全文获取类型
收费全文 | 3530篇 |
免费 | 203篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 51篇 |
综合类 | 3篇 |
化学工业 | 983篇 |
金属工艺 | 76篇 |
机械仪表 | 87篇 |
建筑科学 | 140篇 |
矿业工程 | 6篇 |
能源动力 | 155篇 |
轻工业 | 267篇 |
水利工程 | 28篇 |
石油天然气 | 3篇 |
无线电 | 361篇 |
一般工业技术 | 708篇 |
冶金工业 | 183篇 |
原子能技术 | 32篇 |
自动化技术 | 656篇 |
出版年
2023年 | 25篇 |
2022年 | 69篇 |
2021年 | 106篇 |
2020年 | 55篇 |
2019年 | 76篇 |
2018年 | 86篇 |
2017年 | 91篇 |
2016年 | 121篇 |
2015年 | 105篇 |
2014年 | 149篇 |
2013年 | 242篇 |
2012年 | 226篇 |
2011年 | 286篇 |
2010年 | 183篇 |
2009年 | 221篇 |
2008年 | 229篇 |
2007年 | 168篇 |
2006年 | 181篇 |
2005年 | 124篇 |
2004年 | 111篇 |
2003年 | 103篇 |
2002年 | 121篇 |
2001年 | 55篇 |
2000年 | 53篇 |
1999年 | 50篇 |
1998年 | 68篇 |
1997年 | 72篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 38篇 |
1993年 | 26篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有3739条查询结果,搜索用时 15 毫秒
111.
This work is the first part of an overall project the aim of which is the development of general mix design rules for concrete containing different kinds of mineral admixtures. The separation of the different physical effects responsible for the modification of cement hydration, when chemically inert quartz powders are used in mortars, is presented. The phenomenological approach, based on semi-adiabatic calorimetry, is only associated with first-order phenomena, and the study excludes the complex physicochemical details involved in the chemistry of cement. The results, obtained for a wide range of fineness (between 180 and 2000 m2/kg) and replacement rates (up to 75%), show that short-term degrees of hydration in mortars containing a chemically inert mineral admixture (quartz) are always higher than for a reference mortar. This study confirms that cement hydration is enhanced by inert mineral admixtures. The two main physical effects responsible for the modification of the hydration of cement are identified as the dilution effect and heterogeneous nucleation. The dilution effect of the cement is highlighted with a coarse mineral admixture. The heterogeneous nucleation effect, although it increases with fineness of mineral admixtures, presents an optimum depending on the replacement rate. In the following part of this work, these results will be used for the development of an empirical model allowing us to quantify both physical effects. 相似文献
112.
Wim Kellens Wouter Vanneuville Els Verfaillie Ellen Meire Pieter Deckers Philippe De Maeyer 《Water Resources Management》2013,27(10):3585-3606
This paper presents the state of the art of flood risk management in Flanders, a low-lying region in the northern part of Belgium which is vulnerable to flooding. Possible flood hazard sources are not only the many rivers which pass through the Flemish inland, but also the North Sea, which is sensitive to the predicted sea level rise and which can affect large parts of the Flemish coastal area. Due to the expected increase in flood risks in the 21st century, the Flemish government has changed its flood management strategy from a flood control approach to a risk-based approach. Instead of focusing on protection against a certain water level, the objective now is to assure protection against the consequences of a flood, while considering its probability. In the first part, attention is given to the reasoning and functioning of the risk-based approach. Recent improvements to the approach are discussed, as well as the GIS-implementation of the entire model. The functioning of the approach is subsequently demonstrated in two case studies. The second part of the paper discusses future challenges for the flood risk management in Flanders. The driving force behind these challenges is the European Directive on the assessment and management of flood risks, which entered into force in 2007. The Flemish implementation of the directive is discussed and situated in the European landscape. Finally, attention is given to the communication of flood risks to the general public, since the “availability” of flood risk management plans is among the requirements of the EU Floods Directive. 相似文献
113.
