全文获取类型
收费全文 | 1423篇 |
免费 | 61篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 362篇 |
金属工艺 | 28篇 |
机械仪表 | 50篇 |
建筑科学 | 28篇 |
矿业工程 | 1篇 |
能源动力 | 112篇 |
轻工业 | 89篇 |
水利工程 | 11篇 |
石油天然气 | 9篇 |
无线电 | 160篇 |
一般工业技术 | 361篇 |
冶金工业 | 56篇 |
原子能技术 | 13篇 |
自动化技术 | 192篇 |
出版年
2024年 | 6篇 |
2023年 | 24篇 |
2022年 | 82篇 |
2021年 | 70篇 |
2020年 | 71篇 |
2019年 | 46篇 |
2018年 | 88篇 |
2017年 | 67篇 |
2016年 | 46篇 |
2015年 | 39篇 |
2014年 | 81篇 |
2013年 | 138篇 |
2012年 | 74篇 |
2011年 | 104篇 |
2010年 | 71篇 |
2009年 | 79篇 |
2008年 | 73篇 |
2007年 | 59篇 |
2006年 | 42篇 |
2005年 | 50篇 |
2004年 | 39篇 |
2003年 | 15篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有1495条查询结果,搜索用时 15 毫秒
91.
92.
This investigation analyses the failure of left barrel used in engine of an aircraft. The barrel was subjected to detailed examination using standard non-destructive and destructive testing methods in order to identify the cause of failure of left barrel. The experimental results include fractography, chemical analysis, coating analysis and optical microstructure. The investigation concludes that failure is caused by the formation of corrosion pits which act as stress raiser and fatigue has assisted in propagation of the crack. 相似文献
93.
A couple of non-convex search strategies, based on the genetic algorithm, are suggested and numerically explored in the context
of large-deflection analysis of planar, elastic beams. The first of these strategies is based on the stationarity of the energy
functional in the equilibrium state and may therefore be considered weak. The second approach, on the other hand, attempts
to directly solve the governing differential equation within an optimisation framework and such a solution may be thought
of as strong. Several numerical illustrations and verifications with ‘exact’ solutions, if available, are provided
For communication 相似文献
94.
We have developed a custom analog CMOS circuit to perform the signal processing for an optical coherence tomography imaging system. The circuit is realized in a 1.5 /spl mu/m low-noise analog CMOS technology. The circuitry extracts the Doppler frequency from the signal and electrically mixes this with the original signal to provide a filtered A-scan. The circuitry was used to produce a two-dimensional image of an onion. 相似文献
95.
Magan Lal Agrawal Rajesh Gupta Pramod R. Bhave 《Canadian Metallurgical Quarterly》2007,133(3):319-330
A water distribution network (WDN) is designed to meet time-varying demands with sufficient pressure, taking into consideration an appropriate demand during peak hours. Therefore, a network has inherent redundancy in the sense that under abnormal conditions such as those arising due to pipe breaks or pump failures, deficiency in supply during peak hours can be met through additional supply during off-peak periods. However, this necessitates a storage facility at the consumer end of the network, which is normally available in the form of a sump or an overhead tank in developing countries. Such a storage enables the consumer to store water during the off-peak period and then use it during the peak period. Reliability of a WDN is assessed herein considering nodal storage, and an iterative method is proposed for the optimal design of Level 1 redundant WDNs, i.e., networks that can sustain a single pipe failure without affecting consumer services either in part or in full. The method is illustrated through an example and the designs of a network with and without storage are compared. Provision of a nodal storage is found to reduce the total cost of the network. 相似文献
96.
Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2 总被引:1,自引:0,他引:1
Rajesh J. Tayade Praveen K. Surolia Ramchandra G. Kulkarni Raksh V. Jasra 《Science and Technology of Advanced Materials》2007,8(6):455-462
Nanocrystalline TiO2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N2 adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst. 相似文献
97.
98.
Rajesh Singh V. Vishal T. N. Singh P. G. Ranjith 《Neural computing & applications》2013,23(2):499-506
The engineering properties of rocks play a significant role in planning and designing of mining and civil engineering projects. A laboratory database of mechanical and engineering properties of rocks is always required for site characterization and mineral exploitation. Due to discontinuous and variable nature of rock masses, it is difficult to obtain all physicomechanical properties of rocks precisely. Prediction of unconfined compressive strength from seismic wave velocities (Compressional wave, Shear wave) and density of rock using generalized regression neural network (GRNN) and adaptive neuro-fuzzy inference systems (ANFIS) can be appropriate and alternate methods to minimize the time and cost of tests. GRNN and ANFIS models were trained with 41 data sets using conjugate gradient descent algorithms and hybrid learning algorithm, respectively. Performance of both the models was examined with 15 testing data sets. In the present study, obtained network performance indices such as correlation coefficient, mean absolute percentage error, root mean square error and variance account for indicate high performance of predictive capability of GRNN system and closer to actual data over the ANFIS. 相似文献
99.
In the article ‘Supervisory control for fault-tolerant scheduling of real-time multiprocessor systems with aperiodic tasks’, Park and Cho presented a systematic way of computing a largest fault-tolerant and schedulable language that provides information on whether the scheduler (i.e., supervisor) should accept or reject a newly arrived aperiodic task. The computation of such a language is mainly dependent on the task execution model presented in their paper. However, the task execution model is unable to capture the situation when the fault of a processor occurs even before the task has arrived. Consequently, a task execution model that does not capture this fact may possibly be assigned for execution on a faulty processor. This problem has been illustrated with an appropriate example. Then, the task execution model of Park and Cho has been modified to strengthen the requirement that none of the tasks are assigned for execution on a faulty processor. 相似文献
100.
This paper presents an observer design technique for a newly developed non-intrusive position estimation system based on magnetic sensors. Typically, the magnetic field of an object as a function of position needs to be represented by a highly nonlinear measurement equation. Previous results on observer design for nonlinear systems have mostly assumed that the measurement equation is linear, even if the process dynamics are nonlinear. Hence, a new nonlinear observer design method for a Wiener system composed of a linear process model together with a nonlinear measurement equation is developed in this paper. First, the design of a two degree-of-freedom nonlinear observer is proposed that relies on a Lure system representation of the observer error dynamics. To improve the performance in the presence of parametric uncertainty in the measurement model, the nonlinear observer is augmented to estimate both the state and unknown parameters simultaneously. A rigorous nonlinear observability analysis is also presented to show that a dual sensor configuration is a sufficient and necessary condition for simultaneous state and parameter estimation. Finally, the developed observer design technique is applied to non-intrusive position estimation of the piston inside a pneumatic cylinder. Experimental results show that both position and unknown parameters can be reliably estimated in this application. 相似文献