全文获取类型
收费全文 | 3018篇 |
免费 | 130篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 30篇 |
综合类 | 2篇 |
化学工业 | 809篇 |
金属工艺 | 62篇 |
机械仪表 | 67篇 |
建筑科学 | 94篇 |
矿业工程 | 4篇 |
能源动力 | 96篇 |
轻工业 | 182篇 |
水利工程 | 16篇 |
石油天然气 | 9篇 |
无线电 | 289篇 |
一般工业技术 | 622篇 |
冶金工业 | 459篇 |
原子能技术 | 17篇 |
自动化技术 | 391篇 |
出版年
2023年 | 24篇 |
2022年 | 51篇 |
2021年 | 84篇 |
2020年 | 61篇 |
2019年 | 67篇 |
2018年 | 75篇 |
2017年 | 57篇 |
2016年 | 93篇 |
2015年 | 60篇 |
2014年 | 85篇 |
2013年 | 161篇 |
2012年 | 149篇 |
2011年 | 163篇 |
2010年 | 134篇 |
2009年 | 113篇 |
2008年 | 150篇 |
2007年 | 135篇 |
2006年 | 110篇 |
2005年 | 101篇 |
2004年 | 97篇 |
2003年 | 68篇 |
2002年 | 74篇 |
2001年 | 59篇 |
2000年 | 58篇 |
1999年 | 45篇 |
1998年 | 98篇 |
1997年 | 59篇 |
1996年 | 61篇 |
1995年 | 58篇 |
1994年 | 44篇 |
1993年 | 44篇 |
1992年 | 33篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 28篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 23篇 |
1975年 | 17篇 |
1974年 | 17篇 |
1973年 | 15篇 |
排序方式: 共有3149条查询结果,搜索用时 0 毫秒
61.
62.
Mikael B. Skov Jesper Kjeldskov Jeni Paay Niels Husted Jacob Nørskov Kenneth Pedersen 《Pervasive and Mobile Computing》2013,9(2):216-227
Some movements within modern architecture particularly emphasise the importance of matching buildings to their surroundings. However, practicing such “contextual architecture” is highly challenging and typically not something the future inhabitants of a building are well equipped for participating in. This paper explores the potentials of using mobile phone technology for facilitating such client participation in the parts of an architecture process that take place on the building site. For this we introduce ArchiLens, a mobile system for interactive on-site 3D visualisation of houses, and findings from a field study with 40 participants in the process of building or modifying their home. The study showed that using the system helped evoke people’s imagination of the look and feel of their future house, and envision it in context. This enabled them to participate more closely in the design process on-site by iteratively reviewing design alternatives and exploring, for example, other placements and materials. 相似文献
63.
Jing Yu Sathya Chary Saurabh Das John Tamelier Noshir S. Pesika Kimberly L. Turner Jacob N. Israelachvili 《Advanced functional materials》2011,21(16):3010-3018
Most geckos can rapidly attach and detach from almost any kind of surface. This ability is attributed to the hierarchical structure of their feet (involving toe pads, setal arrays, and spatulae), and how they are moved (articulated) to generate strong adhesion and friction forces on gripping that rapidly relax on releasing. Inspired by the gecko's bioadhesive system, various structured surfaces have been fabricated suitable for robotic applications. In this study, x–y–z asymmetric, micrometer‐sized rectangular flaps composed of polydimethylsiloxane (PDMS) were fabricated using massively parallel micro‐electromechanical systems (MEMS) techniques with the intention of creating directionally responsive, high‐to‐low frictional‐adhesion toe pads exhibiting properties similar to those found in geckos. Using a surface forces apparatus (SFA), the friction and adhesion forces of both vertical (symmetric) and angled/tilted (x–y–z asymmetric) microflaps under various loading, unloading and shearing conditIons were investigated. It was found that the anisotropic structure of tilted microflaps gives very different adhesion and tribological forces when articulated along different x–y–z directions: high friction and adhesion forces when articulated in the y–z plane along the tilt (+y) direction, which is also the direction of motion, and weak friction and adhesion forces when articulated against the tilt (–y) direction. These results demonstrate that asymmetric angled structures, as occur in geckos, are required to enable the gecko to optimize the requirements of high friction and adhesion on gripping, and low frictional‐adhesion on releasing. These properties are intimately coupled to a (also optimum) articulation mechanism. We discuss how both of these features can be simultaneously optimized in the design of robotic systems that can mimic the gecko adhesive system. 相似文献
64.
