全文获取类型
收费全文 | 89699篇 |
免费 | 7777篇 |
国内免费 | 4044篇 |
专业分类
电工技术 | 5691篇 |
技术理论 | 2篇 |
综合类 | 5761篇 |
化学工业 | 13822篇 |
金属工艺 | 4934篇 |
机械仪表 | 5221篇 |
建筑科学 | 6690篇 |
矿业工程 | 1819篇 |
能源动力 | 2647篇 |
轻工业 | 6975篇 |
水利工程 | 1803篇 |
石油天然气 | 3811篇 |
武器工业 | 678篇 |
无线电 | 11973篇 |
一般工业技术 | 11571篇 |
冶金工业 | 4476篇 |
原子能技术 | 1029篇 |
自动化技术 | 12617篇 |
出版年
2024年 | 295篇 |
2023年 | 1295篇 |
2022年 | 2370篇 |
2021年 | 3531篇 |
2020年 | 2439篇 |
2019年 | 2071篇 |
2018年 | 2322篇 |
2017年 | 2716篇 |
2016年 | 2409篇 |
2015年 | 3353篇 |
2014年 | 4396篇 |
2013年 | 5641篇 |
2012年 | 6040篇 |
2011年 | 6756篇 |
2010年 | 5853篇 |
2009年 | 5652篇 |
2008年 | 5585篇 |
2007年 | 5344篇 |
2006年 | 5124篇 |
2005年 | 4187篇 |
2004年 | 2847篇 |
2003年 | 2351篇 |
2002年 | 2366篇 |
2001年 | 2023篇 |
2000年 | 1912篇 |
1999年 | 1936篇 |
1998年 | 1820篇 |
1997年 | 1568篇 |
1996年 | 1401篇 |
1995年 | 1181篇 |
1994年 | 922篇 |
1993年 | 760篇 |
1992年 | 604篇 |
1991年 | 459篇 |
1990年 | 381篇 |
1989年 | 296篇 |
1988年 | 249篇 |
1987年 | 177篇 |
1986年 | 149篇 |
1985年 | 133篇 |
1984年 | 94篇 |
1983年 | 67篇 |
1982年 | 65篇 |
1981年 | 58篇 |
1980年 | 51篇 |
1979年 | 35篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 54篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
介绍了以天然气为燃料的纸浆模塑烘干线的设计过程 ,以及该套设备的制造和安装要点。由于使用了清洁能源 ,所以该套设备能生产出清洁度较高的纸浆模塑包装制品 ,满足电子工业和食品工业对包装制品的要求 相似文献
932.
The partial oxidation of methane to synthesis gas was studied at atmospheric pressure and in the temperature range of 550–800°C over -Al2O3-supported bimetallic Pt–Co, and monometallic Pt and Co catalysts, respectively. Both methane conversion and CO selectivity over a bimetallic Pt0.5Co1 catalyst were higher than those over monometallic Pt0.5 and Co1 catalysts. Furthermore, the addition of platinum in Pt–Co bimetallic catalysts effectively improved their resistance to carbon deposition with no coking occurring on Pt0.5Co1 during 80 h reaction. The FTIR study of CO adsorption observed only linearly bonded CO on bimetallic Pt–Co catalysts. TPR and XPS showed enhanced formation of a cobalt surface phase (CSP) in bimetallic Pt–Co catalysts. The origins of the good coking resistivity of bimetallic Pt–Co catalysts were discussed. 相似文献
933.
借助化学分析方法、X射线衍射、差示扫描量热法等测试手段研究了Fe2O3对无水硫铝酸钙矿物(C4A3S)形成过程的影响.研究表明:掺杂Fe2O3可促进熟料中游离氧化钙(f-CaO)的吸收,增加液相量,改善C4A3-S矿物生料的易烧性;不掺杂Fe2O3的矿物生料,C4A3-S单矿物在850℃以下几乎不生成,在1 000℃开始大量生成,在1 300℃达到最高值;掺杂1?2O3的试样中C4A3S含量与不掺杂试样在同温度下达到最大值,但绝对含量有一定幅度的下降;掺杂3%及5?2O3的试样中C4A3S含量在1 350℃达到最大值,达到最大值的时间比原来延迟0.5h,并且绝对含量有较大幅度的下降;掺杂Fe2O3的试样在1 200℃至1400℃时,Fe3 和C4A3-S中的Al3 发生置换,使Fe3 固熔到C4A3-S中形成固熔体C4(A0.95F0.05)6O12(SO4). 相似文献
934.
