全文获取类型
收费全文 | 92336篇 |
免费 | 6960篇 |
国内免费 | 3254篇 |
专业分类
电工技术 | 4797篇 |
技术理论 | 9篇 |
综合类 | 5033篇 |
化学工业 | 16585篇 |
金属工艺 | 4911篇 |
机械仪表 | 5595篇 |
建筑科学 | 7435篇 |
矿业工程 | 2105篇 |
能源动力 | 2612篇 |
轻工业 | 5555篇 |
水利工程 | 1631篇 |
石油天然气 | 4971篇 |
武器工业 | 536篇 |
无线电 | 10953篇 |
一般工业技术 | 11915篇 |
冶金工业 | 4892篇 |
原子能技术 | 876篇 |
自动化技术 | 12139篇 |
出版年
2024年 | 357篇 |
2023年 | 1427篇 |
2022年 | 2483篇 |
2021年 | 3370篇 |
2020年 | 2573篇 |
2019年 | 2208篇 |
2018年 | 2421篇 |
2017年 | 2737篇 |
2016年 | 2525篇 |
2015年 | 3204篇 |
2014年 | 4329篇 |
2013年 | 5458篇 |
2012年 | 5698篇 |
2011年 | 5978篇 |
2010年 | 5310篇 |
2009年 | 5084篇 |
2008年 | 4790篇 |
2007年 | 4732篇 |
2006年 | 4945篇 |
2005年 | 4398篇 |
2004年 | 2957篇 |
2003年 | 2668篇 |
2002年 | 2352篇 |
2001年 | 2149篇 |
2000年 | 2414篇 |
1999年 | 2733篇 |
1998年 | 2489篇 |
1997年 | 1973篇 |
1996年 | 1818篇 |
1995年 | 1496篇 |
1994年 | 1260篇 |
1993年 | 913篇 |
1992年 | 681篇 |
1991年 | 559篇 |
1990年 | 424篇 |
1989年 | 371篇 |
1988年 | 323篇 |
1987年 | 177篇 |
1986年 | 166篇 |
1985年 | 112篇 |
1984年 | 98篇 |
1983年 | 63篇 |
1982年 | 61篇 |
1981年 | 54篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
JuYing Wu ChengXi Zhou QingWen Zhu EnRong Li Ge Dai Long Ba YuHong Huang Jun Mei 《中国科学E辑(英文版)》2009,52(12):3497-3503
The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles
in air, which were synthesized by using the thermal reduction in the polyol solution. The rutile structure of the ruthenium
oxide was proved by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The oxide has
good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent. The assembling
of the silane to the oxide surface was proved by Infrared (IR) absorption spectroscopy. By mixing the nanoparticles with poly(methylvinylsiloxane)
(PMVS) silicone rubber, a composite filled with dispersive conducting phase was fabricated. The temperature dependent conductivity
shows that the electron transportation through composite is mainly dominated by tunneling. The measurement of piezoresistance
shows that the composite at low strain has high piezoresistance repeatability. The 3D reconstruction images of the composite
filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites.
The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence. 相似文献
992.
The ablation in solid-propellant rocket nozzle is a coupling process resulted by chemistry, heat and mass transfer. Based on the heat and mass transfer theory, the aero-thermo-dynamic, and thermo-chemical kinetics, the thermal-chemical ablation model is established. Simulations are completed on the heat flow field and chemical ablation in the nozzle with different concentrations, frequency factors and activation energy of H2. The calculation results show that the concentration and the activation energy of H... 相似文献
993.
994.
995.
环氧化反式-1,4-聚异戊二烯的结构与性能 总被引:3,自引:1,他引:3
研究了水相悬浮法合成环氧化反式-1,4-聚异戊二烯(ETPI)的结构与性能。结果表明,反式-1,4-聚异戊二烯TPI粉粒的晶区和无定形区均能发生环氧化反应,但因二者反应性不同,导致环氧基团在同一分子链无定形区链段部分数目较多而在晶区链段部分数目较少,形成类嵌段结构,在微观上整个分子链的环氧化不均匀;随环氧度的增加,ETPI分子链的刚性、极性增加,结晶性变差,生胶在非极性溶剂中的溶解性变差,在甲苯中的特性黏数降低,熔点降低,邵尔A型硬度先降低后升高,密度、凝胶质量分数增加,门尼黏度升高,加工性变差。 相似文献
996.
