全文获取类型
收费全文 | 3228篇 |
免费 | 132篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 70篇 |
综合类 | 3篇 |
化学工业 | 706篇 |
金属工艺 | 107篇 |
机械仪表 | 86篇 |
建筑科学 | 49篇 |
矿业工程 | 6篇 |
能源动力 | 129篇 |
轻工业 | 149篇 |
水利工程 | 27篇 |
石油天然气 | 31篇 |
无线电 | 348篇 |
一般工业技术 | 702篇 |
冶金工业 | 499篇 |
原子能技术 | 40篇 |
自动化技术 | 431篇 |
出版年
2023年 | 46篇 |
2022年 | 63篇 |
2021年 | 100篇 |
2020年 | 112篇 |
2019年 | 79篇 |
2018年 | 95篇 |
2017年 | 120篇 |
2016年 | 103篇 |
2015年 | 79篇 |
2014年 | 113篇 |
2013年 | 259篇 |
2012年 | 121篇 |
2011年 | 175篇 |
2010年 | 144篇 |
2009年 | 146篇 |
2008年 | 146篇 |
2007年 | 136篇 |
2006年 | 105篇 |
2005年 | 73篇 |
2004年 | 69篇 |
2003年 | 57篇 |
2002年 | 62篇 |
2001年 | 44篇 |
2000年 | 49篇 |
1999年 | 47篇 |
1998年 | 113篇 |
1997年 | 85篇 |
1996年 | 56篇 |
1995年 | 61篇 |
1994年 | 69篇 |
1993年 | 30篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 29篇 |
1975年 | 13篇 |
1971年 | 9篇 |
排序方式: 共有3383条查询结果,搜索用时 15 毫秒
71.
Francis E. H. Tay Sumit Kanti Sikdar M. A. Mannan 《Journal of Materials Processing Technology》2002,120(1-3)
In many applications, topography represents the main external features of a surface. This paper describes the topography of the flank wear surface and also presents the relationship between the maximum flank wear and the topography parameters (roughness parameters) of the flank wear surface during the turning operation. A modern CNC lathe machine (Okuma LH35-N) was used for the machine turning operation. Three-dimensional surface roughness parameters of the flank wear surface were measured by a surface texture instrument (from Talysurf series) using surface topography software (Talymap). Based on the resulting experimental data, it is found that as the flank wear increases, the roughness parameters (sRa, sRq, and sRt) on the flank surface increase significantly. The greater the roughness value of the flank wear surface, the higher the friction of the tool on the workpiece and the greater the heat generation that will occur, thus ultimately causing tool failure. On the other hand, positive skewness (sRsk) indicates the presence of a small number of spikes on the flank surface of the cutting tool, which could quickly wear off during the machining process. 相似文献
72.
Naizhuo Zhao Tilottama Ghosh Nathan Allen Currit Christopher D. Elvidge 《Water Resources Management》2011,25(9):2241-2250
Global water resources are vulnerable to depletion due to the increasing demand of an ever-increasing human population. A
country’s water footprint is a measure of the total volume of water needed to produce the goods and services consumed by the
country, including water originating beyond its own borders. The water footprint can be a critical indicator of global water
resource use, but its practical application is hindered by a lack of comparable data across national boundaries. The purpose
of this article is to test the applicability of the nighttime imagery products produced by the Defense Meteorological Satellite
Program’s Operational Linescan System (DMSP-OLS) for the assessment of the global water footprint. To accomplish this purpose,
the average areal extent of nighttime lighting (lit area) is calculated from 1997 to 2001. Next, lit area is regressed on
the total water footprint for each country, as indicated by the Water Footprint Network (WFN), to estimate that country’s
total water footprint using nighttime imagery. Model residuals are analyzed at the national scale to understand the appropriateness
of nighttime imagery for assessing water consumption. Results indicate strong positive correlations between lit area and total
water footprint (TWF), domestic water withdrawal (DWW), and industrial water consumption (IWC) at the national scale. Overall,
the analyses reveal that the rate of agricultural water consumption to total water footprint (AWCR) and population density
can affect the precision of estimates when lit area is selected as a proxy to estimate water footprints. 相似文献
73.
Sandip Ghosh Sarit K. Das Goshaidas Ray 《International Journal of Control, Automation and Systems》2009,7(2):311-317
Adaptive stabilization of a class of linear systems with matched and unmatched uncertainties is considered in this paper.
The proposed controller indeed stabilizes the uncertain system for any positive values of its non-adaptive gain that may be
tuned to enhance dynamic response of system. The performance of uncertain system along with the Algebraic Riccati Equation
that arises from the adaptive stabilizing controller is now formulated as a multi-objective Linear Matrix Inequality optimization
problem. The decay rate and a factor governing the ultimate bound of the system states are considered to characterize the
closed loop system performance. Finally, the effectiveness of the proposed controller is illustrated via stabilizing a mass-spring
system.
Recommended by Editorial Board member Gang Tao under the direction of Editor Young Il Lee. The authors would like to thank
the reviewers for their valuable comments and suggestions that have improved the quality of this paper.
Sandip Ghosh received the B.E. in Electrical Engineering from Bengal Engineering College (D.U.), Howrah, and Master in Control System
Engineering from Jadavpur University, Kolkata, India, in 1999 and 2003 respectively. Presently he is pursuing the Ph.D. degree
at Indian Institute of Technology, Kharagpur, India. His research interests include adaptive control, robust control and control
of time-delay systems.
Sarit K. Das is a Professor of Electrical Engineering Department, Indian Institute of Technology, Kharagpur, India. He received the Ph.D.
degree in 1985 from the same department. His research interests include design of periodic controller, decoupling of multivariable
systems, modeling and robust control of complex systems.
