全文获取类型
收费全文 | 55965篇 |
免费 | 2653篇 |
国内免费 | 60篇 |
专业分类
电工技术 | 340篇 |
综合类 | 44篇 |
化学工业 | 10363篇 |
金属工艺 | 932篇 |
机械仪表 | 958篇 |
建筑科学 | 1467篇 |
矿业工程 | 98篇 |
能源动力 | 1292篇 |
轻工业 | 8320篇 |
水利工程 | 440篇 |
石油天然气 | 217篇 |
武器工业 | 8篇 |
无线电 | 1876篇 |
一般工业技术 | 7495篇 |
冶金工业 | 18077篇 |
原子能技术 | 274篇 |
自动化技术 | 6477篇 |
出版年
2023年 | 365篇 |
2022年 | 588篇 |
2021年 | 1292篇 |
2020年 | 925篇 |
2019年 | 1107篇 |
2018年 | 1624篇 |
2017年 | 1622篇 |
2016年 | 1726篇 |
2015年 | 1356篇 |
2014年 | 1730篇 |
2013年 | 3433篇 |
2012年 | 2695篇 |
2011年 | 2902篇 |
2010年 | 2269篇 |
2009年 | 2177篇 |
2008年 | 2003篇 |
2007年 | 1782篇 |
2006年 | 1376篇 |
2005年 | 1215篇 |
2004年 | 1124篇 |
2003年 | 1005篇 |
2002年 | 927篇 |
2001年 | 667篇 |
2000年 | 667篇 |
1999年 | 968篇 |
1998年 | 5667篇 |
1997年 | 3532篇 |
1996年 | 2313篇 |
1995年 | 1350篇 |
1994年 | 1084篇 |
1993年 | 1250篇 |
1992年 | 341篇 |
1991年 | 384篇 |
1990年 | 300篇 |
1989年 | 313篇 |
1988年 | 310篇 |
1987年 | 291篇 |
1986年 | 259篇 |
1985年 | 278篇 |
1984年 | 169篇 |
1983年 | 139篇 |
1982年 | 198篇 |
1981年 | 211篇 |
1980年 | 264篇 |
1979年 | 99篇 |
1978年 | 108篇 |
1977年 | 528篇 |
1976年 | 1164篇 |
1975年 | 81篇 |
1973年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Maritza F. Díaz José A. Gavín Magali Gómez Vicente Curtielles Frank Hernández 《臭氧:科学与工程》2006,28(1):59-63
Prior studies have proven that ozonated vegetable oils present a high germicidal power. Ozonation of sunflower oil at different applied ozone dosage was carried out and peroxide and aldehydes indices along with antimicrobial activity were determined. The reaction products were identified using Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR). The principal signals intensity values were used for following the reaction course between ozone and sunflower oil. The reaction was following up to peroxide index values of 1202 mmol-equi/kg. The intensities of olefinic proton signals decreased with the gradual increase in ozone concentration but without disappearing completely. The Criegee ozonides obtained at 107.1 mg/g of ozone doses were approximately 3.9-fold higher than that at beginning of the reaction. The aldehyde protons were observed as a weak intensity signal in all the spectra. The signals belonging to olefinic protons from hydroperoxides appeared weak and increased with the increase in ozone doses. Signals from other oxygenated groups were assigned. The highest action spectrum of antimicrobial activity was obtained with the higher peroxide index. It was concluded that at higher applied ozone doses, the higher the antimicrobial activity potential of ozonized sunflower oil 相似文献
992.
S.?M.?NolascoEmail author L.?A.?N.?Aguirrezábal G.?H.?Crapiste 《Journal of the American Oil Chemists' Society》2004,81(11):1045-1051
Tocopherols are natural antioxidants that increase the stability of fat-containing foods and perform important biological
activities. Significant variations (389 to 1873 μg g oil−1) in the total tocopherol concentration of sunflower seed oil have been reported. The main objectives of this work were to
determine the influence of intercepted photosynthetically active radiation on tocopherol concentration during seed filling
and to establish and validate relationships between tocopherol concentration in oil and other quality variables of the seed.
Seven sunflower hybrids were grown under good water and nutritional conditions in two similar experiments carried out in two
contrasting environments. Treatments were applied to modify the amount of radiation intercepted per plant during seed filling
in order to obtain a range in oil yield per plant and its components. Greater per plant intercepted radiation decreased the
tocopherol concentration in oil. Tocopherol concentration decreased when oil weight per seed increased. Tocopherol concentration
stabilized for oil weight per seed higher than 23 mg oil seed−1. This exponential relationship accounted for 73% of the variability in tocopherol concentration (507 to 1203 μg g oil−1) despite differences in hull type, locations, hybrids, and radiation treatments. The proposed relationship acceptably predicted
independent results. Crop management techniques could lead to seeds with greater concentrations of tocopherols. 相似文献
993.
