全文获取类型
收费全文 | 247篇 |
免费 | 18篇 |
出版年
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 18篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 3篇 |
1998年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
1954年 | 2篇 |
1952年 | 1篇 |
1938年 | 2篇 |
1937年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 697 毫秒
51.
Raymond L. Stallings A. Christine Munk Jonathan L. Longmire James H. Jett Mark E. Wilder Michael J. Siciliano Gerald M. Adair Brian D. Crawford 《Chromosoma》1985,92(2):156-163
Proto-oncogenes, which represent the cellular progenitors of the transforming genes harbored by acute transforming oncogenic retroviruses, have been highly conserved during vertebrate evolution. In this report, we have assigned experimentally a subset of proto-oncogenes (SRC, ABL, FES, and FMS — all related to the SRC family) to Chinese hamster chromosomes by Southern filter hybridization analyses of DNAs isolated from both somatic cell hybrids and flow-sorted hamster chromosomes. These results demonstrate that several autosomal linkage groups containing proto-oncogenes originated prior to the radiation and speciation of mammals and have remained remarkably stable for nearly 80 million years. 相似文献
52.
A CD4+, CD8+ derivative of the CD4+, CD8– cell line SAKRTLS 12.1 was isolated by fluorescence activated cell sorting for CD8+ cells. This derivative showed a co-ordinate change in a number of independent characters: The parental cell line was CD4+, CD8–, CD3+, CD5hi, HSA+, DEXR, CD44hi, while the derivative was CD4+, CD8+, CD3–, CD510, HSA+, DEXS, CD4410. The derivative expressed the Thy-1.1, Ly-2.1, and Ly-3.1 surface antigens, consistent with origin from the SAKRTLS 12.1 parental cell line, and showed a drug resistance profile identical to that of the parent. It was not possible to isolate revertants with a phenotype identical to that of the parental cell line. Activation of the structural gene coding for CD8 chain was correlated with demethylation at several sites. We interpret these results to mean that this CD8+ derivative of SAKRTLS 12.1 arose as a result of an alteration of a gene that coordinately regulates multiple genes whose expression changes during thymocyte differentiation. Gene methylation may contribute, directly or indirectly, to some or all of the changes in gene expression observed.
Address correspondence and offprint requests to: R. Hyman. 相似文献
53.
54.
The fertility of lactating Holstein cows is severely reduced during periods of heat stress. Despite this reduction in fertility, however, some inseminations conducted during heat stress result in successful pregnancies from which heifer calves are born. Many of these heifer calves are retained and raised to enter the milking herd as replacement animals. Heat stress experienced by these females around the time they were conceived may confer long-lasting effects that alter subsequent milk production capacity. The objective of this study was to examine the relationship between periconceptional heat stress and subsequent milk production of primiparous cows. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records included Holstein cows that had completed at least one lactation in one of three states with large populations of dairy cattle and which are known for having hot, humid summers: Georgia, Florida or Texas. Dates of conception were calculated by subtracting 276 d from the recorded birth date of each individual cow. Records for cows conceived within the months of June, July, and August were retained as heat stress-conceived (HSC) cows (n = 94,440); cows conceived within the months of December, January, and February were retained as thermoneutral-conceived (TNC) contemporaries (n = 141,365). In order to account for the effects of environmental conditions on total milk production for a given lactation, cows were blocked by season of calving (winter, spring, summer or fall). Adjusted 305-day mature-equivalent milk production was evaluated with a mixed model ANOVA using SAS, in which random effects were used to account for variability between herds. Of the cows that calved in the summer, fall and winter, TNC cows had higher milk yield than the HSC cows in all states. Interestingly, the cows that calved in the spring presented a unique relationship, with HSC cows producing more milk. Overall however, heat stress at the time of conception is associated with lower milk production during the first lactation. While this association does not prove cause and effect, it does provide justification for additional investigation into whether heat stress around the time of conception results in long-term, detrimental consequences for the conceptus. 相似文献
55.
Genetic effects of chromosomal rearrangements in Chinese hamster ovary cells: expression and chromosomal assignment of TK, GALK, ACP1, ADA, and ITPA loci. 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R L Stallings G M Adair J Siciliano J Greenspan M J Siciliano 《Molecular and cellular biology》1983,3(11):1967-1974
Polyethylene glycol-mediated fusion of Chinese hamster ovary (CHO) cells with mouse Cl1D cells produced interspecific somatic cell hybrids which slowly segregated CHO chromosomes. Cytogenetic and isozyme analysis of HAT- and bromodeoxyuridine-selected hybrid subclones and of members of a hybrid clone panel retaining different combinations of CHO chromosomes enabled provisional assignments of the following enzyme loci to CHO chromosomes: TK, GALK, and ACP1 to chromosome 7; TK and GALK to chromosome Z13; ACP1, ADA, and ITPA to chromosome Z8; and ADA and ITPA to chromosome Z9. These genetic markers reflect the origin of each of these Z group chromosomes and indicate the functional activity of alleles located on rearranged chromosomes. Identification of diploid electrophoretic shift mutations for ADA and ITPA was consistent with those observations. Assignment of the functional TK locus in TK+/- CHO-AT3-2 cells indicated that gene deletion may be responsible for TK hemizygosity in this subline. 相似文献
56.
