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31.
Undecylenic acid, glycerol, and CO2 were used as building blocks for obtaining a fully bio-based carbonated monomer, useful for polyurethanes. The functionality of the monomer was close to 3 cyclic carbonates/mol, located in terminal positions. In a first stage, a synthetic triglyceride was obtained with 99% selectivity by esterification of glycerol and undecylenic acid at 160°C. The triglyceride was then epoxidized using H2O2 and Amberlyst 15 or Amberlite IR-120 acidic exchange resins at 57°C. The selectivity to epoxide was kept constant at 98% using Amberlite IR-120. Terminal cyclic carbonates were then inserted through epoxide moieties under mild conditions by the chemical fixation of CO2 at 80°C and 6 MPa in 6 h. A complete conversion was obtained in 6 h reaction while the selectivity to carbonate groups was near to 99% during all the reaction time. An elastomeric polyhydroxyurethane was obtained by aminolysis of the carbonated monomer with ethylenediamine at 70°C, affording a Young's modulus of 22.6 MPa and Tg of −15.2°C. The material showed a good thermal stability below 240°C. 相似文献
32.
Pablo Cortés Luis Onieva Jesús Muñuzuri José Guadix 《Computers & Industrial Engineering》2013,64(1):403-411
Nowadays is very common the presence of tall buildings in the business centres of the main cities of the world. Such buildings require the installation of numerous lifts that are coordinated and managed under a unique control system. Population working in the buildings follows a similar traffic pattern generating situations of traffic congestion. The problem arises when a passenger makes a hall call wishing to travel to another floor of the building. The dispatching of the most suitable car is the optimization problem we are tackling in this paper. We develop a viral system algorithm which is based on a bio-inspired virus infection analogy to deal with it. The viral system algorithm is compared to genetic algorithms, and tabu search approaches that have proven efficiency in the vertical transportation literature. The experiments undertaken in tall buildings from 10 to 24 floors, and several car configurations from 2 to 6 cars, provide valuable results and show how viral system outperforms such soft computing algorithms. 相似文献
33.
34.
Diego Francisco Cortés‐Rojas Claudia Regina Fernandes Souza Wanderley Pereira Oliveira 《International Journal of Food Science & Technology》2011,46(11):2420-2427
Response surface methodology was used to find the optimum ethanol concentration and temperature which maximises the antioxidant activity (AA) of hydroalcoholic extracts from aerial parts of Bidens pilosa L. A rotatable central composite design was used, and the extracts were characterised by the determination of solid concentration (SC), total flavonoid (TFC) and total polyphenol content (TPC). AA was determined through 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulphonic acid) diammonium salt (ABTS) and 2,2‐diphenyl‐1‐pycrylhydrazyl (DPPH) radical scavenging activity. Mathematical models showed the significant effects of each variable and allowed to select the optimum conditions of ethanol concentration (62.7%) and extraction temperature (66.2 °C). The optimised extract presented an AA of 804.9 ± 12.2 Trolox equivalent antioxidant capacity (TEAC) dry base (d.b.) for DPPH and 515.8 ± 31.8 TEAC d.b. for ABTS. It was observed that both TFC and TPC showed a good correlation with AA of the extracts. 相似文献
35.
This paper studies connectivity maintenance of robotic networks that communicate at discrete times and move in continuous space. We propose a distributed coordination algorithm that allows the robots to decide whether a desired collective motion breaks connectivity. We build on this procedure to design a second coordination algorithm that allows the robots to modify a desired collective motion to guarantee that connectivity is preserved. These algorithms work under imperfect information caused by delays in communication and the robots’ mobility. Under very outdated information, the proposed algorithms might prevent some or all of the robots from moving. We analyze the correctness of our algorithms by formulating them as games against a hypothetical adversary who chooses system states consistent with observed information. The technical approach combines tools from algebraic graph theory, linear algebra, and nonsmooth analysis. 相似文献
36.
R Sala MJ Muntó J de la Calle I Preciado T Miralles A Cortés R Molla M Alcaide 《Canadian Metallurgical Quarterly》1998,27(159):759-766
OBJECTIVE: To determine the frequency of dysphagia in CVA, its natural history and value as a risk factor of respiratory infection, malnutrition and death. PATIENTS AND METHODS: A prospective study was made of 187 consecutive patients with cerebrovascular accidents (CVA). A standardized test for dysphagia was done during the first two days of the illness and repeated three days a week. The levels of urea, total proteins and albumin were determined on admission and on discharge. The patients were questioned by phone after 6 months. RESULTS: There was dysphagia of liquids in 36.4% of the patients. The incidence of dysphagia for semisolids was of the same frequency but more severe. Coma was the cause of inability to swallow in 25.7% of the patients. During their stay in hospital one third of the patients with dysphagia died, one third became normal and one third still had dysphagia when they were discharged. After one week, one, three and six months respectively, the cure rate for dysphagia was 29.4%, 4.1%, 55.9% and 55.9%, and survival 83.8%, 67.6%, 61.8% and 60.3%. Thus after 6 months only 3 patients (4.4%) were alive and dysphagic. Half of the 'cures' occurred in the first week, and none occurred after more than 77 days. As compared to the non-dysphagic patients, the dysphagic patients had 10 times more risk of respiratory infection, 18 times higher risk of death, greater loss of albumin and less loss of urea. CONCLUSIONS: There is a high prevalence of dysphagia in CVA and although functional prognosis is not unfavorable, respiratory infections, malnutrition and death are frequent. 相似文献
37.