Goshaidas Ray is a Professor of Electrical Engineering Department, Indian Institute of Technology, Kharagpur, India. He received the Ph.D.
degree in 1982 from Indian Institute of Technology Delhi, India. His research interests include modeling, estimation, model-based
control, intelligent control, robotic systems and distributed control systems. 相似文献
74.
Subir Kumar Ghosh Anil Maheshwari Sudebkumar Prasant Pal C. E. Veni Madhavan 《The Visual computer》1994,10(8):443-451
A polygonP is said to be apalm polygon if there exists a pointxP such that the Euclidean shortest path fromx to any pointyP makes only left turns or only right turns. The set of all such pointsx is called thepalm kernel. In this paper we propose an O(E) time algorithm for recognizing a palm polygonP, whereE is the size of the visibility graph ofP. The algorithm recognizes the given polygonP as a palm polygon by computing the palm kernel ofP. If the palm kernel is not empty,P is a palm polygon.The extended abstract of this paper was reported at the Second Canadian Conference in Computational Geometry, pp. 246–251, 1990 相似文献
75.
Experimentally the real and imaginary parts of the Fourier spectrum are separated and used to detect the nature of the object, i.e., whether the object is an odd or even function or a combination of both. A modified Twyman-Green setup is used for this purpose. This type of splitting of the object function into even and odd parts may become useful in different fields of image processing. As an application the same technique is used for accurate measurement of the grating frequency. 相似文献
76.
Kindergartens of age group 3-5 years, a distinct and small subgroup of Indian schoolchildren, need special emphasis on human factors. The paper presents the results of an anthropometric survey conducted on schoolchildren. These data, previously lacking in India, can be of benefit for the designers of kindergartens. A set of 81 different body dimensions was taken from a sample of 198 children of age group 3-4 years and 4.1-5 years. Simple anthropometric techniques were used to collect the data. Statistical analyses of the data have been presented in a tabular form for designers as well as for non-technical users. It is emphasized that such data have to be developed at the national level, including every ethnic group, or on a regional basis. Designers, manufacturers and importers of goods should have access to these data. 相似文献
77.
Adaptive relay co-ordination using a busbar splitting approach for a system integrity protection scheme 下载免费PDF全文
Power system faults can often result in excessively high currents. If sustained for a long time, such high currents can damage system equipment. Thus, it is desirable to operate the relays in the minimum possible time. In this paper, a busbar splitting approach is used for adaptive relay setting and co-ordination purposes for a system integrity protection scheme (SIPS). Whenever a fault occurs, the busbar splitting scheme splits a bus to convert a loop into a radial structure. The splitting schemes are chosen such that the net fault current is also reduced. Busbar splitting eliminates the dependency upon minimum breakpoints set (MBPS) and reduces the relay operating time, thus making it adaptive. The proposed methodology is incorporated into the IEEE 14-bus and IEEE 30-bus systems with single and multiple fault conditions. The modeling and simulation carried out in ETAP, and the results of the proposed busbar splitting-based relay co-ordination are compared with the MBPS splitting-based relay co-ordination. 相似文献
78.
Fatigue crack growth prediction in nuclear piping using Markov chain Monte Carlo simulation 下载免费PDF全文
R. Rastogi S. Ghosh A. K. Ghosh K. K. Vaze P. K. Singh 《Fatigue & Fracture of Engineering Materials & Structures》2017,40(1):145-156
In this paper, we present and demonstrate a methodology to improve probabilistic fatigue crack growth (FCG) predictions by using the concept of Bayesian updating using Markov chain Monte Carlo simulations. The methodology is demonstrated on a cracked pipe undergoing fatigue loading. Initial estimates of the FCG rate are made using the Paris law. The prior probability distributions of the Paris law parameters are taken from the tests on specimen made of the same material as that of pipe. Measured data on crack depth over number of loading cycles are used to update the prior distribution using the Markov chain Monte Carlo. The confidence interval on the predicted FCG rate is also estimated. In actual piping placed in a plant, the measured data can be considered equivalent to the data received from in-service inspection. It is shown that the proposed methodology improves the fatigue life prediction. The number of observations used for updating is found to leave a significant effect on the accuracy of the updated prediction. 相似文献
79.
The literature is replete with models that examine various aspects of cellular manufacturing (CM), such as optimisation of cell layouts. However, many firms may realise zero to marginal returns from CM. Given this uncertainty, the manager should first determine the value of CM to the firm before deploying it. Although traditional valuation models employing discounted cash flow analysis allow for uncertainty, they treat future investments as fixed when computing the investment’s present value. The real options (RO) logic of valuation allows the manager to exercise the option to invest in or abandon a project based on expected outcomes. Future investments are thus options. This paper presents an RO model for CM migration that addresses whether a firm should migrate to CM; and it prescribes the sequence of cell deployment, which has not been addressed in the literature. Our model is also much more transparent and accessible to practitioners, with an accompanying software tool for prospective users. Finally, we use simulation extensively to discover the drivers of the optimal cell deployment sequence. Our results show that there is a complex interplay between net present value, speed of cellularisation, inter-cell learning and volatility in terms of their influence on the cell sequence. 相似文献
80.
随着纳米技术的快速发展,大量的纳米碳管(CNTs)不可避免地释放到环境中。由于其较大的憎水性表面,CNTs与有机污染物和天然有机质(NOM)强烈地相互作用。综述了NOM存在下CNTs的环境行为,包括NOM对CNTs分散特性和吸附有机污染物特性的影响。着重论述了NOM的理化性质对CNTs分散的影响,"拉拉链"或"胶束包裹"是主要的分散机制。强调应该对不同分散机制下分散的CNTs与有机污染物的相互作用给予更多的关注,提出了目前在液相环境中直接测定CNTs表面积的新思路,并对今后的研究方向进行了展望。 相似文献