全文获取类型
收费全文 | 6031篇 |
免费 | 356篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 125篇 |
综合类 | 4篇 |
化学工业 | 1391篇 |
金属工艺 | 239篇 |
机械仪表 | 388篇 |
建筑科学 | 113篇 |
矿业工程 | 2篇 |
能源动力 | 335篇 |
轻工业 | 511篇 |
水利工程 | 23篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 943篇 |
一般工业技术 | 1437篇 |
冶金工业 | 302篇 |
原子能技术 | 66篇 |
自动化技术 | 521篇 |
出版年
2024年 | 5篇 |
2023年 | 74篇 |
2022年 | 99篇 |
2021年 | 167篇 |
2020年 | 151篇 |
2019年 | 139篇 |
2018年 | 191篇 |
2017年 | 186篇 |
2016年 | 210篇 |
2015年 | 157篇 |
2014年 | 267篇 |
2013年 | 357篇 |
2012年 | 442篇 |
2011年 | 507篇 |
2010年 | 355篇 |
2009年 | 409篇 |
2008年 | 366篇 |
2007年 | 302篇 |
2006年 | 228篇 |
2005年 | 219篇 |
2004年 | 183篇 |
2003年 | 161篇 |
2002年 | 166篇 |
2001年 | 132篇 |
2000年 | 133篇 |
1999年 | 108篇 |
1998年 | 143篇 |
1997年 | 120篇 |
1996年 | 86篇 |
1995年 | 72篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有6408条查询结果,搜索用时 15 毫秒
991.
Dong-Soo Yoon Hong Koo Baik Sung-Man Lee 《Journal of the American Ceramic Society》2000,83(4):949-951
The electrical properties of a Ta layer prepared with and without RuO2 addition were investigated. The Ta + RuO2 /TiSi2 /poly-Si/SiO2 /Si contact system exhibited lower total resistance and ohmic characteristics up to 800°C. Meanwhile, the Ta/TiSi2 /poly-Si/SiO2 /Si contact system showed higher total resistance and nonohmic behavior after annealing at 650°C, attributed to the oxidation of both Ta and TiSi2 layers. In the former case, a Ta + RuO2 diffusion barrier showed an amorphous Ta microstructure and embedded RuO x nanocrystals in the as-deposited state. The conductive RuO2 crystalline phase in the Ta + RuO2 film was formed by reaction between the nanocrystalline RuO x and oxygen indiffused from air during annealing. When the Ta layer was deposited with RuO2 addition, therefore, both the electrical properties and the oxidation resistance of the Ta + RuO2 diffusion barrier were better than those of TiN, TaN, and Ta-Si-N barriers. 相似文献
992.
Geelsu Hwang Sung Ryeol Park Chang-Ha Lee Ik-Sung Ahn Yeo-Joon Yoon Byung Jin Mhin 《Journal of hazardous materials》2009,172(1):491-493
In an earlier study, Pseudomonas putida NCIB 9816-4, which was one of the most studied naphthalene-degrading bacteria, showed the preferred adhesion to the naphthalene-contaminated soil when it was in the exponential growth phase. The adhesion was found to take place through a hydrophobic interaction. We postulated that the surface hydrophobicity of P. putida NCIB 9816-4 in the exponential growth phase might be increased during the uptake of naphthalene, which caused the preferred adhesion to the naphthalene-contaminated soil. To verify this postulate, a plasmid-cured strain of P. putida NCIB 9816-4 was obtained in this study and compared with the wild-type for adhesion to the naphthalene-contaminated soil. Only the wild-type in the exponential growth phase showed increased adhesion to naphthalene-contaminated soil. The water contact angles of the two strains were measured in the presence and in the absence of naphthalene as indices of surface hydrophobicity. The water contact angle of the wild-type increased in the presence of naphthalene, whereas that of the cured strain did not change. We conclude that the uptake of naphthalene during naphthalene biodegradation in the exponential growth phase of P. putida NCIB 9816-4 made the cell surface more hydrophobic, resulting in increased adhesion to naphthalene-contaminated soil. 相似文献
993.
The devices using individual ZnO nanowire have been manufactured by FIB. Its specific resistance and microstructural characterization has been investigated using nano manipulator and transmission electron microscopy (TEM) observations. The specific resistance was 0.2-0.4 Ω cm. With increasing the RTA temperature, the specific resistance began to be decreased and was abruptly decreased at the RTA temperature above 500 °C. The Pt junction of as-manufactured device consisted of the Pt nanoparticles of 5 nm and the amorphous carbon of 9.1 wt.%. After RTA, the size of Pt nanoparticles grew up to 100 nm, the contents of carbon were decreased within the Pt junction, and the conductivity was enhanced due to Au diffusion into the Pt junction. It was strongly suggested that the contents of carbon is the most important factor for the electrical enhancement. 相似文献
994.
