全文获取类型
收费全文 | 9086篇 |
免费 | 793篇 |
国内免费 | 4471篇 |
专业分类
电工技术 | 183篇 |
综合类 | 1053篇 |
化学工业 | 1280篇 |
金属工艺 | 226篇 |
机械仪表 | 659篇 |
建筑科学 | 5083篇 |
矿业工程 | 479篇 |
能源动力 | 193篇 |
轻工业 | 98篇 |
水利工程 | 325篇 |
石油天然气 | 376篇 |
武器工业 | 1076篇 |
无线电 | 143篇 |
一般工业技术 | 2313篇 |
冶金工业 | 201篇 |
原子能技术 | 50篇 |
自动化技术 | 612篇 |
出版年
2024年 | 15篇 |
2023年 | 66篇 |
2022年 | 122篇 |
2021年 | 211篇 |
2020年 | 221篇 |
2019年 | 215篇 |
2018年 | 221篇 |
2017年 | 426篇 |
2016年 | 437篇 |
2015年 | 480篇 |
2014年 | 570篇 |
2013年 | 825篇 |
2012年 | 725篇 |
2011年 | 922篇 |
2010年 | 775篇 |
2009年 | 863篇 |
2008年 | 819篇 |
2007年 | 931篇 |
2006年 | 985篇 |
2005年 | 1039篇 |
2004年 | 921篇 |
2003年 | 586篇 |
2002年 | 329篇 |
2001年 | 212篇 |
2000年 | 223篇 |
1999年 | 205篇 |
1998年 | 192篇 |
1997年 | 159篇 |
1996年 | 116篇 |
1995年 | 124篇 |
1994年 | 74篇 |
1993年 | 67篇 |
1992年 | 51篇 |
1991年 | 37篇 |
1990年 | 42篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1958年 | 1篇 |
1955年 | 4篇 |
1954年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 271 毫秒
51.
A. Samuelsson O. C. Zienkiewicz 《International journal for numerical methods in engineering》2006,67(2):149-157
This paper presents a brief history of the development of the stiffness method. We start by tracing the evolution of the method to solve discrete‐type problems such as trusses and frames composed of two node members. We then describe the method as it is applied to solve continuum problems modelled by finite‐difference and finite‐element methods. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
52.
It is generally appreciated that the mechanical behavior of granular media depends fundamentally on the interaction of the
constituent particles, and that the validity of numerical models of granular media would be greatly improved with knowledge
of the grain-scale mechanics. However, most supporting experimental work has been conducted on highly idealized materials,
and a limited amount of information exists on grain-scale force–displacement relationships for naturally occurring materials.
To address this shortcoming, we are conducting a program that integrates laboratory experiments on grains of naturally occurring
aggregate with the discrete element modeling method, with the goal of relating the grain-scale physical and mechanical properties
of granular media to bulk behavior. The paper describes the equipment and methods that have been developed to conduct close-loop
controlled, grain-scale experiments under monotonic and cyclic loading conditions, and presents results from an initial set
of experiments on unbonded grains. The implications of the grain-scale results to the discrete element model are discussed.
Discussions center on the applicability of a physically based approach to the mechanics of granular media in general. In light
of future exploration missions and the resulting need to predict the mechanical properties of lunar and planetary regoliths,
the paper examines the potential usefulness of our physically based approach to the problem of predicting the behavior of
the types of materials found in those environments. 相似文献
53.
铰链式井下动力钻具组合是当前短半径水平钻井中最先进的一种新型工具。本文首先建立了铰接式井下动力钻具组合在二维井身条件下的力学模型并介绍了该模型的求解方法和过程,详细分析了若干结构学数、井身几何参数和钻井工艺参数对钻头侧向力的定量影响,为铰接式井下动力钻具组合的结构设计和短半径水平井轨道控制提供了力学分析基础。 相似文献
54.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
55.
M. M. I. HAMMOUDA I. G. EL-BATANONY H. E. M. SALLAM 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(7):627-639
An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area. 相似文献
56.
Anastasia Dobroskok Larissa Fradkin Gennady Mishuris 《Engineering Fracture Mechanics》2007,74(11):1719-1726
In the current paper crack redirection due to a strategic placing of a heat source in the vicinity of a crack tip is studied. Analysis suggests that for PMMA and considered temperature range the only factor responsible for the deviation of crack trajectory is thermal stress. The simulation of crack growth in PMMA under external tension and secondary heat loading shows that a moving heat source in the vicinity of a crack tip can serve as a pointer for the crack trajectory. In highly conductive materials, redirection can be possibly effected with low-power thermal dipoles. 相似文献
57.
58.
泥页岩稳定性的化学与力学耦合研究 总被引:17,自引:9,他引:8
泥页岩井壁失稳的化学与力学耦合作用是井壁稳定性研究中较为关注的问题,对该问题的国内外研究现状作了较为详细的调研,对泥页岩水化和泥页岩稳定问题进行了全面的研究回顾与现状分析。尤其是重点分析了90年代以来出现的将泥页岩水化的力学问题与化学问题相互耦合的研究。 相似文献
59.
60.
LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING 总被引:4,自引:0,他引:4
X. Chen Q. Gao X.-F. Sun 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(7):839-854
A series of strain-controlled, low-cycle fatigue experiments have been conducted on 42CrMo steel under various loading paths including circular, square, cruciform, and rectangular paths. Present experiments have shown that there is additional hardening under non-proportional cyclic loading. Non-proportional cyclic additional hardening also results in a shorter life for multiaxial low cycle fatigue. A non-proportionality measure of strain path based on both a physical basis and macromechanical phenomena is proposed. The loading path effect on additional hardening is also described well. Low-cycle fatigue damage accumulation and the evolution process under non-proportional loading is analysed via the Continuum Damage Mechanics Model of Chaboche. A non-proportinality measure is introduced in the damage evolution equation and a modified Coffin-Manson type formula is derived. A novel fatigue life prediction approach based on the critical-plane concept of Brown and Miller is proposed. 相似文献