全文获取类型
| 收费全文 | 1606篇 |
| 免费 | 230篇 |
| 国内免费 | 29篇 |
专业分类
| 电工技术 | 61篇 |
| 综合类 | 76篇 |
| 化学工业 | 108篇 |
| 金属工艺 | 60篇 |
| 机械仪表 | 158篇 |
| 建筑科学 | 69篇 |
| 矿业工程 | 37篇 |
| 能源动力 | 156篇 |
| 轻工业 | 37篇 |
| 水利工程 | 49篇 |
| 石油天然气 | 93篇 |
| 武器工业 | 11篇 |
| 无线电 | 388篇 |
| 一般工业技术 | 199篇 |
| 冶金工业 | 136篇 |
| 原子能技术 | 17篇 |
| 自动化技术 | 210篇 |
出版年
| 2025年 | 2篇 |
| 2024年 | 15篇 |
| 2023年 | 27篇 |
| 2022年 | 30篇 |
| 2021年 | 25篇 |
| 2020年 | 32篇 |
| 2019年 | 33篇 |
| 2018年 | 28篇 |
| 2017年 | 31篇 |
| 2016年 | 56篇 |
| 2015年 | 58篇 |
| 2014年 | 80篇 |
| 2013年 | 78篇 |
| 2012年 | 83篇 |
| 2011年 | 107篇 |
| 2010年 | 103篇 |
| 2009年 | 103篇 |
| 2008年 | 84篇 |
| 2007年 | 94篇 |
| 2006年 | 104篇 |
| 2005年 | 86篇 |
| 2004年 | 80篇 |
| 2003年 | 75篇 |
| 2002年 | 56篇 |
| 2001年 | 38篇 |
| 2000年 | 27篇 |
| 1999年 | 52篇 |
| 1998年 | 38篇 |
| 1997年 | 50篇 |
| 1996年 | 48篇 |
| 1995年 | 20篇 |
| 1994年 | 24篇 |
| 1993年 | 25篇 |
| 1992年 | 14篇 |
| 1991年 | 23篇 |
| 1990年 | 13篇 |
| 1989年 | 5篇 |
| 1988年 | 8篇 |
| 1987年 | 3篇 |
| 1986年 | 2篇 |
| 1985年 | 1篇 |
| 1983年 | 1篇 |
| 1981年 | 1篇 |
| 1979年 | 1篇 |
| 1973年 | 1篇 |
排序方式： 共有1865条查询结果，搜索用时 15 毫秒
991.
992.
S.P. Levitsky R.M. Bergman J. Haddad 《International Journal of Engineering Science》2004,42(19-20):2079-2086
Propagation of longitudinal waves in a liquid-filled layer between two thin coaxial shells is investigated. Both liquid viscosity and elasticity of the shells are accounted for. Dynamics of the shells is treated using the Kirchhoff–Love approximation. The elastic deformations of the shells in the sound wave are coupled with the liquid flow in the gap through appropriate dynamic and kinematic boundary conditions. Hydrodynamics of the liquid is described using the quasi-one-dimensional (hydraulic) approach. It is assumed that the external and internal shells are composed of different isotropic elastic materials and have different widths. The dispersion equation for harmonic waves in the system is obtained; it is valid in the low frequency range where the wave length is greater than the external shell radius. In the limiting case for an ideal liquid the dispersion equation yields water hammer speed in the system. The analysis of the dispersion equation has shown strong influence of viscous losses on dispersion and attenuation of pressure signals in the low frequency region. The wave speed and attenuation are highly dependent on the geometrical parameters of the system and elastic properties of the shells. 相似文献
993.
介绍一台新型的ECR-PECVD装置.这一装置设计和采用了一种由单个电磁线圈和永磁体单元组合的新型磁场,使整个装置结构明显简化.为提高装置的微波转换效率,通过计算机仿真微波场在等离子体室的分布,选择和采用了一种新型的矩形耦合波导.应用这一装置分解H2稀释的SiH4气体以沉积a-Si:H薄膜,获得了2 nm/s以上的高沉积速率. 相似文献
994.
