全文获取类型
收费全文 | 1323篇 |
免费 | 85篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 25篇 |
综合类 | 5篇 |
化学工业 | 299篇 |
金属工艺 | 36篇 |
机械仪表 | 79篇 |
建筑科学 | 48篇 |
矿业工程 | 1篇 |
能源动力 | 90篇 |
轻工业 | 130篇 |
水利工程 | 21篇 |
石油天然气 | 27篇 |
无线电 | 109篇 |
一般工业技术 | 251篇 |
冶金工业 | 68篇 |
原子能技术 | 6篇 |
自动化技术 | 225篇 |
出版年
2024年 | 5篇 |
2023年 | 26篇 |
2022年 | 22篇 |
2021年 | 78篇 |
2020年 | 71篇 |
2019年 | 95篇 |
2018年 | 125篇 |
2017年 | 93篇 |
2016年 | 98篇 |
2015年 | 39篇 |
2014年 | 76篇 |
2013年 | 159篇 |
2012年 | 78篇 |
2011年 | 95篇 |
2010年 | 57篇 |
2009年 | 56篇 |
2008年 | 31篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 16篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 4篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1970年 | 5篇 |
1966年 | 6篇 |
1961年 | 3篇 |
排序方式: 共有1420条查询结果,搜索用时 15 毫秒
11.
Design, fabrication and analysis of micromachined high sensitivity and 0% cross-axis sensitivity capacitive accelerometers 总被引:1,自引:1,他引:0
This paper presents the design and fabrication of three MEMS based capacitive accelerometers. The first design illustrates
the achievement of an accelerometer with 0% cross-axis sensitivity and has been fabricated using PolyMUMPs, a multi-user surface-micromachining
process. A unidirectional parallel plate configuration is utilized in this design to illustrate the achievement of 0% cross-axis
sensitivity and an acceptable performance range. In addition, a method is introduced to improve the sensitivity of a capacitive
sensor employing a transverse configuration based on the relationship of initial gaps setup in comb-finger arrangements. A
design based on this technique and the PolyMUMPs fabrication process is illustrated which demonstrates a sensitivity value
of 4.07 fF/μm, with a nonlinearity of 2.05% for a ±3 μm sensor operating range. The last design based on this method and the
SOIMUMPs fabrication process exhibits a sensitivity of 3.45 pF/μm for ±1 μm operating range of the sensor. 相似文献
12.
13.
In this article, the influences of rotational speed and velocity of viscous fluid flow on free vibration behavior of spinning single-walled carbon nanotubes (SWCNTs) are investigated using the modified couple stress theory (MCST). Taking attention to the first-order shear deformation theory, the modeled rotating SWCNT and its equations of motion are derived using Hamilton’s principle. The formulations include Coriolis, centrifugal and initial hoop tension effects due to rotation of the SWCNT. This system is conveying viscous fluid, and the related force is calculated by modified Navier–Stokes relation considering slip boundary condition and Knudsen number. The accuracy of the presented model is validated with some cases in the literatures. Novelty of this study is considering the effects of spinning, conveying viscous flow and MCST in addition to considering the various boundary conditions of the SWCNT. Generalized differential quadrature method is used to approximately discretize the model and to approximate the equations of motion. Then, influence of material length scale parameter, velocity of viscous fluid flow, angular velocity, length, length-to-radius ratio, radius-to-thickness ratio and boundary conditions on critical speed, critical velocity and natural frequency of the rotating SWCNT conveying viscous fluid flow are investigated. 相似文献
14.
