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排序方式: 共有86条查询结果,搜索用时 15 毫秒
1.
Liquid propylene was polymerized in a 5‐L autoclave batch reactor using a commercially available TiCl4/MgCl2/Al(ethyl)3/DCPDMS Ziegler–Natta catalyst, with a phthalate ester as internal electron donor. The powders from these polymerizations were characterized using laser diffraction particle size distribution (PSD) analysis, scanning electron microscopy (SEM), and bulk density measurements. These characteristics were analyzed as a function of the process conditions, including hydrogen and monomer concentration, polymerization temperature, and the prepolymerization method. It was shown that polymerization temperature influences the powder morphology to a large extent. At low temperatures, high‐density particles were obtained, showing regular shaped particle surfaces and low porosities. With increasing temperature, the morphology gradually was transferred into a more open structure, with irregular surfaces and poor replication of the shape of the catalyst particle. When using a prepolymerization step at a relatively low temperature, the morphology obtained was determined by this prepolymerization step and was independent from conditions in main polymerization. The morphology obtained was the same as that observed after a full polymerization at temperature. Even when using a short polymerization at an increasing temperature, the morphology was strongly influenced by the initial conditions. The effect of variation in hydrogen concentration supported the conclusion that the initial polymerization rate determines the powder morphology. In the absence of hydrogen, high bulk densities, and regularly shaped particles were obtained, even at high temperatures. With increasing hydrogen concentration, the reaction rates increased rapidly, and with that changed the morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1421–1435, 2003 相似文献
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Aleksandra Maria Staszak Tomasz Andrzej Paw?owski 《International journal of molecular sciences》2014,15(6):10868-10891
The proteome of zygotic embryos of Acer platanoides L. was analyzed via high-resolution 2D-SDS-PAGE and MS/MS in order to: (1) identify significant physiological processes associated with embryo development; and (2) identify changes in the proteome of the embryo associated with the acquisition of seed dormancy. Seventeen spots were identified as associated with morphogenesis at 10 to 13 weeks after flowering (WAF). Thirty-three spots were associated with maturation of the embryo at 14 to 22 WAF. The greatest changes in protein abundance occurred at 22 WAF, when seeds become fully mature. Overall, the stage of morphogenesis was characterized by changes in the abundance of proteins (tubulins and actin) associated with the growth and development of the embryo. Enzymes related to energy supply were especially elevated, most likely due to the energy demand associated with rapid growth and cell division. The stage of maturation is crucial to the establishment of seed dormancy and is associated with a higher abundance of proteins involved in genetic information processing, energy and carbon metabolism and cellular and antioxidant processes. Results indicated that a glycine-rich RNA-binding protein and proteasome proteins may be directly involved in dormancy acquisition control, and future studies are warranted to verify this association. 相似文献
4.
Inhibition of yeast‐to‐filamentous growth transitions in Candida albicans by a small molecule inducer of mammalian apoptosis 下载免费PDF全文
The opportunistic fungal pathogen of humans Candida albicans is able to grow in different morphological forms such as round or oval yeasts and filamentous hyphae and pseudohyphae. Morphogenesis, the ability to switch between the yeast and filamentous growth forms, is important for adapting to new microenvironments in the human host and for pathogenesis. The molecular pathways governing morphogenesis are complex and incompletely understood. Previously, we identified several small organic molecules that specifically inhibit the initiation of hyphal growth in C. albicans without affecting cell viability or budded growth. One molecule from that screen is known to induce apoptosis in mammalian cells. In this study, we have screened additional inducers of mammalian apoptosis and identified BH3I‐1, as well as several structural derivatives of BH3I‐1, that act as specific inhibitors of morphogenesis under a variety of environmental conditions. Chemical epistasis experiments suggest that BH3I‐1 acts downstream of the hypha‐specific gene regulators Rfg1, Nrg1 and Ume6. 相似文献
5.
Fangzhi Huang Yuhua Shen Anjian Xie Li Zhang Wanghua Xu Shikuo Li Wensheng Lu 《Reactive and Functional Polymers》2009,69(11):843-850
We have developed a novel 3D polymer template composed of a self-assembled film (SAF, insoluble polylactide film) and a soluble modifier (poly allylamine) and used this template to synthesize barium carbonate with a complex superstructure. Controlled synthesis of barium carbonate with novel morphologies such as spherical crystals consisting of needle-like building blocks, flower-like congeries consisting of one pronounced backbone and many shuttle-like petals, raft-like barium carbonate bundles consisting of tiny fractions etc., was realized by finely tuning the alignment and self-assembly of rods using the double template. The observed crystallization can proceed along the so-called rod-dumbbell-sphere formation process. This approach will be further extended to polymer-controlled fabrication of related minerals with novel, complex superstructures. 相似文献
6.
