全文获取类型
收费全文 | 34086篇 |
免费 | 1702篇 |
国内免费 | 491篇 |
专业分类
电工技术 | 993篇 |
技术理论 | 1篇 |
综合类 | 2820篇 |
化学工业 | 2123篇 |
金属工艺 | 449篇 |
机械仪表 | 620篇 |
建筑科学 | 19008篇 |
矿业工程 | 555篇 |
能源动力 | 1235篇 |
轻工业 | 493篇 |
水利工程 | 536篇 |
石油天然气 | 307篇 |
武器工业 | 60篇 |
无线电 | 692篇 |
一般工业技术 | 2765篇 |
冶金工业 | 444篇 |
原子能技术 | 95篇 |
自动化技术 | 3083篇 |
出版年
2024年 | 50篇 |
2023年 | 225篇 |
2022年 | 479篇 |
2021年 | 568篇 |
2020年 | 619篇 |
2019年 | 578篇 |
2018年 | 533篇 |
2017年 | 788篇 |
2016年 | 907篇 |
2015年 | 1045篇 |
2014年 | 3487篇 |
2013年 | 2515篇 |
2012年 | 2236篇 |
2011年 | 2406篇 |
2010年 | 2045篇 |
2009年 | 2296篇 |
2008年 | 2021篇 |
2007年 | 2280篇 |
2006年 | 1690篇 |
2005年 | 1502篇 |
2004年 | 1241篇 |
2003年 | 1067篇 |
2002年 | 898篇 |
2001年 | 796篇 |
2000年 | 661篇 |
1999年 | 617篇 |
1998年 | 511篇 |
1997年 | 378篇 |
1996年 | 396篇 |
1995年 | 258篇 |
1994年 | 226篇 |
1993年 | 185篇 |
1992年 | 155篇 |
1991年 | 124篇 |
1990年 | 68篇 |
1989年 | 56篇 |
1988年 | 48篇 |
1987年 | 56篇 |
1986年 | 29篇 |
1985年 | 54篇 |
1984年 | 39篇 |
1983年 | 43篇 |
1982年 | 24篇 |
1981年 | 11篇 |
1980年 | 39篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
P. PAPANIKOS K. I. TSERPES SP. PANTELAKIS 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):37-47
A progressive fatigue damage model has been developed for predicting damage accumulation and life of carbon fibre‐reinforced plastics (CFRP) laminates with arbitrary geometry and stacking sequence subjected to constant amplitude cyclic loading. The model comprises the components of stress analysis, fatigue failure analysis and fatigue material property degradation. Stress analysis of the composite laminate was performed by creating a three‐dimensional finite element model in the ANSYS FE code. Fatigue failure analysis was performed by using a set of Hashin‐type failure criteria and the Ye‐delamination criterion. Two types of material property degradations on the basis of element stiffness and strength were applied: a sudden degradation because of sudden failure detected by the fatigue failure criteria and a gradual degradation because of the nature of cyclic loading, which is driven by the increased number of cycles. The gradual degradation of the composite material was modelled by using functions relating the residual stiffness and residual strength of the laminate to the number of cycles. All model components have been programmed in the ANSYS FE code in order to create a user‐friendly macro‐routine. The model has been applied in two different quasi‐isotropic CFRP laminates subjected to tension–compression (T–C) fatigue and the predictions of fatigue life and damage accumulation as a function of the number of cycles were compared with experimental data available in the literature. A very good agreement was obtained. 相似文献
82.
This study focuses on numerical simulation of ductile failure in the Co binder phase of WC–Co hardmetal. The growth of edge cracks under mode I loading is considered. A computational micromechanics approach is taken where the Co binder ligaments are explicitly represented in finite element models. An embedding technique is employed. Crystal plasticity theory is used to represent plastic deformation in the Co ligaments. Crack propagation in the binder is simulated using an element removal technique based on a modified Rice and Tracey model for ductile void growth, and fracture resistance curves are generated. Parameter studies are performed for variations in microstructrual parameters such as numbers of Co ligaments ahead of the crack tip and local Co volume fraction. The importance of thermal residual stresses and finite element mesh density are also investigated. 相似文献
83.
Gülü Insel Derin Orhon Peter A Vanrolleghem 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):437-445
Hydrolysis mechanism plays a dominant role in the delicate balance of electron donor/electron acceptor ratios in BNR and EBPR systems as an important carbon source. In this study, the surface‐saturation‐type hydrolysis kinetics was investigated based on respirometric measurements, within the context of the theoretical and the practical identifiability of mathematical models. The identifiable parameters of a selected model were derived from respirograms. In addition, the information from the experiments was evaluated on the basis of Optimal Experimental Design (OED) methodology for different initial conditions of the batch respirometric experiment. © 2003 Society of Chemical Industry 相似文献
84.
M. R. JOYCE K. K. LEE S. SYNGELLAKIS P. A. S. REED 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(11):1025-1036
Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack. 相似文献
85.
建设工程质量保证体系存在的问题及对策 总被引:13,自引:2,他引:11
结合建筑业市场管理体制的改革及其发展态势,就建筑工程质量保证体系存在的问题作了阐述,从加强勘察设计资格的管理,完善监理法规等方面,提出了健全和完善质保体系的措施。 相似文献
86.
利用Excel表格进行供暖系统计算 总被引:2,自引:0,他引:2
利用Excel表格进行供暖工程设计计算,可以减少工作量,提高工作效率。介绍了房间热负荷和供暖管道水力计算方法。 相似文献
87.
88.
89.
The efficient, economical and often elegant transformation from a design schema to an embodied design solution containing real components is essential for the commercial success of a product. More often the ability of the designer to explore an optimum solution is severely frustrated by the analytically intensive and time-consuming aspects of embodying a concept. This paper presents a computer based system-modelling tool that is to be used by designers during the transformation of a concept to an embodied solution particularly to deal with standard components. This environment provides for the representation of conceptual schemas and subsequent embodiment from computer based component selection modules. These selection modules encompass the full range of electronic representations for standard mechanical components. The strategy for representing a mechanical system, its included components and their associated representations is discussed. The process of constructing a system model, specifying the desired performance characteristics and system resolution are also described. 相似文献
90.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献