全文获取类型
收费全文 | 3205篇 |
免费 | 157篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 35篇 |
综合类 | 3篇 |
化学工业 | 838篇 |
金属工艺 | 58篇 |
机械仪表 | 85篇 |
建筑科学 | 95篇 |
矿业工程 | 35篇 |
能源动力 | 151篇 |
轻工业 | 391篇 |
水利工程 | 29篇 |
石油天然气 | 8篇 |
无线电 | 260篇 |
一般工业技术 | 436篇 |
冶金工业 | 368篇 |
原子能技术 | 32篇 |
自动化技术 | 542篇 |
出版年
2024年 | 10篇 |
2023年 | 42篇 |
2022年 | 104篇 |
2021年 | 150篇 |
2020年 | 98篇 |
2019年 | 81篇 |
2018年 | 102篇 |
2017年 | 90篇 |
2016年 | 108篇 |
2015年 | 79篇 |
2014年 | 148篇 |
2013年 | 212篇 |
2012年 | 208篇 |
2011年 | 213篇 |
2010年 | 167篇 |
2009年 | 129篇 |
2008年 | 162篇 |
2007年 | 132篇 |
2006年 | 92篇 |
2005年 | 85篇 |
2004年 | 63篇 |
2003年 | 46篇 |
2002年 | 55篇 |
2001年 | 45篇 |
2000年 | 41篇 |
1999年 | 39篇 |
1998年 | 66篇 |
1997年 | 48篇 |
1996年 | 47篇 |
1995年 | 45篇 |
1994年 | 29篇 |
1993年 | 40篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1977年 | 15篇 |
1972年 | 11篇 |
1944年 | 10篇 |
1943年 | 21篇 |
排序方式: 共有3366条查询结果,搜索用时 15 毫秒
31.
Reaction‐induced vitrification takes place in the network‐forming epoxy–amine system diglycidyl ether of bisphenol A (DGEBA) + methylenedianiline (MDA) when the glass‐transition temperature (Tg) rises above the cure temperature (Tcure). This chemorheological transition results in diffusion‐controlled reaction and can be followed simultaneously with the reaction rate in modulated‐temperature DSC (MTDSC). To predict the effect of Tcure and the NH/epoxy molar mixing ratio (r) on the reaction rate in chemically controlled conditions, a mechanistic approach was used based on the nonreversing heat flow and heat capacity MTDSC signals, in which the reaction steps of primary (E1OH = 44 kJ mol?1) and secondary amine (E2OH = 48 kJ mol?1) with the epoxy–hydroxyl complex predominating. The diffusion factor DF as defined by the Rabinowitch approach expresses whether the chemical reaction rate or the diffusion rate determines the overall reaction rate. A model based on the free volume theory together with an Arrhenius temperature dependency was used to calculate the diffusion rate constant in DF as a function of conversion (x) and Tcure. The relation between x, r, and Tg, needed in this model, can be predicted with the Couchman equation. An experimental approximation for DF is the mobility factor DF* obtained from the heat capacity signal at a modulation frequency of 1/60 Hz, normalized for the effect of the reaction heat capacity in the liquid state and the change in Cp in the glassy region with x and Tcure. In this way, an optimized set of diffusion parameters was obtained that, together with the optimized kinetic parameters set, can predict the reaction rate for different cure schedules and for stoichiometric and off‐stoichiometric mixtures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2814–2833, 2004 相似文献
32.
Maria A. Grompone Bruno Irigaray Martín Gil 《European Journal of Lipid Science and Technology》2005,107(10):762-766
The rhea (Rhea americana) is a large running bird of the ratite family, native to South America. Oil extracted from rhea fat tissue is used in cosmetic manufacture. Here, the thermal behaviour and the fatty acid and triacylglycerol composition of Uruguayan rhea oil are studied. The results are compared with those obtained from two commercial samples of emu oil. The fatty acid profiles of emu and rhea oils are similar. Small variations are reflected in the non‐identical thermal behaviour of the oils. The solid content of both oils is fairly similar at room temperature. Thus, emu oil and rhea oil may replace one another in certain formulations, without resulting in important changes in physicochemical behaviour. The semisolid rhea oil was fractionated in two successive stages: an olein was obtained at 15 °C, which was refractionated at 10 °C. The thermogram of the olein obtained by cooling at 15 °C does not have the peak found at 34 °C in the thermogram of the original oil and is a softer product than the original oil. A further stage of fractionation of this olein produced a new liquid phase of slightly different thermal behaviour from that of the original olein. This product has a solid fat index around 7% at 15 °C and has melted completely at 20 °C. This second olein has more appropriate physical characteristics than those of the olein obtained from the first fractionation when used in liquid cosmetic formulations. 相似文献
33.
34.
Production of a combustible for coal-fired power stations based on sewage sludge . This article describes various means of achieving more extensive mechanical dewatering of sewage sludges. The heat content of the sludge solids can become available for combustion processes. The sludge filter cakes obtained by the “CarboSed” process can be disposed of with minimum energy consumption by fluidized bed combustion or be used after appropriate work-up as a combustible in coal-fired power stations with full exploitation of their heat content for generation of steam and electric current. Partial substitution of primary energy sources such as coal and fuel oil by sludge filter cake is feasible in all cases. The processes thus make a contribution to the saving of energy resources and the disposal of sludge. 相似文献
35.
