全文获取类型
收费全文 | 1544篇 |
免费 | 94篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 26篇 |
综合类 | 2篇 |
化学工业 | 338篇 |
金属工艺 | 35篇 |
机械仪表 | 40篇 |
建筑科学 | 36篇 |
矿业工程 | 2篇 |
能源动力 | 103篇 |
轻工业 | 147篇 |
水利工程 | 12篇 |
石油天然气 | 39篇 |
无线电 | 191篇 |
一般工业技术 | 324篇 |
冶金工业 | 77篇 |
原子能技术 | 10篇 |
自动化技术 | 263篇 |
出版年
2024年 | 4篇 |
2023年 | 44篇 |
2022年 | 71篇 |
2021年 | 98篇 |
2020年 | 69篇 |
2019年 | 55篇 |
2018年 | 83篇 |
2017年 | 77篇 |
2016年 | 76篇 |
2015年 | 43篇 |
2014年 | 61篇 |
2013年 | 128篇 |
2012年 | 96篇 |
2011年 | 107篇 |
2010年 | 62篇 |
2009年 | 77篇 |
2008年 | 60篇 |
2007年 | 73篇 |
2006年 | 51篇 |
2005年 | 36篇 |
2004年 | 30篇 |
2003年 | 28篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有1645条查询结果,搜索用时 0 毫秒
151.
In recent years, numerous investigations have addressed the shear strengthening of reinforced concrete (RC) beams with externally bonded fiber-reinforced polymer (FRP) composites. Despite this research effort, the mechanisms of shear resistance that are developed in such a strengthening system have not yet been fully documented and explained. This clearly inhibits the development of rational and reliable code specifications. This paper aims to contribute to the understanding of the shear resistance mechanisms involved in RC beams strengthened in shear with externally bonded FRP. It is based on results obtained from an experimental program, involving 17 tests, performed on full size T beams, and using a comprehensive and carefully optimized measuring device. The resistance mechanisms are studied by observing the evolution of the behavior of the strengthened beams as the applied loads are increased. The local behavior of the FRP and the transverse steel, in particular in the failure zones, are thoroughly examined. The operative resistance mechanisms are also studied through the load sharing among the concrete, the FRP, and the transverse steel, at increasing levels of applied load. 相似文献
152.
Waschbusch Daniel A.; Porter Stephen; Carrey Normand; Kazmi S. Omar; Roach Kerry A.; D'Amico Delia A. 《Canadian Metallurgical Quarterly》2004,36(2):97
We evaluated parent and teacher ratings of a large sample (N=1579) of elementary-school children in Canada to determine how different conceptualizations of disruptive behaviour are co-related and related to other measures of functioning. Parent and teacher ratings were consistent, and suggested three separate but correlated aspects of disruptive behaviour in children: (1) reactive/oppositional behaviour, (2) proactive/callous behaviour; and (3) inattention-impulsive-overactive behaviour. These were uniquely and significantly related to DSM-IV diagnostic scores and to other measure of impairment, indicating that they measure distinct aspects of disruptive behaviour in children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
153.
Peter Bettess Joseph Shirron Omar Laghrouche Bernard Peseux Rie Sugimoto Jon Trevelyan 《International journal for numerical methods in engineering》2003,56(4):531-552
The theory for integrating the element matrices for rectangular, triangular and quadrilateral finite elements for the solution of the Helmholtz equation for very short waves is presented. A numerical integration scheme is developed. Samples of Maple and Fortran code for the evaluation of integration abscissæ and weights are made available. The results are compared with those obtained using large numbers of Gauss–Legendre integration points for a range of testing wave problems. The results demonstrate that the method gives correct results, which gives confidence in the procedures, and show that large savings in computation time can be achieved. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
154.
Joël Andrieu Yves Raingeaud Omar Dafif Bernard Jecko Daniel Negret Bernard Pecqueux 《电信纪事》1992,47(1-2):73-85
This paper presents the qualification of an iemn exploitation original system, intended to create a realistic electromagnetic environment on large structures (planes, missiles, land vehicles). It consists in a horizontal polarization transmission line simulator which is supplied by a high voltage generator. The transient currents, induced on the wires, are solved by using integral equations in the space-time domain. The electromagnetic fields evaluated inside the working volumes are determined in each point and at each time. We include numerous comparisons with the experiments carried out by the Centre d’études de Gramat. 相似文献
155.
