全文获取类型
收费全文 | 12332篇 |
免费 | 1929篇 |
国内免费 | 822篇 |
专业分类
电工技术 | 321篇 |
综合类 | 803篇 |
化学工业 | 4902篇 |
金属工艺 | 1539篇 |
机械仪表 | 759篇 |
建筑科学 | 482篇 |
矿业工程 | 184篇 |
能源动力 | 175篇 |
轻工业 | 652篇 |
水利工程 | 172篇 |
石油天然气 | 349篇 |
武器工业 | 115篇 |
无线电 | 940篇 |
一般工业技术 | 1965篇 |
冶金工业 | 499篇 |
原子能技术 | 60篇 |
自动化技术 | 1166篇 |
出版年
2024年 | 73篇 |
2023年 | 239篇 |
2022年 | 344篇 |
2021年 | 507篇 |
2020年 | 498篇 |
2019年 | 471篇 |
2018年 | 487篇 |
2017年 | 576篇 |
2016年 | 620篇 |
2015年 | 602篇 |
2014年 | 765篇 |
2013年 | 861篇 |
2012年 | 873篇 |
2011年 | 888篇 |
2010年 | 697篇 |
2009年 | 712篇 |
2008年 | 677篇 |
2007年 | 766篇 |
2006年 | 730篇 |
2005年 | 545篇 |
2004年 | 500篇 |
2003年 | 447篇 |
2002年 | 339篇 |
2001年 | 264篇 |
2000年 | 224篇 |
1999年 | 202篇 |
1998年 | 187篇 |
1997年 | 184篇 |
1996年 | 93篇 |
1995年 | 110篇 |
1994年 | 86篇 |
1993年 | 76篇 |
1992年 | 84篇 |
1991年 | 80篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 23篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 33篇 |
1981年 | 8篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
对锆英石陶瓷的生产工艺对材料的显微结构、力学性能的影响进行了研究.结果表明:造粒粉颗粒的硬壳与空洞在坯体中形成大颗粒,如果在成型过程中末被完全破坏遗留在烧结体中而引起材料内部气孔的存在,使材料的力学性能明显下降.制定合理的锆英石材料生产工艺、控制气孔的产生,是提高材料强度和可靠性的有效措施. 相似文献
952.
含有活性或惰性掺合料的复合胶凝材料硬化浆体的微观结构特征 总被引:7,自引:0,他引:7
用压汞法测定了不同温度条件下养护的含有粉煤灰或石英粉的复合胶凝材料硬化浆体的孔隙率.用扫描电镜观察了硬化浆体的微观形貌,同时测定了各种组成的复合胶凝材料的净浆强度.常温水化初期,活性与惰性矿物掺合料都只具有物理填充的作用,硬化浆体的孔隙率和强度由矿物掺合料的掺量所决定.高温水化条件下粉煤灰的火山灰反应提前发生.随水化龄期延长,粉煤灰逐渐发生火山灰反应,使硬化浆体结构密实,其强度逐步提高.活性与惰性矿物掺合料对复合胶凝材料浆体结构与性能的影响的差异在水化后期逐渐显现. 相似文献
953.
To investigate the correlation between structure characteristics and wear resistance of CO2 corrosion product scales at high temperature and high pressure, an autoclave was used to prepare CO2 corrosion product scales on N80 steel in carbon dioxide corrosion environment. The correlation between wear resistance of the scales and many other factors, such as temperature, pressure, morphology, structure, velocity of fluid medium, sand grain size, and so on, was comparatively analyzed by a self assembled wear device, and the scale morphologies before or after being worn were observed by scanning electron microscope (SEM). And then the surface grain size and thickness of scale were measured. The results showed that the cross section of the corrosion scale was of a double layer structure, the outer layer of which was composed of regular crystals, whereas the inner layer was a thin scale of fine grains. The outer grain size and thickness of scale varied with temperature, and the initial wear loss was consistent with the surface grain size; at the same time, the total wear loss corresponded to the thickness of scale. Compared to wear resistance in different depths of the scale, it was found that the structure of scale was a double layer structure in cross section, and the wear resistance of inner layer was better than that of the outer layer; the closer the scale to the matrix, the greater was the wear resistance of scale; and the larger the size or the higher the rotary speed of solid grain in multiphase flowing medium, the more was the wear loss of scale. 相似文献
954.
955.
通过正交试验确定了最佳镀镍复合添加剂配方:吡啶衍生物(NPB)15 mg/L,糖精钠(BSI)1 000 mg/L,苯亚磺酸钠(BSS)120 mg/L,2–乙基己烷磺酸钠(EHS)500 mg/L,烯丙基磺酸钠(SAS)1 500 mg/L和丙炔磺酸钠(PS)45 mg/L。研究了各组分对镀层光亮度和镀液分散能力的影响,结果表明,各组分对镀层亮度的影响大小顺序为NPB>BSS>EHS>SAS>PS>BSI;对镀液分散能力影响的大小顺序为BSS>NPB>EHS>BSI>PS>SAS。与某市售镀镍添加剂相比,该复合添加剂在镀层亮度、镀液分散能力、微观形貌和降低孔隙率等方面都有所提高。 相似文献
956.