A three‐dimensional braided carbon fiber–epoxy (C3D/EP) composite was prepared by the vacuum‐assisted resin transfer molding (VARTM) technique. Its moisture absorption behavior under different media was characterized and compared with a unidirectional composite. Similar to the unidirectional composite, diffusion in the 3D composite obeys Fick's second law of diffusion when immersed in distilled water and phosphate‐buffered saline. In HCl and NaOH solutions, no Fickian behavior was observed. The similarity between the unidirectional and 3D composites suggests that fiber structure does not change diffusion pattern. However, the two composites showed different diffusion parameters (k, D, and Me) in each medium studied. The 3D composite showed lower k, D, and Me values because of its stronger hindrance effect to transport of moisture molecules. Diffusion in PBS is slower than that in distilled water because of the presence of heavy ions, but the diffusion pattern remains unchanged. In HCl, the diffusion behavior of the two composites cannot be described by Fick's law. In addition, the k value calculated from the initial linear part of the moisture sorption curve is much lower than that in distilled water. Diffusion in NaOH is unusual; the uptake initially increases rather rapidly but quickly drops, which is likely caused by the extensive solubility of the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 507–512, 2005 相似文献
997.
998.
Hydroxyl‐terminated polybutadiene (HTPB), 4,4′‐dicyclohexyl methane diiscyanate (H12MDI), and 1,4‐butane diol are used to synthesize polyurethane (PU) solutions by two‐stage process. Interpenetrating networks (IPNs) of HTPB‐based PU and poly(methyl methacrylate) (PMMA) with HTPB/MMA (wt/wt % ratio) = 2.0, 1.5, 1.0, 1.5, 0.8, and 0.6, which are designated as IPN1 to IPN5, respectively, are synthesized by sequential polymerization technique. Thermal properties, tensile strength, and contact angle of membranes increase with the increase of MMA content, while the elongation of membranes show the reverse trend. Characterization of membranes are investigated by C?C/C?O absorption ratio and infrared absorption frequency shiftment. These PU and IPN membranes are used for the separation of ethanol/water and isopropanol/water solution by pervaporation test. IPN3 membrane possesses the largest pervaporation permeability and the separation factor. The pervaporation results of ethanol/water feed has the same trend as that of isopropyl alcohol (IPA)/water solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
999.
Qinyun Chen Huang Shi Chi-Tang Ho 《Journal of the American Oil Chemists' Society》1992,69(10):999-1002
Rosemary (Rosemarinus officinalis L.) leaves were extracted with three different solvents, namely hexane, acetone and methanol. A reverse-phase high-performance
liquid chromatography system in combination with a mass detector was used to quantitate the content of carnosol, carnosic
acid and ursolic acid in the rosemary extracts. All rosemary extracts showed strong inhibitory effects on lipid oxidation
and soybean lipoxygenase activity. 相似文献
1000.
Yinfeng Liu Lai Chen Bei Su Aiming Huang Jiadong Hua Wenbin Sang Jiahua Min Zhongyan Meng 《应用聚合物科学杂志》2002,84(6):1263-1268
In this article nano‐sized CdS crystal embedded in a PEO matrix was successfully prepared by a complex transformation method that is universal for preparing nanosized compounds containing transition metals. The size of embedded CdS particles was in the nanoscale from 2 to 10 nm determined by X‐ray diffusion. The nanosized CdS displayed the expected blue shift of the onset absorbance in the UV spectrum. The amount of blue shift depends upon the dipping time of the PEO–cadmium complex film in a sodium sulfide solution as well as its concentration. The most effective means for adjusting the size of CdS nanocrystals is to change the ratio of the oxygen along with the PEO chain to the cadmium ion in the complex film. The alkali salt in the film would contribute to the conductivity of the composite film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1263–1268, 2002; DOI 10.1002/app.10459 相似文献