Laurent Dusoulier Samuel Denis Philippe Vanderbemden Michel Dirickx Marcel Ausloos Rudi Cloots Bénédicte Vertruyen 《Journal of Materials Science》2006,41(24):8109-8114
YBa2Cu3O7-x
thick films have been realised by the Electrophoretic Deposition method (EPD). The influence of several parameters (powder and iodine concentrations in the suspension, applied voltage and deposition time) on the EPD process has been studied by measuring the conductivity of the suspension and the amount of YBa2Cu3O7-x
particles deposited on the electrode. Superconducting coatings onto silver substrates have been produced by a multilayer process during different deposition times. The highest critical current density value of these coatings measured by the four-point probe method is about 103 A/cm2 (77 K), in a suitable range for magnetic shielding applications. 相似文献
114.
Complex system reliability modelling with Dynamic Object Oriented Bayesian Networks (DOOBN) 总被引:2,自引:2,他引:2
Nowadays, the complex manufacturing processes have to be dynamically modelled and controlled to optimise the diagnosis and the maintenance policies. This article presents a methodology that will help developing Dynamic Object Oriented Bayesian Networks (DOOBNs) to formalise such complex dynamic models. The goal is to have a general reliability evaluation of a manufacturing process, from its implementation to its operating phase. The added value of this formalisation methodology consists in using the a priori knowledge of both the system's functioning and malfunctioning. Networks are built on principles of adaptability and integrate uncertainties on the relationships between causes and effects. Thus, the purpose is to evaluate, in terms of reliability, the impact of several decisions on the maintenance of the system. This methodology has been tested, in an industrial context, to model the reliability of a water (immersion) heater system. 相似文献
115.
This paper introduces an algorithm for finding eukaryotic genes. It particularly addresses the problem of orphan genes, that is of genes that cannot, based on homology alone, be connected to any known gene family and to which it is therefore not possible to apply traditional gene finding methods. To the best of our knowledge, this is also the first algorithm that attempts to compare in an exact way two DNA sequences that contain both coding (i.e. exonic) and non-coding (i.e. intronic and, possibly, intergenic) parts. The comparison is performed following an algorithmical model of a gene that is as close as possible to the biological one (we consider in this paper the “one ORF, one gene” problem only). A gene is seen as a set of exons that are pieces of an assembly and are not independent. The algorithm is efficient enough: although the constants are higher than for usual sequence comparison, its time complexity is proportional to the product of the sequences lengths while its space complexity scales linearly with the length of the smallest sequence. 相似文献
116.
117.
H2 and H∞ control design methodologies are known to be efficient to deal with multivariable control problems. However, most of them do not take explicitly the parametric uncertainties into account. This paper proposes a low parametric sensitivity H2 control design method as an alternative to µ‐synthesis or robust H2 control design. In addition to the standard H2 criterion, the H2 norm of the parametric sensitivity function is introduced in order to improve the robustness of the resulting controller. Unfortunately, this problem is a difficult one. Its equivalence to structured feedback H2 control problem will be shown. The underlying BMI will be solved by making use of an iterative LMI procedure. Two examples will illustrate the interest of the approach. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
118.
The atomic force microscope (AFM) is a powerful tool for the measurement of forces at the micro/nano scale when calibrated cantilevers are used. Besides many existing calibration techniques, the thermal calibration is one of the simplest and fastest methods for the dynamic characterization of an AFM cantilever. This method is efficient provided that the Brownian motion (thermal noise) is the most important source of excitation during the calibration process. Otherwise, the value of spring constant is underestimated. This paper investigates noise interference ranges in low stiffness AFM cantilevers taking into account thermal fluctuations and acoustic pressures as two main sources of noise. As a result, a preliminary knowledge about the conditions in which thermal fluctuations and acoustic pressures have closely the same effect on the AFM cantilever (noise interference) is provided with both theoretical and experimental arguments. Consequently, beyond the noise interference range, commercial low stiffness AFM cantilevers are calibrated in two ways: using the thermal noise (in a wide temperature range) and acoustic pressures generated by a loudspeaker. We then demonstrate that acoustic noises can also be used for an efficient characterization and calibration of low stiffness AFM cantilevers. The accuracy of the acoustic characterization is evaluated by comparison with results from the thermal calibration. 相似文献
119.
120.
Challita Stphanie Korte Fabian Erbel Johannes Zalila Faiez Grabowski Jens Merle Philippe 《Software and Systems Modeling》2021,20(5):1609-1631
Software and Systems Modeling - With the advent of cloud computing, different cloud providers with heterogeneous cloud services (compute, storage, network, applications, etc.) and their related... 相似文献