全文获取类型
收费全文 | 611篇 |
免费 | 34篇 |
国内免费 | 3篇 |
学科分类
工业技术 | 648篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 23篇 |
2017年 | 22篇 |
2016年 | 27篇 |
2015年 | 25篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 36篇 |
2011年 | 43篇 |
2010年 | 22篇 |
2009年 | 27篇 |
2008年 | 28篇 |
2007年 | 17篇 |
2006年 | 30篇 |
2005年 | 16篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 16篇 |
1997年 | 3篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有648条查询结果,搜索用时 15 毫秒
81.
Thermo-mechanical properties and erosion performance of short carbon fibre reinforced vinyl ester resin based isotropic polymer composites with four different fibre weight fractions have been investigated. The storage, loss and damping characteristics were analysed to assess the energy absorption/viscous recoverable energy dissipation and reinforcement efficiency of the composites as a function of fibre content in the temperature range of 0–140 °C. The composite with 30 wt.% of short carbon fibres has been observed to exhibit superior thermo-mechanical response with highest energy dissipation/damping ability accompanied with a constant storage modulus without any substantial decay till 60 °C. The erosion rates (Er) of these composites are evaluated at different impingement angles (30–90°), fibre loadings (20–50 wt.%), impact velocities (43–76 m/s), stand-off distances (55–85 mm) and erodent sizes (250–600 μm) following the erosion test schedule in an air jet type test rig. An optimal parameter combination is determined and subsequently validated for erosion rate minimization following Taguchi method and by conducting confirmation experiments. A correlation between the loss-modulus inverse and the erosion rate has been observed which conceptually establishes a possible mechanistic equivalence between erosion and dynamic mechanical loading modes. The morphologies of eroded surface are examined by the scanning electron microscopy to investigate the nature of wear-craters, material damage mode and other qualitative attributes responsible for promoting erosion. 相似文献
82.
Bhabani?K.?SatapathyEmail author Arijit?Das Amar?Patnaik 《Journal of Materials Science》2011,46(6):1963-1974
Cenosphere-filled polypropylene (PP) composites were fabricated and characterized for their structural/morphological and fracture
mechanical behaviour. The fracture properties were studied following the essential work of fracture (EWF) approach based on
post-yield fracture mechanics (PYFM) concept. The structural attributes and its consequent effects on the dynamic mechanical
properties were characterized by wide angle X-ray diffraction (WAXD), hot-stage polarized light optical microscopy (PLOM)
and dynamic mechanical analysis (DMA). The WAXD studies have revealed a decrease in crystallinity of the composites with increase
in cenosphere content. PLOM studies reveals a threefold reduction in the diameter of the spherulite in case of composite with
10 wt% of cenosphere compared to that of PP followed by an increase of ~50% in the composite with 20 wt% of cenosphere compared
to that of the composite with 10 wt% cenosphere. DMA revealed an enhancement in the energy dissipation ability of the composite
with 10 wt% of cenosphere and an increase in the storage modulus up to ~30% in the composites relative to the soft PP phase.
The non-essential work of fracture (NEWF: βw
p) as the resistance to stable crack propagation has shown a maximum at 10 wt% of cenosphere followed by a sharp drop at higher
cenosphere content indicating a cenosphere-induced ductile-to-brittle transition (DBT). Fractured surface morphology investigations revealed that the failure mode of the composites undergo
a systematic transition from matrix-controlled shear deformation to filler-controlled quasi-brittle modes above a cenosphere
loading of 10 wt% in the composites reiterating the possibility of filler-induced semiductile-to-DBT transition. 相似文献
83.
To define conserved sequences for mat1 imprinting and silencing of the mat2,3 region of Schizosaccharomyces pombe, we determined the DNA sequence of the cognate region (mat2,3 region) of another fission yeast, Sz. kambucha, a yeast species isolated from Kambucha tea mix. The entire mat2,3 region shows more than 98% identity between the two species. Sequence similarity is even higher (99.3%) for mating-type cassettes; deduced amino acid sequences of three of the four Mat peptides (Pi, Pc and Mi) are identical between the two species, while the fourth (Mc) has a single amino acid polymorphism. Comparison of the sequence motif of the imprint site essential for mat1 switching shows that mat-P of Sz. kambucha has a sequence identical to the conserved motif present in Sz. pombe. However, this sequence motif of nine bases differs by one base for mat-M of Sz. kambucha. The sequence of the K region shows about 98% identity between the two species, with the cenH region showing 98.3% homology. Thus, the arrangement of the mat2,3 region in both yeasts is conserved and shows 1-2% nucleotide sequence variation throughout the region. The DNA sequence of the mat2,3 region from Sz. kambucha has been submitted to GenBank under Accession No. AY271822. 相似文献
84.