Indirect identification methods are applied when direct measurement is unfeasible. One example is the measurement of the contact force between wheel and rail in railway traffic. This paper focuses on optimization-based methods for the identification of contact forces with the aim of developing a reliable and robust load identification scheme. A particular issue discussed here is the choice of discretization in space–time, enabling the sampling instances of the measurements, the parameterization of the sought input and the discretization of the pertinent state equations to be decoupled, in contrast to traditional methods such as, e.g. dynamic programming.In the present preliminary study where a 2-D disc is considered as a representative of a train wheel, a radial concentrated force rotates around the disc’s perimeter, representing the contact force acting on the rim of the wheel, while radial strains are measured on a set of points corresponding to the strain gauges position. The strain history data is then used in the identification procedure where the applied force is sought to minimize the discrepancy between the predicted and measured strain history. In particular the convergence of the results with respect to the temporal discretization of the model and the time parameterization of the sought loading history are investigated under the influence of noise. It is seen that choosing a discretization of the sought load that is coarser than that of the state variable gives a more robust scheme. The traditional Tikhonov regularization can also be added within the current framework. Furthermore, with the aid of a sensitivity analysis, the influence of measurement noise can be quantified. 相似文献
15.
Hamed Samarghandi 《国际生产研究杂志》2013,51(9):2853-2870
This paper considers the no-wait flow shop scheduling problem with due date constraints. In the no-wait flow shop problem, waiting time is not allowed between successive operations of jobs. Moreover, a due date is associated with the completion of each job. The considered objective function is makespan. This problem is proved to be strongly NP-Hard. In this paper, a particle swarm optimisation (PSO) is developed to deal with the problem. Moreover, the effect of some dispatching rules for generating initial solutions are studied. A Taguchi-based design of experience approach has been followed to determine the effect of the different values of the parameters on the performance of the algorithm. To evaluate the performance of the proposed PSO, a large number of benchmark problems are selected from the literature and solved with different due date and penalty settings. Computational results confirm that the proposed PSO is efficient and competitive; the developed framework is able to improve many of the best-known solutions of the test problems available in the literature. 相似文献
16.
Three‐Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications 下载免费PDF全文
Rouhollah D. Farahani Martine Dubé Daniel Therriault 《Advanced materials (Deerfield Beach, Fla.)》2016,28(28):5794-5821
The integration of nanotechnology into three‐dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro‐ and microscale made of nanocomposite materials is reviewed here. The current state‐of‐the‐art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal‐ and carbon‐based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D‐printing techniques. Several methods, including but not limited to micro‐stereolithography, extrusion‐based direct‐write technologies, inkjet‐printing techniques, and popular powder‐bed technology, are discussed. Various examples of 3D nanocomposite macro‐ and microstructures manufactured using different 3D‐printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab‐on‐a‐chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites. 相似文献
17.
Nazmi Abdel Latif Kassab Mohamed Helmy El Nagdy Hamed Abdel Reheem Ead 《Advanced Synthesis \u0026amp; Catalysis》1973,315(2):265-273
The reaction of 5-arylidene-4-arylimino-2-thiazolidinones 4 with GRIGNARD reagents effected 1,4-addition to the exocyclic CC bond with the formation of 5 . Alkylation of the arylidene derivatives 4 with diazomethane or methyl iodide results in the formation of the N-methyl derivatives 6 . Treatment of 6 with phenylmagnesium bromide effects addition of the reagent to the double bond of the lateral chain to yield products, proved to have structure 8 . The 5-arylazo derivatives 9 of 4-arylimino-2-thiazolidinones were obtained by coupling 4 with aromatic diazonium chlorides. Compounds 9 were N-methylated with diazomethane to yield 10 . 相似文献
18.
The flow-induced motion(FIM)of an elastically mounted square-section cylinder is experimentally investigated over a wide range of Reynolds numbers(1.5×104<Re<7.... 相似文献
19.
20.
Behnam Fahimnia Reza Zanjirani Farahani Romeo Marian Lee Luong 《Journal of Manufacturing Systems》2013
Optimisation modelling of integrated production–distribution (P–D) plans has raised significant interest among both researchers and practitioners over the past two decades. This paper provides the readers with a comprehensive review and critique on the current P–D planning and optimisation literature. We classify the published P–D planning models into seven categories based on their degree of complexity and hence capability in addressing real-life scenarios. Summary tables highlight the main characteristics of the selected models at each category. Next, the paper reclassifies and evaluates the proposed models based on the solution techniques used. Lastly, the unaddressed areas in the current literature are highlighted, important managerial implications are proposed and directions for future research in the area are suggested. 相似文献