全文获取类型
收费全文 | 1167篇 |
免费 | 121篇 |
专业分类
电工技术 | 12篇 |
综合类 | 2篇 |
化学工业 | 317篇 |
金属工艺 | 8篇 |
机械仪表 | 21篇 |
建筑科学 | 66篇 |
矿业工程 | 1篇 |
能源动力 | 32篇 |
轻工业 | 260篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 46篇 |
一般工业技术 | 197篇 |
冶金工业 | 38篇 |
原子能技术 | 1篇 |
自动化技术 | 277篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 21篇 |
2021年 | 48篇 |
2020年 | 43篇 |
2019年 | 38篇 |
2018年 | 66篇 |
2017年 | 56篇 |
2016年 | 63篇 |
2015年 | 47篇 |
2014年 | 73篇 |
2013年 | 123篇 |
2012年 | 104篇 |
2011年 | 100篇 |
2010年 | 63篇 |
2009年 | 71篇 |
2008年 | 58篇 |
2007年 | 75篇 |
2006年 | 42篇 |
2005年 | 37篇 |
2004年 | 35篇 |
2003年 | 40篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有1288条查询结果,搜索用时 125 毫秒
11.
Juan José Jiménez José Luis Bernal María Jesús del Nozal Laura Toribio José Bernal 《European Journal of Lipid Science and Technology》2007,109(7):682-690
The concentrations of 102 chemical compounds (saturated and unsaturated hydrocarbons, palmitates, total and free acids, total hydroxyacids, total and free alcohols, acidic monoesters and monoesterified 1,2,3‐propanetriols) have been determined by GC/FID on white and yellow comb beeswax of Apis mellifera from different regions of Spain. Guide‐value ranges are proposed for its characterization and to discriminate adulterated foundation beeswax sheets. The concentrations of many compounds resulted to be statistically different for white and yellow beeswaxes, while the observation of concentrations out of normal in some marketed foundation beeswax sheets suggested their adulteration. However, the measurement of anomalous concentrations in foundation beeswax sheets did not imply necessarily their rejection by the bees. 相似文献
12.
Alfaro Mde J Alvarez I El Khor S de Padilla FC 《Archivos latinoamericanos de nutrición》2004,54(2):223-228
The functional properties of Caryodendron orinocense protein product were investigated and compared with those of soybean (Glycina maxima). The product protein content was 24.47 g/100 g (Nx6.25). Solubility increased at both sides of the isoelectric point (pH 4.0) and with increased NaCl concentration up to 0.5M. Compared with soybean flour (50% protein), the protein product exhibited higher water and oil absorption, but lower emulsifying activity, emulsion stability, foaming capacity, and foam stability, the last one increase at higher pH. Emulsifying activity, foaming capacity, and foam stability were ionic strength dependent. C. orinocense protein product increased its emulsifying activity steadily from 0.05M to 0.75M NaCl, while it remained almost constant for soybean flour. Foaming capacity increased drastically at pH 10. The minimum time and concentration to form a gel was 20% in 4 min and 10% in 8 min for the Caryodendron protein product and soybean flour, respectively. The bulk density was 0.5056+/-0.0041 g/mL. 相似文献
13.
F. Pedro-García L.G. Betancourt-Cantera A.M. Bolarín-Miró C.A. Cortés-Escobedo A. Barba-Pingarrón F. Sánchez-De Jesús 《Ceramics International》2019,45(8):10114-10119
We report the effects of the Sr2+ and Ni2+ co-doping of BiFeO3 on the crystal structure and multiferroic properties of Bi1?xSrxFe1-yNiyO3 (x?=?0.05, 0.0?≤?y?≤?0.10, and Δy?=?0.05) that is synthesized using assisted high-energy ball milling. The mixtures of Bi2O3, Fe2O3, SrO and NiO were milled for 5?h, pressed at 900?MPa, and sintered at 800?°C in order to obtain cylindrical test pieces. X-ray diffraction and Rietveld refinement elucidated the effects of Sr2+ and Ni2+ on the crystal structure. Co-doping with SrNi in suitable proportions stabilizes rhombohedral BiFeO3. High contents of Ni2+ promote the precipitation of secondary phases in the forms of NiFe2O4 and Bi25FeO40. The magnetic behavior was examined by means of vibrating sample magnetometry. The results showed a change in the magnetic order from antiferromagnetic for the undoped sample to the ferromagnetic order for the co-doped samples. This change is attributed to the modulations in the magnetic moment due to crystal structure distortions. All samples show high relative permittivity values, which were enhanced by doping with Sr2+. Ni2+ cations increase the dielectric dissipation factor; this enhancement is related to their interactions with cations of a different oxidation state, such as Fe3+, Fe2+, Ni2+, Bi3+ and Sr2+ in the crystal structure of BiFeO3. The magnetoelectric coupling that was evaluated using magnetodielectric measurements was above 4% at 1?kHz for the higher applied magnetic field of 18?kOe. 相似文献
14.
Daniel Escolar María R. Haro Jesús Ayuso 《Journal of the American Oil Chemists' Society》2002,79(8):769-774
Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic
coordinates and the chroma—L
*, a
*, b
*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480
and 670 nm. These are as follows: L
*=0.556458(A480)2−2.51145A480+0.55504(A670)2−8.53016A670+98.4089; a
*=0.177372(A480)2+2.1363A480+1.43254(A670)2−0.789231A670−13.9246; b
*=−16.0277(A480)2+79.8932A480−5.06558(A670)2+3.36169A670+31.9405; C=−15.8439(A480)2+78.9312A480−5.26784(A670)2+3.56917A670+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale
d’Eclairage (CIE) L
*
a
*
b
*
system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex
equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from
the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed
and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L
*
, a
*
, b
*
, and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R
2-terms also confirmed the validity of the method. 相似文献
15.