The Influence of Blend Ratio on the Morphology,Mechanical, Thermal,and Rheological Properties of PP/LDPE Blends
下载免费PDF全文
![点击此处可从《大分子材料与工程》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper reports on how the blend ratio and morphology influence the mechanical, thermal, thermomechanical, and rheological properties of poly(propylene) (PP)/low density polyethylene (LDPE) blends. The blend morphology is composed of the major matrix phase and the minor phase, with subinclusions of the major matrix existing within the minor phase. Blends containing low amounts (<20 wt%) of either phase exhibit partial miscibility but the phases are immiscible at higher contents. Partial miscibility of the blends is revealed by scanning electron microscopy studies showing fibril‐like structures and confirmed by rheology. The tensile modulus of the blends decreases with increasing amounts of LDPE, but low LDPE contents exhibit positive deviation from the mixing rule of mixture due to partial compatibility. The crystallinity of PP is affected less than that of LDPE in the blends. Thermomechanical and rheological properties of neat polymers are significantly influenced by blending. The blend ratio and morphology influence impact strength and elongation at break, and the result demonstrates that the 80/20 PP/LDPE blend offers a balance among the mechanical and material properties that are essential for flexible packaging applications.
957.
采用动态硫化法制备了炭黑增强高抗冲聚苯乙烯(HIPS)/苯乙烯-丁二烯-苯乙烯(SBS)/丁苯橡胶(SBR)热塑性硫化胶(TPV),考察了炭黑填充量对其力学性能的影响,通过场发射扫描电子显微镜(FE-SEM)观察了动态硫化过程中橡胶相的形态演变。结果表明,在TPV的分散相SBR中填充炭黑,可使TPV的力学性能获显著改善;随着动态硫化的进行,橡胶相在交联的同时逐渐被撕碎为分散相,在动态硫化至8 min时橡胶相呈稳定的类球状形貌,其粒径为3~6 μm,且表面呈现出纳米乱片层状结构。 相似文献
958.
Phenolic resin‐crosslinked natural rubber/clay nanocomposites: Influence of clay loading and interfacial adhesion on strain‐induced crystallization behavior
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Abdulhakim Masa Ryota Saito Hiromu Saito Tadamoto Sakai Azizon Kaesaman Natinee Lopattananon 《应用聚合物科学杂志》2016,133(12)
Nanocomposites of natural rubber (NR) and pristine clay (clay) were prepared by latex mixing, then crosslinked with phenolic resin (PhOH). For comparative study, the PhOH‐crosslinked neat NR was also prepared. Influence of clay loading (i.e., 1, 3, 5, and 10 phr) on mechanical properties and structural change of PhOH‐crosslinked NR/clay nanocomposites was studied through X‐ray diffraction (XRD), transmission electron microscopic (TEM), wide‐angle X‐ray diffraction (WAXD), tensile property measurement, and Fourier transform infrared spectroscopy (FTIR). XRD and TEM showed that the clay was partly intercalated and aggregated, and that the dispersion state of clay was non‐uniform at higher clay loading (>5 phr). From tensile test measurement, it was found that the pronounced upturn of tensile stress was observed when the clay loading was increased and a maximum tensile strength of the PhOH‐crosslinked NR/clay nanocomposites was obtained at 5 phr clay. WAXD observations showed that an increased addition of clay induced more orientation and alignment of NR chains, thereby lowering onset strain of strain‐induced crystallization and promoting crystallinity of the NR matrix during tensile deformation. FTIR investigation indicated a strong interfacial adhesion between NR matrix and clay filler through a phenolic resin bridge. This suggested that the PhOH did not only act as curative agent for crosslinking of NR, but it also worked as coupling agent for promoting interfacial reaction between NR and clay. The presence of strong interfacial adhesion was found to play an important role in the crystallization process, leading to promotion of mechanical properties of the PhOH‐crosslinked NR/clay nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43214. 相似文献
959.
The melt rheological properties of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were investigated with special reference to the effect of blend ratio, temperature, shear rate, compatibilization, and dynamic vulcanization. The melt viscosity of the blends determined with a capillary rheometer is found to decrease with an increase of shear rate, which is an indication of pseudoplastic behavior. The viscosity of the blend was found to be a nonadditive function of the viscosities of the component polymers. A negative deviation was observed because of the interlayer slip between the polar EVA and the nonpolar LLDPE phases. The melt viscosity of these blends decreases with the increased concentration of EVA. The morphology of the extrudate of the blends at different shear rates and blend ratios was studied and the size and distribution of the domains were examined by scanning electron microscopy. The morphology was found to depend on shear rate and blend ratio. Compatibilization of the blends with phenolic‐ and maleic‐modified LLDPE increased the melt viscosity at lower wt % of compatibilizer and then leveled off. Dynamic vulcanization is found to increase the melt viscosity at a lower concentration of DCP. The effect of temperature on melt viscosity of the blends was also studied. Finally, attempts were made to correlate the experimental data on melt viscosity and cocontinuity region with different theoretical models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3210–3225, 2002 相似文献
960.
Impact toughness,viscoelastic behavior,and morphology of polypropylene–jute–viscose hybrid composites
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this investigation, we studied the impact toughness and viscoelastic behavior of polypropylene (PP)–jute composites. In this study, we used viscose fiber as an impact modifier and maleated PP as a compatibilizer. The toughness of the composites was studied with conventional Charpy and instrumental falling‐weight impact tests. The composites’ viscoelastic properties were studied with dynamic mechanical analysis. The results show that the incorporation of viscose fibers improved the impact strength and toughness to 134 and 65% compared to those of the PP–jute composites. The tan δ peak amplitude also increased with the addition of the impact modifier and indicated a greater degree of molecular mobility. The thermal stability of the composites was evaluated with thermogravimetric analysis. The addition of 2 wt % maleated polypropylene (MAPP) to the impact‐modified composite improved the impact strength and toughness to 144 and 93%, respectively. The fiber–matrix morphology of the fracture surface and the Fourier transform infrared spectra were also studied to ascertain the existence of the type of interfacial bonds. Microstructural analysis showed the retention of viscose fibers in the composites compared to the more separated jute fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42981. 相似文献