全文获取类型
收费全文 | 40337篇 |
免费 | 5294篇 |
国内免费 | 3236篇 |
专业分类
电工技术 | 4076篇 |
技术理论 | 1篇 |
综合类 | 4432篇 |
化学工业 | 3789篇 |
金属工艺 | 1036篇 |
机械仪表 | 2068篇 |
建筑科学 | 2875篇 |
矿业工程 | 895篇 |
能源动力 | 1091篇 |
轻工业 | 1950篇 |
水利工程 | 840篇 |
石油天然气 | 1615篇 |
武器工业 | 629篇 |
无线电 | 5405篇 |
一般工业技术 | 3753篇 |
冶金工业 | 1842篇 |
原子能技术 | 576篇 |
自动化技术 | 11994篇 |
出版年
2024年 | 169篇 |
2023年 | 521篇 |
2022年 | 1018篇 |
2021年 | 1161篇 |
2020年 | 1436篇 |
2019年 | 1352篇 |
2018年 | 1184篇 |
2017年 | 1582篇 |
2016年 | 1747篇 |
2015年 | 1849篇 |
2014年 | 2489篇 |
2013年 | 2886篇 |
2012年 | 2878篇 |
2011年 | 3035篇 |
2010年 | 2289篇 |
2009年 | 2431篇 |
2008年 | 2317篇 |
2007年 | 2725篇 |
2006年 | 2561篇 |
2005年 | 2108篇 |
2004年 | 1715篇 |
2003年 | 1610篇 |
2002年 | 1389篇 |
2001年 | 1187篇 |
2000年 | 1012篇 |
1999年 | 753篇 |
1998年 | 604篇 |
1997年 | 536篇 |
1996年 | 403篇 |
1995年 | 330篇 |
1994年 | 276篇 |
1993年 | 226篇 |
1992年 | 162篇 |
1991年 | 152篇 |
1990年 | 108篇 |
1989年 | 94篇 |
1988年 | 65篇 |
1987年 | 68篇 |
1986年 | 52篇 |
1985年 | 55篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 28篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1964年 | 12篇 |
1956年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Stefan Turek Ludmila Rivkind Jaroslav Hron Roland Glowinski 《Journal of scientific computing》2006,28(2-3):533-547
In [Turek (1996). Int. J. Numer. Meth. Fluids
22, 987–1011], we had performed numerical comparisons for different time stepping schemes for the incompressible Navier–Stokes equations. In this paper, we present the numerical analysis in the context of the Navier–Stokes equations for a modified time-stepping θ-scheme which has been recently proposed by Glowinski [Glowinski (2003). In: Ciarlet, P. G., and Lions, J. L. (eds.), Handbook of Numerical Analysis, Vol. IX, North-Holland, Amsterdam, pp. 3–1176]. Like the well-known classical Fractional-Step-θ-scheme which had been introduced by Glowinski [Glowinski (1985). In Murman, E. M. and Abarbanel, S. S. (eds.), Progress and Supercomputing in Computational Fluid Dynamics, Birkh?user, Boston MA; Bristeau et al. (1987). Comput. Phys. Rep. 6, 73–187], too, and which is still one of the most popular time stepping schemes, with or without operator splitting techniques, this new scheme consists of 3 substeps with nonequidistant substepping to build one macro time step. However, in contrast to the Fractional-Step-θ-scheme, the second substep can be formulated as an extrapolation step for previously computed data only, and the two remaining substeps look like a Backward Euler step so that no expensive operator evaluations for the right hand side vector with older solutions, as for instance in the Crank–Nicolson scheme, have to be performed. This modified scheme is implicit, strongly A-stable and second order accurate, too, which promises some advantageous behavior, particularly in implicit CFD simulations for the nonstationary Navier–Stokes equations. Representative numerical results, based on the software package FEATFLOW [Turek (2000). FEATFLOW Finite element software for the incompressible Navier–Stokes equations: User Manual, Release 1.2, University of Dortmund] are obtained for typical flow problems with benchmark character which provide a fair rating of the solution schemes, particularly in long time simulations.Dedicated to David Gottlieb on the occasion of his 60th anniversary 相似文献
82.
83.
Delevoye-Turrell Yvonne; Giersch Anne; Wing Alan M.; Danion Jean-Marie 《Canadian Metallurgical Quarterly》2007,116(1):56
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
SD2300是兴威帆电子公司生产的一种新型高精度实时时钟芯片。TMS320F2812是TI公司最新推出的DSP芯片,该芯片广泛地运用于测控和控制场合。文中给出了基于SD2300和TMS320F2812的时钟输入、低功耗“软件时间锁”的硬件和软件设计方法。 相似文献
85.
86.
RT-AGVS是物流管理中十分重要的课题,车辆位置监测网是其重要的组成部分。本文详细介绍了一个基于单片机系统的车辆位置实时监测网,本监测网设计先进,性能价格比高,它的设计方法和技术对其他许多领域有借鉴作用。 相似文献
87.
A neural network model for fault detection in conjunction with a programmable logic controller 总被引:2,自引:0,他引:2
This paper discusses the feasibility of using neural networks as a tool in the fault detection process. A neural network is integrated with a state language programmable logic controller, an important device in an automatic control system. Time series data related to time spent in a state is gathered and used as input into a neural network, for the purpose of identifying when a fault has occurred. A feedforward neural network is used to identify which (if any) of three types of faults may have occurred. Experimental results related to sensitivity and accuracy measures are presented. A brief review of related applications and research is also presented. 相似文献
88.
四种别藻蓝蛋白三聚体的时间分辨荧光光谱研究 总被引:6,自引:0,他引:6
研究了从Anabanavaribilis中提取的4种别藻蓝蛋白APCI,APCII,APCII及APCB三聚体的稳态光谱和皮秒荧光光谱。采用Monte-Carlo方法对瞬态荧光光谱进行拟合,实验结果表明:APCI荧光有两个带,其中第一个带位于662nm,有两个时间组分:35.8ps和1.67ns;第二个带位于680nm,有两个时间组分:34.2ps和1.64ns;APCII瞬态荧光位于660nm,有两个时间组分:20.4ps和1.64ns;APCII瞬态荧光位于660nm,有两个时间组分:23.8ps和1.76ns;APCB瞬态荧光有两个带,其中第一个带位于662nm,有两个时间组分:36.6ps和1.45ns;第二个带位于680nm,有两个时间组分:25.8ps和1.62ns。实验结果一方面说明了藻胆体核内4种别藻蓝蛋白形成能量传递的两条途径;另一方面瞬态荧光解叠结果揭示了APCI和APCB三聚体内能量传递的超快过程。 相似文献
89.
利用光学方法测量气体状态参数的关键在于确定气体折射率场的变化。光线通过稳定的非均匀折射率场时发生偏折,并且在强折射对称场中会产生交叉,使得条纹位移量的判读困难。本文首先分析了光线在轴对称折射率场中的偏折效应,在此基础上,给出了一种利用成像透镜对强折射轴对称场中折射率的干涉再现方法。该方法与其它方法相比较能够精确地确定折射率n(r)的值。 相似文献
90.
A method is proposed for analytical estimation of the high-temperature long-term strength of structures with material discontinuities, which are stress raisers. We consider the processes involving the formation of diffusion pores. Diffusion processes in metals are strongly enhanced with increasing temperature and stresses. 相似文献