65.
A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and 314 stainless steel metal foams with different relative densities and pores per inch (p.p.i.) were undertaken in the present investigation to determine the effect of microstructural parameters on the relative densities of metal foams. Several elements of the microstructure, such as major and minor cell sizes, cell areas and perimeters, ligament dimensions, cell shapes, and area fractions of closed and open cells, were measured. The cross-sections of the foam ligaments showed numerous pores, and their circularity factors and average sizes were determined. The area fractions of the open cells and ligaments decreased, whereas that of the closed cells increased linearly with increasing relative density. The relative densities and p.p.i. were not significantly dependent on cell size, cell perimeter, and ligament dimensions within the limits of experimental scatter. A phenomenological model is proposed to rationalize the present microstructural observations. 相似文献
66.
The mechanism of the hydrogenation of aliphatic C4–C6 dinitriles (succinonitrile, glutaronitrile, and adiponitrile) over Raney-type Ni catalysts was investigated in a fed-batch autoclave at 350 K and 5.0 MPa. The results are interpreted based on the strength of adsorption, the interaction with the solvent and intramolecular interactions. The kinetics of the hydrogenation of aliphatic dinitriles is highly dependent on the hydrocarbon chain length. Short dinitriles like succinonitrile adsorb stronger on the catalyst surface than longer dinitriles like adiponitrile. The yield of the intermediate aminonitriles decreases with increasing hydrocarbon chain length, due to the enhanced competitiveness of dinitrile and aminonitrile for the same active sites. It is proposed that the reactivity of dinitriles and aminonitriles is caused by difference in solvent interaction. It is remarkable that the stronger the adsorption, the higher the reactivity. The reactivity decreases in the order: succinonitrile > glutaronitrile > adiponitrile. In contrast, the reaction rate of the aminonitriles is fairly independent of the hydrocarbon chain length. The formation of undesired secondary amines in the form of cyclic compounds is under kinetic control and increases with decreasing chain length. It is found that adiponitrile can be very selectively hydrogenated to primary diamines. Promoting Raney-type Ni catalysts with traces of Mo, Cr or Fe enhances the performance in the hydrogenation of dinitriles. This gives the best opportunity for process improvement towards the desired primary amines. 相似文献
67.
68.
69.
Nina Kunov Henrieta Havalov Gabriela Ondrovi
ov Barbora Stojkovi
ov Jacob A. Bauer Vladena Bauerov-Hlinkov Vladimir Pevala Eva Kutejov 《International journal of molecular sciences》2022,23(3)
Mitochondrial proteins are encoded by both nuclear and mitochondrial DNA. While some of the essential subunits of the oxidative phosphorylation (OXPHOS) complexes responsible for cellular ATP production are synthesized directly in the mitochondria, most mitochondrial proteins are first translated in the cytosol and then imported into the organelle using a sophisticated transport system. These proteins are directed mainly by targeting presequences at their N-termini. These presequences need to be cleaved to allow the proper folding and assembly of the pre-proteins into functional protein complexes. In the mitochondria, the presequences are removed by several processing peptidases, including the mitochondrial processing peptidase (MPP), the inner membrane processing peptidase (IMP), the inter-membrane processing peptidase (MIP), and the mitochondrial rhomboid protease (Pcp1/PARL). Their proper functioning is essential for mitochondrial homeostasis as the disruption of any of them is lethal in yeast and severely impacts the lifespan and survival in humans. In this review, we focus on characterizing the structure, function, and substrate specificities of mitochondrial processing peptidases, as well as the connection of their malfunctions to severe human diseases. 相似文献
70.
M.E. Hawley D.J. Devlin C.J. Reichhardt K.E. Sickafus I.O. Usov J.A. Valdez Y.Q. Wang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):3269-3272
This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO2 layers. HfO2 served as a surrogate fissile material for UO2 while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO2 layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au3+ ions at a range of fluences from 5 × 1013 to 3.74 × 1016 ions/cm2. Separate single layer constituent films and the substrate were also irradiated at 5 × 1015 and 8 × 1014 and 2 × 1016, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences. 相似文献