocyte DNA, i.e., amplification does not occur. Therefore, the large number of multiple nucleoli seen in the growing oocytes has to be interpreted as the fully extended and fully active set of chromosomal rRNA genes. The total rRNA gene number was determined by dot blot hybridization to be about 3300 genes/haploid genome. 相似文献
2.
3.
Summary Immunohistochemical properties of the terminal nerve network in the rat heart were assessed by use of the elution-restaining method. The colocalization of the enzymes involved in catecholamine synthesis (tyrosine hydroxylase — TH, dopamine--hydroxylase — DBH) as well as the respective distributions of the neuropeptides associated with the adrenergic nervous system (neuropeptide tyrosine — NPY, C-terminal flanking peptide of neuropeptide Y — C-PON) were studied in series of serial sections throughout the interatrial septum and the atrioventricular junction. Our data suggest that ganglion cells of sulcus terminalis as well as the epicardial ganglia enclosed between the superior vena cava and ascending aorta are VIP- and TH-negative, but neuropeptide Y- and DBH-immunoreactive. They give rise to three intraseptal nerves directed towards the specialised structures of the atrioventricular junction. These nerve fascicles contain abundant, thick TH-immunoreactive nerve fibres and scarce, thin NPY- and DBH-immunoreactive fibres. The cell bodies of the intramural ganglion cells localized between the right and left branches of the bundle of His (Moravec and Moravec 1984) are strongly TH- and DBH-immunoreactive. They are innervated by thick nerve fibres having the same immunohistochemical properties (NPY- and DBH-immunoreactivities) as those of a subpopulation of the epicardial ganglion cells and seem to supply some of the TH-immunoreactive nerve fibres directed via the intraseptal nerves to the epicardial ganglia. The existence of a multicomponent nerve network, characterized by a reciprocal innervation of the sinus node and atrioventricular node areas, is suggested by our immunohistochemical data. 相似文献
4.
Cystic fibrosis typing with DNA probes and screening for ΔF508 deletion in families from Southern France 总被引:1,自引:1,他引:0
Mireille Claustres Marie Desgeorges Paule Kjellherg Hélène Bellet Jacques Demaille Michelle Ramsay 《Human genetics》1990,85(4):398-399
Summary A sample of 235 individuals from 49 French cystic fibrosis (CF) families with at least one living affected child was typed
with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CF gene, and was screened for
the ΔF508 mutation. Using a combination of six probes, 44 out of the 49 families were sufficiently informative to enable prenatal
diagnosis or carrier determination. As in many other populations, linkage disequilibrium was found between the CF locus and
the haplotype B (XV2c: allele 1; KM19: allele 2), which accounts for about 78% of CF chromosomes in our families. The ΔF508
deletion was present in 64.3% of CF chromosomes. 相似文献
5.
Membrane polypeptides (relative mass (Mr) 48,000--55,000) associated with the equilibrative transport of nucleosides were identified in cultured murine leukemia (L1210/C2) cells by site-specific photolabeling with [3H]nitrobenzylthioinosine ([3H]NBMPR). Growth of cells in the presence of tunicamycin resulted in the gradual conversion of 3H-labeled polypeptides to a form that migrated more rapidly (Mr 42,000--47,000) during sodium dodecyl sulfate (SDS)--polyacrylamide gel electrophoresis. When plasma membrane fractions were photolabeled and incubated with O-glycanase or endoglycosidase F, the [3H]NBMPR-labeled polypeptides migrated in SDS-polyacrylamide gels with the same mobility as native NBMPR-binding polypeptides, whereas incubation with either N-glycanase or trifluoromethane sulfonic acid converted [3H]NBMPR-labeled polypeptides to the more rapidly migrating form (Mr 41,000--48,000). These observations are consistent with the presence of N-linked oligosaccharides of the complex type on the NBMPR-binding polypeptides of L1210/C2 cells. Tunicamycin exposures that reduced incorporation of [3H]mannose into plasma membrane fractions by greater than 95% had little, if any, effect on either the affinity (Kd values, 0.1-0.2 nM) or abundance (Bmax values, 200,000--220,000 sites/cell) of NBMPR-binding sites, whereas uridine transport kinetics at 37 degrees C were altered in a complex way. Thus, although N-linked glycosylation is not required for insertion of the NBMPR-binding protein into the plasma membrane or for interaction of NBMPR with the high-affinity binding sites, it is important for function of at least one of the three nucleoside transporters expressed by L1210/C2 cells. 相似文献
6.
