全文获取类型
收费全文 | 416篇 |
免费 | 56篇 |
出版年
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 17篇 |
2015年 | 17篇 |
2014年 | 26篇 |
2013年 | 26篇 |
2012年 | 30篇 |
2011年 | 30篇 |
2010年 | 14篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1965年 | 4篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1952年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有472条查询结果,搜索用时 62 毫秒
81.
B. Shay Y. Gruenbaum-Cohen A.S. Tucker A.L. Taylor E. Rosenfeld A. Haze L. Dafni Y. Leiser E. Fermon T. Danieli A. Blumenfeld D. Deutsch 《Protein expression and purification》2009,68(1):90-98
Tuftelin is an acidic protein expressed at very early stages of mouse odontogenesis. It was suggested to play a role during epithelial–mesenchymal interactions, and later, when enamel formation commences, to be involved in enamel mineralization. Tuftelin was also detected in several normal soft tissues of different origins and some of their corresponding cancerous tissues. Tuftelin is expressed in low quantities, and undergoes degradation in the enamel extracellular matrix. To investigate the structure and function of tuftelin, the full length recombinant human tuftelin protein was produced. The full length human tuftelin cDNA was cloned using GatewayTM recombination into the Bac-to-BacTM system compatible transfer vector pDest10. This vector adds a hexahistidine tag to the N-terminus of the expressed protein, enabling one-step affinity purification on nickel column. The recombinant human tuftelin protein was transposed into the bacmid and expressed in Spodoptera frugiperda (Sf9) insect cells. The yield of the purified, his-tagged recombinant full length human Tuftelin (rHTuft+) was 5–8 mg/L culture. rHTuft+ was characterized by SDS–PAGE, Western blot, ESI-TOF spectrometry, restriction mapping and MS/MS sequencing. The availability of the purified, full length recombinant human tuftelin protein opened up the possibility to investigate novel functions of tuftelin. Application of rHTuft+ agarose beads onto embryonic mouse mandibular explants caused changes in the surrounding epithelial cells, including morphology, orientation and spatial organization. Further studies using DiI labeling, revealed that rHTuft+, placed on the tooth germ region, brought about recruitment of adjacent embryonic mesenchymal cells. These findings support the hypothesis that tuftelin plays an important role during embryogenesis. 相似文献
82.
Koh CJ Delo DM Lee JW Siddiqui MM Lanza RP Soker S Yoo JJ Atala A 《Methods (San Diego, Calif.)》2009,47(2):90-97
Embryonic stem cells are envisioned as a viable source of pluripotent cells for use in regenerative medicine applications when donor tissue is not available. However, most current harvest techniques for embryonic stem cells require the destruction of embryos, which has led to significant political and ethical limitations on their usage. Parthenogenesis, the process by which an egg can develop into an embryo in the absence of sperm, may be a potential source of embryonic stem cells that may avoid some of the political and ethical concerns surrounding embryonic stem cells. Here we provide the technical aspects of embryonic stem cell isolation and expansion from the parthenogenetic activation of oocytes. These cells were characterized for their stem-cell properties. In addition, these cells were induced to differentiate to the myogenic, osteogenic, adipogenic, and endothelial lineages, and were able to form muscle-like and bony-like tissue in vivo. Furthermore, parthenogenetic stem cells were able to integrate into injured muscle tissue. Together, these results demonstrate that parthenogenetic stem cells can be successfully isolated and utilized for various tissue engineering applications. 相似文献
83.
84.
Asja Korajkic Brian R. McMinn Orin C. Shanks Mano Sivaganesan G. Shay Fout Nicholas J. Ashbolt 《Applied and environmental microbiology》2014,80(13):3952-3961
The sanitary quality of recreational waters that may be impacted by sewage is assessed by enumerating fecal indicator bacteria (FIB) (Escherichia coli and enterococci); these organisms are found in the gastrointestinal tracts of humans and many other animals, and hence their presence provides no information about the pollution source. Microbial source tracking (MST) methods can discriminate between different pollution sources, providing critical information to water quality managers, but relatively little is known about factors influencing the decay of FIB and MST genetic markers following release into aquatic environments. An in situ mesocosm was deployed at a temperate recreational beach in the Mississippi River to evaluate the effects of ambient sunlight and biotic interactions (predation, competition, and viral lysis) on the decay of culture-based FIB, as well as molecularly based FIB (Entero1a and GenBac3) and human-associated MST genetic markers (HF183 and HumM2) measured by quantitative real-time PCR (qPCR). In general, culturable FIB decayed the fastest, while molecularly based FIB and human-associated genetic markers decayed more slowly. There was a strong correlation between the decay of molecularly based FIB and that of human-associated genetic markers (r2, 0.96 to 0.98; P < 0.0001) but not between culturable FIB and any qPCR measurement. Overall, exposure to ambient sunlight may be an important factor in the early-stage decay dynamics but generally was not after continued exposure (i.e., after 120 h), when biotic interactions tended to be the only/major influential determinant of persistence. 相似文献
85.
Telomerase and differentiation in multicellular organisms: turn it off, turn it on, and turn it off again 总被引:19,自引:0,他引:19
Forsyth NR Wright WE Shay JW 《Differentiation; research in biological diversity》2002,69(4-5):188-197
Telomerase is a ribonucleoprotein complex that catalyses the addition of TTAGGG repeats onto telomeres, repetitive DNA structures found at the ends of linear chromosomes. The majority of human somatic tissues do not display telomerase activity and undergo telomeric shortening with consecutive divisions. This telomeric shortening results in replicative senescence in vitro and likely in vivo. Telomerase activity is present in the vast majority of tumors, preventing telomeric shortening and thereby enabling indefinite cell divisions. Telomerase activity is regulated throughout human development, undergoing silencing in almost all organ systems from embryogenesis onwards. However, regulated telomerase activity is seen in basal/stem cell compartments of highly regenerative tissues, such as those of the immune system, skin, and intestine. Avian species display telomerase repression and telomeric shortening similar to that seen in humans. However, rodents retain telomerase-competency throughout their lifespan and have not been shown to display division-dependent telomere shortening. The regulation of telomerase activity in plants is less well understood, although early indications suggest ubiquitous competency. The aim of this review is to present current data regarding developmental regulation of telomerase in humans, mice, chickens and flowering plants. Differentiation, quiescence and telomerase activity regulation will then be addressed in three human representative tissue systems; blood, skin, and intestine. We will also highlight similarities, differences and misconceptions in the developing field of telomere and telomerase biology. 相似文献
86.
87.
Junzhi Zhou Beibei Mao Qi Zhou Deqiang Ding Miao Wang Peng Guo Yuhao Gao Jerry W. Shay Zengqiang Yuan Yu‐Sheng Cong 《Aging cell》2014,13(1):197-200
Telomerase contributes to cell proliferation and survival through both telomere‐dependent and telomere‐independent mechanisms. In this report, we discovered that endoplasmic reticulum (ER) stress transiently activates the catalytic components of telomerase (TERT) expression in human cancer cell lines and murine primary neural cells. Importantly, we show that depletion of hTERT sensitizes cells to undergo apoptosis under ER stress, whereas increased hTERT expression reduces ER stress‐induced cell death independent of catalytically active enzyme or DNA damage signaling. Our findings establish a functional link between ER stress and telomerase, both of which have important implications in the pathologies associated with aging and cancer. 相似文献
88.
89.
90.
Justin R. Ortiz Kathleen M. Neuzil Colin R. Cooke Moni B. Neradilek Christopher H. Goss David K. Shay 《PloS one》2014,9(11)