The dielectric absorption and dispersion of poly(vinyl chloride), M Mv = 49 000, in THF and in cyclohexanone have been studied over a frequency range of 120 kHz to 11·0 MHz, at temperatures from ?22·5 to 35°C, and at concentrations ranging from 4 to 12·0(w/v)% PVC/THF and from 2 to 8·0(w/v)% PVC/cyclohexanone. The viscosities of the two systems have also been measured at temperatures from 20 to 50°C. A single relaxation time was found (β = 0·8–1·0), which indicates that relaxation occurs by segmental rotation. The dielectric and viscous activation energies have been calculated. The dipole moment associated with the relaxation process has also been calculated. The relaxation time, dielectric and viscous activation energies and the dipole moment were found to be dependent on the type of solvent. The dipole moment also showed a molecular weight dependence. The influence of the concentration and temperature on the apparent dipole moment and on the relaxation time is discussed. 相似文献
156.
The aim of this paper is to compare the implementation of computational fluid dynamics (CFD) and Network models for airflow rate estimation in buildings. The CFD software used is Fluent 5.5. Comparison between the predicted and simulated airflow rate is suggested as a validation method of the implemented CFD code, while the common practice is to compare CFD outputs to wind tunnel or full-scale measurements. This could be useful for studies that have no access to laboratory or full-scale testing facilities. Results obtained from testing a number of cases have been compared and analysed, considering normal and oblique wind directions. The comparison held between mathematical and CFD results generally showed a good agreement, which seems to justify the use of CFD code for predicting natural ventilation in buildings. 相似文献
157.
Corrosion inhibition of benzyl triethanol ammonium chloride and its ethoxylate on steel in sulphuric acid solution 总被引:2,自引:0,他引:2
The inhibitive effect of benzyl triethanol ammonium chloride (BTAC) and ethoxylated benzyl triethanol ammonium chloride (EBTAC) on the corrosion of carbon steel in sulphuric acid solution is measured by the weight loss method. The adsorption of these compounds (surfactants) leads to the formation of a monolayer on the metal surface. The relationships between the concentrations of these inhibitors and their surface properties, thermodynamic properties, surface coverage (θ) and inhibiting efficiency have been investigated. The results indicate that EBTAC is superior to BTAC. 相似文献
158.
Omar Hatamleh Joacim Beek Royce Forman Venkataraman Shivakumar Jed Lyons 《International Journal of Fracture》2005,134(3-4):251-265
A new numerical method based on the strip yield analysis approach was developed for calculating the Crack Tip Opening Displacement
(CTOD). This approach can be applied to any crack geometry, of either infinite or finite extent, with arbitrary applied loading
conditions. The technique is an adaptation of the dislocation-density based boundary element method to obtain crack-face opening
displacements at any point on a crack, and succeeds in obtaining the requisite values as a series of definite integrals, the
functional parts of each of which are evaluated exactly in closed form. The power of the technique is demonstrated by obtaining
solutions to several crack configurations of practical interest. 相似文献
159.
J. M. Cabrera A. Al Omar J. M. Prado J. J. Jonas 《Metallurgical and Materials Transactions A》1997,28(11):2233-2244
The constitutive equations for the flow behavior of a commercial 0.34 pct C-1.5 pct Mn-0.7 pct Si-0.083 pct V-0.018 pct Ti
microalloyed steel were determined. For this purpose, uniaxial hot compression tests were carried out over a wide range of
strain rates (10−4 to 10 s−1) and temperatures (1123 to 1423 K). In combination with models developed in the literature, the experimental results permit
the flow stress of the present steel to be predicted within ± 5 pct. It is shown that the classical constitutive equations
must be modified to take the grain size into account, particularly when the latter is below 30 μm. 相似文献
160.
Sherman Jeffrey W.; Stroessner Steven J.; Conrey Frederica R.; Azam Omar A. 《Canadian Metallurgical Quarterly》2005,89(4):607
Three experiments examined the relationship between prejudice and processing of stereotypic information. Higher levels of prejudice were associated with greater attention to and more thorough encoding of stereotype-inconsistent than stereotype-consistent behaviors but only when processing capacity was plentiful (Experiments 1 and 3). High-prejudice participants attributed consistent behaviors to internal factors and inconsistent behaviors to external forces (Experiment 2). Together, these results suggest that high-prejudice people attend carefully to inconsistent behaviors to explain them away but only if they have sufficient resources to do so. Results also showed that low-prejudice but not high-prejudice participants formed individuated impressions by integrating the implications of the target's behaviors (i.e., individuating). High levels of prejudice appear to be associated with biased encoding and judgment processes that may serve to maintain stereotypes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献