全文获取类型
收费全文 | 5411篇 |
免费 | 358篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 106篇 |
综合类 | 5篇 |
化学工业 | 1545篇 |
金属工艺 | 176篇 |
机械仪表 | 148篇 |
建筑科学 | 221篇 |
矿业工程 | 12篇 |
能源动力 | 282篇 |
轻工业 | 553篇 |
水利工程 | 40篇 |
石油天然气 | 91篇 |
无线电 | 531篇 |
一般工业技术 | 995篇 |
冶金工业 | 331篇 |
原子能技术 | 37篇 |
自动化技术 | 727篇 |
出版年
2023年 | 56篇 |
2022年 | 150篇 |
2021年 | 190篇 |
2020年 | 152篇 |
2019年 | 215篇 |
2018年 | 303篇 |
2017年 | 218篇 |
2016年 | 233篇 |
2015年 | 185篇 |
2014年 | 219篇 |
2013年 | 474篇 |
2012年 | 266篇 |
2011年 | 330篇 |
2010年 | 286篇 |
2009年 | 284篇 |
2008年 | 257篇 |
2007年 | 178篇 |
2006年 | 195篇 |
2005年 | 123篇 |
2004年 | 117篇 |
2003年 | 153篇 |
2002年 | 112篇 |
2001年 | 84篇 |
2000年 | 97篇 |
1999年 | 79篇 |
1998年 | 116篇 |
1997年 | 68篇 |
1996年 | 56篇 |
1995年 | 48篇 |
1994年 | 37篇 |
1993年 | 34篇 |
1992年 | 21篇 |
1991年 | 29篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 41篇 |
1986年 | 23篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 25篇 |
1979年 | 14篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1976年 | 26篇 |
1975年 | 21篇 |
1973年 | 18篇 |
排序方式: 共有5800条查询结果,搜索用时 15 毫秒
71.
Hamza El Marouazi Benoit van der Schueren Damien Favier Anaëlle Bolley Samuel Dagorne Thierry Dintzer Izabela Janowska 《应用聚合物科学杂志》2021,138(44):51300
Four series of polylactide (PLA) based composite films containing horizontally aligned few layer graphene (FLG) flakes of high aspect ratio and adsorbed albumin are prepared. The mechanical and thermal properties varies with percentage, dispersion degree and size of FLG flakes. Great improvement up to 290% and 360% of tensile modulus and strength respectively were obtained for the composite containing high lateral size of FLG at 0.17% wt, and up to 60% and 80% for the composite with very well dispersed 0.02% wt FLG. The composites of PLA and PEG-PLLA containing very well dispersed FLG flakes at 0.07% wt are ductile showing enhancement of elongation at break up to respectively 80% and 88%. Relatively high electrical conductivity, 5 × 10−3 S/cm, is measured for PLA film charged with 3% of FLG. 相似文献
72.
This article investigates the prediction of the crack growth angle of an existing internal crack under mixed mode loading at the crack tip for an unfilled ethylene propylene diene terpolymer rubber (EPDM). For the realization of mixed mode loading, the cracks of the uniaxial loaded specimens were oriented with different angles to the loading direction. The energy density factor was used as a potential criterion for determining the crack growth angle. The determination of the strain energy density factor was carried out simulatively in Abaqus. The second-order Ogden model was used to describe the rubber-like material behavior. The relative local minimum of the strain energy density factor provides the possible growth angle. The experimental investigations show that the initial cracks grow orthogonally to the loading direction for the different crack orientation angles. For the crack orientation angle parallel to the load direction, the crack growth was observed because the strong stretching of the specimen caused strong necking in the crack region. The crack growth for the remaining crack orientation angles were induced due to shear loading at the crack tip. The predictive angle of different crack orientation angles shows very good accordance to the measured crack growth angles. 相似文献
73.
