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排序方式: 共有35条查询结果,搜索用时 15 毫秒
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Sandra Classen Elena Rahlf Johannes Jungwirth Nina Albers Luca Philipp Hebestreit Alexandra Zielinski Lena Poole Marco Groth Philipp Koch Thomas Liehr Stefanie Kankel Nils Cordes Cordula Petersen Kai Rothkamm Helmut Pospiech Kerstin Borgmann 《International journal of molecular sciences》2022,23(21)
BRCA1 is a well-known breast cancer risk gene, involved in DNA damage repair via homologous recombination (HR) and replication fork protection. Therapy resistance was linked to loss and amplification of the BRCA1 gene causing inferior survival of breast cancer patients. Most studies have focused on the analysis of complete loss or mutations in functional domains of BRCA1. How mutations in non-functional domains contribute to resistance mechanisms remains elusive and was the focus of this study. Therefore, clones of the breast cancer cell line MCF7 with indels in BRCA1 exon 9 and 14 were generated using CRISPR/Cas9. Clones with successful introduced BRCA1 mutations were evaluated regarding their capacity to perform HR, how they handle DNA replication stress (RS), and the consequences on the sensitivity to MMC, PARP1 inhibition, and ionizing radiation. Unexpectedly, BRCA1 mutations resulted in both increased sensitivity and resistance to exogenous DNA damage, despite a reduction of HR capacity in all clones. Resistance was associated with improved DNA double-strand break repair and reduction in replication stress (RS). Lower RS was accompanied by increased activation and interaction of proteins essential for the S phase-specific DNA damage response consisting of HR proteins, FANCD2, and CHK1. 相似文献
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Cordula A. Robinson 《International journal of remote sensing》2013,34(19):4101-4113
SIR-C and Radarsat radar data have been used to map structural and fluvial features in south-western Egypt in order to identify new ground-water resources in fracture rock aquifer settings. These radar data show broad areas of the desert are dissected by a dense fluvial network of palaeochannels. Radar data are ideal for mapping palaeochannels since some are sand covered (L- band has the ability to penetrate to at least 2 m beneath the sand in arid areas) and many show pronounced structural control (radar clearly depicts the scarp faces of faults). Strong structural control of drainage is consistent with the development of fracture rock aquifers. Five types of channel morphologies have been identified. These are: channels with a stepwise pattern; braided channels; dendritic and trellis-like channels with pronounced structural control; and flood features that follow regionally extensive faults (up to 50 km length). The regionally extensive faults drain numerous wadis and extend for tens of kilometres in length, and likely reflect the existence of several connecting horizontal aquifers in the subsurface. These regional faults converge on the Kharga Depression, indicating a principal megawatershed in south-western Egypt leads to the subsurface here. The other fault types are more local in extent, thus reflect fracture rock aquifers of more limited areal extent. 相似文献
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Internal Magnetic Structure of Nanoparticles Dominates Time‐Dependent Relaxation Processes in a Magnetic Field 下载免费PDF全文
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Kienberger F Stroh C Kada G Moser R Baumgartner W Pastushenko V Rankl C Schmidt U Müller H Orlova E LeGrimellec C Drenckhahn D Blaas D Hinterdorfer P 《Ultramicroscopy》2003,97(1-4):229-237
We employed magnetic ACmode atomic force microscopy (MACmode AFM) as a novel dynamic force microscopy method to image surfaces of biological membranes in their native environments. The lateral resolution achieved under optimized imaging conditions was in the nanometer range, even when the sample was only weakly attached to the support. Purple membranes (PM) from Halobacterium salinarum were used as a test standard for topographical imaging. The hexagonal arrangement of the bacteriorhodopsin trimers on the cytoplasmic side of PM was resolved with 1.5nm lateral accuracy, a resolution similar to images obtained in contact and tapping-mode AFM. Human rhinovirus 2 (HRV2) particles were attached to mica surfaces via nonspecific interactions. The capsid structure and 2nm sized protein loops of HRV2 were routinely obtained without any displacement of the virus. Globular and filamentous structures on living and fixed endothelial cells were observed with a resolution of 5-20nm. These examples show that MACmode AFM is a favorable method in studying the topography of soft and weakly attached biological samples with high resolution under physiological conditions. 相似文献