Redundancy of signal and anchor functions in the NH2-terminal uncharged region of influenza virus neuraminidase, a class II membrane glycoprotein 总被引:5,自引:0,他引:5
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Class II membrane glycoproteins share a common topology of the NH2 terminus inside and the COOH terminus outside the cell. Their transport to the cell surface is initiated by the function of a single hydrophobic domain near the NH2 terminus. This functional domain serves both as an uncleaved signal sequence and as a transmembrane anchor. We examined the signal and anchor functions of influenza virus neuraminidase, a prototype class II membrane glycoprotein, by deletion analysis of its long, uncharged amino-terminal region. The results presented here show that the entire stretch of 29 uncharged amino acids (7 to 35) is not required for either a signal sequence or an anchor sequence function. On the basis of translocation and membrane stability data for different mutants, we suggest that the first 20 amino acid residues (7 to 27) are likely to provide the hydrophobic core for these functions and that within this putative subdomain some sequences are more efficient than the other sequences in providing a translocation function. Finally, it appears that neuraminidase and its mutant proteins are translocated with the proper orientation, regardless of the characteristics of the flanking sequences. 相似文献
7.
The organotypic culture of human skin keratinocytes and fibroblasts to achieve form and function 总被引:6,自引:0,他引:6
Dr. Nancy L. Parenteau Patrick Bilbo Cynthia J. M. Nolte Valerie S. Mason Mireille Rosenberg 《Cytotechnology》1992,9(1-3):163-171
We describe an organotypic model of human skin comprised of a stratified layer of human epidermal keratinocytes and dermal
fibroblasts within a contracted collagen lattice. Feasible and reproducible production of the skin construct has required
the use of traditional as well as specialized culture techniques. The configuration of the construct has been engineered to
maintain polarity and permit extended culture at the air-liquid interface. Morphological, biochemical and kinetic parameters
were assessed and functional assays were performed to determine the degree of similarity to human skin. Light and ultrastructural
morphology of the epidermis closely resembled human skin. The immunocytochemical localization of a number of differentiation
markers and extracellular matrix proteins was also similar to human skin. Kinetic data showed a transition of the epidermal
layer to a morein vivo-like growth rate during the development of the construct at the air-liquid interface. The barrier properties of the construct
also increased with time reaching a permeability to water of less than 2%·h after approximately 2 weeks at the air-liquid
interface which is still on average 30-fold more water-permeable than normal human skin. The construct is currently used forin vitro research and testing and is also being tested in clinical applications. 相似文献
8.
Underwater effects on coral reefs of the six hurricanes which ravaged French Polynesia between December 82 and April 83 were observed by SCUBA diving around high islands and atolls during September and October 1983. Special attention was paid to Tikehau atoll reef formations (Tuamotu archipelago) where quantitative studies on scleractinians, cryptofauna and fishes were conducted in 1982 immediatly prior to the hurricanes. On outer reef slopes coral destruction, varying from 50 to 100%, was a function of depth. Upper slope coral communities composed of small colonies well adapted to high energy level environments, suffered less than deeper formations. However, there is a narrow erosional trough in this zone at a depth of 6 m that was probably the result of storm-wave action (plunge point). Coral destruction was spectacular at depths greater than 12 m: 60 to 80% between 12 m and 30 m and 100% beyond 35 m, whereas earlier living coral coverage ranged from 60 to 75% in these zones. The outer slope was transformed into a scree zone covered with coarse sand and dead coral rubble. Dives on different sites around steep outer slopes (>45°) of the atolls and more gentle slopes (<25°) of some parts of the high islands permitted the formulation of an explanatory hypothesis: direct coral destruction by hurricane-induced waves occurred between the surface and 18–20 m; on low-angle slopes broken colonies were thrown up on reef flats and beaches; on steep slopes avalanches destroyed much of the living corals and left scree slopes of rubble and sand. 相似文献
9.
10.