Caroline Cagnin Bruno Matheus Simões Fábio Yamashita Gizilene Maria de Carvalho Maria Victória Eiras Grossmann 《Polymer Engineering and Science》2021,61(2):388-396
This work aims to develop hydrogel films of starch and carboxymethyl cellulose (CMC) crosslinked with sodium trimetaphosphate (STMP) and to characterize some of their properties. Starch and STMP (S/T), starch and CMC (S/C), and mixed (S/T/C) films were prepared by casting. The degree of substitution, morphology, swelling degree, FTIR, mechanical properties, and sorption isotherms were studied. Reticulated samples (S/T and S/T/C) showed the same degree of substitution (0.050 ± 0.001). All films presented homogeneous morphology, but the mixed film showed greater roughness. Crosslinking increased the swelling capacity of the mixed hydrogel at pH 7, although it remained decreased concerning the S/T hydrogel. However, this property was sensitive to pH variations. The mixed film (S/T/C) showed greater mechanical resistance. The casting process was efficient to produce hydrogel films of starch/CMC crosslinked with STMP and the general results demonstrated the advantages of the mixed hydrogel. 相似文献
36.
Expert finding is an information retrieval task that is concerned with the search for the most knowledgeable people with respect to a specific topic, and the search is based on documents that describe people's activities. The task involves taking a user query as input and returning a list of people who are sorted by their level of expertise with respect to the user query. Despite recent interest in the area, the current state‐of‐the‐art techniques lack in principled approaches for optimally combining different sources of evidence. This article proposes two frameworks for combining multiple estimators of expertise. These estimators are derived from textual contents, from graph‐structure of the citation patterns for the community of experts and from profile information about the experts. More specifically, this article explores the use of supervised learning to rank methods, as well as rank aggregation approaches, for combining all of the estimators of expertise. Several supervised learning algorithms, which are representative of the pointwise, pairwise and listwise approaches, were tested, and various state‐of‐the‐art data fusion techniques were also explored for the rank aggregation framework. Experiments that were performed on a dataset of academic publications from the Computer Science domain attest the adequacy of the proposed approaches. 相似文献
37.
38.
Fuzzy c-means (FCMs) is an important and popular unsupervised partitioning algorithm used in several application domains such as pattern recognition, machine learning and data mining. Although the FCM has shown good performance in detecting clusters, the membership values for each individual computed to each of the clusters cannot indicate how well the individuals are classified. In this paper, a new approach to handle the memberships based on the inherent information in each feature is presented. The algorithm produces a membership matrix for each individual, the membership values are between zero and one and measure the similarity of this individual to the center of each cluster according to each feature. These values can change at each iteration of the algorithm and they are different from one feature to another and from one cluster to another in order to increase the performance of the fuzzy c-means clustering algorithm. To obtain a fuzzy partition by class of the input data set, a way to compute the class membership values is also proposed in this work. Experiments with synthetic and real data sets show that the proposed approach produces good quality of clustering. 相似文献
39.
In this paper we present two tests which can decide whether a given pointx
0
N
is locally efficient or not with respect to a given finite set of real valued continuously differentiable functions defined on
N
. Examples indicate that the tests may fail on a nowhere dense set. 相似文献
40.
Summary Distributed Mutual Exclusion algorithms have been mainly compared using the number of messages exchanged per critical section execution. In such algorithms, no attention has been paid to the serialization order of the requests. Indeed, they adopt FCFS discipline. Conversely, the insertion of priority serialization disciplines, such as Short-Job-First, Head-Of-Line, Shortest-Remaining-Job-First etc., can be useful in many applications to optimize some performance indices. However, such priority disciplines are prone to starvation. The goal of this paper is to investigate and evaluate the impact of the insertion of a priority discipline in Maekawa-type algorithms. Priority serialization disciplines will be inserted by means of agated batch mechanism which avoids starvation. In a distributed algorithm, such a mechanism needs synchronizations among the processes. In order to highlight the usefulness of the priority based serialization discipline, we show how it can be used to improve theaverage response time compared to the FCFS discipline. The gated batch approach exhibits other advantages: algorithms are inherently deadlock-free and messages do not need to piggyback timestamps. We also show that, under heavy demand, algorithms using gated batch exchange less messages than Maekawa-type algorithms per critical section excution.
Roberto Baldoni was born in Rome on February 1, 1965. He received the Laurea degree in electronic engineering in 1990 from the University of Rome La Sapienza and the Ph.D. degree in Computer Science from the University of Rome La Sapienza in 1994. Currently, he is a researcher in computer science at IRISA, Rennes (France). His research interests include operating systems, distributed algorithms, network protocols and real-time multimedia applications.
Bruno Ciciani received the Laurea degree in electronic engineering in 1980 from the University of Rome La Sapienza. From 1983 to 1991 he has been a researcher at the University of Rome Tor Vergata. He is currently full professor in Computer Science at the University of Rome La Sapienza. His research activities include distributed computer systems, fault-tolerant computing, languages for parallel processing, and computer system performance and reliability evaluation. He has published in IEEE Trans. on Computers, IEEE Trans. on Knowledge and Data Engineering, IEEE Trans. on Software Engineering and IEEE Trans. on Reliability. He is the author of a book titled Manufactoring Yield Evaluation of VLSI/WSI Systems to be published by IEEE Computer Society Press.This research was supported in part by the Consiglio Nazionale delle Ricerche under grant 93.02294.CT12This author is also supported by a grant of the Human Capital and Mobility project of the European Community under contract No. 3702 CABERNET 相似文献