T. R. Vijaybabu T. Ramesh Suman Pandipati Sujit Mishra G Sridevi C Pradeep Raja Rhoda Afriyie Mensah Oisik Das Manjusri Misra Amar Mohanty Karthik Babu NB 《大分子材料与工程》2023,308(7):2300001
The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials. 相似文献
85.
86.
在ε-己内酯(CL)和丙烯酸丁酯(BA)单体共存的体系中,用预先合成的双键功能化烷氧基钛化合物和过氧化物作引发剂对CL和BA进行聚合。通过位于原位形成的以钛为中心的四臂聚己内酯末端的双键参与BA的自由基共聚合,形成了CL与BA交联的新型共聚物。采用多频流变法证实了共聚中交联凝胶的存在。 相似文献
87.
88.
Bertino E. Carminati B. Ferrari E. Thuraisingham B. Amar Gupta 《Knowledge and Data Engineering, IEEE Transactions on》2004,16(10):1263-1278
Third-party architectures for data publishing over the Internet today are receiving growing attention, due to their scalability properties and to the ability of efficiently managing large number of subjects and great amount of data. In a third-party architecture, there is a distinction between the Owner and the Publisher of information. The Owner is the producer of information, whereas Publishers are responsible for managing (a portion of) the Owner information and for answering subject queries. A relevant issue in this architecture is how the Owner can ensure a secure and selective publishing of its data, even if the data are managed by a third-party, which can prune some of the nodes of the original document on the basis of subject queries and access control policies. An approach can be that of requiring the Publisher to be trusted with regard to the considered security properties. However, the serious drawback of this solution is that large Web-based systems cannot be easily verified to be secure and can be easily penetrated. For these reasons, we propose an alternative approach, based on the use of digital signature techniques, which does not require the Publisher to be trusted. The security properties we consider are authenticity and completeness of a query response, where completeness is intended with regard to the access control policies stated by the information Owner. In particular, we show that, by embedding in the query response one digital signature generated by the Owner and some hash values, a subject is able to locally verify the authenticity of a query response. Moreover, we present an approach that, for a wide range of queries, allows a subject to verify the completeness of query results. 相似文献
89.
Deformation-induced phase transformation and strain hardening in type 304 austenitic stainless steel 总被引:1,自引:0,他引:1
Amar K. De John G. Speer David K. Matlock David C. Murdock Martin C. Mataya Robert J. Comstock Jr. 《Metallurgical and Materials Transactions A》2006,37(6):1875-1886
Deformation-induced phase transformation in a type 304 austenitic stainless steel has been studied in tension at room temperature
and −50 °C. The evolution of transformation products was monitored using X-ray diffraction (XRD) line profile analysis of
diffraction peaks from a single XRD scan employing the direct comparison method. Crystallographic texture transitions due
to deformation strain have been evaluated using (111)
γ
pole figures. The tensile stress-strain data have been analyzed to explain the influence of underlying deformation-induced
microstructural changes and associated texture changes in the steel. It is found that the initial stage of rapidly decreasing
strain hardening rate in type 304 steel is primarily influenced by hcp ɛ-martensite formation, and the second stage of increasing
strain hardening rate is associated with an increase in the α′-martensite formation. The formation of ɛ-martensite is associated
with a gradual strengthening of the copper-type texture components up to 15 pct strain and decreasing with further strain
at −50 °C. Texture changes during low-temperature deformation not only change the mechanism of ɛ-martensite formation but
also influence the strain rate sensitivity of the present steel. 相似文献
90.
An efficient analytical integration technique for computation of spatial method of moments (MoM) integrals in conjunction with numerical matched loads is presented. The current distribution on the device is solved by using the well-known Galerkin’s MoM procedure applied to mixed potential integral equation in the spatial domain. The scattering parameters are determined by considering infinite lines at each port where only the fundamental mode is assumed to propagate. The contribution of this work is the development of an integration technique for the computation of spatial domain integrals, that is fast and rigorous. This technique is based on a Taylor series expansion of the integrands involving only polynomial functions. The use of polynomial forms in the integrals leads an immediate analytical integration, and the computation time will be considerably reduced. 相似文献