全文获取类型
收费全文 | 9523篇 |
免费 | 1087篇 |
国内免费 | 530篇 |
专业分类
电工技术 | 614篇 |
技术理论 | 1篇 |
综合类 | 507篇 |
化学工业 | 1601篇 |
金属工艺 | 560篇 |
机械仪表 | 448篇 |
建筑科学 | 690篇 |
矿业工程 | 325篇 |
能源动力 | 305篇 |
轻工业 | 800篇 |
水利工程 | 241篇 |
石油天然气 | 380篇 |
武器工业 | 87篇 |
无线电 | 1434篇 |
一般工业技术 | 1341篇 |
冶金工业 | 521篇 |
原子能技术 | 96篇 |
自动化技术 | 1189篇 |
出版年
2024年 | 47篇 |
2023年 | 165篇 |
2022年 | 306篇 |
2021年 | 446篇 |
2020年 | 342篇 |
2019年 | 307篇 |
2018年 | 332篇 |
2017年 | 357篇 |
2016年 | 359篇 |
2015年 | 418篇 |
2014年 | 507篇 |
2013年 | 713篇 |
2012年 | 624篇 |
2011年 | 662篇 |
2010年 | 559篇 |
2009年 | 569篇 |
2008年 | 525篇 |
2007年 | 494篇 |
2006年 | 480篇 |
2005年 | 447篇 |
2004年 | 288篇 |
2003年 | 285篇 |
2002年 | 251篇 |
2001年 | 208篇 |
2000年 | 219篇 |
1999年 | 205篇 |
1998年 | 166篇 |
1997年 | 141篇 |
1996年 | 121篇 |
1995年 | 97篇 |
1994年 | 80篇 |
1993年 | 79篇 |
1992年 | 44篇 |
1991年 | 55篇 |
1990年 | 34篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
2.
Sien Chi Jeng-Cherng Dung Senfar Wen 《Lightwave Technology, Journal of》1995,13(6):1121-1126
The maximum bit rate of a soliton communication system with lumped amplifiers and optical filters is considered. When the dispersion of the fiber varies from one amplifier spacing to another amplifier spacing, the maximum bit rate is significantly reduced. To overcome the effect, the amplitude of the soliton is amplified so that it is still the average soliton corresponding to the fiber dispersion for an amplifier spacing. Thus, the maximum bit rate is only slightly less than that without the dispersion variations. For a given distance, the maximum bit rate limited by the stability and soliton interaction is obtained. The result is compared with that limited by the Gordon-Haus effect. For shorter transmission distance, the maximum bit rate is limited by the stability and soliton interaction. For longer transmission distance, the maximum bit rate is limited by the Gordon-Haus effect 相似文献
3.
我国聚甲醛工业的供需分析 总被引:3,自引:0,他引:3
从国内聚甲醛树脂的生产、贸易及消费状况出发 ,分析了国内聚甲醛工业的供需现状并提出短期预测。 相似文献
4.
Ching‐Nan Chuang Liang Chao Ying‐Jie Huang Tar‐Hwa Hsieh Hung‐Yi Chuang Shu‐Chi Lin Ko‐Shan Ho 《应用聚合物科学杂志》2008,107(6):3917-3924
The synthesis of a p‐toluidine/formaldehyde (PTF) resin was performed, and the effects of the molar ratio of the individual monomers and the polymerization conditions on the structure of the PTF resin were studied. Fourier transform infrared and 13C‐NMR spectra were used to characterize the PTF. Wide‐angle X‐ray diffraction patterns revealed the crystalline structures of various PTFs. Polarized optical microscopy revealed that the molar ratio of the monomers had a strong effect on the crystalline morphologies. A longer polymerization time turned out a polymer with a higher intrinsic viscosity and molecular weight, which led to differences in the proton conductivity. All of the PTFs showed a higher proton conductivity than a commercial Nafion membrane at 90–100°C and 0% relative humidity. The proton conductivity of the PTF series could be improved by sulfonation with sulfuric acid and could be maintained after blending with polyurethane. Pure methanol could be used as a fuel source because of the insolubility and nonwetting properties of PTF in methanol to increase the output current density for a PTF membrane electrode assembly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
5.