V. M. El’kin E. A. Kozlov E. V. Kakshina Yu. S. Moreva 《The Physics of Metals and Metallography》2006,101(3):208-217
A thermodynamically complete equation of two-phase (γ, α) state of cerium was derived in terms of a pseudobinary solid-solution model developed by Aptekar’ and Ponyatovskii. According to the model, unalloyed cerium is considered to be a substitutional solid solution whose components are represented by atoms with different electron configurations. The free energy of the individual phases (solid-solution components) is represented as a sum of three terms that describe the atomic interaction at T = 0 K, quasi-harmonic lattice vibrations, and the combined contribution of the anharmonicity and thermally excited electrons. The equation of state is shown to adequately describe the unusual behavior of cerium under the effect of static actions. In this work, calculations of the dynamic compression of cerium are performed. The calculations indicate that, up to the completion of the γ-α transition, the formation of the shockwave front in cerium is impossible and compression of cerium occurs in an isentropic wave of simple compression. As the pressure increases, a multiwave configuration with the participation of isentropic and shock waves is realized in cerium. The initial state in which the shock wave is propagated changes depending on the wave intensity; i.e., the initial state “slides” along the leading isentropic wave. The shock adiabat was shown to not pass through the very complex range of metastable existence of α-, α′-, and α″ phases. This provides prerequisites for experimental finding the α-ε transformation which can occur in the shock wave and is not masked with the preceding α-α′ and α′-α″ transformations. When assuming the absence of the α-ε transformation, the calculated coordinates of the point corresponding to the start of melting in the shock wave are p melt = 11.3 GPa and T melt = 1130 K. 相似文献
74.
E.E Abd El Aal 《Corrosion Science》2003,45(4):759-775
The effect of Cl−, Br− and I− anions as aggressive agents on the anodic behaviour of nickel electrode in deaerated Na2B4O7 solutions have been investigated by galvanostatic polarization technique. Lower concentrations of the halide anions have no effect on the mechanism of nickel passivation. An increase in the halide anions concentration causes oscillation of the potential in the oxygen evolution region. This could be attributed to the destruction of the passivity by halide anions and repassivation of the film by anodic current and/or OH− anions. Higher aggressive anion concentrations cause breakdown of the passive film and initiated pitting corrosion. As the temperature increases, the breakdown potential is shifted towards the more negative direction. On the other hand, as the pH of the solution increases, the breakdown potential is shifted toward more positive direction, indicating increased protection of the passive film. The activation energy, , of the oxide film formation in the presence of Cl− anions was calculated and was found to be 21 kJ/mol. 相似文献
75.
L. Bamoulid F. Benoît-Marquié A. Guenbour M.-T. Maurette S. El Hajjaji 《Surface & coatings technology》2006,201(6):2791-2795
In this study, the formation and characterization of conversion coatings modified by a sol-gel TiO2 deposit were investigated as a way to develop a new photocatalyst for water and air depollution. The conversion coating, characterised by strong interfacial adhesion, high roughness and high surface area facilitates the sol-gel deposition of titania and enhances its adhesion to the substrate. The conversion treatment is carried out in an acid solution. Observation by Scanning Electron Microscopy (SEM) reveals a rough surface with pores and cavities. According to SIMS measurements, the thickness of the initial conversion layer is evaluated at about 1.5 μm. On this pre-functionalised support, the titanium dioxide was deposited by the sol-gel method. The roughness measurements coupled with SIMS analysis allowed a precise evaluation of the surface state of the final layers. The coating consists of two layers: a TiO2 outer layer and an inner layer containing iron chromium oxides. Characterization by X-ray diffraction (XRD) showed the existence of the TiO2 anatase structure as the main compound. 相似文献
76.
Guy Jobbins Jack Kalpakian Abdelouahid Chriyaa Ahmed Legrouri El Houssine El Mzouri 《国际水资源开发杂志》2015,31(3):393-406
This article draws on three case studies of drip irrigation adoption in Morocco to consider the water–energy–food nexus concept from a bottom-up perspective. Findings indicate that small farmers' adoption of drip irrigation is conditional, that water and energy efficiency does not necessarily reduce overall consumption, and that adoption of drip irrigation (and policies supporting it) can create winners and losers. The article concludes that, although the water–energy–food WEF nexus concept may offer useful insights, its use in policy formulation should be tempered with caution. Technical options that appear beneficial at the conceptual level can have unintended consequences in practice, and policies focused on issues of scarcity and efficiency may exacerbate other dimensions of poverty and inequality. 相似文献
77.
