全文获取类型
收费全文 | 19176篇 |
免费 | 3521篇 |
国内免费 | 663篇 |
专业分类
电工技术 | 106篇 |
综合类 | 996篇 |
化学工业 | 8670篇 |
金属工艺 | 2086篇 |
机械仪表 | 572篇 |
建筑科学 | 318篇 |
矿业工程 | 104篇 |
能源动力 | 158篇 |
轻工业 | 1687篇 |
水利工程 | 19篇 |
石油天然气 | 37篇 |
武器工业 | 121篇 |
无线电 | 418篇 |
一般工业技术 | 7514篇 |
冶金工业 | 375篇 |
原子能技术 | 33篇 |
自动化技术 | 146篇 |
出版年
2024年 | 83篇 |
2023年 | 379篇 |
2022年 | 455篇 |
2021年 | 829篇 |
2020年 | 750篇 |
2019年 | 771篇 |
2018年 | 816篇 |
2017年 | 867篇 |
2016年 | 1056篇 |
2015年 | 1352篇 |
2014年 | 1189篇 |
2013年 | 1382篇 |
2012年 | 1209篇 |
2011年 | 1268篇 |
2010年 | 1070篇 |
2009年 | 1107篇 |
2008年 | 834篇 |
2007年 | 1079篇 |
2006年 | 1079篇 |
2005年 | 904篇 |
2004年 | 787篇 |
2003年 | 742篇 |
2002年 | 613篇 |
2001年 | 473篇 |
2000年 | 436篇 |
1999年 | 333篇 |
1998年 | 311篇 |
1997年 | 225篇 |
1996年 | 175篇 |
1995年 | 158篇 |
1994年 | 131篇 |
1993年 | 82篇 |
1992年 | 80篇 |
1991年 | 82篇 |
1990年 | 102篇 |
1989年 | 74篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 34 毫秒
101.
An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered. 相似文献
102.
103.
104.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002 相似文献
105.
Typical finite element formulations and models for unidirectional composite materials are reviewed. The application of micromechanical finite element analysis to the modelling of unidirectional fibre-reinforced metal-matrix composites is demonstrated by presenting some studies from recent publications. It is shown that while analytical models offer a simple tool for obtaining the overall response of composites, finite element analysis provides more accurate and detailed characterisation of composite properties for complicated geometries and constituent property variations. Various effects that influence the stress/strain response and fibre/matrix deformation of composites are studied through modelling. These effects include the fibre coating and reaction layer, fibre shape and distribution, metallurgical and environmental factors, stress distributions and damage. It is demonstrated that the properties and constituent phase interaction of metal-matrix composites are best modelled by finite element analysis. It is emphasized that in order to obtain good predictions, the models must be coupled with first-hand characterisations of the constituent phases and their interactions, including the thermal history of the specimens. 相似文献
106.
This paper concerns a study of the combined effects of curing conditions and environmental exposure on the ultimate properties of two commercial woven carbon/epoxy laminates. Curing parameters (heating rate and applied pressure) were varied so as to obtain six different conditions for each material. Moisture saturation was also achieved by exposing some of the cured samples to environmental conditions of 70°C and 95% relative humidity. Four different tests (tensile, impact, Mode I and Mode II interlaminar fracture resistance) were therefore performed, and the results obtained on the different materials before and after moisture saturation compared. Neither curing pressure nor heating rate nor moisture absorption were observed to have any practical effect on tensile and impact properties. On the contrary, one noticeable effect was the interlaminar fracture resistance of the laminates. The results are discussed and interpreted in terms of damage formation and stress intensification mechanisms. 相似文献
107.
108.
High dielectric constant (high-k) polymer composites are of great interest for embedded capacitor applications. Previously,
we demonstrated that epoxy—aluminum composites are promising for embedded capacitor applications, because they have a high
dielectric constant and a low dielectric loss due to the core—shell structure of the self-passivated aluminum particles. In
this work, to further understand the dielectric behavior of aluminum composites, lower-loss polymers such as silicone, polyimide,
polynorbornene, and benzocyclobutene were explored as matrices for the aluminum composites. It is found that the polymer matrices
can significantly change the dielectric properties of the aluminum composites. A polymer matrix with a lower dielectric constant
generally results in a lower dielectric constant of its aluminum composites. In this regard, polymer—aluminum composites have
a similar dielectric characteristic as polymer—ceramic composites. Thermomechanical properties of aluminum composites were
characterized by a thermomechanical analyzer. 相似文献
109.
Thermochemical analyses of interfacial reactions in titanium, zirconium, and hafnium diboride reinforced oxidematrix composites have been carried out to evaluate the chemical compatibility. The chemical reactivity of these diborides with oxygen and the high volatility of B2 O3 ( l ) at reduced oxygen pressures are concerns during processing and operating conditions. The thermochemical stability and the vaporization behavior of B2 O3 ( l ) are discussed in terms of partial pressures of dominant gaseous species of the boron-oxygen system at 1700 and 2300 K. The TiB2 /ZrO2 and TiB2 /HfO2 systems are thermodynamically stable in a limited oxygen pressure range. The TiB2 /Al2 O3 system is stable, but the reactions in this system may apparently be accompanied by formation of gaseous products (B2 O3 , AlO, Al2 O, and lower boron oxides) in the presence of elemental oxygen. These thermochemical considerations are very useful in evaluating the effectiveness of oxides as diffusion barrier coatings on diboride reinforcements. 相似文献
110.
T. Chatterjee K. Yurekli V.G. Hadjiev R. Krishnamoorti 《Advanced functional materials》2005,15(11):1832-1838
Dispersions of single‐walled carbon nanotubes (SWNTs) in poly(ethylene oxide) (PEO) assisted by a lithium‐based anionic surfactant demonstrate an electrical percolation of 0.03 wt.‐% and a geometrical percolation, inferred from melt rheometry, of 0.09 wt.‐%. Both the melting temperature and the extent of crystallinity of the PEO crystals decrease with increasing SWNT loading. Raman spectroscopy of the nanocomposites indicates a down‐shift of the SWNT G‐modes and suggests that the nanotubes are subjected to tensile stress transfer from the polymer at room temperature. 相似文献