全文获取类型
收费全文 | 968篇 |
免费 | 73篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 24篇 |
综合类 | 29篇 |
化学工业 | 254篇 |
金属工艺 | 25篇 |
机械仪表 | 39篇 |
建筑科学 | 35篇 |
矿业工程 | 5篇 |
能源动力 | 41篇 |
轻工业 | 113篇 |
水利工程 | 11篇 |
石油天然气 | 17篇 |
武器工业 | 1篇 |
无线电 | 94篇 |
一般工业技术 | 160篇 |
冶金工业 | 79篇 |
原子能技术 | 8篇 |
自动化技术 | 111篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 31篇 |
2021年 | 54篇 |
2020年 | 39篇 |
2019年 | 44篇 |
2018年 | 57篇 |
2017年 | 45篇 |
2016年 | 40篇 |
2015年 | 53篇 |
2014年 | 43篇 |
2013年 | 86篇 |
2012年 | 53篇 |
2011年 | 48篇 |
2010年 | 43篇 |
2009年 | 34篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 35篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 13篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1967年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有1046条查询结果,搜索用时 15 毫秒
91.
Mir Masoud Seyyed Fakhrabadi Abbas Rastgoo Mohammad Taghi Ahmadian Mahmoud Mosavi Mashhadi 《Acta Mechanica》2014,225(6):1523-1535
Modified couple stress theory is a size-dependent theorem capturing the micro/nanoscale effects influencing the mechanical behaviors of the micro- and nanostructures. In this paper, it is applied to investigate the nonlinear vibration of carbon nanotubes under step DC voltage. The vibration, natural frequencies and dynamic pull-in characteristics of the carbon nanotubes are studied in detail. Moreover, the effects of various boundary conditions and geometries are scrutinized on the dynamic characteristics. The results reveal that application of this theory leads to the higher values of the natural frequencies and dynamic pull-in voltages. 相似文献
92.
Khairayu Badron Ahmad Fadzil Ismail Md Rafiqul Islam Khaizuran Abdullah Jafri Din Abdul Rahman Tharek 《International Journal of Satellite Communications and Networking》2015,33(1):57-67
Radio wave propagation plays a very important part in the design and eventually dictates performance of space communication systems. Over time, the requirements of satellite communication have grown extensively where higher capacity communications systems are needed. Escalating demands of microwave and millimetre wave communications are causing frequency spectrum congestion. Hence, existing and future satellite system operators are planning to employ frequency bands well above 10 GHz. The challenge in operating at such high frequencies for communication purposes is that there exists stronger electromagnetic interaction between the radio signals and atmospheric hydrometeors. Such instances will degrade the performance of such high frequency satellite communication systems. The development of a revised model for a better‐improved rain fade prediction of signal propagations in tropical region is considered very important. Researchers and engineers can employ the model to accurately plan the future high frequencies satellite services. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
93.
A detailed numerical study has been conducted in order to analyse the combined buoyancy effects of thermal and mass diffusion on the turbulent mixed convection tube flows. Numerical results for air-water system are presented under different conditions. A low Reynolds number k-ε turbulent model is used with combined heat and mass transfer analysis in a vertical heated tube. The local heat fluxes, Nusselt and Sherwood numbers are reported to obtain an understanding of the physical phenomena. Predicted results show that a better heat transfer results for a higher gas flow Reynolds number Re, a higher heat flux qw or a lower inlet water flow Γ0. Additionally, the results indicate that the convection of heat by the flowing water film becomes the main mechanism for heat removal from the wall. 相似文献
94.
95.
Parab HJ Huang JH Lai TC Jan YH Liu RS Wang JL Hsiao M Chen CH Hwu YK Tsai DP Chuang SY Pang JH 《Nanotechnology》2011,22(39):395706
The feasibility of using gold nanoparticles (AuNPs) for biomedical applications has led to considerable interest in the development of novel synthetic protocols and surface modification strategies for AuNPs to produce biocompatible molecular probes. This investigation is, to our knowledge, the first to elucidate the synthesis and characterization of sodium hexametaphosphate (HMP)-stabilized gold nanoparticles (Au-HMP) in an aqueous medium. The role of HMP, a food additive, as a polymeric stabilizing and protecting agent for AuNPs is elucidated. The surface modification of Au-HMP nanoparticles was carried out using polyethylene glycol and transferrin to produce molecular probes for possible clinical applications. In vitro cell viability studies performed using as-synthesized Au-HMP nanoparticles and their surface-modified counterparts reveal the biocompatibility of the nanoparticles. The transferrin-conjugated nanoparticles have significantly higher cellular uptake in J5 cells (liver cancer cells) than control cells (oral mucosa fibroblast cells), as determined by inductively coupled plasma mass spectrometry. This study demonstrates the possibility of using an inexpensive and non-toxic food additive, HMP, as a stabilizer in the large-scale generation of biocompatible and monodispersed AuNPs, which may have future diagnostic and therapeutic applications. 相似文献
96.