A novel treatment process combining a membrane with outside-in flow configuration and a fluidized pellet rector for removing hardness was studied. The effects of influent water quality, e.g., concentrations of natural organic matter (NOM) and phosphate along with the hydrophobicity of NOM, on the hardness removal efficiency of the novel process were investigated. The hardness removal efficiency decreases with increasing NOM concentration. However, the NOM removal efficiency is independent of NOM concentration and is related to the hydrophobicity of NOM samples. Raw water containing phosphate has adverse impact on the hardness removal efficiency, which decreases from 85% for treating water containing no phosphate to only 38% and 14% for water containing 0.33 mg/L and 1.63 mg/L of phosphate, respectively. 相似文献
935.
936.
介绍了纳米TiO2光催化的机理和特点、纳米TiO2可见光催化零VOC内墙乳胶漆的性能和应用等。表明其不仅是零VOC无毒无害,而且是一种能在一般室内照明条件下净化空气的内墙乳胶漆。 相似文献
937.
The Effects of Phenyltrimethoxysilane Coupling Agents on the Properties of PTFE/Silica Composites 总被引:2,自引:1,他引:2
A study on PTFE reinforced with SiO2 was described. This study included the manufactural process of SiO2-reinforced PTFE and the effects of the content of silane (Z6124) on the properties of the composites material, such as thermal, dielectric properties, tensile strength and morphology, etc. PTFE/silica composites of 60 wt% SiO2 loaded with a different coupling agent content were mixed by a high-speed dispersion machine and prepared by a two-roll milling machine. Our results show that the sample treated with 3 wt% silane has the highest tensile strength and optimum dielectric properties. Furthermore, the tensile strength and coefficient of thermal expansion (CTE) increase, and the water absorption decreases, with an increasing silane content. These experiments reveal that silane treatment can reduce the overall hydrophilicity of the composites. Finally, predictions on dielectric and CTE properties are discussed. It has been found that experimental values of the dielectric constant agree well with those predicted by the rule of mixture. 相似文献
938.
Polyacrylonitrile (PAN)/Na-montmorillonite (Na-MMT)/SiO2 nanocomposites were prepared via in situ emulsion polymerization. X-ray diffraction (XRD) results suggest that the Na-MMT layers are exfoliated during the polymerization process. As evidenced by the transmission electron microscope (TEM), the Na-MMT and nano SiO2 particles exhibit good dispersion in the polymer matrix. It was found that the PAN/Na-MMT/SiO2 nanocomposites exhibit considerably enhanced mechanical properties compared with the PAN/Na-MMT and PAN/SiO2 nanocomposites. 相似文献
939.
Hai‐Xia Yang Yan‐Feng Li Jin‐Gang Liu Shi‐Yong Yang Da‐Xue Yin Lincheng Zhou Lin Fan 《应用聚合物科学杂志》2004,91(6):3981-3990
A series of new polymerized monomer reactants (PMR) matrix resins of poly(pyrrolone‐benzimidazole)s containing a pyridine unit (PPBP) were synthesized by polycondensation of monoethyl ester of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid, 2,6‐diphenyl ester pyridinedicarboxylic acid or 3,5‐diphenyl ester pyridinedicarboxylic acid, and diethyl ester of 4,4′‐oxydiphthalic acid with 3,3′‐diaminobenzidine in a mixing solution of anhydrous ethyl alcohol and N‐methylpyrrolidone under given temperature and pressure conditions. The resulting resin solutions showed good solubility in polar organic solvents and stability at room temperature. The corresponding PPBP matrix resin, molded powder, and molded plate were prepared by undergoing amidation, imidization, cyclization, and crosslinking reactions when the reaction temperature was increased from 80 to 350°C, successively; the crosslinking structure was formed by the reverse Diels–Alder reaction at 270–290°C under 50 MPa pressure (2.5–3.5 MPa displayed by the pressure meter). The chemical reactions and properties of the resulting PPBP were studied by means of FTIR, TGA, and DMA methods, and the results indicated that the kinds of PPBP materials retain excellent thermal stability and processability; when the initial decomposition temperature was above 620°C the Tg was at 413.5°C for 3,5‐PPBP‐20 molded plate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3981–3990, 2004 相似文献
940.
A fall detection method based on depth image analysis is proposed in this paper. As different from the conventional methods, if the pedestrians are partially overlapped or partially occluded, the proposed method is still able to detect fall events and has the following advantages: (1) single or multiple pedestrian detection; (2) recognition of human and non-human objects; (3) compensation for illumination, which is applicable in scenarios using indoor light sources of different colors; (4) using the central line of a human silhouette to obtain the pedestrian tilt angle; and (5) avoiding misrecognition of a squat or stoop as a fall. According to the experimental results, the precision of the proposed fall detection method is 94.31% and the recall is 85.57%. The proposed method is verified to be robust and specifically suitable for applying in family homes, corridors and other public places. 相似文献