全文获取类型
收费全文 | 164篇 |
免费 | 12篇 |
出版年
2018年 | 3篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2011年 | 5篇 |
2010年 | 5篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1958年 | 1篇 |
1950年 | 1篇 |
1949年 | 1篇 |
1948年 | 3篇 |
排序方式: 共有176条查询结果,搜索用时 78 毫秒
1.
2.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
3.
Proliferation of cells undergoing chondrogenesis in vitro 总被引:3,自引:0,他引:3
Mindy George Kenneth P. Chepenik Martin H. Schneiderman 《Differentiation; research in biological diversity》1983,24(1-3):245-249
Abstract. Continuous exposure of chicken embryo limb bud mesenchyme cells undergoing chondrogenesis in vitro to [3 H] thymidine ([3 H]TdR) revealed that more than 90% of the cells synthesized DNA at least once during 120 h of culture. When cells were exposed to [3 H]TdR for 24 h beginning at various times throughout the culture period, the percentage of cells which incorporated [3 H]TdR during each period was approximately 92%. However, when the period for incorporation of radioisotope was limited to two hours, the number of cells which incorporated [3 H]TdR was found to decline during chondrogenesis in vitro. This decline was coincident with the appearance of extracellular matrix material and occurred in those cells which had, and had not, expressed the cartilage phenotype.
We conclude from these studies that (1) practically all of the cells continue to proliferate while chondrogenesis is occurring in vitro, (2) there is an increase in the length of the cell cycle during chondrogenesis in vitro, and (3) withdrawal from the cell cycle is not required for differentiation of mesenchyme into cartilage. 相似文献
We conclude from these studies that (1) practically all of the cells continue to proliferate while chondrogenesis is occurring in vitro, (2) there is an increase in the length of the cell cycle during chondrogenesis in vitro, and (3) withdrawal from the cell cycle is not required for differentiation of mesenchyme into cartilage. 相似文献
4.
5.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
6.
Hyperpolarizing potentials in guinea pig hippocampal CA3 neurons 总被引:2,自引:0,他引:2
W. Douglas Knowles Jacob H. Schneiderman Howard V. Wheal Carl E. Stafstrom Philip A. Schwartzkroin 《Cellular and molecular neurobiology》1984,4(3):207-230
There is a bewildering variety of hyperpolarizing potentials which control activity in hippocampal pyramidal cells. These include an inhibitory postsynaptic potential (IPSP) with early and late components, voltage- and calcium-dependent potassium conductances, a voltage-dependent potassium conductance modulated by muscarinic agents (the M-current), and a complex and poorly understood afterhyperpolarization following epileptiform bursts. In hippocampal CA3 pyramidal cells, mossy fiber stimulation elicits an IPSP which is made up of two readily separable components. Using the in vitro slice preparation, we investigated the underlying ionic basis of these IPSP components and compared them to other hyperpolarizing potentials characteristic of the CA3 neurons. Intracellular recordings were obtained and then tissue was exposed to bathing medium low in chloride concentration or high in potassium concentration; the ion "blockers" EGTA (intracellular); tetraethylammonium (TEA) (intra- and extracellular), and barium and cobalt (extracellular); and the gamma-aminobutyric acid (GABA)/chloride antagonists penicillin, bicuculline and picrotoxin. 相似文献
7.
Genes encoding alpha-heavy chains of rabbit IgA: characterization of cDNA encoding IgA-g subclass alpha-chains 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
cDNA molecules encoding rabbit IgA alpha-heavy chains have been synthesized and six of these have been characterized. The complete nucleotide sequence of one cDNA, p 19 (942bp), showed that it encoded all but the N-terminal 57 amino acid residues of the constant region of alpha-chains. The cDNA molecules were subcloned into the expression vector pUC8 and E. coli were transformed. Radioimmunoassay of the molecules synthesized by these clones showed that all six cDNA molecules encoded alpha-chains of the IgA-g subclass. Comparison of the amino acids encoded by the alpha-cDNA with the amino acid sequence of mouse and human alpha-chains showed that although all of the intradomain disulfide bonds appear to be conserved, some positions, probably involved in interchain disulfide bonds, are not conserved. We propose that secretory component is covalently bound to cysteine 299 and/or cysteine 301 of the CH2 domain of mouse and human alpha-chains. The results from Southern blot analysis of genomic DNA with 32P-cDNA suggests that the rabbit genome has multiple C alpha genes. 相似文献
8.
Cocaine and its major metabolites are incorporated into hair during the growth of the shaft and stay there for the whole life of the hair. Cocaine crosses the placenta and its metabolites for example Benzoylecgonine (BZ), have been found in neonatal urine, meconium and hair. In order to utilize hair measurements of cocaine as a biological marker of systemic exposure, we conducted both animal and human investigations on the dose response characteristics of this phenomenon. Our data suggest that both maternal and fetal accumulation of cocaine and its metabolite follow a linear pattern within the clinically used doses. Similarly, a good correlation was observed in animals between maternal dose and fetal hair accumulation. 相似文献
9.
Chinese hamster ovary cells were synchronized at the G1/S-phase boundary of the cell cycle and pulse-labeled for 10 min with 125I-iododeoxyuridine 30 min after entering the S phase. Cell samples were harvested for freezing and 125I-decay accumulation at intervals ranging from 15 to 480 min after termination of labeling. The survival data showed a marked shift from cell killing characteristic of low-LET radiation to that more characteristic of killing by high-LET radiation with increasing intervals between DNA pulse-labeling and decay accumulation. Cells harvested and frozen within 1 h after pulse-labeling yielded a low-LET radiation survival response with a pronounced shoulder and a large D0 of up to 0.9 Gy. With longer chase periods the shoulder and the D0 decreased progressively, and cells harvested 5 h after pulse-labeling or later exhibited a high-LET survival response (D0: 0.13 Gy). Two interpretations for these findings are discussed. (1) If DNA is the sole target for radiation death, the results indicate that DNA maturation increases radiation damage to DNA or reduces damage repair. (2) If radiation cell death involves damage to higher-order structures in the cell nucleus, the findings suggest that newly replicated DNA is not attached to these structures during the initial low-LET period, but 125I starts to induce high-LET radiation effects as labeled DNA segments become associated with the target structure(s). On balance, or data favor the latter interpretation. 相似文献
10.
The yield of hybrid colonies after fusion of mammalian cells with polyethylene glycol (PEG) is increased if the cells are fused in Ca2+-free medium, and kept in Ca2+-free medium for at least 15 min after fusion. The protective effect of Ca2+-free medium is much more obvious when Baker PEG is used than when fusion is carried out with Koch-Light PEG. The increased yield of hybrid colonies is shown to be due to a reduced toxicity rather than to an increased efficiency of cell fusion. These improvements have been found to apply to a variety of cell lines, and also when cell fusion is carried out in suspension. This technique should be particularly useful in studies on mammalian cell hybridization using cell lines that are particularly sensitive to the toxic effect of PEG. 相似文献