Summary
New NLO-functionalized poly(1,4-phenylenevinylene) (PDNAPV) containing 2,4-dinitroanilino group, was synthesized through organic-soluble
precursor pathway. The prepared polymer was characterized with NMR, FT-IR, UV-visible and other spectroscopic methods to identify
its properties. The result from the thermal analyses and spectroscopic techniques showed that the precursor was converted
into PDNAPV around at 200°C without any decomposition of 2,4-dinitroanilino group. The second-order NLO coefficient (χ(2)) of poled PDNAPV film was determined by second-harmonic generation technique. The resonant χ(2) value was 26 pm/V and the resonance-corrected value (χ(2)(0)) was 12 pm/V, which was stable at room temperature for a month
Received: 16 February 2001/Accepted: 13 March 2001 相似文献
995.
Jungwon Yoon Jeha Ryu 《Mechatronics, IEEE/ASME Transactions on》2001,6(3):221-233
This paper presents design, fabrication, and evaluation of a new 6-DOF haptic device for interfacing with virtual reality by using a parallel mechanism. The mechanism is composed of three pantograph mechanisms that are driven by ground-fixed servomotors, three spherical joints between the top of the pantograph mechanisms and the connecting bars, and three revolute joints between the connecting bars and a mobile joystick handle. Forward and inverse kinematic analyses are performed and the Jacobian matrix is derived. Performance indexes such as global payload index, global conditioning index, translation and orientation workspaces, and sensitivity are evaluated to find optimal parameters in the design stage. The proposed haptic mechanism has better load capability than those of the pre-existing haptic mechanisms due to the fact that the motors are fixed at the base. It has also a wider orientation workspace mainly due to a RRR-type spherical joint. A control method is presented with gravity compensation and force feedback by a force/torque sensor to compensate for the effects of unmodeled dynamics such as friction and inertia. Also, the dynamic performance is evaluated for force characteristics. Virtual wall simulation with the developed haptic device is demonstrated 相似文献
996.
The electronic structures of the Ga1−xInxNyAs1−y/GaAs compressively strained quantum wells (QW) are investigated using 6×6 k·p Hamiltonian including the heavy hole, light hole and spin–orbit splitting band. The curves of dependence of transition energy on well width and N mole fraction are obtained. The valence subband energy dispersion curves, density of state and TE and TM squared optical transition matrix elements of three possible QW structures for emitting 1.3 μm wavelength are given. 相似文献
997.
Jaimyun Jung Seung Chae Yoon Hyun-Joon Jun Hyoung Seop Kim 《Journal of Materials Engineering and Performance》2013,22(11):3222-3227
Equal channel angular pressing (ECAP) is the most promising and interesting process for refining the grain size to an ultrafine grain or nanosize by imposing severe plastic deformation into the workpiece and repeating the process while maintaining the original cross-section of the workpiece. In this paper, we simulated the batch type ECAP and the continuous type equal channel multi-angular pressing (ECMAP), which can impose large deformation by repeating the shear deformation, using the finite element method and investigated the similarity and difference of the two processes. In particular, modified die design of the continuous type ECMAP was proposed for strain uniformity. 相似文献
998.
999.
Janghyeok Yoon Kwangsoo Kim 《Expert systems with applications》2012,39(3):2927-2938
Technology intelligence systems are vital components for planning of technology development and formulation of technology strategies. Although such systems provide computation supports for technology analysis, much effort and intervention of experts, who may be expensive or unavailable, is required in gathering processes of information for analysis. As a remedy, this paper proposes TrendPerceptor, a system that uses a property-function based approach. The proposed system assists experts (1) to identify trends in invention concepts from patents, and (2) to perform evolution trend analysis of patents for technology forecasting. For this purpose, a module of the system uses grammatical analysis of textual information to automatically extract properties and functions, which show innovation directions in a given technology. Using the identified properties and functions, a module for invention concept analysis based on network analysis and a module for evolution trend analysis based on TRIZ (Russian acronym of the Theory of Inventive Problem Solving) trends are suggested. This paper describes the architecture of a system composed of these three modules, and illustrates two case studies using the system. 相似文献
1000.
Kang Soo Lee Sang Youl Yoon Sang Bok Kim Kyung Heon Lee Hyung Jin Sung Sang Soo Kim 《Microfluidics and nanofluidics》2012,13(1):9-17
This paper describes the optical and hydrodynamic characteristics of particle motion in a cross-type optical particle separator. The retention distance modulated by the optical force on a particle was measured in three dimensions for various vertical and horizontal positions via ??-defocusing digital particle image velocimetry. The experimental data showed that the actual retention distance was smaller than the predicted retention distance under the assumption that the approaching velocity was constant through the cross-section of a microfluidic channel. The retention distance was shown to increase as the injection position of the particle shifted toward the channel side wall at a given vertical position due to a higher residence time within the region of influence of the laser beam. In contrast, the retention distance decreased as the injection position shifted toward the channel top/bottom walls at a given horizontal position. A theoretical modeling study was conducted to support and interpret the experimental measurements. The resolution of the particle separation procedure, which did not require adjusting the flow rate, laser power, or working fluid properties, was studied. 相似文献