全文获取类型
收费全文 | 7343篇 |
免费 | 564篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 105篇 |
综合类 | 9篇 |
化学工业 | 2117篇 |
金属工艺 | 78篇 |
机械仪表 | 169篇 |
建筑科学 | 265篇 |
矿业工程 | 10篇 |
能源动力 | 328篇 |
轻工业 | 1329篇 |
水利工程 | 40篇 |
石油天然气 | 42篇 |
无线电 | 517篇 |
一般工业技术 | 1131篇 |
冶金工业 | 190篇 |
原子能技术 | 65篇 |
自动化技术 | 1522篇 |
出版年
2024年 | 8篇 |
2023年 | 77篇 |
2022年 | 316篇 |
2021年 | 332篇 |
2020年 | 215篇 |
2019年 | 225篇 |
2018年 | 261篇 |
2017年 | 290篇 |
2016年 | 330篇 |
2015年 | 227篇 |
2014年 | 384篇 |
2013年 | 606篇 |
2012年 | 496篇 |
2011年 | 597篇 |
2010年 | 468篇 |
2009年 | 465篇 |
2008年 | 441篇 |
2007年 | 369篇 |
2006年 | 285篇 |
2005年 | 219篇 |
2004年 | 190篇 |
2003年 | 165篇 |
2002年 | 183篇 |
2001年 | 98篇 |
2000年 | 74篇 |
1999年 | 77篇 |
1998年 | 76篇 |
1997年 | 43篇 |
1996年 | 47篇 |
1995年 | 47篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1975年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有7917条查询结果,搜索用时 31 毫秒
51.
Antonio Sarcos-Portillo Alfredo Navarro-Cerpa Hildrun García-Legl 《Canadian Metallurgical Quarterly》2003,8(4):223-228
In 1997 and 1999, inspection works were carried out in the 384 cable stays of the six central piers of General Rafael Urdaneta Bridge, located in Maracaibo, Venezuela. Inspection indicated the presence of water and significant settlings in the sockets of the cables and corrosion along each cable and socket. The tension of the cables was also measured, and differences of up to 30% in the tension of the cables of some of the 24 groups corresponding to the six central piers (four groups of 16 for each pier) were found. The results suggested the need to retension the cables. This paper shows the outcome of the inspection and indicates the procedure and results of the process of retension, finished in July 2000. 相似文献
52.
Elena Crespi Antonio Capolongo Davide Fissore Antonello A. Barresi 《Drying Technology》2008,26(3):349-356
The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed. 相似文献
53.
Intelligent multisensor surveillance systems consist of several types of sensors, which are installed on fixed and mobile devices. These components provide a huge quantity of information that has to be contrasted, correlated and integrated in order to recognize and react on special situations. These systems work in highly dynamic environments, with severe security and robustness requirements. All these characteristics imply the need for distributed solutions. In these solutions, scattered components can decide and act with some degree of autonomy (for instance, if they become isolated), or cooperate and coordinate for a complete tracking of special situations. In order to cope with these requirements and to better structure the solution, we have decided to design surveillance system control as a multiagent system. This is done by applying an agent-orientated methodology, which is assessed with concrete scenarios. 相似文献
54.
A comprehensive model to evaluate the seismic reliability of electric power transmission systems is presented. The model provides information on the probability of structural failure of critical equipment at the major substations, from which the corresponding probabilities of power disruption to a given service area are determined. With the proposed methodology earthquake ground motions are defined as stochastic processes, and seismic capacities of electrical equipment are determined on the basis of available test data and simple modeling, from which fragility functions of critical equipment and specific substations are developed. Probabilities of power disruption resulting from network disconnectivity and abnormal power flow are assessed through Monte Carlo simulation. As a case study, the proposed model is applied to the electric power network in San Francisco and vicinity under the 1989 Loma Prieta earthquake, and the probabilities of power interruption are contrasted with the actual power failures observed during that earthquake. 相似文献
55.