Anas Hatim Said Belkouch Mohamed El Aakif Moha M’rabet Hassani Noureddine Chabini 《Multimedia Tools and Applications》2013,67(3):667-685
The Discrete Cosine Transform (DCT) is one of the most widely used techniques for image compression. Several algorithms are proposed to implement the DCT-2D. The scaled SDCT algorithm is an optimization of the DCT-1D, which consists in gathering all the multiplications at the end. In this paper, in addition to the hardware implementation on an FPGA, an extended optimization has been performed by merging the multiplications in the quantization block without having an impact on the image quality. A simplified quantization has been performed also to keep higher the performances of the all chain. Tests using MATLAB environment have shown that our proposed approach produces images with nearly the same quality of the ones obtained using the JPEG standard. FPGA-based implementations of this proposed approach is presented and compared to other state of the art techniques. The target is an an Altera Cyclone II FPGA using the Quartus synthesis tool. Results show that our approach outperforms the other ones in terms of processing-speed, used resources and power consumption. A comparison has been done between this architecture and a distributed arithmetic based architecture. 相似文献
78.
Abdelwahab Hamam Mohamad Eid Abdulmotaleb El Saddik 《Multimedia Tools and Applications》2013,67(2):455-472
Haptic technologies and applications have received enormous attention in the last decade. The incorporation of haptic modality into multimedia applications adds excitement and enjoyment to an application. It also adds a more natural feel to multimedia applications, that otherwise would be limited to vision and audition, by engaging as well the user’s sense of touch, giving a more intrinsic feel essential for ambient intelligent applications. However, the improvement of an application’s Quality of Experience (QoE) by the addition of haptic feedback is still not completely understood. The research presented in this paper focuses on the effect of haptic feedback and what it potentially adds to the experience of the user as opposed to the traditional visual and auditory feedback. In essence, it investigates certain issues regarding stylus-based haptic education applications and haptic-enhanced entertainment videos. To this end, we used two haptic applications: the haptic handwriting learning tool to experiment with force feedback haptic interaction and the tactile YouTube application for tactile haptic feedback. In both applications, our analysis shows that the addition of haptic feedback will increase the QoE in the absence of fatigue or discomfort for this category of applications. This implies that the incorporation of haptic modality (both force feedback as well as tactile feedback) has positively contributed to the overall QoE for the users. 相似文献
79.
Anas El Husseini Abdallah M’Hamed Bachar El Hassan Mounir Mokhtari 《Personal and Ubiquitous Computing》2013,17(5):1013-1023
In smart environments, pervasive computing contributes in improving daily life activities for dependent people by providing personalized services. Nevertheless, those environments do not guarantee a satisfactory level for protecting the user privacy and ensuring the trust between communicating entities. In this study, we propose a trust evaluation model based on user past and present behavior. This model is associated with a lightweight authentication key agreement protocol (Elliptic Curve-based Simple Authentication Key Agreement). The aim is to enable the communicating entities to establish a level of trust and then succeed in a mutual authentication using a scheme suitable for low-resource devices in smart environments. An innovation in our trust model is that it uses an accurate approach to calculate trust in different situations and includes a human-based feature for trust feedback, which is user rating. Finally, we tested and implemented our scheme on Android mobile phones in a smart environment dedicated for handicapped people. 相似文献
80.
Seungmin Rho Naveen Chilamkurti Karim El Defrawy 《Personal and Ubiquitous Computing》2013,17(8):1667-1669
In ubiquitous computing environments, providing appropriate services and information to users at the right place in the right way is challenging for many reasons: different user interests, heterogeneous devices and services, dynamic networks, information overload, or differing privacy levels, for example. Agent technology is a paradigm expected to play an increasing role in complex computing environments, and due to the increasing popularity of social networking services, we expect to see the convergence of agent and social web technologies. The goal of this theme issue is to bring together state-of-the-art research contributions that examine the convergence of agent technologies and social networks for ubiquitous computing. 相似文献