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排序方式: 共有230条查询结果,搜索用时 15 毫秒
41.
Wonhye Lee Vivian Lee Samuel Polio Phillip Keegan Jong‐Hwan Lee Krisztina Fischer Je‐Kyun Park Seung‐Schik Yoo 《Biotechnology and bioengineering》2010,105(6):1178-1186
One of the challenges in tissue engineering is to provide adequate supplies of oxygen and nutrients to cells within the engineered tissue construct. Soft‐lithographic techniques have allowed the generation of hydrogel scaffolds containing a network of fluidic channels, but at the cost of complicated and often time‐consuming manufacturing steps. We report a three‐dimensional (3D) direct printing technique to construct hydrogel scaffolds containing fluidic channels. Cells can also be printed on to and embedded in the scaffold with this technique. Collagen hydrogel precursor was printed and subsequently crosslinked via nebulized sodium bicarbonate solution. A heated gelatin solution, which served as a sacrificial element for the fluidic channels, was printed between the collagen layers. The process was repeated layer‐by‐layer to form a 3D hydrogel block. The printed hydrogel block was heated to 37°C, which allowed the gelatin to be selectively liquefied and drained, generating a hollow channel within the collagen scaffold. The dermal fibroblasts grown in a scaffold containing fluidic channels showed significantly elevated cell viability compared to the ones without any channels. The on‐demand capability to print fluidic channel structures and cells in a 3D hydrogel scaffold offers flexibility in generating perfusable 3D artificial tissue composites. Biotechnol. Bioeng. 2010;105: 1178–1186. © 2009 Wiley Periodicals, Inc. 相似文献
42.
Processing of a mammalian hematopoietic microRNA precursor is suppressed when it is edited by ADARs. The edited pri-miRNA can subsequently be degraded by Tudor-SN. 相似文献
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44.
In this report, we establish that Drosophila ADAR (adenosine deaminase acting on RNA) forms a dimer on double-stranded (ds) RNA, a process essential for editing activity. The minimum region required for dimerization is the N-terminus and dsRNA-binding domain 1 (dsRBD1). Single point mutations within dsRBD1 abolish RNA-binding activity and dimer formation. These mutations and glycerol gradient analysis indicate that binding to dsRNA is important for dimerization. However, dimerization can be uncoupled from dsRNA-binding activity, as a deletion of the N-terminus (amino acids 1-46) yields a monomeric ADAR that retains the ability to bind dsRNA but is inactive in an editing assay, demonstrating that ADAR is only active as a dimer. Different isoforms of ADAR with different editing activities can form heterodimers and this can have a significant effect on editing in vitro as well as in vivo. We propose a model for ADAR dimerization whereby ADAR monomers first contact dsRNA; however, it is only when the second monomer binds and a dimer is formed that deamination occurs. 相似文献
45.
Denichiro Otsuga Brian R. Keegan Ellen Brisch John W. Thatcher Greg J. Hermann William Bleazard Janet M. Shaw 《The Journal of cell biology》1998,143(2):333-349
The Saccharomyces cerevisiae Dnm1 protein is structurally related to dynamin, a GTPase required for membrane scission during endocytosis. Here we show that Dnm1p is essential for the maintenance of mitochondrial morphology. Disruption of the DNM1 gene causes the wild-type network of tubular mitochondrial membranes to collapse to one side of the cell but does not affect the morphology or distribution of other cytoplasmic organelles. Dnm1 proteins containing point mutations in the predicted GTP-binding domain or completely lacking the GTP-binding domain fail to rescue mitochondrial morphology defects in a dnm1 mutant and induce dominant mitochondrial morphology defects in wild-type cells. Indirect immunofluorescence reveals that Dnm1p is distributed in punctate structures at the cell cortex that colocalize with the mitochondrial compartment. These Dnm1p-containing structures remain associated with the spherical mitochondria found in an mdm10 mutant strain. In addition, a portion of Dnm1p cofractionates with mitochondrial membranes during differential sedimentation and sucrose gradient fractionation of wild-type cells. Our results demonstrate that Dnm1p is required for the cortical distribution of the mitochondrial network in yeast, a novel function for a dynamin-related protein. 相似文献
46.
47.
In this study, we examined the suitability of a three dimensional preparation technique for studying chromosome behaviour
in the first meiotic prophase in the mouse chromosomal mutant T(1;13)H/T(1;13)Wa. To preserve cellular shape, primary spermatocytes
were encapsulated in a fibrin clot. Conventionally sedimented prophase nuclei served as controls. Axial elements and lateral
synaptonemal complex components were subsequently stained by immunofluorescence and the presence of axial elements at the
pachytene stage was highlighted with indirect immunofluorescence against the Atr protein. We compared the distribution of
Atr signal in the fibrin-embedded spermatocytes with surface-spread preparations and immunohistochemically stained histological
sections of seminiferous tubules. Furthermore, fluorescence in situ hybridisation of the mouse minor satellite DNA was done
on fibrin-embedded spermatocytes. The Atr signal is most conspicuous in fibrin-embedded nuclei on unpaired axial elements
during pachytene, both for sex chromosomal and for autosomal segments, and expanding from these elements into the surrounding
chromatin. Both spread and encapsulated zygotene nuclei with extended axial element formation proved to be positive for Atr.
Mid- to late zygotene nuclei were devoid of 3,3′-diaminodibenzene deposition in the histological sections. Highlighting the
unpaired axial elements in the small heteromorphic 113H;113Wa bivalent with an Atr signal enabled meiotic analysis of this bivalent to be carried out in a three-dimensional context.
Thus, proximity of this bivalent with the sex chromosomes is found more often in three-dimensional preparations than in spread
preparations. Furthermore, the development of the Atr signal over the sex chromosomes as pachytene proceeds helps in substaging
of this long and heterogeneous meiotic phase, in sedimented but especially in fibrin-encapsulated nuclei.
Received: 22 September 1999; in revised form: 20 December 1999 / Accepted: 21 December 1999 相似文献
48.
49.
NF-kappa B/Rel participation in the lymphokine-dependent proliferation of T lymphoid cells 总被引:2,自引:0,他引:2
Mora A Youn J Keegan A Boothby M 《Journal of immunology (Baltimore, Md. : 1950)》2001,166(4):2218-2227
50.
Adenosine deaminases acting on RNA (ADARs): RNA-editing enzymes 总被引:1,自引:0,他引:1