全文获取类型
收费全文 | 40173篇 |
免费 | 4523篇 |
国内免费 | 3580篇 |
专业分类
电工技术 | 2137篇 |
技术理论 | 2篇 |
综合类 | 3252篇 |
化学工业 | 1895篇 |
金属工艺 | 1203篇 |
机械仪表 | 2595篇 |
建筑科学 | 2272篇 |
矿业工程 | 1687篇 |
能源动力 | 1100篇 |
轻工业 | 883篇 |
水利工程 | 1519篇 |
石油天然气 | 3019篇 |
武器工业 | 488篇 |
无线电 | 3993篇 |
一般工业技术 | 2464篇 |
冶金工业 | 1450篇 |
原子能技术 | 338篇 |
自动化技术 | 17979篇 |
出版年
2024年 | 286篇 |
2023年 | 857篇 |
2022年 | 1485篇 |
2021年 | 1570篇 |
2020年 | 1528篇 |
2019年 | 1203篇 |
2018年 | 1116篇 |
2017年 | 1322篇 |
2016年 | 1558篇 |
2015年 | 1510篇 |
2014年 | 2440篇 |
2013年 | 2157篇 |
2012年 | 2559篇 |
2011年 | 2974篇 |
2010年 | 2122篇 |
2009年 | 2189篇 |
2008年 | 2328篇 |
2007年 | 2739篇 |
2006年 | 2524篇 |
2005年 | 2331篇 |
2004年 | 2031篇 |
2003年 | 1859篇 |
2002年 | 1412篇 |
2001年 | 1133篇 |
2000年 | 865篇 |
1999年 | 759篇 |
1998年 | 586篇 |
1997年 | 497篇 |
1996年 | 425篇 |
1995年 | 381篇 |
1994年 | 278篇 |
1993年 | 197篇 |
1992年 | 145篇 |
1991年 | 132篇 |
1990年 | 104篇 |
1989年 | 99篇 |
1988年 | 76篇 |
1987年 | 54篇 |
1986年 | 47篇 |
1985年 | 46篇 |
1984年 | 42篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 40篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 32篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
22.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
23.
A new type of a single-axis azimuthal tracker is presented. The novel feature of this tracker is the ability to move the collector’s plane in two directions through a special support structure. This structure consists of a sliding mechanism on the central axis and a curved window on the cylindrical surface coaxial to the central axis. Consequently, the proposed novel heliotrope behaves similarly to a two-axis tracker. Two different windows designed on the cylindrical surface may be used to provide very high efficiencies throughout a year. Several performance measurements have been conducted on this novel tracker, a polar tracker and the reference two-axis tracker. Pyranometers, appropriately calibrated, were installed on all three systems to record the global incoming irradiance on the collector’s plane. It is shown that the new tracker system can be very efficient since its plane intercepts, at least, 98% of the insolation with respect to a two-axis tracker. The proposed system can be utilized in solar-related applications (photovoltaic or thermal). 相似文献
24.
说明了在异步串行通信(RS-232)的工作方式下,对所接收的数据进行接收、处理,丢弃乱码,并进行保存的可靠方法,并给出了相关的VC 语言程序. 相似文献
25.