As networks grow in size and complexity, both the probability and the impact of failures increase. The pre-allocated backup
bandwidth cannot provide 100% protection guarantee when multiple failures occur in a network. In this article, we focus on
how to recover the protecting capabilities of FIPP (Failure-independent path-protecting) p-cycles against the subsequent links
failure on WDM networks, after recovering the working paths affected by the failure of link. Two recovering policies are designed
to recover the protecting capabilities of the FIPP p-cycles if possible, unless there is no sufficient network resource. They
are Cycle Recovery Policy and Path Recovery Policy. In addition, a Cycle Adjust algorithm is proposed and used to recover the affected cycles. The simulation results of the proposed methods are also given. 相似文献
97.
Yuan Hsing Fu Ai Qun Liu Wei Ming Zhu Xu Ming Zhang Din Ping Tsai Jing Bo Zhang Ting Mei Ji Fang Tao Hong Chen Guo Xin Hai Zhang Jing Hua Teng Nikolay I. Zheludev Guo Qiang Lo Dim Lee Kwong 《Advanced functional materials》2011,21(18):3589-3594
A micromachined reconfigurable metamaterial is presented, whose unit cell consists of a pair of asymmetric split‐ring resonators (ASRRs); one is fixed to the substrate while the other is patterned on a movable frame. The reconfigurable metamaterial and the supporting structures (e.g., microactuators, anchors, supporting frames, etc.) are fabricated on a silicon‐on‐insulator wafer using deep reactive‐ion etching (DRIE). By adjusting the distance between the two ASRRs, the strength of dipole–dipole coupling can be tuned continuously using the micromachined actuators and this enables tailoring of the electromagnetic response. The reconfiguration of unit cells endows the micromachined reconfigurable metamaterials with unique merits such as electromagnetic response under normal incidence and wide tuning of resonant frequency (measured as 31% and 22% for transverse electric polarization and transverse magnetic polarization, respectively). The reconfiguration could also allow switching between the polarization‐dependent and polarization‐independent states. With these features, the micromachined reconfigurable metamaterials may find potential applications in transformation optics devices, sensors, intelligent detectors, tunable frequency‐selective surfaces, and spectral filters. 相似文献
98.
Shahid Ud Din Wani Mohammed Iqbal Zargar Mubashir Hussain Masoodi Sultan Alshehri Prawez Alam Mohammed M. Ghoneim Areej Alshlowi H. G. Shivakumar Mohammad Ali Faiyaz Shakeel 《International journal of molecular sciences》2022,23(22)
Silk fibroin (SF), an organic material obtained from the cocoons of a silkworm Bombyx mori, is used in several applications and has a proven track record in biomedicine owing to its superior compatibility with the human body, superb mechanical characteristics, and its controllable propensity to decay. Due to its robust biocompatibility, less immunogenic, non-toxic, non-carcinogenic, and biodegradable properties, it has been widely used in biological and biomedical fields, including wound healing. The key strategies for building diverse SF-based drug delivery systems are discussed in this review, as well as the most recent ways for developing functionalized SF for controlled or redirected medicines, gene therapy, and wound healing. Understanding the features of SF and the various ways to manipulate its physicochemical and mechanical properties enables the development of more effective drug delivery devices. Drugs are encapsulated in SF-based drug delivery systems to extend their shelf life and control their release, allowing them to travel further across the bloodstream and thus extend their range of operation. Furthermore, due to their tunable properties, SF-based drug delivery systems open up new possibilities for drug delivery, gene therapy, and wound healing. 相似文献
99.
The thermometric, the weight-loss and the galvanostatic polarization techniques wereused to establish the inhibition of the dissolution of Al and Zn in HCl and NaOH by different concentrations of aqueous extract of Hibiscus subdariffa (Karkade). The extent of corrosion inhibition as measured by the three techniques is comparable. The results indicated that the additive acts by way of adsorption on both cathodic and anodic corrosion areas. Curves representing the variation of the reaction number (R.N.), in thermometric experiments, and the decrease in weight as a function of the concentration of the additive, are invariably sigmoid in nature. When present in enough amounts, the additive decreases the dissolution rate by as much as 85 per cent of the value recorded in its absence. 相似文献
100.
Two concepts of communication network reliability are considered. The first one, the ‘s-t’ reliability, is relevant for communication between a source station and a terminal station as in the case of a two way telephone communication. The second one, the overall reliability, is a measure of simultaneous connectedness among all stations in the network. An algorthm is presented which selects the optimal set of links that maximizes the overall reliability of the network subject to a cost restriction, given the allowable node-link incidences, the link costs and the link reliabilities. The algorithm employs a variaton of the simulated annealing approach coupled with a hierarchical strategy to achieve the gobal optimum. For complex networks, the present algorithm is advantageous over the traditional heuristic procedures. The solutions of two representative example network optimization problems are presented to illustrate the present algorithm. The potential utilization of parallel computing strategies in the present algorithm is also identified. 相似文献