In this paper, the effectiveness of the approximate motion equations of a flexible structure, obtained by the RitzKantorovich method, is analysed by using Lyapunov functions. The analysis, which is restricted to the case of a single flexible beam for the sake of simplicity, is carried out under the assumption that a partial dissipation is present, affecting only the first degrees of freedom of the system. By means of suitable Lyapunov functions, an overbounding estimate of the quadratic approximation error is determined as a decreasing function of the approximation order. The analysis is completed by considering the two ‘extreme’ cases: the theoretical absence of dissipation and the presence of structural dissipation, affecting all the infinite degrees of freedom. 相似文献
56.
Mario Mariani Ugo Ravasio Armando Buttafava Antonio Faucitano 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,265(1):245-250
The effect of gamma irradiation in air is investigated in two thermoplastic polyesters (PET and PEN), in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. EPR measurements were carried out to detect radical stability against oxygen permeation and to provide radical characterization. Viscometric data reveal a different behaviour between films and thick samples. Positron annihilation spectra show a decrease of ortho-positronium intensity, which is more marked in film samples. ortho-positronium lifetime does not depend on the radiation dose. 相似文献
57.
A Ruiz Pérez M Santana A?e B Villaverde A?e F Bandera Tirado N Santana Santos 《Canadian Metallurgical Quarterly》1995,47(3):219-220
Patients who have a unicornuate uterus with a noncommunicating rudimentary horn that contains an endometrial cavity are at risk for endometriosis and obstetric complications. As in this case, resection of the rudimentary horn can be performed laparoscopically without increased risk to the patient and with some potential benefit. 相似文献
58.
Jose Miguel Leiva-Murillo Antonio Artés-Rodríguez 《Neural Networks, IEEE Transactions on》2007,18(5):1433-1441
In this paper, we present a novel scheme for linear feature extraction in classification. The method is based on the maximization of the mutual information (MI) between the features extracted and the classes. The sum of the MI corresponding to each of the features is taken as an heuristic that approximates the MI of the whole output vector. Then, a component-by-component gradient-ascent method is proposed for the maximization of the MI, similar to the gradient-based entropy optimization used in independent component analysis (ICA). The simulation results show that not only is the method competitive when compared to existing supervised feature extraction methods in all cases studied, but it also remarkably outperform them when the data are characterized by strongly nonlinear boundaries between classes. 相似文献
59.
Relaxed stability and performance conditions for Takagi-Sugeno fuzzy systems with knowledge on membership function overlap. 总被引:1,自引:0,他引:1
Antonio Sala Carlos Ari?o 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(3):727-732
This correspondence presents a relaxation of some earlier linear matrix inequality (LMI) conditions, which allow setting up less conservative stability or performance conditions for Takagi-Sugeno fuzzy models. Unlike the previous literature, this correspondence takes into account the knowledge of the membership functions' shape by considering bounds on them and their cross products (interpreted as an overlap measure), introducing auxiliary LMI variables. Numerical examples illustrate the achieved improvements. 相似文献
60.
Antonio M. Locci Roberto Orrù Giacomo Cao Zuhair A. Munir 《Journal of the American Ceramic Society》2006,89(3):848-855
The simultaneous synthesis and densification of dense TiC–TiB2 composite has been investigated starting from Ti, B4 C, and C as reactants, and using the spark plasma sintering (SPS) technique. The optimal conditions for complete conversion of the reactants to the composite were determined for different applied DC current levels. A kinetic investigation performed allows us to conclude that solid-state diffusion is the mechanism governing the synthesis process. It is seen that TiC is the first phase formed, while TiB2 formation occurs afterward. Two intermediate boride phases, i.e. TiB and Ti3 B4 , are also formed but, as the SPS holding time was augmented, they were gradually and completely converted to TiB2 . Moreover, it is found that in order to reach relatively high dense products, an electric current needs to be applied for time intervals longer than those required for obtaining complete conversion. A pure dense product (relative density ∼98%) was obtained when an electric pulsed current of 1100 A and a mechanical pressure of 20 MPa were applied for about 4 min. 相似文献