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We studied the frequency response of a magnetically driven atomic force microscope (AFM) cantilever close to a sample surface in liquids. Amplitude–frequency (tuning) curves showed pronounced differences in dependence on the tip–sample separation (from 1 to 50 μm), with significant shifts of the resonance peak. A model was developed in which the cantilever was described in a full shape manner and the hydrodynamic forces acting on the cantilever were approximately calculated. The slight inclination of the cantilever to the surface (15°) leads to a force profile along the cantilever. Therefore, the mathematical problem can be strictly solved only numerically. For an approximate analytical solution, the hydrodynamic force profile was approximated by a constant force along the cantilever for large separations and by a point force acting on the tip of the cantilever for small separations. The theoretical results calculated within this model agreed well with the experimental data and allowed to determine the cantilever mass in liquid M*, the joint mass at the tip end mt*, and the coefficient of viscous interaction of the cantilever with free liquid, γ∞. 相似文献
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Patrina SP Poh Cordula Hege Mohit P Chhaya Elizabeth R Balmayor Peter Foehr Rainer H Burgkart Jan‐Thorsten Schantz Stefan M Schiller Arndt F Schilling Dietmar W Hutmacher 《Polymer International》2017,66(1):77-84
The potential of the copolymer polycaprolactone‐co‐ poly‐d ,l ‐lactic acid (PCLLA ) as a biomaterial for scaffold‐based therapy for breast tissue engineering applications was assessed. First, the synthesized PCLLA was evaluated for its processability by means of additive manufacturing (AM ). We found that the synthesized PCLLA could be fabricated into scaffolds with an overall gross morphology and porosity similar to that of polycaprolactone. The PCLLA scaffolds possessed a compressive Young's modulus (ca 46 kPa ) similar to that of native breast (0.5 ? 25 kPa ), but lacked thermal stability and underwent thermal degradation during the fabrication process. The PCLLA scaffolds underwent rapid degradation in vitro which was characterized by loss of the scaffolds' mechanical integrity and a drastic decrease in mass‐average molar mass (M w) and number‐average molar mass (M n) after 4 weeks of immersion in phosphate buffer solution maintained at 37 °C. The tin‐catalysed PCLLA scaffold was also found to have cytotoxic effects on cells. Although the initial mechanical properties of the PCLLA scaffolds generally showed potential for applications in breast tissue regeneration, the thermal stability of the copolymer for AM processes, biocompatibility towards cells and degradation rate is not satisfactory at this stage. Therefore, we conclude that research efforts should be geared towards fine‐tuning the copolymer synthesizing methods. © 2016 Society of Chemical Industry 相似文献
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Formation of By‐products in Pure and Aqueous Acrylic Acid – Kinetic Measurements and Formation Mechanisms 下载免费PDF全文
Christian A. Pfeifer Cordula Scholz Kevin Vogel Alfons Drochner Herbert Vogel 《化学工程与技术》2017,40(4):755-759
During acrylic acid (AA) storage, a quality loss occurs due to the formation of by‐products such as diacrylic acid (DiAA), triacrylic acid (TriAA), and higher oligomers. This problem intensifies in the presence of water since the formation rate of oligomers increases and further by‐products such as 3‐hydroxypropionic acid (3‐HPA) and 3‐hydroxydiacrylic acid (3‐HDiAA) are formed. However, water is often essential during storage and transport to raise the flash point or reduce the melting point. In this work, the formation kinetics are investigated for all mentioned components in pure and aqueous AA. The formation mechanisms of 3‐HPA and 3‐HDiAA are assumed as acid‐catalyzed ester hydrolyses of DiAA or TriAA. The introduced reactions are modeled with the measured kinetic data in order to confirm the proposed reactions. 相似文献