Esteban Alfaro Cortés Matías Gámez Martínez Noelia García Rubio 《Applied Intelligence》2007,27(1):29-37
Predicting corporate failure is an important management science problem. This is a typical classification question where the
objective is to determine which indicators are involved in the failure/success of a corporation. Despite the importance of
this problem, until now only classical machine learning tools have been considered to tackle this classification task. The
objective of this paper is twofold. On the one hand, we introduce novel discerning measures to rank independent variables
in a generic classification task. On the other hand, we apply boosting techniques to improve the accuracy of a classification
tree. We apply this methodology to a set of European firms, considering the usual predicting variables such as financial ratios,
as well as including novel variables rarely used before in corporate failure prediction, such as firm size, activity and legal
structure. We show that our approach decreases the generalization error about thirty percent with respect to the error produced
with a classification tree. In addition, the most important ratios deal with profitability and indebtedness, as is usual in
failure prediction studies.
E. A. Cortés · M. G. Martínez · N. G. Rubio. The authors teach Statistics at the Faculty of Economic and Business Sciences in the University of Castilla-La Mancha. Esteban
Alfaro completed his degree in Business in 1999 and got his Ph.D. in Economics in 2005, both in the University of Castilla-La
Mancha. His thesis dealt with the application of ensemble classifiers to corporate failure prediction. Matías Gámez got his
degree in Mathematics at the University of Granada in 1991 and finished a Master in Applied Statistics a year after. He completed
his Ph.D. in Economics at the University of Castilla-La Mancha in 1998 on the application of geo-statistical techniques to
the estimation of housing prices. Noelia García got her degree in Economics at the University of Madrid (UAM) in 1996 and
completed her Ph.D. in Economics in 2004 on the construction of an intelligent and automated system for property valuation
through the combination of neural nets and a geographic information system (GIS). Current research deals with spatial statistics
and the combination of classifiers (decision trees and neural nets) for solving heated topics in the Economics. 相似文献
38.
J. Rodríguez R. Cortés M. A. Martínez V. Sánchez-Gálvez C. Navarro 《Journal of Materials Science》1995,30(18):4720-4725
A numerical and experimental assessment of the compression test in the split Hopkinson pressure bar (SHPB) has been made. The DYNA2D finite element code was employed in the numerical part. The aim of the work was to establish the influence of an important reduction in the specimen diameter on the results. To this end, several numerical experiments were carried out with different diameters. Experimental measurements using the SHPB technique were also performed. The material studied was the 7017 T73 aluminium alloy. In the simulations, stress histories were registered at different places in the incident and output bars, as well as in the test specimen. Numerical simulations show important three-dimensional effects in the SHPB, increasing for smaller diameters. Experiments show the same tendencies evinced by the numerical simulation. Care must be taken to minimize them to achieve the desirable uniaxial stress condition on the specimen. 相似文献
39.
Johns Josephine M.; Noonan Linda R.; Zimmerman Laura I.; Li Li; Pedersen Cort A. 《Canadian Metallurgical Quarterly》1995,109(2):257
Reports an error in the original article by J. M. Johns et al (Behavioral Neuroscience, 1994[Feb], Vol 108[1], 107–212). On page 108, in the Results, Maternal Behavior, the phrase in parentheses, "(8 min to crouch for 8 min or more of 30 min)' should read: "(6 min to crouch for 8 min or more of 30 min).' On page 109, the label on the upper right panel of Figure 1, "Percent That Crouch in 8 Minutes,' should read: "Percent That Crouch in 6 Minutes.' (The following abstract of this article originally appeared in record 1994-24731-001.) Pregnant rats (N?=?17) were treated either throughout gestation (Gestational Day 1–20) with 30 mg/kg per day (chronic cocaine) or with 1 15-mg/kg dose immediately following parturition (acute cocaine). Chronic and acute cocaine treatment delayed or diminished the postpartum onset of some components of maternal behavior, and chronically treated dams were significantly more aggressive toward a male intruder than acute cocaine-treated or saline-treated dams. Cocaine increased the latency to crouch over pups and decreased crouch duration during a 30-min observation period that immediately followed parturition. Latencies to nest build were also longer in more chronic cocaine-treated dams than in saline controls.… (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
Mark A. Anastasio Xiaochuan Pan 《International journal of imaging systems and technology》2002,12(2):84-91
It is widely believed that measurements from a full angular range of 2π are generally required to exactly reconstruct a complex‐valued refractive index distribution in diffraction tomography (DT). In this work, we developed a new class of minimal‐scan reconstruction algorithms for DT that utilizes measurements only over the angular range 0 ≤ ? ≤ 3π/2 to perform an exact reconstruction. These algorithms, referred to as minimal‐scan estimate‐combination (MS‐E‐C) reconstruction algorithms, effectively operate by transforming the DT reconstruction problem into a conventional x‐ray CT reconstruction problem that requires inversion of the Radon transform. We performed computer simulations to compare the noise and numerical properties of the MS‐E‐C algorithms against existing filtered backpropagation‐based algorithms. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 84–91, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10014 相似文献