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排序方式: 共有1290条查询结果,搜索用时 31 毫秒
61.
Ana Isabel Rodríguez-Bernaldo De Quirós Julia López-Hernández María José González-Castro Carlos De la Cruz-García Jesús Simal-Lozano 《European Food Research and Technology》2000,210(3):226-230
The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on
the volatile component profile of green beans were evaluated. Volatile compounds in raw and cooked beans were analysed by
means of dynamic headspace sampling onto an adsorbent, followed by microwave desorption into a gas chromatograph equipped
with a mass spectrometric detector. Twenty-seven compounds were identified, including alcohols, aldehydes, ketones, esters,
terpenes, sulphur compounds and alkenes. All of the thermal treatments caused important changes in the volatile compound profile
in particular an increase in carbonyl compounds and a decrease in alcohol compounds, most notably in the case of the covered
pot. It is concluded that the change in aroma during the cooking of green beans depends on compounds from lipid oxidation
as well as compounds from other types of reactions, for instance the Strecker degradation.
Received: 8 March 1999 / Revised version: 23 April 1999 相似文献
62.
Measurement of research activity still remains a controversial question. The use of the impact factor from the Institute for
Scientific Information (ISI) is quite widespread nowadays to carry out evaluations of all kinds; however, the calculation
formula employed by ISI in order to construct its impact factors biases the results in favour of knowledge fields which are
better represented in the sample, cite more in average and whose citations are concentrated in the early years of the articles.
In the present work, we put forward a theoretical proposal regarding how aggregated normalization should be carried out with
these biases, which allows comparing scientific production between fields, institutions and/or authors in a neutral manner.
The technical complexity of such work, together with data limitations, lead us to propose some adjustments on the impact factor
proposed by ISI which — although they do not completely solve the problem — reduce it and allow glimpsing the path towards
more neutral evaluations. The proposal is empirically applied to three analysis levels: single journals, knowledge fields
and the set of journals from the Journal Citation Report. 相似文献
63.
64.
Nelly Abigail Rodríguez Efrain Almanza María de Jesús Pérez Carlos Rodrigo Mu?iz Scott Packer Russell Steel 《Frontiers of Materials Science in China》2010,4(4):415-419
This study evaluates the degree of sensitization (DOS) of 304 stainless steel joined by friction stir welding (FSW). Single-loop
electrochemical potentiokinetic reactivation tests were performed using a 0.5 mol/L H2SO4 + 0.01 mol/L KSCN solution. Sensitization was promoted by exposition of the stainless steel at temperatures between 400°C
and 850°C. The microstructure was characterized using optical microscopy to identify the weld zone and the base metal. The
samples treated at 550°C showed the most severe intergranular corrosion. The DOS was lower in the weld zone than in the base
metal after heat treatments. This reduction in the DOS for the weld zone indicates that FSW is a beneficial process in joining
stainless steel. 相似文献
65.
Physicochemical properties of ready‐to‐eat extruded nixtamalized maize‐based snacks enriched with grasshopper
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Rubí Cuj‐Laines Betsabé Hernández‐Santos Damian Reyes‐Jaquez Efren Delgado‐Licon José M. Juárez‐Barrientos Jesús Rodríguez‐Miranda 《International Journal of Food Science & Technology》2018,53(8):1889-1895
The aim of this research was to prepare an extruded snack based on nixtamalized maize flour (Zea mays L.) (NMF) enriched with grasshopper meal (Sphenarium purpurascens Ch.) (GM) using a single screw extruder with a compression screw ratio of 3:1. A central experimental design comprising three independent variables, namely, extrusion temperature (T = 120–180 °C), feed moisture content (FMC = 18–22 g/100 g) and the grasshopper meal proportion (GMP = 0–40 g/100 g), was used. Increasing T decreased (P < 0.05) the expansion index (EI), bulk density (BD) and hardness (H). Increasing the FMC increased (P < 0.05) the EI. Increasing the GMP decreased (P < 0.05) the EI, H and water absorption index (WAI) and increased (P < 0.05) the BD and total colour difference (ΔE). The treatments that resulted in better general acceptability were those that contained a lower GMP. An extruded snack acceptable to the consumer can be obtained from a blend of NMF and GM, and up to 8.11 g/100 g of GM can be incorporated without affecting the physicochemical properties and acceptance of the snack. 相似文献
66.
Ursula Torres-Parejo Jesús R. Campaña M. Amparo Vila Miguel Delgado 《Knowledge and Information Systems》2014,40(2):315-347
This paper presents a new approach to information retrieval from non-structured attributes in databases, which involves the processing of text attributes. To make retrieval more effective, frequent text sequences are extracted and mathematically represented as intermediate forms which permit a clearer and more precise definition of operations on texts. These intermediate forms appear to users in the form of tag clouds to facilitate content identification, exploration, and querying. In this sense, tag cloud visualization is a simple, user-friendly visual interface to data. This paper proposes a theoretical model for the representation of frequent text sequences and their operations as well as a general procedure for generating tag clouds from text attributes in databases. The tag clouds thus obtained were compared with conventional tag clouds composed of single terms. Our study showed that automatically generated multi-term tag clouds provide better results than mono-term tag clouds. 相似文献
67.
This paper addresses the estimation of specific growth rate and substrate concentration from biomass measurements in fermentation processes. Specifically, sliding-mode observers are proposed, for which finite-time global convergence is demonstrated using Lyapunov stability theory and concepts of variable structure systems. Two observers are developed for specific growth rate estimation, one producing a discontinuous estimation which is used afterwards for substrate estimation, and the other one – based on high-gain observers – that generates a smooth estimation with first-order dynamics and finite-time bounded convergence error. In the case of substrate estimation, an observer that increases the convergence rate to a vicinity of the real substrate concentration while achieving asymptotic convergence despite kinetic model uncertainties in properly excited processes is designed. This observer also exhibits first-order dynamics. 相似文献
68.
69.
Study of the photon down‐conversion effect produced by thin silicon‐rich oxide films on silicon solar cells
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Israel Vivaldo Jesús Carrillo Osvaldo López Sandra Jiménez Jesús Martínez Dulce Murias José Alberto López 《国际能源研究杂志》2017,41(3):410-416
In the present work, we studied the photon down‐conversion effect produced by thin films of silicon oxide with embedded silicon nanocrystals also called silicon‐rich oxide (SRO). These films have been used to absorb high energy light and the re‐emission of two or more low energy photons (~1.1 eV) with the goal of improving the external quantum efficiency and consequently the conversion efficiency of silicon solar cells. According to our results, the incorporation of a thin SRO film on the solar cell surface increases the short circuit current and the FF of the silicon solar cells; the enhancement of spectral response is due to the high photoluminescence intensity of the SRO in the visible region when irradiated with UV light. An improvement of 38% in the solar cell efficiency has been observed in our particular solar cell fabrication process by the use of an SRO film with high photoluminescence intensity, which replaces the conventional silicon dioxide film. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
70.
Alejandro Peña P Jesús A. Hernández Victoria M. Toro 《Environmental Modelling & Software》2010,25(12):1890-1893
This article presents a model based on the principles of evolutionary computation and on the principles of dispersion of an Inverse lagrangian puff model of the type Backward gaussian puff tracking in order to determine the spatial behavior over time of the concentration for PM2.5 and PM10 in a study area. 相似文献