16.
Maria del Rosario Martínez-Macias Rocio Janeth Aguilar-Ruiz Omar Nateras-Ramírez Dalia Isabel Sánchez-Machado Jaime López-Cervantes Germán Eduardo Dévora-Isiordia Jesús Álvarez-Sánchez Nidia Josefina Ríos-Vázquez 《Journal of the American Oil Chemists' Society》2021,98(10):993-1000
Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m−2 s−1, yielding 3.5 × 108 cells ml−1, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m−2 s−1 with 1.7 × 108 cells ml−1. The highest total lipid contents (% g lipid × g dry biomass−1) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m−2 s−1 and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m−2 s−1, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m−2 s−1) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m−2 s−1, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m−2 s−1 contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%). 相似文献
17.
Saeed Salah Gabriel Maciá-Fernández Jesús E. Díaz-Verdejo Leovigildo Sánchez-Casado 《Journal of Network and Systems Management》2016,24(1):57-91
In Information Technology Service Management (ITSM), network management teams typically use an Incident Ticket System (ITS) as a tool to track, troubleshoot, and coordinate the resolution of network incidents that occur during the daily operation of the network. A well organized ITS may positively impact on the efficiency of the incident management process. Nevertheless, in many cases the handling of tickets by the management team is not completely systematic and may be incoherent and inefficient. This way, irrelevant or redundant tickets for the same incident may be issued, thus creating a redundancy in the system that leads to inefficiencies. In this paper, we suggest a model aimed to correlate redundant tickets in order to reduce the information to a single ticket per incident. We validate the proposed correlation model by evaluating it with two datasets taken from a real ticketing system of a telecommunications network company. Using this model as a basis, we also develop and evaluate a methodology that assesses the efficiency of the management team during the process of tickets creation and management. Based on it, we also get some insights on the performance of the different management groups involved in the ticket creation process. These analyses can be leveraged for improving both the management groups functioning and the policies for the tickets’ creation. 相似文献
18.
H. SiraRamˇrez A. Hernandez MEndez J. Linares Flores A. Luviano Juarez 《控制理论与应用(英文版)》2016,14(3):224-236
The article deals with the design and implementation of a flat filter tracking digital controller for a boost dc-dc power converter. A highly perturbed switched boost converter circuit is shown to be efficiently controlled, in a trajectory tracking task for its non-minimum phase output, by means of a suitable linear filter, here addressed as a flat filter. Flat filtering is a natural robust
version of generalized proportional integral control (GPIC) by which the effects of arbitrary time varying exogenous disturbances, unknown endogenous nonlinearities and un-modeled dynamics can be jointly attenuated in a conceptually similar fashion to observer-based active disturbance rejection control (ADRC) and algebraic identification based model free control (MFC) but: a)
without using extended state observers and b) respecting the original system order in a time-varying simplified model while avoiding algebraic estimation techniques. The proposed control technique based on the TMS320F28335 digital signal processor chip is tested by means of realistic simulations and experimental setup. 相似文献
19.
Luis Martí Jesús García Antonio Berlanga José M. Molina 《Annals of Mathematics and Artificial Intelligence》2013,68(4):247-273
The introduction of learning to the search mechanisms of optimization algorithms has been nominated as one of the viable approaches when dealing with complex optimization problems, in particular with multi-objective ones. One of the forms of carrying out this hybridization process is by using multi-objective optimization estimation of distribution algorithms (MOEDAs). However, it has been pointed out that current MOEDAs have an intrinsic shortcoming in their model-building algorithms that hamper their performance. In this work, we put forward the argument that error-based learning, the class of learning most commonly used in MOEDAs is responsible for current MOEDA underachievement. We present adaptive resonance theory (ART) as a suitable learning paradigm alternative and present a novel algorithm called multi-objective ART-based EDA (MARTEDA) that uses a Gaussian ART neural network for model-building and a hypervolume-based selector as described for the HypE algorithm. In order to assert the improvement obtained by combining two cutting-edge approaches to optimization an extensive set of experiments are carried out. These experiments also test the scalability of MARTEDA as the number of objective functions increases. 相似文献
20.
Jesús Gallardo Crescencio Bravo Miguel A. Redondo Juan de Lara 《Journal of Visual Languages and Computing》2013,24(1):10-23
Over the last two decades, Collaborative Systems have become increasingly popular thanks to the many advances made in networks, communications and software tools. Within this field, Collaborative Modeling Systems apply the collaborative paradigm to the construction of (often visual) models, where users build diagrams from building blocks and the relationships between them. In these kinds of applications, the work is usually arranged into sessions, with the definition of some kind of time organization between those sessions. This organization is known as a collaboration protocol. Unfortunately, it is not usually easy to define these protocols, and many applications do not allow users to make any use of them.In an effort to overcome these difficulties, in this paper we propose a visual language for defining collaboration protocols for these systems. As such, in our language, sessions, artifacts and the transformations between them can be specified visually, and different coordination relationships (such as fork and join) can be defined. The visual language is included in a development method for collaborative systems that take advantage of the Eclipse platform in order to develop model-driven graphical editors that are enhanced with collaboration capabilities. 相似文献