全文获取类型
收费全文 | 59763篇 |
免费 | 4175篇 |
国内免费 | 1907篇 |
专业分类
电工技术 | 1088篇 |
综合类 | 3862篇 |
化学工业 | 7142篇 |
金属工艺 | 6700篇 |
机械仪表 | 11526篇 |
建筑科学 | 1214篇 |
矿业工程 | 1640篇 |
能源动力 | 7066篇 |
轻工业 | 1690篇 |
水利工程 | 167篇 |
石油天然气 | 981篇 |
武器工业 | 445篇 |
无线电 | 2619篇 |
一般工业技术 | 10666篇 |
冶金工业 | 1523篇 |
原子能技术 | 301篇 |
自动化技术 | 7215篇 |
出版年
2024年 | 162篇 |
2023年 | 2087篇 |
2022年 | 1997篇 |
2021年 | 2186篇 |
2020年 | 2829篇 |
2019年 | 2155篇 |
2018年 | 1677篇 |
2017年 | 2403篇 |
2016年 | 2698篇 |
2015年 | 3210篇 |
2014年 | 4067篇 |
2013年 | 4522篇 |
2012年 | 5533篇 |
2011年 | 5040篇 |
2010年 | 3840篇 |
2009年 | 3948篇 |
2008年 | 1803篇 |
2007年 | 3212篇 |
2006年 | 2912篇 |
2005年 | 1360篇 |
2004年 | 615篇 |
2003年 | 711篇 |
2002年 | 799篇 |
2001年 | 749篇 |
2000年 | 518篇 |
1999年 | 581篇 |
1998年 | 306篇 |
1997年 | 216篇 |
1996年 | 249篇 |
1995年 | 237篇 |
1994年 | 191篇 |
1993年 | 207篇 |
1992年 | 156篇 |
1991年 | 182篇 |
1990年 | 165篇 |
1989年 | 157篇 |
1988年 | 277篇 |
1987年 | 611篇 |
1986年 | 528篇 |
1985年 | 182篇 |
1984年 | 52篇 |
1983年 | 47篇 |
1982年 | 52篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 57篇 |
1978年 | 32篇 |
1977年 | 31篇 |
1976年 | 37篇 |
1974年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Guidelines for managing the mixture formation process in a high-performance four-stroke Gasoline Direct Injection (GDI) engine for two-wheel applications are discussed, as derived from a multidimensional modelling of the in-cylinder processes. Gasoline adduction from a multi-hole injector is simulated by resorting to a properly developed model that accounts for the dependence of the initial droplets size distribution upon injection pressure. The model portability is preliminary demonstrated by comparison with experimental measurements carried out on sprays entering a confined vessel at controlled conditions.The simulation of different engine operating conditions highlights the capability to work under the so-called “mixed mode” boosting with spray guided mixture formation. 相似文献
992.
K.C. Park R. Ohayon C.A. Felippa J.A. González 《Computer Methods in Applied Mechanics and Engineering》2010,199(9-12):723-733
This paper presents a partitioned modeling of internal and gravity fluid waves that interact with flexible structures. The governing interaction model consists of three completely partitioned entities: fluid model, structural model, and interface model that acts as an internal constraint on the fluid–structure interface boundary. Thus, the proposed partitioned multi-physics modeling can employ two completely modular fluid and structure software modules plus an interface solver, hence amenable to partitioned solution algorithms. The interface discretization can exploit the nonmatching interface algorithm previously developed via the method of localized Lagrange multipliers. Also noted is that the present fluid model can make use of widely available finite element software for standard Poisson-type problems. 相似文献
993.
Ignacio Romero 《Computer Methods in Applied Mechanics and Engineering》2010,199(33-36):2235-2248
This article proposes a new type of discretizations for initial boundary value problems of thermodynamical systems. Based on a combination of finite elements in space and fractional step methods in time, we formulate algorithms that exactly preserve the symmetries and the laws of thermodynamics of the continuum problem. The algorithmic design is based on the GENERIC formalism of irreversible thermodynamics which naturally suggests the split of the evolution operator upon which our fractional step method is based. Although the emphasis of the article is on the generality of the results, as an illustration, a discretization of nonlinear, finite strain, thermoelasticity is presented. Numerical simulations are provided that verify the excellent performance of the new methods. 相似文献
994.
T. Nguyen-Thoi H.C. Vu-Do T. Rabczuk H. Nguyen-Xuan 《Computer Methods in Applied Mechanics and Engineering》2010,199(45-48):3005-3027
A node-based smoothed finite element method (NS-FEM) was recently proposed for the solid mechanics problems. In the NS-FEM, the system stiffness matrix is computed using the smoothed strains over the smoothing domains associated with nodes of element mesh. In this paper, the NS-FEM is further extended to more complicated visco-elastoplastic analyses of 2D and 3D solids using triangular and tetrahedral meshes, respectively. The material behavior includes perfect visco-elastoplasticity and visco-elastoplasticity with isotropic hardening and linear kinematic hardening. A dual formulation for the NS-FEM with displacements and stresses as the main variables is performed. The von-Mises yield function and the Prandtl–Reuss flow rule are used. In the numerical procedure, however, the stress variables are eliminated and the problem becomes only displacement-dependent. The numerical results show that the NS-FEM has higher computational cost than the FEM. However the NS-FEM is much more accurate than the FEM, and hence the NS-FEM is more efficient than the FEM. It is also observed from the numerical results that the NS-FEM possesses the upper bound property which is very meaningful for the visco-elastoplastic analyses which almost have not got the analytical solutions. This suggests that we can use two models, NS-FEM and FEM, to bound the solution, and can even estimate the global relative error of numerical solutions. 相似文献
995.
Ikuro Mizumoto Daisuke Ikeda Tadashi Hirahata Zenta Iwai 《Control Engineering Practice》2010,18(2):168-176
This paper deals with the design of an adaptive PID control system with a parallel feedforward compensator (PFC) for discrete-time SISO systems and its application to water level control of a 3-tank system. The proposed method utilizes the characteristics of almost strict positive realness (ASPR) of the controlled plant. A conventional design scheme of a PFC which realizes an ASPR augmented controlled plant is also proposed. Further it is shown that the introduction of an internal model improves the control performance of the control system with the PFC. The effectiveness of the proposed method is confirmed through water level control experiments on a three-tank SISO system. 相似文献
996.
997.
998.
999.
基于ARM9的嵌入式指纹图像处理算法研究 总被引:1,自引:0,他引:1
随着指纹识别技术的发展和嵌入式系统的广泛应用,指纹识别逐渐向嵌入式方向发展。针对ARM9嵌入式开发平台,提出了一种适合于嵌入式系统的指纹图像预处理算法。该算法改进了传统的Gabor增强,消除了奇异点处脊线断裂和错连的问题,并采用了复合细化算法对二值图像进行细化以及细化去噪处理。实验表明,该算法具有良好的实用性和快速性,满足了嵌入式指纹识别系统的要求。 相似文献
1000.
为了满足人们在美工设计中对计算机国画艺术效果仿真的需求,研究和分析了水墨扩散LBE(lattice Boltzmann equation,网格波尔兹曼)算法,提出运用亮度决定水粒子的初始分布,用CMY粒子进行扩散模拟.通过对LBE算法进一步推导而提出疑问,并对扩散及受阻方程进行修正.使用Wintab 1.1压感设备接口完成用户压感数据的读取,借助图像处理函数库IPL98 2.0进行扩散实验数据结构和实验流程设计,实现了国画水墨扩散效果的模拟,证明了该方法的可行性和有效性. 相似文献