采用波传播法研究了低频下水中壳体的振动与响应。水中壳体由有限长加流体载荷的圆柱壳和两端的圆形端板组成,其中外部流体载荷用无限长模型进行近似处理。为了模拟推动系统的激励及船体上某一点激励,分别考虑了不同位置的轴向载荷和径向载荷,讨论了单个周向模态下的位移在总位移中的比重。主要研究了4种载荷,即作用在端板中心的轴对称载荷、作用在端板与圆柱连接处的轴向载荷、作用在连接处的径向载荷和作用在壳体中间的径向载荷,比较得出了轴对称和非轴对称、同一点不同方向载荷、同一方向不同位置载荷的响应位移的不同。此外,还研究了两端端板对不同载荷下水中壳体响应的影响,得出了端板主要抑制了壳体的较高阶模态下径向位移的结论。解析法结果与有限元法结果进行了比较,验证了该方法的正确性。 相似文献
995.
996.
The large diameter (up to 100 mm) Split Hopkinson Pressure Bar (SHPB) setup is used throughout the world to test large-cell heterogeneous materials, small structures, etc. This paper proposes a correction method to take into account the non-uniform distribution of stress and particle velocity (non-plane wave effect) in large diameter setups, following the theory of wave propagation in an infinite cylindrical elastic or viscoelastic rod. Such a non-plane wave effect depends on the pressure bar diameter and the high-frequency components contained in the signals. This correction procedure can be performed together with the wave dispersion correction, which is already incorporated for many large diameter bars used. For the various metallic and Nylon viscoelastic bars (up to 60 mm diameter) available in our laboratory, the relative difference between the average values of the particle velocity (and stress) in a cross-section and that calculated with a standard one-dimensional analysis is found to be inferior to 5%. However, this difference increases with a higher impact velocity, because signals containing more important high-frequency components are generated by higher impact velocities. In order to find an upper limit of the potential error for bars of various diameters, the theoretical pulse signal for a perfect impact between two infinite cylindrical rods is used, which gives the highest signal spectrum. With this theoretical pulse, such an upper limit of the potential error for different bar diameters (up to 200 mm) is found. It shows that the potential average error can reach up to 12% for a 100-mm-diameter bar currently used in the world. 相似文献
997.
Ocean waves exhibit more or less a Gaussian distribution for the instantaneous water surface height, and there is a need to develop simple models for generation of the characteristic non-Gaussian statistics, namely the asymmetric distributions of water surface height and wave slope. We argue that a simple class of non-linear oscillators can reproduce some of the characteristic features of random water wave processes and linear or non-linear response to ocean waves. We describe the Slepian model for the Gaussian case, and explain the use of the regression approximation for level crossing distances and associated variables, such as wave period and amplitude. Finally we speculate about a generalization of the regression technique to the non-linear Markov process case. 相似文献
998.
Where should the first wave farm in a region be installed? The nearshore area with the largest resource is the prime candidate. But how should this area be determined? Wave resource analyses typically consider a small number of wave patterns. Does the number of wave patterns influence the outcome? And, more generally, what is the best procedure for selecting the area? This work proposes an approach based on a large number of nearshore wave patterns and applies it to the Galician Southwest, where the first administrative concession for a wave farm (at a site to be determined) is expected to be issued shortly. The sensitivity of the results to the number of wave patterns, hence to the percentages of the total annual energy and time covered in the analysis, is investigated. It is found that the area that emerges as having the largest resource does depend on these percentages. For this reason, conventional analyses based on a small number of wave patterns are not sufficient to reliably determine the area with the largest resource. It is necessary to ensure that a sufficiently large percentage of the total energy is considered, using a procedure like the one proposed in this work. 相似文献
999.
各向异性介质中弹性波传播特征的伪谱法模拟研究 总被引：6，自引：1，他引：5
本文首先研究了各向导性介质中弹性波动方程伪谱法求解的稳定性条件;然后应用伪谱法模拟研究了各向异性介质中三种常见震源（垂直力源、压力源和剪切源）的辐射特征和三种各向导性模型（PTL、EDA和正交介质）的波传播快照特征;最后模拟研究了力源作用于裂隙诱导各向导性介质时VSP记录的特征。所有这些工作表明用伪谱法研究各向异性介质中弹性波传播是有效的。与此同时,我们也获得了一些各向异性介质中波传播的有益认识。 相似文献
1000.
应用Strata软件进行波阻抗反演的几点认识 总被引：11，自引：1，他引：10
地震波阻抗反演技术已日益成为油气藏勘探、开发中储集层横向预测的重要手段。针对反演的不适应性和非线性特点,通过大量试验和分析对比,文章就Ｓｔｒａｔａ软件在反演处理流程中几个对结果影响较大的问题提出了经验的方法,主要内容包括：地震子波的提取、剩余相位校正、反褶积和测井约束反演方法及参数使用等。并对波阻抗反演在准噶尔盆地腹部的勘探生产中的应用效果进行分析和对比 相似文献