全文获取类型
收费全文 | 60811篇 |
免费 | 7764篇 |
国内免费 | 5255篇 |
专业分类
电工技术 | 5169篇 |
技术理论 | 14篇 |
综合类 | 7891篇 |
化学工业 | 3554篇 |
金属工艺 | 2159篇 |
机械仪表 | 3442篇 |
建筑科学 | 12045篇 |
矿业工程 | 1840篇 |
能源动力 | 1342篇 |
轻工业 | 1978篇 |
水利工程 | 1341篇 |
石油天然气 | 2811篇 |
武器工业 | 587篇 |
无线电 | 7295篇 |
一般工业技术 | 5123篇 |
冶金工业 | 1182篇 |
原子能技术 | 525篇 |
自动化技术 | 15532篇 |
出版年
2024年 | 237篇 |
2023年 | 866篇 |
2022年 | 1531篇 |
2021年 | 1778篇 |
2020年 | 1909篇 |
2019年 | 1632篇 |
2018年 | 1571篇 |
2017年 | 2031篇 |
2016年 | 2233篇 |
2015年 | 2610篇 |
2014年 | 4127篇 |
2013年 | 3677篇 |
2012年 | 4624篇 |
2011年 | 5050篇 |
2010年 | 4112篇 |
2009年 | 4084篇 |
2008年 | 4085篇 |
2007年 | 4656篇 |
2006年 | 3992篇 |
2005年 | 3231篇 |
2004年 | 2738篇 |
2003年 | 2210篇 |
2002年 | 1937篇 |
2001年 | 1590篇 |
2000年 | 1366篇 |
1999年 | 1108篇 |
1998年 | 883篇 |
1997年 | 620篇 |
1996年 | 606篇 |
1995年 | 536篇 |
1994年 | 459篇 |
1993年 | 328篇 |
1992年 | 303篇 |
1991年 | 175篇 |
1990年 | 168篇 |
1989年 | 163篇 |
1988年 | 98篇 |
1987年 | 73篇 |
1986年 | 60篇 |
1985年 | 65篇 |
1984年 | 47篇 |
1983年 | 40篇 |
1982年 | 43篇 |
1981年 | 31篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1975年 | 8篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Experiments were carried out to investigate the characteristics of oil-gas flow in a horizontal pipe on a large scale (with the inner diameter D = 125 mm). With the experimental data, the flow patterns were presented. Through the analyses for the flow regime transition, it was found that there was a critical superficial velocity of liquid phase for the flow regime transiting from stratified flow to slug flow. The slug flow could not occur until the superficial velocity of liquid phase was higher than the critical velocity. For the flow pattern transiting from stratified to slug flow, the transmitting velocity of gas phase decreases with the augmentation of superficial velocity of liquid phase. On the basis of the experiments, numerical simulations of different flow patterns and their transitions were performed with the use of the Volume Of Fluid (VOF) technique. The results of the computations are shown to match well with the measured data in the experiments. 相似文献
92.
J. L. Barron R. E. Mercer X. Chen P. Joe 《International journal of imaging systems and technology》2005,15(3):189-198
We present local least squares and regularization frameworks for computing 3D velocity (3D optical flow) from 3D radial velocity measured by a Doppler radar. We demonstrate the performance of our algorithms quantitatively on synthetic radial velocity data and qualitatively on real radial velocity data, obtained from the Doppler radar at Kurnell Radar station, Botany Bay, New South Wales, Australia. Radial velocity can be used to predict the future positions of storms in sequences of Doppler radar datasets.© 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 189–198, 2005 相似文献
93.
Many problems consist in splitting a set of objects into different groups so that each group verifies some properties. In practice, a partitioning is often encoded by an array mapping each object to its group numbering. In fact, the group number of an object does not really matter, and one can simply rename each group to obtain a new encoding. That is what we call the symmetry of the search space in a partitioning problem. This property may be prejudicial for optimization methods such as evolutionary algorithms (EA) which require some diversity during the search. 相似文献
94.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
95.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
96.
Lie‐Fern Hsu 《Quality and Reliability Engineering International》2007,23(2):269-272
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
97.
A 320×240 CMOS image sensor is demonstrated,which is implemented by a standard 0.6 μm 2P2M CMOS process.For reducing the chip area,each 2×2-pixel block shares a sample/hold circuit,analog-to-digital converter and 1-b memory.The 2×2 pixel pitch has an area of 40 μm×40 μm and the fill factor is about 16%.While operating at a low frame rate,the sensor dissipates a very low power by power-management circuit making pixel-level comparators in an idle state.A digital correlated double sampling,which eliminates fixed pattern noise,improves SNR of the sensor, and multiple sampling operations make the sensor have a wide dynamic range. 相似文献
98.
动态多目标决策问题的灰色分析方法 总被引:2,自引:0,他引:2
将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形,引入局部理想最优效果和整体理想最优效果的概念,提出一种新型的动态多目标决策问题的灰色关联模型,并通过算例说明该方法的合理可行性。 相似文献
99.
D. Roy 《International journal for numerical methods in engineering》2004,61(5):764-790
Sample pathwise numerical integration of noise-driven engineering dynamical systems cannot generally be performed beyond a limited level of accuracy, especially when the noise processes are modelled using (filtered) white noises. Recently, a locally transversal linearization (LTL) strategy has been proposed by the author (Proc Roy Soc London A 2001; 457 :539–566) for direct integration of deterministic and stochastic non-linear dynamical systems. The present effort is focussed on a host of extensions along with detailed theoretical error analyses of the linearization approach, especially as applied to problems in non-linear stochastic engineering dynamics. Thus, to begin with, estimates of local and global error orders in the basic LTL scheme are obtained separately for the displacement and velocity vectors when the system is driven either by a set of additive noises or by an arbitrary combination of (independently evolving) additive and multiplicative noises. Following this, a new family of higher-order LTL schemes is proposed in order to improve upon the basic LTL method and the associated error orders are established. A stepwise implementation of the lower- and higher-order versions of the LTL method, along with certain computational aspects, is also outlined. The proposed schemes are numerically illustrated, to a limited extent, for a single degree-of-freedom (SDOF) and a two degree-of-freedom (TDOF) non-linear engineering systems under additive and/or multiplicative white noise excitations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
100.