全文获取类型
收费全文 | 7098篇 |
免费 | 324篇 |
国内免费 | 53篇 |
专业分类
电工技术 | 133篇 |
综合类 | 26篇 |
化学工业 | 1786篇 |
金属工艺 | 118篇 |
机械仪表 | 214篇 |
建筑科学 | 277篇 |
矿业工程 | 6篇 |
能源动力 | 462篇 |
轻工业 | 725篇 |
水利工程 | 76篇 |
石油天然气 | 115篇 |
无线电 | 653篇 |
一般工业技术 | 1143篇 |
冶金工业 | 337篇 |
原子能技术 | 84篇 |
自动化技术 | 1320篇 |
出版年
2024年 | 24篇 |
2023年 | 151篇 |
2022年 | 317篇 |
2021年 | 405篇 |
2020年 | 295篇 |
2019年 | 335篇 |
2018年 | 416篇 |
2017年 | 360篇 |
2016年 | 356篇 |
2015年 | 237篇 |
2014年 | 320篇 |
2013年 | 641篇 |
2012年 | 356篇 |
2011年 | 505篇 |
2010年 | 350篇 |
2009年 | 326篇 |
2008年 | 288篇 |
2007年 | 217篇 |
2006年 | 201篇 |
2005年 | 140篇 |
2004年 | 111篇 |
2003年 | 117篇 |
2002年 | 90篇 |
2001年 | 64篇 |
2000年 | 73篇 |
1999年 | 50篇 |
1998年 | 77篇 |
1997年 | 41篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1974年 | 12篇 |
排序方式: 共有7475条查询结果,搜索用时 15 毫秒
141.
This study considers the content of the papers published by ASCE’s Journal of Management in Engineering, which has witnessed a growth in number of papers and breadth of participation, particularly of international origin, during the 1985–2002 period. The content is analyzed in two main dimensions: the type of subject and its composing topics, and the type of contributors to the journal. The analysis shows the evolution of the engineering management discipline as represented in the journal. Over the years the discipline has been enriched by an increasing number of contributions on corporate strategies and programs, organizational change, and cultures issues, as well as a growing interest in project management topics, such as quality planning and evaluation of alternative project delivery systems. The number of papers by practitioners, initially the largest contributing group to the journal, has declined significantly over the years. 相似文献
142.
Ahmad A. Hamid Wael W. El-Dakhakhni Zeyad H. R. Hakam Mohamed Elgaaly 《Canadian Metallurgical Quarterly》2005,9(1):73-83
An experimental investigation was conducted to study the in-plane behavior of face shell mortar bedded unreinforced masonry (URM) wall assemblages retrofitted with fiber-reinforced polymer (FRP) laminates. Forty-two URM assemblages were tested under different stress conditions present in masonry shear and infill walls. Tests included prisms loaded in compression with different bed joint orientation (on/off-axis compression), diagonal tension specimens, and specimens loaded under joint shear. The behavior of each specimen type is discussed with emphasis on modes of failure, strength and deformation characteristics. Results showed that the application of FRP laminates on URM has a great influence on strength, postpeak behavior, as well as altering failure modes and maintaining the specimen integrity. The retrofitted specimens reached compressive strength of 1.62–5.64 times that of their unretrofitted counterparts, depending on the bed joint orientation, and joint shear strength increased by eightfold. 相似文献
143.
The paper pursues two main goals. First, an attempt is made to specify and verify protocols in a completely rigorous manner using the formalisms of temporal logic and algebraic specification. Second––and even more important––the protocol specifications are not presented as monolithic pieces of text, but rather are developed in a stepwise process, evolving from simple genotypes into the final complex products. This is illustrated with selected fragments of the TCP/IP protocol. 相似文献
144.
A database system of mechanical components based on geometric and topological similarity. Part I: representation 总被引:3,自引:0,他引:3
A database of mechanical components is an important issue for some manufacturing activities such as cost estimation, process planning, and design by case-based reasoning. In this paper, we give the representation scheme of the CAD model in such a database. Components are represented using attributed graphs in which the nodes correspond to the surfaces of the component and the links correspond to the edges of the component. The graph is based on the standard for the exchange of product information (STEP) physical file of the component. STEP file should be unique for a single component regardless of the underlying CAD system. The process of creating the graph of a component constitutes two sub-tasks: (i) importing the CAD model from the CAD system in STEP format and (ii) transforming the STEP data into attributed graph-based representation. The graph and its attributes describe the topology of the component completely together with some geometric data that are not dependent on any coordinate system such as surface type and curve type. These geometric data are helpful in the retrieval and matching processes in the database. 相似文献
145.
