全文获取类型
收费全文 | 37594篇 |
免费 | 3990篇 |
国内免费 | 2495篇 |
专业分类
电工技术 | 879篇 |
综合类 | 1861篇 |
化学工业 | 8553篇 |
金属工艺 | 3233篇 |
机械仪表 | 1118篇 |
建筑科学 | 2276篇 |
矿业工程 | 727篇 |
能源动力 | 2109篇 |
轻工业 | 1439篇 |
水利工程 | 259篇 |
石油天然气 | 269篇 |
武器工业 | 474篇 |
无线电 | 4151篇 |
一般工业技术 | 13766篇 |
冶金工业 | 2002篇 |
原子能技术 | 358篇 |
自动化技术 | 605篇 |
出版年
2024年 | 168篇 |
2023年 | 913篇 |
2022年 | 964篇 |
2021年 | 1397篇 |
2020年 | 1629篇 |
2019年 | 1428篇 |
2018年 | 1306篇 |
2017年 | 1409篇 |
2016年 | 1345篇 |
2015年 | 1342篇 |
2014年 | 1972篇 |
2013年 | 2164篇 |
2012年 | 2340篇 |
2011年 | 3238篇 |
2010年 | 2328篇 |
2009年 | 2460篇 |
2008年 | 2208篇 |
2007年 | 2510篇 |
2006年 | 2169篇 |
2005年 | 2010篇 |
2004年 | 1600篇 |
2003年 | 1421篇 |
2002年 | 1151篇 |
2001年 | 833篇 |
2000年 | 758篇 |
1999年 | 523篇 |
1998年 | 494篇 |
1997年 | 345篇 |
1996年 | 293篇 |
1995年 | 226篇 |
1994年 | 232篇 |
1993年 | 165篇 |
1992年 | 133篇 |
1991年 | 134篇 |
1990年 | 122篇 |
1989年 | 99篇 |
1988年 | 47篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 28篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1963年 | 2篇 |
1955年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The fabrication of functional textiles able to provide thermal regulation and comfort for the body has attracted increasing interest in recent years. This research investigated fabric coatings containing energy absorbing, temperature stabilizing, phase‐change material microcapsules (PCMMcs), and their methods of application. Specifically, a coated fabric was directly prepared by a dual‐type coating method, in which the PCMMcs were dispersed in a polyurethane coating solution with no binder. The thermal performances of the dual‐coated samples were evaluated by differential scanning calorimetry, and their physical characteristics were examined by scanning electron microscopy, thermal vision camera, porosity, water vapor transmission rate (WVTR), and water entry pressure (WEP) analyses. Furthermore, the microclimate characteristics of the thermally enhanced fabrics were investigated under experimental conditions using a human‐clothing‐environment (HCE) simulator system. The study results confirmed the superior performance of the dual‐coated fabrics in terms of thermal regulation and body comfort, compared with those coated by the dry or wet coating method, because of the improved WEP, WVTR, and thermal performance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
102.
103.
104.
The flexural and shear rigidity of pultruded composite sheet pile panels consisting of E-glass fiber-reinforced polyester are studied in this paper. The analysis consists of an experimental investigation and an analytical modeling to determine the resistance of the sheet pile panels to the deflections for design of composite sheet pile walls. Timoshenko’s beam theory was used to experimentally determine the flexural rigidity (EI) and shear rigidity (kAG) of the panel. Three- and four-point bending tests were performed on six different span lengths and the results were self-compared from the two independent tests. Analytical expressions for the flexural and shear rigidities were derived to allow the prediction based on the layered structure of pultruded shapes. The values computed from the analytical expressions were examined with the experimental results. 相似文献
105.
T.S. Gates G.M. Odegard S.J.V. Frankland T.C. Clancy 《Composites Science and Technology》2005,65(15-16):2416
The paper provides details on the current approach to multi-scale modeling and simulation of advanced materials for structural applications. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation are highlighted and discussed. 相似文献
106.
107.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献
108.
Elena Crespi Antonio Capolongo Davide Fissore Antonello A. Barresi 《Drying Technology》2008,26(3):349-356
The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed. 相似文献
109.
In this work the synergistic effects of microwave (MW) irradiation induced oxidation processes and CoFe2O4 were studied for the degradation of brilliant green (BG) from aqueous solutions. Under the optimum condition, the ratio of solid to liquid was 1:167 (0.3 g CoFe2O4 mixed with 50 mL of 20 mg L−1 BG solution), MW power 600 W, and the time of the irradiation 2 min. And the decolorization rate could reach up to 100%. Further investigation showed that BG was degraded by MW-induced oxidation combined with CoFe2O4 surface adsorption. The CoFe2O4 could increase the efficiencies of MW degradation and be used repeatedly. The experimental results indicated that the method of MW degradation BG in the presence of CoFe2O4 could reduce reaction time and increase product yield. 相似文献
110.
Effect of Rare Earth Elements on Thermal Fatigue Property of Low Chromium Semi-Steel 总被引:3,自引:0,他引:3
The effect of rare earth elements on eutectic carbide‘s morphology of low chromium semi-steel in as-cast state and after heat treatment was investigated, and accordingly, the thermal fatigue property of this material was studied. The results show that RE can improve the eutectic carbide‘s morphology, inhibit the formation and propagation of thermal fatigue cracks, therefore, promote the thermal fatigue property, which is more noticeable in case of the RE modification in combination with heat treatment. The optimal thermal fatigue property can be obtained when treated with 0.2% RE modification as well as normalization at 950℃ for 3h. 相似文献