全文获取类型
收费全文 | 2628篇 |
免费 | 181篇 |
国内免费 | 228篇 |
专业分类
电工技术 | 27篇 |
综合类 | 181篇 |
化学工业 | 228篇 |
金属工艺 | 922篇 |
机械仪表 | 76篇 |
建筑科学 | 44篇 |
矿业工程 | 45篇 |
能源动力 | 50篇 |
轻工业 | 42篇 |
水利工程 | 9篇 |
石油天然气 | 29篇 |
武器工业 | 18篇 |
无线电 | 68篇 |
一般工业技术 | 512篇 |
冶金工业 | 252篇 |
原子能技术 | 12篇 |
自动化技术 | 522篇 |
出版年
2024年 | 5篇 |
2023年 | 54篇 |
2022年 | 86篇 |
2021年 | 99篇 |
2020年 | 100篇 |
2019年 | 85篇 |
2018年 | 87篇 |
2017年 | 103篇 |
2016年 | 70篇 |
2015年 | 75篇 |
2014年 | 134篇 |
2013年 | 180篇 |
2012年 | 131篇 |
2011年 | 214篇 |
2010年 | 136篇 |
2009年 | 167篇 |
2008年 | 143篇 |
2007年 | 159篇 |
2006年 | 191篇 |
2005年 | 146篇 |
2004年 | 131篇 |
2003年 | 108篇 |
2002年 | 87篇 |
2001年 | 60篇 |
2000年 | 50篇 |
1999年 | 49篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 3篇 |
排序方式: 共有3037条查询结果,搜索用时 187 毫秒
991.
本文基于LINUX采用C 语言,开发了实现虚拟产品设计的基础组成部分。应用B-rep建模方法描述实体,转换三维CAD系统图形文件数据成为可渲染虚拟现实软件系统RENDERIZER的文件格式,并对实体进行细化和分面,为构建在ACIS和OPEN INVENTOR工具软件上的虚拟产品设计集成系统打下坚定的基础。 相似文献
992.
A. N. Fitch 《Journal of research of the National Institute of Standards and Technology》2004,109(1):133-142
The optical design and performance of the high-resolution powder diffraction beam line BM16 at ESRF are discussed and illustrated. Some recent studies carried out on BM16 are described, including crystal structure solution and refinement, anomalous scattering, in situ measurements, residual strain in engineering components, investigation of microstructure, and grazing-incidence diffraction from surface layers. The beam line is built on a bending magnet, and operates in the energy range from 5 keV to 40 keV. After the move to an undulator source in 2002, it will benefit from an extented energy range up to 60 keV and increased flux and resolution. It is anticipated that enhancements to the data quality will be achieved, leading to the solution of larger crystal structures, and improvements in the accuracy of refined structures. The systematic exploitation of anisotropic thermal expansion will help reduce the effects of peak overlap in the analysis of powder diffraction data. 相似文献
993.
Construction and stepwise refinement of dependability models 总被引:8,自引:0,他引:8
This paper presents a stepwise approach for dependability modeling, based on generalized stochastic Petri nets (GSPNs). The first-step model called functional-level model, is built based on the system’s functional specifications and then completed by the structural model as soon as the system’s architecture is known. It can then be refined according to three complementary aspects: component decomposition, state and event fine-tuning and distribution adjustment to take into account increasing event rates. We define specific rules to make the successive transformations as easy and systematic as possible. This approach allows the various dependencies to be taken into account at the right level of abstraction: functional dependency, structural dependency and those induced by non-exponential distributions. A part of the approach is applied to an instrumentation and control (I&C) system in power plants. 相似文献
994.
995.
铸造镁合金的晶粒细化技术 总被引:49,自引:0,他引:49
从晶粒细化方法和晶粒细化机理两个方面总结了不含锆铸造镁合金和含锆铸造镁合金晶粒细化技术的研究进展,并指出新型高效晶粒细化剂的开发和晶粒细化机理的研究是镁合金晶粒细化技术研究的重点. 相似文献
996.