Different methods to prepare supported metal nanoparticles of uniform size are discussed. (i) Supported ruthenium particles were generated from Ru and Ru-Fe bimetallic molecular metal carbonyl cluster precursors (MCC). (ii) Gold nanoparticle formation in the supercage of Y zeolite was studied on Au/NaY, Au/HY and Au-Fe/HY system. (iii) Palladium nanoparticles were grown in liquid phase then deposited on an SiO2 support or they were grown on the support surface in a solid-liquid interfacial layer. The particle size control was more efficient in the latter two cases than in the preparation starting from MCC. 相似文献
994.
M. Kubín 《应用聚合物科学杂志》1982,27(8):2933-2941
Relationships have been derived between the spreading factor and the respective slopes of actual and effective linear calibrations in size-exclusion chromatography. On this basis a new calibration procedure has been developed for determining simultaneously the dependences of sample molecular weight and of the spreading factor on elution volume from chromatograms of polydisperse polymer samples with known values of number-and weight-average molecular weight. No assumptions about the shape of sample molecular weight distribution are required. If necessary, the calibration dependences may be further improved by an iteration procedure described. 相似文献
995.
996.
Carlos Rivas-Costa Luis Anido-Rifón Miguel A. Gómez-Carballa Sonia Valladares-Rodríguez Roberto Soto-Barreiros 《International journal of human-computer interaction》2014,30(6):480-494
This article discusses a modular, accessible platform that provides a computing environment for people with disabilities accessible through adapted control devices and the television set at users’ homes. Relying on a standard television set as the presentation device allows dependent individuals, especially people with disabilities, to introduce new technological advances in communication and information management in their everyday lives. As a proof-of-concept, the solution presented offers a collection of educational and training services related to teleworking and the search of employment targeted to people with disabilities. A smart job advisor included among these services, which was designed to help our target users to locate job offers that best suit the abilities and disabilities of a particular individual, is also discussed to illustrate how semantic technologies can be applied to increase the perceived accessibility and inclusion by reducing the dependence from other persons. The platform developed, the introduction of semantic technologies, and the way adapted interfacing and presentation devices were integrated may also serve as inspiration to provide services to people with disabilities. 相似文献
997.
In this paper, we present an invariant‐set‐based method for actuator and sensor fault detection and isolation in Lure systems. The Lure plant is controlled by an observer‐based feedback tracking controller, designed for the nominal (fault‐free) system. Suitable residual signals are constructed from measurable system outputs and estimates associated with the nominal observer. Faults are diagnosed by online contrasting the residual signal trajectories against sets of values that the residuals are shown to attain under healthy or faulty operation. These values are obtained via set‐invariance analysis of the system closed‐loop trajectories. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
998.
In the search for suitable materials to be used as anode supports in the periodic current reversal refining process this work covers the study of austenitic AISI 304 stainless steel. Experimental results show that the resistance of this steel to the aggressive action of the refining electrolyte is good at the working temperature of 60°C since no corrosion was detected after 24 h of electrolysis. The periodic polarization of this material results in a progressive passivation which was observed by operating under different initial surface conditions and by detecting remnant anodic currents which gradually decreased with time. For time ratios lower than twenty, a build up of metallic copper deposit on the steel part of the mixed anode occurred whatever the current density used. 相似文献
999.
Cláudio Teixeira Joaquim Sousa Pinto Ricardo Azevedo Tiago Batista André Monteiro 《Journal of Network and Systems Management》2014,22(1):75-99
Traditional cloud computing providers enable developers to program and deploy applications in the cloud by using platform as a service (PaaS) providers. Despite the benefits of such an approach, this service model usually comes with a high level of the lock in effect into the service provider. The lock in effect occurs when a software developer needs to change its cloud provider. When this happens, it usually means a major application rewrite, specific for the new PaaS. This paper details the initial results of a project whose goal is to build a PaaS where vendor lock in does not occur. With this PaaS, developers wishing to deploy their applications into the cloud may continue to program using their usual development environments. There are no necessary changes required to make the application PaaS compatible. As a proof of concept, we developed an open source PaaS management application as a regular web application and then deployed it on the cloud. 相似文献
1000.
Iván Jachmanián Lucía Margenat Ana I. Torres Maria A. Grompone 《Journal of the American Oil Chemists' Society》2007,84(6):597-601
The solubility of different ethyl esters derivatized from hake liver oil in supercritical carbon dioxide was studied. A selectivity
factor was used to determine optimal conditions to fractionate the ethyl ester mixture. A strong influence of solvent pressure
and temperature was observed within 8.63–18.04 MPa and 40–70 °C. The lowest total solubility of the ethyl ester mixture was
obtained when using supercritical carbon dioxide at the lowest density (the lowest pressure and the highest temperatures value
tested). The highest discrimination against long-chain polyunsaturated fatty acids (e.g. EPA and DHA) was also obtained at
these above conditions. Conversely, higher solubility and lower selectivity were obtained when solvent density increased.
Considering this inverse correlation between selectivity and solubility, a single-step batch-fractionation process was designed
to increase the 22:6 ethyl ester content from an initial value of 17.5% in the starting material to 55% in the final extract. 相似文献