全文获取类型
收费全文 | 3933篇 |
免费 | 231篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 170篇 |
综合类 | 52篇 |
化学工业 | 788篇 |
金属工艺 | 109篇 |
机械仪表 | 154篇 |
建筑科学 | 93篇 |
矿业工程 | 19篇 |
能源动力 | 141篇 |
轻工业 | 201篇 |
水利工程 | 31篇 |
石油天然气 | 30篇 |
武器工业 | 8篇 |
无线电 | 813篇 |
一般工业技术 | 675篇 |
冶金工业 | 372篇 |
原子能技术 | 29篇 |
自动化技术 | 545篇 |
出版年
2024年 | 7篇 |
2023年 | 27篇 |
2022年 | 62篇 |
2021年 | 127篇 |
2020年 | 77篇 |
2019年 | 64篇 |
2018年 | 87篇 |
2017年 | 93篇 |
2016年 | 95篇 |
2015年 | 114篇 |
2014年 | 176篇 |
2013年 | 323篇 |
2012年 | 261篇 |
2011年 | 266篇 |
2010年 | 216篇 |
2009年 | 204篇 |
2008年 | 205篇 |
2007年 | 195篇 |
2006年 | 187篇 |
2005年 | 108篇 |
2004年 | 108篇 |
2003年 | 105篇 |
2002年 | 82篇 |
2001年 | 63篇 |
2000年 | 65篇 |
1999年 | 68篇 |
1998年 | 152篇 |
1997年 | 108篇 |
1996年 | 83篇 |
1995年 | 53篇 |
1994年 | 68篇 |
1993年 | 55篇 |
1992年 | 49篇 |
1991年 | 32篇 |
1990年 | 36篇 |
1989年 | 35篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4230条查询结果,搜索用时 281 毫秒
991.
In this study, a quantitative approach is proposed to understand the effect of the accelerating voltage and the probe current on the physical resolution of EBSD. The accelerating voltage was varied from 5 to 30kV and probe currents of 1, 10, and 40nA were selected. The lateral, longitudinal, and depth resolutions at 10kV and 1nA were 34.5, 44.7, and 46nm for copper, respectively. When the accelerating voltage was in the range of 5-20kV, the ratio of the longitudinal to the lateral resolution was below the theoretical ratio of 2.9. Considering the channeling effect, the best physical depth resolution of 38nm was achieved at 5kV and 10nA. The physical depth resolution in an EBSD measurement is much larger due to the channel effect than that obtained without considering this effect. 相似文献
992.
Investigation of the friction effect at pin joints for the five-point double-toggle clamping mechanisms of injection molding machines 总被引:1,自引:0,他引:1
In this study, an analytical formulation for the necessary thrust of the crosshead of the five-point double-toggle clamping mechanism during real-mold clamping operation is proposed in order to investigate the effect of the friction at pin joints. The friction is considered to be a Coulomb friction. The inertia effects are not considered.Numerical examples are studied for different values of coefficient of friction to investigate the effects of friction at pin joints. In order to estimate the kinetic friction coefficient at pin joints, the motor torques required for real-mold clamping obtained by the present study are adjusted by using different values of coefficient of friction and mechanical efficiency to fit the experimental data. 相似文献
993.
A fast multigrid approach is presented for the analysis of thermal elastohydrodynamic lubrication (EHL) under rolling/sliding circular contacts at high loads and high slip ratios with low computing time on a personal computer. This fast solver combines directiteration, multigrid, Newton-Raphson, Gauss-Seidel iteration, and multilevel multi-integration methods into one working environment that can reduce the computational complexity from O(n3 to O(nlnn) for the thermal EHL problem under rolling/sliding circular contacts. Since the couped Reynolds and energy equations are simultaneously solved by the Newton-Raphson scheme, the iteration for the convergence solution is less than those of the classical approach. Results show that thermal effects on the pressure profile and film thickness are significant for a wide range of loads, speeds and slip ratios. The maximum midfilm and surface temperature rise in the Hertzian contact region increases with increasing slip ratio, dimensionless speed, and load. The minimum film thickness decreases with increasing load and slip ratio, and decreasing dimensionless speed. 相似文献
994.