Jost John T.; Glaser Jack; Kruglanski Arie W.; Sulloway Frank J. 《Canadian Metallurgical Quarterly》2003,129(3):383
A meta-analysis by J. T. Jost, J. Glaser, A. W. Kruglanski, and F. J. Sulloway (2003) concluded that political conservatism is partially motivated by the management of uncertainty and threat. In this reply to J. Greenberg and E. Jonas (2003), conceptual issues are clarified, numerous political anomalies are explained, and alleged counterexamples are incorporated with a dynamic model that takes into account differences between "young" and "old" movements. Studies directly pitting the rigidity-of-the-right hypothesis against the ideological extremity hypothesis demonstrate strong support for the former. Medium to large effect sizes describe relations between political conservatism and dogmatism and intolerance of ambiguity; lack of openness to experience; uncertainty avoidance; personal needs for order, structure, and closure; fear of death; and system threat. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
The dynamic flexibility (DF) and improved dynamic flexibility (IDF) methods can be applied to extract constrained structural modes from free-free modal test data. The residual flexibility method is also good for boundaries of constrained structure with rigid supports. Under elastic support boundary conditions both the DF and residual flexibility methods cannot produce accurate results. This paper expands the previously published IDF method to become a more general approach for structural design engineers. A new method called the general dynamic flexibility (GDF) method has been developed in this paper to extract constrained structural modes from free test data. The GDF method can always be applied as follows: (1) when the boundary support stiffness is very stiff, the GDF method can accurately obtain results from rigid support as by Liu et al. in 2001 and Zhang and Wei in 2003; (2) when the support stiffness is soft, the present method can produce results similar to those free-free modal parameters measured by hanging structures using rubber band; (3) when the support stiffness is zero, the method can reproduce true free-free modal parameters; and (4) when the support stiffness has any finite values, the GDF method can also achieve satisfactory results for engineering use. The algorithm included in the GDF method converges rapidly and is numerically stable in the analysis. This feature is very practical for many engineering applications for using the GDF method. 相似文献
27.
Awareness of the construction environment can be improved by automatic three-dimensional (3D) sensing and modeling of job sites in real time. Commercially available 3D modeling approaches based on range scanning techniques are capable of modeling static objects only, and thus cannot model dynamic objects in real time in an environment comprised of moving humans, equipment, and materials. Emerging prototype video range cameras offer an alternative by facilitating affordable, wide field of view, dynamic object tracking at frame rates better than 1?Hz (real time). This paper describes a methodology to model, detect, and track the position of static and moving objects in real time, based on data obtained from video range cameras. Experiments with this technology have produced results that indicate that video rate 3D data acquisition and analysis of construction environments can support effective modeling, detection, and tracking of project resources. This approach to job site awareness has inherent value and broad application. In combination with effective management practices and other sensing techniques, this technology has the potential to significantly improve safety on construction job sites. 相似文献
28.
R. Boroch J. Wiaranowski R. Mueller-Fiedler M. Ebert J. Bagdahn 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(1):2-12
The aim of this work is to characterize the strength properties of polycrystalline silicon (polysilicon) with the use of tensile and bending test specimens. The strength of thin polysilicon films with different geometry, size and stress concentrations has been measured and correlated with the effective size of the specimen and its stress distribution. The test results are evaluated using a probabilistic strength approach based on the weakest link theory with the use of STAU software. The use of statistic methods of strength prediction of polysilicon test structures with a complex geometry and loading based on test values for standard material tests specimen has been evaluated. 相似文献
29.
Dragan Simić Svetlana Simić 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(12):1185-1192
A concept of business intelligent system for financial prediction is considered in this paper. It provides data needed for
fast, precise and good business decision support to all levels of management. The aim of the project is the development of
a new online analytical processing oriented on case-based reasoning (CBR) where a previous experience for every new problem
is taken into account. Methodological aspects have been tested in practice as a part of the management information system
development project of “Novi Sad Fair”. A case study of an improved application of CBR in prediction of future payments is
discussed in the paper.
This paper is originally presented at The International Conference on Hybrid Information Technology 2006, at the special session
on “Intelligent Information Systems for Financial Engineering”, November 2006 in Cheju Island, Korea. 相似文献
30.
本文在分析CIMS环境中数据模式冲关类型的基础上,提出一种互连数据库系统模式结构,论述了在异构数据库集成中解决模式冲突的基本方法.在这种方法体系中,不需要建立整个企业的全局数据模式,各局部DBA以简单的方式定义应用所需的模式变换,系统根据这种定义自动完成各种转换,使用户看到的模式和数据结果与应用要求的一致. 相似文献