Microstructure evolution and precipitation behavior of low carbon steel hot strips produced by CSP 总被引:1,自引:0,他引:1
The microstructures of low carbon steel before, during and after rolling deformation of each stand were observed using optical microscope. The result showed that the microstructures were very fine after six passes rolling deformation. The effect of the first stand reduction on microstructure refinement was very distinct. During the rolling process, with the increase of the accumulated strain, the microstructures would further refine, and the density of dislocation would increase at the same time. In continuous casting thin slabs and each finishing stand, lots of observed precipitates were mainly A12O3 and MnS along the grain boundaries or in grains,which played an important role in the mechanical properties of the hot strips of low carbon steel produced by CSP (compact strip production) technology. 相似文献
997.
Finite element analysis is perhaps the most commonly used numerical method to model plasticity-induced fatigue crack closure. The state-of-the-art is reviewed and a comprehensive overview is presented, summarizing issues which must be considered and emphasizing potential difficulties. These include mesh refinement level, crack advancement schemes, crack shape evolution, geometry effects, and crack opening value assessment techniques. 相似文献
998.
Ko‐Foa Tchon Julien Dompierre Ricardo sCamarero 《International journal for numerical methods in engineering》2004,59(12):1539-1562
Conformal refinement using a shrink and connect strategy, known as pillowing or buffer insertion, contracts and reconnects contiguous elements of an all‐quadrilateral or an all‐hexahedral mesh in order to locally increase vertex density without introducing hanging nodes or non‐cubical elements. Using layers as shrink sets, the present method automates the anisotropic refinement of such meshes according to a prescribed size map expressed as a Riemannian metric field. An anisotropic smoother further enhances vertex clustering to capture the features of the metric. Both two‐ and three‐dimensional test cases with analytic control metrics confirm the feasibility of the present approach and explore strategies to minimize the trade‐off between element shape quality and size conformity. Additional examples using discrete metric maps illustrate possible practical applications. Although local vertex removal and reconnection capabilities have yet to be developed, the present refinement method is a step towards an automated tool for conformal adaptation of all‐quadrilateral and all‐hexahedral meshes. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
999.
We present a tetrahedral mesh generation algorithm designed for the Lagrangian simulation of deformable bodies. The algorithm’s
input is a level set (i.e., a signed distance function on a Cartesian grid or octree). First a bounding box of the object
is covered with a uniform lattice of subdivision-invariant tetrahedra. The level set is then used to guide a red green adaptive
subdivision procedure that is based on both the local curvature and the proximity to the object boundary. The final topology
is carefully chosen so that the connectivity is suitable for large deformation and the mesh approximates the desired shape.
Finally, this candidate mesh is compressed to match the object boundary. To maintain element quality during this compression
phase we relax the positions of the nodes using finite elements, masses and springs, or an optimization procedure. The resulting
mesh is well suited for simulation since it is highly structured, has topology chosen specifically for large deformations,
and is readily refined if required during subsequent simulation. We then use this algorithm to generate meshes for the simulation
of skeletal muscle from level set representations of the anatomy. The geometric complexity of biological materials makes it
very difficult to generate these models procedurally and as a result we obtain most if not all data from an actual human subject.
Our current method involves using voxelized data from the Visible Male [1] to create level set representations of muscle and bone geometries. Given this representation, we use simple level set operations
to rebuild and repair errors in the segmented data as well as to smooth aliasing inherent in the voxelized data. 相似文献
1000.
Chevaugeon N. Xin J. Hu P. Li X. Cler D. Flaherty J.E. Shephard M.S. 《Journal of scientific computing》2005,22(1-3):227-243
We describe procedures to model transient shock interaction problems using discontinuous Galerkin methods to solve the compressible Euler equations. The problems are motivated by blast flows surrounding cannons with perforated muzzle brakes. The goal is to predict shock strengths and blast over pressure. This application illustrates several computational difficulties. The software must handle complex geometries. The problems feature strong interacting shocks, with pressure ratios on the order of 1000 as well as weaker precursor shocks traveling rearward that also must be accurately captured. These aspects are addressed using anisotropic mesh adaptation. A shock detector is used to control the adaptation and limiting. We also describe procedures to track projectile motion in the flow by a level-set procedure.This revised version was published online in July 2005 with corrected volume and issue numbers. 相似文献