Chung-Feng Jeffrey Kuo Chih-Hui Hsu Cheng-Chih Tsai 《The International Journal of Advanced Manufacturing Technology》2007,32(7-8):757-763
This paper is concerned with the topics in the speed control of a permanent magnet synchronous motor (PMSM). First, the vector
control scheme in the synchronously rotating reference frame is used to formulate the PMSM model as the system plant. Then,
the modern control theory using a sliding mode with fuzzy controller is presented to design the corresponding closed-loop
system and Matlab/Simulink software is used for computer simulation. The original PMSM is stable, sluggish with large overshoot
deficiency. It can be shown that the proposed fuzzy sliding-mode controller not only can delete the overshoot problem and
achieve very good tracking performance without zero steady-state errors, but can also obtain good robustness to system parameter
uncertainty. This proposed fuzzy-sliding mode controller for PMSM can be applied to the positioning control of the robot arms
to suppress unnecessary vibrations. For assembly lines, this proposed controller can be used to obtain fast tracking ability,
less steady-state errors, and robustness for different velocity movements. 相似文献
995.
C.-L. Kuo J.-D. Huang H.-Y. Liang J.-D. Huang 《The International Journal of Advanced Manufacturing Technology》2003,21(10-11):796-800
A fabrication technique for 3D metal microstructures using hybrid process integrated micromachining and welding on a workstation is described in the paper. The system uses a micro-EDM (micro electro-discharge machining) process to fabricate microparts, and Nd-YAG laser welding to microassemble these microparts precisely. A diverse pattern of 3D metal microstructures or micromoulds can be attained via further machining procedures controlled by a CAD/CAM path after assembling. Since the product is completed in one integrated manufacturing process, some particular problems resulting from their small dimensions can be overcome, e.g. their high failure sensitivity, and the required micro-precision in the microassembly process. Using these procedures, diverse patterns, and high aspect ratios and high joint strength microstructures can be created precisely. To illustrate the microassembly strategies and procedures, a diverse pin–plate metal microstructure has been used and discussed in the study. It requires that the perpendicular tolerance between pin and plate, and the parallel tolerance between pins are good, and the twisting strength at the joint is strong. A diverse feature on the top of the pin was then further machined as a square, or hollow construction having an equiangular partition. 相似文献
996.
Yi-Cherng Yeh Yau-Hwaug Kuo Deh-Shiu Hsu 《Computer-Aided Civil and Infrastructure Engineering》1992,7(3):223-233
Abstract: Debugging of the input data of a structural analysis program is a troublesome task which is heavily dependent on empirical knowledge. The paper describes an effort that applies machine learning to build an expert system for debugging faults in structural analysis program input data. ID3 decision tree induction algorithm is employed to build the automatic learning mechanism. This method Oflkrs an attractive potential for knowledge acquisition in the civil engineering domain in which expertise plays a dominant role. This paper is novel in at least three aspects: (1) machine learning is employed to build expert systems automatically; (2) a novel impurity function is proposed for splitting the decision tree; (3) a formulated comparison is proposed for evaluating learning results. 相似文献
997.
Since independence in 1965, housing conditions in the city‐state of Singapore, with a population of 2.6 million in 1988, have improved considerably. Much of the credit for this must be attributed to the government's policy of building homes for the lower income groups. One objective of the housing policy is 100 per cent home ownership for public housing. In pursuing this policy the political and social aspects are often emphasised. This paper attempts an economic evaluation of the 100 per cent home ownership target. It examines the demand and supply side policies that are employed to achieve the target. In analysing the economic implications of the policy, it is observed that such a policy distorts household expenditure, leads to overconsumption of housing and results in a thinner rental market and constrains tenure choice. These economic losses need to be recognised even while accepting the political and social importance of the policy. 相似文献
998.
Daniel Y. Chao Ting‐Yu Chen Jiun‐Ting Chen Kuo‐Chiang Wu 《Asian journal of control》2012,14(1):278-283
This study proposes a new approach that recovers the system from deadlock states to its former live states, and reaches the same number of states as the original uncontrolled model by adding monitors (and control arcs) with no new problematic siphons. We further propose a lossless approach by coloring some arcs to avoid the material loss. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
999.
1000.