全文获取类型
收费全文 | 13810篇 |
免费 | 1678篇 |
国内免费 | 995篇 |
专业分类
电工技术 | 165篇 |
综合类 | 2040篇 |
化学工业 | 1632篇 |
金属工艺 | 1064篇 |
机械仪表 | 520篇 |
建筑科学 | 5120篇 |
矿业工程 | 386篇 |
能源动力 | 246篇 |
轻工业 | 351篇 |
水利工程 | 840篇 |
石油天然气 | 517篇 |
武器工业 | 118篇 |
无线电 | 369篇 |
一般工业技术 | 2326篇 |
冶金工业 | 521篇 |
原子能技术 | 57篇 |
自动化技术 | 211篇 |
出版年
2024年 | 70篇 |
2023年 | 184篇 |
2022年 | 372篇 |
2021年 | 438篇 |
2020年 | 511篇 |
2019年 | 497篇 |
2018年 | 536篇 |
2017年 | 578篇 |
2016年 | 577篇 |
2015年 | 566篇 |
2014年 | 895篇 |
2013年 | 1003篇 |
2012年 | 955篇 |
2011年 | 1053篇 |
2010年 | 745篇 |
2009年 | 767篇 |
2008年 | 787篇 |
2007年 | 826篇 |
2006年 | 823篇 |
2005年 | 634篇 |
2004年 | 520篇 |
2003年 | 430篇 |
2002年 | 411篇 |
2001年 | 366篇 |
2000年 | 318篇 |
1999年 | 297篇 |
1998年 | 230篇 |
1997年 | 191篇 |
1996年 | 159篇 |
1995年 | 134篇 |
1994年 | 125篇 |
1993年 | 99篇 |
1992年 | 94篇 |
1991年 | 57篇 |
1990年 | 39篇 |
1989年 | 52篇 |
1988年 | 25篇 |
1987年 | 33篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1961年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
岩石物理横波速度曲线计算技术 总被引:15,自引:3,他引:12
横波速度是地震勘探中的重要参数。针对实际生产中缺乏横波速度测井曲线资料,利用经验公式计算精确度不高的问题,通过对横波速度计算理论模型的研究分析,选择Blot-Gassman模型法,利用岩石矿物成分、流体成分、孔隙度及密度等测井曲线进行横波速度测井曲线的计算,并对横波速度计算技术和流程进行研究。在实际工区进行了横波速度曲线计算,计算结果与实测横波吻合程度较高,误差小于10%,该技术在储层和流体识别预测的应用中取得了较好效果。 相似文献
2.
3.
G. Ranzi M. A. Bradford B. Uy 《International journal for numerical methods in engineering》2004,61(5):657-672
The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
The primary aim of this paper is to present results describing in detail the behaviour of ±45° E-glass/MY750 (GRP) tubes, of various wall thicknesses, subjected to equal biaxial tension–compression loading, generated under combined internal pressure and axial compression. The role played by the non-linear lamina shear has also been assessed by comparing various shear stress–strain curves for embedded laminae (extracted from tests on ±45° tubes subjected to circumferential: axial stress ratios SR=1:0, 1:−1 and 2.3:−1) with that of an ‘isolated’ lamina (measured from torsion of 90° tubes). Extracted shear failure strains, for embedded laminae, were more than four fold larger than those measured at ultimate failure for an ‘isolated’ lamina. Soft characteristics were observed in the embedded lamina and these were believed to be due to interaction between early matrix damage initiation (and propagation) and shear. Factors affecting the behaviour of the tubes, such as bulging, scissoring, thermal stresses and stress variation through the thickness are discussed. 相似文献
5.
在宝钢2030mm冷轧厂酸洗机组中,为了满足厚规格IF钢的生产,拟将原有的气动式剪切机改成液压式剪切机。为此,设计了一套中高压大流量的液压系统以满足3号横剪大剪切力(最高达700kN)和快速剪切(3秒/次)的需要。由于采用了蓄能器增速回路和二通插装阀控制技术,使该液压系统较传统的剪切机液压系统具有响应速度快、体积小、重量轻、发热少和降低电机能耗等优点。 相似文献
6.
当地弹性地基梁法计算非岩石地基的水闸底板应力时,首先要求解出不平衡剪力,当闸墩截面选择梯形时(主要是边墩),常用方法是作图法,这既有误差又繁琐。所以就此推导出一个公式,可直接求解平衡剪力。 相似文献
7.
凌树森 《理化检验(物理分册)》1998,34(3):15-18,36
对圆杆在线弹性阶段,弹-塑性阶段和全塑性阶段的扭转剪应力的计算公式作了分析,并推导了在材料的应力-应变关系(τ-γ关系)不服从虎克定律时,扭转真实剪应力的计算公式。文中对扭转强度计算公式的来源,物理含义及其都作了详细的说明。这对执行和理解国家GB10128-88《金属室温扭转试验方法》是有益的,而且对高校中材料力学的教学具有一定的参考价值。 相似文献
8.
济钢350m^3高炉高富氧生产技术 总被引:1,自引:1,他引:0
分析了济钢350m^3高炉高富氧对产量,理论燃烧温度,炉况顺行状况,焦比和生产效益的影响,高富氧可提高产量,但升高焦比和高炉理论燃烧温度,一定程度上影响高炉顺行,存在富氧效益最大化的适宜富氧率.高炉生产应低富氧高喷煤,根据钢目前的情况,富氧率经2%-3%为宜. 相似文献
9.
10.
J. K. G. Dhont 《International Journal of Thermophysics》1994,15(6):1157-1168
A derivation of an expression for the shear rate-dependent Ornstein Zernike structure factor is discussed, together with the resulting anomalous behavior of the turbidity. The predicted scaling behavior of the turbidity, comprising the effect of both temperature and shear rate, is in good agreement with experiments on binary fluids. Then initial spinodal decomposition is discussed, and an explicit expression for the time- and shear rate-dependent effective diffusion coefficient is derived, which shows all the typical characteristics of anisotropic light scattering patterns that are observed experimentally for binary fluids. Next it is shown that the spinodal is shifted linearly with the (bare) Peclet number for not too large Peclet numbers, whereas the cloud point is singularly displaced into the unstable region due to a shear now. This is in agreement with an experiment on a two-polymer/solvent mixture and binary fluid mixtures. It is argued that light scattering is useless to determine the location of the spinodal of a sheared system.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献