Frederik Weissenborn 《建筑学研究前沿(英文版)》2022,11(4):630-641
Material Engagement Theory (MET) theorizes artefacts as the emergent outcomes of non-linear processes of formation in which both human and non-human forms of agency are involved. It has proved a useful framework for exploring the architectural design process – which typically involves the mobilisation of multiple tools and materialities – but has not yet been applied to urban design. This paper argues that MET can be applied to the analysis of urban form, helping explain the distributed processes of urban formation. In sketching out an outline theory of urban material engagement, the paper facilitates a dialogue between MET and two theories of urban morphogenesis – SIRN and Space Syntax theory – which explain formal emergence in the urban surface and the urban grid, respectively. Exploring these theories’ analyses of urban formation – and the relationship between urban form and urban social behaviour – the paper outlines a theoretical synthesis which centres on the artefactual nature of urban form. 相似文献
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Schizosaccharomyces pombe cells are rod-shaped and grow along a single axis from their two ends. Microtubules extend from the cell centre terminating at the cell ends. The ERM(ezrin/radixin/moesin)-like proteins Tea1p and Tea3p, and the Dyrk-like kinase Pom1p are cell end markers involved in the regulation of growth and microtubular dynamics at the cell ends. We have analysed the relative contribution of these three proteins to the determination of cell ends as sites both for cell growth and for microtubular termination. Pom1Delta, in combination with Tea1Delta or Tea3Delta, has the greatest difficulty in relocalizing actin to the cell ends following actin depolymerization and generates the most defective growth pattern. Tea1Delta, in combination with Pom1Delta or Tea3Delta, displays the highest number of microtubules bending round the cell ends. Tea1DeltaPom1Delta, which has the most defective growth pattern and microtubules, also displays the highest number of branched cells. We show that Tea1p, Tea3p and Pom1p all contribute, to different extents, to the determination of cell ends, as sites for both cell growth and microtubular termination. We also show that the fission yeast cell relies on both the positioning of landmarks and a properly organized microtubule cytoskeleton to direct cell growth. 相似文献
8.
该文介绍了细胞结构的计算机仿真方法,二维肥皂泡的计算机仿真方法具有普遍性,这一方法可应用于其它领域类似的课题,生命科学中使用计算机仿真及其独特的优越性,本文还介绍了非洲爪蟾脊索器官形成的计算机仿真方法。 相似文献
9.
Alexandros Tsamis 《Architectural Design》2010,80(6):80-85
The relationship of society to its excrement is telling at both a cultural and social level. The notion of green architecture with its emphasis on the naturally pure has so far eschewed waste as a primary generative material. Alexandros Tsamis here invokes a more inclusive notion of the environment in which by-product becomes intrinsic to any project. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Pinak Samal Philipp Maurer Clemens van Blitterswijk Roman Truckenmüller Stefan Giselbrecht 《Advanced materials (Deerfield Beach, Fla.)》2020,32(24):1907966
Recently developed stem-cell-based in vitro models of morphogenesis can help shed light on the mechanisms involved in embryonic patterning. These models are showcased using traditional cell culture platforms and materials, which allow limited control over the biological system and usually do not support high-content imaging. In contrast, using advanced microengineered tools can help in microscale control, long-term culture, and real-time data acquisition from such biological models and aid in elucidating the underlying mechanisms. Here, a new culturing, manipulation and analysis platform is described to study in vitro morphogenesis using thin polycarbonate film-based microdevices. A pipeline consisting of open-source software to quantify 3D cell movement using 4D image acquisition is developed to analyze cell migration within the multicellular clusters. It is shown that the platform can be used to control and study morphogenesis in non-adherent cultures of the P19C5 mouse stem cell line and mouse embryonic stem cells (mESCs) that show symmetry breaking and axial elongation events similar to early embryonic development. Using the new platform, it is found that localized cell proliferation and coordinated cell migration result in elongation morphogenesis of the P19C5 aggregates. Further, it is found that polarization and elongation of mESC aggregates are dependent on directed cell migration. 相似文献