In this paper we propose a new algorithm to detect the irises of both eyes from a face image. The algorithm first detects the face region in the image and then extracts intensity valleys from the face region. Next, the algorithm extracts iris candidates from the valleys using the feature template of Lin and Wu (IEEE Trans. Image Process. 8 (6) (1999) 834) and the separability filter of Fukui and Yamaguchi (Trans. IEICE Japan J80-D-II (8) (1997) 2170). Finally, using the costs for pairs of iris candidates proposed in this paper, the algorithm selects a pair of iris candidates corresponding to the irises. The costs are computed by using Hough transform, separability filter and template matching. As the results of the experiments, the iris detection rate of the proposed algorithm was 95.3% for 150 face images of 15 persons without spectacles in the database of University of Bern and 96.8% for 63 images of 21 persons without spectacles in the AR database. 相似文献
146.
Analysis of Multi-Dimensional Space-Filling Curves 总被引:7,自引:0,他引:7
147.
Singh Salvinder Abdullah Shahrum Nik Abdullah Nik Mohamed 《Journal of Mechanical Science and Technology》2016,30(8):3539-3551
We studied the effect of mean stress correction factor using the Rainflow counting technique to assess the fatigue damage of an automobile crankshaft under service loading by considering the stochastic process of the Markov chain. The failure of the crankshaft will cause serious damage to the engine and also to other connecting subcomponents. The service loading is computationally generated from the Discrete Markov chain model and the fatigue cycle is counted using the Rainflow counting technique with the consideration of the local minima and maxima load. To quantify the fatigue damage, the strain-life curve using the fatigue mean stresses was used to model the fatigue failure of the material used in for the crankshaft at N f = 10 6 . The fatigue mean stresses were used to estimate the effects of the mean stress on the fatigue strength of the component under service loading condition. Statistical verification with the boundary condition of the 90% confidence level was performed to observe the difference between the stochastic algorithms when compared towards the fatigue life behavior of the ductile cast iron material. We concluded that for the practical application, the proposed stochastic model provides a highly accurate assessment of fatigue damage prediction for improving the safety and controlling the risk factors in terms of structural health monitoring. 相似文献
148.
The second Egyptian research reactor ET-RR-2 went critical on the 27th of November 1997. The National Center of Nuclear Safety and Radiation Control (NCNSRC) has the responsibility of the evaluation and assessment of the safety of this reactor. The purpose of this paper is to present an approach to optimization of the fuel element plate. For an efficient search through the solution space we use a multi objective genetic algorithm which allows us to identify a set of Pareto optimal solutions providing the decision maker with the complete spectrum of optimal solutions with respect to the various targets. The aim of this paper is to propose a new approach for optimizing the fuel element plate in the reactor. The fuel element plate is designed with a view to improve reliability and lifetime and it is one of the most important elements during the shut down. In this present paper, we present a conceptual design approach for fuel element plate, in conjunction with a genetic algorithm to obtain a fuel plate that maximizes a fitness value to optimize the safety design of the fuel plate. 相似文献
149.
Underground tunnels are considered to be a vital infrastructure component in most cities around the world. Careful planning is always necessary to ensure minimum impact on nearby surface and subsurface structures. This study describes the experimental investigation carried out to examine the effect of existing piles installed in cohesive soil and extended to bedrock on the circumferential stresses developing in a newly constructed tunnel supported by a flexible lining system. A small scale testing facility was designed and built to simulate the process of tunnel excavation and lining installation in the close vicinity of preinstalled model piles. Lining stresses were measured for different separation distances between the lining and the existing piles Consistent decrease in the lining load was observed when the piles are located within a distance of one tunnel diameter from the tunnel. The results presented in this study indicated that measuring the lining response near existing pile foundations may be used to evaluate the extent of the interaction between the lining and the surrounding piles. 相似文献
150.
Although many researchers have estimated crash modification factors (CMFs) for specific treatments (or countermeasures), there is a lack of studies that explored the heterogeneous effects of roadway characteristics on crash frequency among treated sites. Generally, the CMF estimated by before–after studies represents overall safety effects of the treatment in a fixed value. However, as each treated site has different roadway characteristics, there is a need to assess the variation of CMFs among the treated sites with different roadway characteristics through crash modification functions (CMFunctions). The main objective of this research is to determine relationships between the safety effects of adding a bike lane and the roadway characteristics through (1) evaluation of CMFs for adding a bike lane using observational before–after with empirical Bayes (EB) and cross-sectional methods, and (2) development of simple and full CMFunctions which are describe the CMF in a function of roadway characteristics of the sites. Data was collected for urban arterials in Florida, and the Florida-specific full SPFs were developed. Moreover, socio-economic parameters were collected and included in CMFunctions and SPFs (1) to capture the effects of the variables that represent volume of bicyclists and (2) to identify general relationship between the CMFs and these characteristics. In order to achieve better performance of CMFunctions, data mining techniques were used. 相似文献