全文获取类型
收费全文 | 33731篇 |
免费 | 3096篇 |
国内免费 | 2481篇 |
专业分类
电工技术 | 784篇 |
综合类 | 3651篇 |
化学工业 | 1006篇 |
金属工艺 | 3943篇 |
机械仪表 | 1926篇 |
建筑科学 | 15220篇 |
矿业工程 | 2645篇 |
能源动力 | 521篇 |
轻工业 | 322篇 |
水利工程 | 2578篇 |
石油天然气 | 732篇 |
武器工业 | 189篇 |
无线电 | 422篇 |
一般工业技术 | 3055篇 |
冶金工业 | 1452篇 |
原子能技术 | 83篇 |
自动化技术 | 779篇 |
出版年
2024年 | 112篇 |
2023年 | 380篇 |
2022年 | 705篇 |
2021年 | 939篇 |
2020年 | 894篇 |
2019年 | 737篇 |
2018年 | 744篇 |
2017年 | 924篇 |
2016年 | 1062篇 |
2015年 | 1179篇 |
2014年 | 2236篇 |
2013年 | 1690篇 |
2012年 | 2468篇 |
2011年 | 2686篇 |
2010年 | 2242篇 |
2009年 | 2369篇 |
2008年 | 2112篇 |
2007年 | 2654篇 |
2006年 | 2317篇 |
2005年 | 1875篇 |
2004年 | 1517篇 |
2003年 | 1374篇 |
2002年 | 1136篇 |
2001年 | 962篇 |
2000年 | 867篇 |
1999年 | 697篇 |
1998年 | 515篇 |
1997年 | 443篇 |
1996年 | 312篇 |
1995年 | 267篇 |
1994年 | 224篇 |
1993年 | 123篇 |
1992年 | 128篇 |
1991年 | 83篇 |
1990年 | 91篇 |
1989年 | 72篇 |
1988年 | 52篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 23篇 |
1975年 | 1篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
71.
简要分析了升船机上闸首基础岩体的特点,在施工期随上部建筑物形成的过程中沉降与水平形变随荷载变化的特征。分析认为:基础岩体形变与其受荷特点相吻合,目前建筑物总体安全状态正常,但部分坝段需引起注意,同时为验证设计、指导施工提供了依据。 相似文献
72.
海水冻融后轻骨料混凝土的双轴压压强度和变形性能 总被引:4,自引:2,他引:2
针对我国渤海湾北部海域轻骨料混凝土结构的工作环境和受力状态,进行了海水中不同冻融循环次数后轻骨料混凝土的双轴压压强度试验,考察了试件的破坏形态和表面裂缝的走向特征。根据试验结果,分析了极限抗压强度随冻融循环次数和应力比的变化规律,并在此基础上建立了考虑海水冻融影响的双轴压压强度准则。探讨了冻融循环作用后轻骨料混凝土的双轴压压变形性能,包括峰值应变、应力-应变关系随冻融循环次数和应力比的变化规律。研究结果说明,随冻融循环次数的增加各种应力比下的应力-应变关系曲线均逐渐扁平,峰值应力点明显下降并右移,说明混凝土的极限抗压强度逐渐降低。 相似文献
73.
The present paper is devoted to the analysis of the contact problems with Coulomb friction and large deformation between two hyperelastic bodies. One approach to separate the material nonlinearity and contact nonlinearity is presented. The total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. Nondifferentiable contact potentials are regularized by means of the augmented Lagrangian method. Numerical examples are carried out in two cases: rigid-deformable contact and deformable-deformable contact with large slips. The numerical results prove that the proposed approach is robust and efficient concerning numerical stability. 相似文献
74.
A mixed biopolymer gel, consisting of a protein (gelatin) and polysaccharide (maltodextrin) mixture has been investigated. By controlling the composition it was possible to construct an ‘emulsion-like’ structure, with included spherical particles of one phase (maltodextrin) within a continuous matrix of the second (gelatin). Large strain deformation and failure behaviour of this system has been examined via in situ environmental scanning electron microscopy (ESEM). ESEM has been employed to explore the changes in the structure of the material, whilst allowing the sample to stay hydrated as it was subjected to tensile strain, thereby allowing simultaneous imaging and determination of stress-strain data of the native sample. Ductile behaviour was observed, which has been attributed to the stretching, tearing and fracture of gelatin ligaments and debonding at the interface between the maltodextrin particles and continuous gelatin matrix. Deformation and fracture of the maltodextrin particles during tensile testing was also observed. The interfacial fracture energy of the composite has been calculated following an elastomer composite-debonding model, although there are several limitations to this approach for the mixed gel. It was found in samples tested after different ageing times that the debonding stress and strain was decreasing with ageing leading to a lower interfacial fracture energy. Samples were also tested after successive loading cycles, which resulted in a mechanical strength decrease after each cycle. 相似文献
75.
M. Komatsu Y. Matsukawa K. Yasunaga M. Kiritani 《Materials Science and Engineering: A》2003,350(1-2):25-29
Heavy plastic deformation of fcc metal thin foils to fracture has been found recently to proceed without involving dislocations, and it results in the formation of high density of vacancy clusters. Thin foil specimens of bcc metals such as V and Mo were plastically deformed to fracture in in situ elongation experiments under an electron microscope. Morphology of thinning and fracture was found to be similar to fcc metals, and no dislocation was observed during heavy deformation. Electron diffraction analysis at the tip of a crack during deformation confirmed a large elastic deformation of up to 5%. Unlike in fcc metal thin foil specimens, point defect clusters were not observed near fractured tips. This difference is attributed to the difference in vacancy reaction, though the deformation in bcc metals without dislocation most likely does produce vacancies. 相似文献
76.
77.
谈影响钻孔灌注桩承载力的因素 总被引:1,自引:1,他引:0
根据目前我国钻孔灌注桩的特点,从施工工艺方面,对控制沉渣、孔壁泥层过厚的问题进行了探讨,提出了合理、有效的措施,以确保桩基础承载力的正常发挥。 相似文献
78.
1 INTRODUCTIONTheapplicationofcastingSiCp/ZA2 7compositesisgreatlylimitedduetotheinhomogeneousdistribu tionofSiCpandtheporosityexistedinthematrix[1] .However,semi solidformingtechnology (SSF )e mergedintherecentyearscannotonlydecreaseore liminatetheporosityandenhancethecompactnessofthematrix ,butalsoimprovetheuniformdistributionofthereinforcementthroughtheredistributionofthereinforcementfromitsuniquecharacteristicsofmouldfilling[2 ] .Inaddition ,SSFisanearnet shapeform ingtechnology … 相似文献
80.