When Thy-1– cell lines derived from different Thy-1+ murine thymic lymphomas are analyzed by complementation analysis, most fall into the A complementation class. A possible explanation for this result is that the Class A phenotype is due to a mutation in a gene on the X chromosome. To test this idea, selection for 6-thioguanine resistance was carried out on Thy-1+ hybrid cell lines between complementary Class A and Class C Thy-1– mutant cell lines. In some hybrid clones, there was complete concordance between 6-thioguanine resistance and a change of the phenotype of the hybrid from Thy-1+ to Thy-1–. Detailed study of one of these hybrid clones showed that 6-thioguanine resistance was accompanied by loss of hypoxanthine guanine phosphoribosyltransferase activity and that the Thy-1– phenotype was attributable to loss of the gene complementing the Class A Thy-1– mutation.Other hybrid clones, however, had some thioguanine resistant lines which remained Thy-1+. The degree of concordance was a characteristic of the particular hybrid clone examined and subclones which showed complete concordance could be derived from clones showing incomplete concordance. The variability in the degree of concordance between 6-thioguanine resistance and the Thy-1– phenotype in different hybrid cell lines was also seen among individual hybrid clones isolated from a fusion between a Class A mutant and normal spleen cell blasts.We conclude from these results that the basis of the Class A Thy-1– phenotype is genetic, but given the variability in the degree of linkage observed, we cannot determine whether the gene determining the Class A mutant phenotype is X-linked in the normal situation. 相似文献
57.
Hybrids between pseudodiploid Thy-1.1+ lymphomas and Thy 1.2– pseudodiploid Abelson-leukemia-virus-induced (ALV-induced) lymphomas express Thy-1 glycoprotein on their cell surface. These Thy-1+ hybrids invariably express the Thy 1.1 allelic form of the glycoprotein and may be either Thy 1.2+ or Thy 1.2–. Sublines expressing both Thy 1.1 and Thy 1.2 can be isolated from Thy 1.1+, Thy 1.2– hybrids by cell sorting. In contrast to hybrids with pseudodiploid ALV-induced lymphomas, hybrids between Thy 1.1+ lymphomas and pseudotetraploid Thy 1.2– Abelson-leukemia-virus-induced lymphomas do not express Thy-1 glycoprotein on their cell surface and Thy-1 glycoprotein cannot be detected in detergent extracts of these cells. Thy-1+ revertants were isolated from one of the Thy-1– hybrids by cell sorting. — These results demonstrate a gene dosage effect for the expression of the Thy-1 glycoprotein in somatic cell hybrids. They are consistent with the idea that diffusable gene products regulate Thy-1-glycoprotein expression in these hybrids. They also suggest that there may be additional, apparentlycis-active, regulatory mechanisms which determine the ability of theThy-1 structural genes of the Abelson-leukemia-virus-induced lymphoma parent to be expressed in somatic cell hybrids. 相似文献
58.
Assignment of genes encoding metallothioneins I and II to Chinese hamster chromosome 3: evidence for the role of chromosome rearrangement in gene amplification. 总被引:3,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R L Stallings A C Munk J L Longmire C E Hildebrand B D Crawford 《Molecular and cellular biology》1984,4(12):2932-2936
Cadmium resistant (Cdr) variants with coordinately amplified metallothionein I and II (MTI and MTII) genes have been derived from both Chinese hamster ovary and near-euploid Chinese hamster cell lines. Cytogenetic analyses of Cdr variants consistently revealed breakage and rearrangement involving chromosome 3p. In situ hybridization with a Chinese hamster MT-encoding cDNA probe localized amplified MT gene sequences near the translocation breakpoint involving chromosome 3p. These observations suggested that both functionally related, isometallothionein loci are linked on Chinese hamster chromosome 3. Southern blot analyses of DNAs isolated from a panel of Chinese hamster X mouse somatic cell hybrids which segregate hamster chromosomes confirmed that both MTI and MTII are located on chromosome 3. We speculate that rearrangement of chromosome 3p could be causally involved with the amplification of MT genes in Cdr hamster cell lines. 相似文献
59.
Reconstruction of the pharynx and esophagus with revascularized segments of jejunum remains a time-proven entity. Most thromboses and subsequent flap failures have occurred within the first 24 hours after revascularization of the flap. What would therefore be desirable is a safe, proven monitoring system to assess the patency of the microvascular anastomoses and subsequent viability of the transferred bowel segment. This paper reports on such a monitoring system, which involves the creation of a surgical window on the anterior cervical flap. The jejunal serosa is tacked to this window, and a thin split-thickness skin graft is placed directly on the bowel. The technique is simple, safe, efficacious, and leaves no significant defect. 相似文献
60.