Using chloroform/dimethylformamide (CF/DMF) co-solvent, electrospinning of poly[(R)-3-hydroxybutyrate] (PHB) solutions was carried out at ambient temperature. The effects of the applied voltage (V), flow-rate (Q), and solution viscoelastic properties on the Taylor cone, electrified jet, and fiber morphology were investigated. In addition, the electric field developed by the needle-plate electrode configuration was calculated using a finite element analysis to reveal the tip-to-collector (H) effect. Among the processing parameters (V, Q and H), it was found that Q played a key role in determining the jet diameter (dj) and electrospun fiber diameter (df), and scaling laws existed between them, i.e., dj-Q0.61 and df-Q0.33. The diameter reduction ratios of Do/dj (Do is the needle diameter) and dj/df were measured as 50-120 and 5-10, respectively; it suggested that major jet stretching took place in the straight electrified jet region, and further chain orientation could be gained by the subsequent process of jet whipping. By changing PHB concentrations from 5 to 15 wt%, the solution viscosity (ηo) was increased from 100 to 4900 cP, whereas the surface tension and solution conductivity remained unchanged; it provided a good model solution to exclusively reveal the ηo effect on the electrospinning process. Our results showed that the ηo-dependence of dj and df also followed simple scaling laws: dj-ηo0.06, and df-ηo0.39, with a prefactor depending on the processing variables, mainly the flow-rate. Regardless of the PHB concentrations used, the obtained PHB fibers showed a similar crystallinity fraction of ca. 0.63 and possession of major α-crystals together with a small amount of β-crystals with zigzag chain conformation. 相似文献
6.
The effect of end groups (2NH2) of poly(ethylene glycol) (PEG) on the miscibility and crystallization behaviors of binary crystalline blends of PEG/poly(L ‐lactic acid) (PLLA) were investigated. The results of conductivity meter and dielectric analyzer (DEA) implied the existence of ions, which could be explained by the amine groups of PEG gaining the protons from the carboxylic acid groups of PLLA. The miscibility of PEG(2NH2)/PLLA blends was the best because of the ionic interaction as compared with PEG(2OH, 1OH‐1CH3, and 2CH3)/PLLA blends. Since the ionic interaction formed only at the chain ends of PEG(2NH2) and PLLA, unlike hydrogen bonds forming at various sites along the chains in the other PEG/PLLA blend systems, the folding of PLLA blended with PEG(2NH2) was affected in a different manner. Thus the fold surface free energy played an important role on the crystallization rate of PLLA for the PEG(2NH2)/PLLA blend system. PLLA had the least fold surface free energy and the fast crystallization rate in the PEG(2NH2)/PLLA blend system, among all the PEG/PLLA systems studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
7.
Han‐Lang Wu Chen‐Chi M. Ma Chun‐Chieh Lin Yie‐Chan Chiu Chih‐Yuan Chen Chin‐Lung Chiang 《应用聚合物科学杂志》2008,107(5):3236-3243
Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
8.
分析了南阳石蜡精细化工厂直馏柴油碱洗乳化的原因,介绍了该厂直馏柴油碱洗抗乳化措施,这些措施包括:优化操作参数,加强生产管理,深度碱洗柴油轻组分然后轻、重组分混合出厂。这些措施的综合应用彻底解决了南阳石蜡精细化工厂直馏柴油碱洗乳化的问题,又保证了柴油收率。 相似文献
9.
The factors affecting the adsorption and desorption kinetics in a TEOM are reviewed in detail with particular attention given to the assumptions required to obtain physical transport parameters from the data. Two models are presented to simulate TEOM adsorption data in the case that concentration differences down the catalyst bed can be neglected, as is appropriate when the amount of catalyst used is small, the carrier gas flowrate is large, and/or the adsorbate partial pressure is low. In the first model, the effective diffusion coefficient, De, is taken to be constant. In the second model, the effective diffusion coefficient is assumed to obey the Darken equation, De=D0/(1−θ). The TEOM results obtained on n-hexane, n heptane, n-octane, toluene and p-xylene on a commercial FCC catalyst and on pure rare-earth exchanged zeolite Y under non-reacting conditions (373-) are analysed in detail. It is found that intracrystalline diffusion is not the limiting factor affecting the overall rates of adsorption and desorption for the systems studied. Instead, it is the transport of molecules between the adsorbed and vapour phases at the edge of zeolite crystallites that is the limiting transport step affecting the overall kinetics. For the FCC catalyst, the limiting step is the transport of molecules at the zeolite-matrix interface rather than, say, the matrix-vapour interface. Local rate constants for the desorption of the hydrocarbons at the rate-controlling interface have been obtained. 相似文献
10.
Due to huge calculation of SAR echo simulation of a three-dimensional (3D) ground scene, a fast simulation method is proposed. First, the data of a 3D ground scene are fractionally interpolated based on the Fractional Brownian Motion (FBM) model. Second, the data interpolated are divided into lots of small facets whose precision meets the simulation requirement, the backscattering coefficients of the small facets are calculated. Third, the shaded area is judged by the comparison method of overlook angles. Three parallel levels are analyzed and the kernel function is designed. Finally, the computing method of reduction adding and external thread are also utilized under the framework of GPU in order to get high efficiency. With the methods mentioned above, the imaging result of experimental DEM data verifies the validity and superiority of the proposed method. 相似文献