全文获取类型
收费全文 | 13042篇 |
免费 | 2532篇 |
国内免费 | 2269篇 |
专业分类
电工技术 | 1041篇 |
技术理论 | 2篇 |
综合类 | 1423篇 |
化学工业 | 443篇 |
金属工艺 | 885篇 |
机械仪表 | 1298篇 |
建筑科学 | 280篇 |
矿业工程 | 265篇 |
能源动力 | 195篇 |
轻工业 | 369篇 |
水利工程 | 146篇 |
石油天然气 | 138篇 |
武器工业 | 127篇 |
无线电 | 1588篇 |
一般工业技术 | 694篇 |
冶金工业 | 291篇 |
原子能技术 | 36篇 |
自动化技术 | 8622篇 |
出版年
2024年 | 107篇 |
2023年 | 292篇 |
2022年 | 529篇 |
2021年 | 593篇 |
2020年 | 692篇 |
2019年 | 544篇 |
2018年 | 566篇 |
2017年 | 633篇 |
2016年 | 711篇 |
2015年 | 774篇 |
2014年 | 1034篇 |
2013年 | 982篇 |
2012年 | 1276篇 |
2011年 | 1338篇 |
2010年 | 1054篇 |
2009年 | 967篇 |
2008年 | 995篇 |
2007年 | 1103篇 |
2006年 | 779篇 |
2005年 | 636篇 |
2004年 | 500篇 |
2003年 | 389篇 |
2002年 | 309篇 |
2001年 | 239篇 |
2000年 | 173篇 |
1999年 | 143篇 |
1998年 | 89篇 |
1997年 | 76篇 |
1996年 | 58篇 |
1995年 | 48篇 |
1994年 | 46篇 |
1993年 | 28篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
M. Liess R. Hua K. Elsenaar 《The International Journal of Advanced Manufacturing Technology》2002,20(1):58-62
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability
owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional
forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers
and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial
off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce
standing-wave effects is also discussed. 相似文献
2.
《IIE Transactions》2007,39(9):879-898
We study an inventory system that consists of two demand classes. The orders in the first class need to be satisfied immediately, whereas the orders in the second class are to be filled in a given demand lead time. The two classes are also of different criticality. For this system, we propose a policy that rations the non-critical orders. Under a one-for-one replenishment policy with backordering and for Poisson demand arrivals for both classes, we first derive expressions for the service levels of both classes. The service level for the critical class is an approximation, whereas the service level for the non-critical class is exact. We then conduct a computational study to show that our approximation works reasonably, the benefits of rationing can be substantial, and the incorporation of demand lead time provides more value when the demand class with demand lead time is the critical class. The research is motivated by the spare parts service system of a major capital equipment manufacturer that faces two types of demand. For this company, the critical down orders need to be satisfied immediately, while the less critical maintenance orders can be satisfied after a fixed demand lead time. We conduct a case study with 64 representative parts and show that significant savings (as much as 14% on inventory on hand) are possible through incorporation of demand lead times and rationing. 相似文献
3.
4.
J. L. Díez J. L. Navarro A. Sala 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(10):973-983
In this work, simple modifications on the cost index of particular local-model fuzzy clustering algorithms are proposed in
order to improve the readability of the resulting models. The final goal is simultaneously providing local linear models (reasonably
close to the plant’s Jacobian) and clustering in the input space so that desirable characteristics (regarding final model
accuracy, and convexity and smoothness of the cluster membership functions) are improved with respect to other proposals in
literature. Some examples illustrate the proposed approach. 相似文献
5.
注塑件熔接缝结构,性能评价及影响因素 总被引:11,自引:2,他引:9
文章介绍了熔接缝形成的原因,接缝类型,接缝外观和断口形态特征以及接缝性能评价方法。分析了接缝类型,塑料材料性质,工艺参数和其它因素对接缝性能的影响。 相似文献
6.
Thomas L. Landers Melinda K. Beavers Malik Sadiq Don E. Stuart 《Computers & Industrial Engineering》1994,27(1-4):245-248
This paper describes an approach, conceptual framework, and software architecture for dynamic reconfiguration of the order picking system. The research and development project was sponsored by the Material Handling Research Center (MHRC), a National Science Foundation sponsored Cooperative Industry/University Research Center. The storage configuration is assumed to be an in-the-aisle order picking system in which stockkeeping units (SKUs) can occupy variable capacity storage locations and stock-splitting is allowed among zones (clusters). The product mix may include multiple product families with different life cycles, correlated demand within families and commonality of demand across families. 相似文献
7.
The paper considers a generalized discrete‐time order‐replacement model for a single unit system, which is subject to random failure when in operation. Two types of discrete randomized lead times are considered for a spare unit; one is for regular (preventive) order and another is for expedited (emergency) order. The model is formulated based on the discounted cost criterion. The underlying two‐dimensional optimization problem is reduced to a simple one‐dimensional one and then the optimal ordering policy for the spare unit is characterized under two extreme conditions: (i) unlimited inventory time and (ii) zero inventory time for the spare unit. A numerical example is used to determine the optimal spare‐ordering policy numerically and to examine the sensitivity of the model parameters. 相似文献
8.
Non-redundant data clustering 总被引:6,自引:6,他引:0
Data clustering is a popular approach for automatically finding classes, concepts, or groups of patterns. In practice, this
discovery process should avoid redundancies with existing knowledge about class structures or groupings, and reveal novel,
previously unknown aspects of the data. In order to deal with this problem, we present an extension of the information bottleneck
framework, called coordinated conditional information bottleneck, which takes negative relevance information into account by maximizing a conditional mutual information score subject to
constraints. Algorithmically, one can apply an alternating optimization scheme that can be used in conjunction with different
types of numeric and non-numeric attributes. We discuss extensions of the technique to the tasks of semi-supervised classification
and enumeration of successive non-redundant clusterings. We present experimental results for applications in text mining and
computer vision. 相似文献
9.
This paper presents the development of an optimization and a computer-simulation model to evaluate the process plans of a manufacturing center by analyzing the effect of tool failure on system performance. The GPSS/PC simulation program that is used in this study has been built with variables, functions and matrices so that many experiments could be conducted with the model. Sensitivity analysis is presented and the developed model has proven to be useful in determining optimum sequencing of parts for various operating policies. 相似文献
10.
The infiltration of compacted cubic BN (cBN) with molten aluminum has been investigated as a potential route for a cheap and easy method of manufacturing cBN/metal composites. CBN compacts have been infiltrated with molten Al at a temperature between 670 and 800 °C and pressure of 15 MPa in vacuum. At these temperatures no pronounced interactions between hexagonal and cubic BN with Al was observed, allowing the complete infiltration of cBN with 12 μm mean grain size. After infiltration at 800 °C, the temperature was increased without pressure to convert aluminum into borides and AlN. The hardness of the resulting materials depends on the content of hexagonal, cubic BN and the rate of conversion of Al into borides and AlN. The infiltration height of less than 1 mm obtained from infiltrating the 3 μm cBN powder green compacts gave a hardness of 22.0 ± 0.6 GPa after heat treatment. 相似文献