全文获取类型
收费全文 | 38234篇 |
免费 | 4306篇 |
国内免费 | 2345篇 |
专业分类
电工技术 | 1370篇 |
综合类 | 3256篇 |
化学工业 | 9946篇 |
金属工艺 | 4817篇 |
机械仪表 | 1741篇 |
建筑科学 | 5398篇 |
矿业工程 | 818篇 |
能源动力 | 857篇 |
轻工业 | 1955篇 |
水利工程 | 432篇 |
石油天然气 | 874篇 |
武器工业 | 620篇 |
无线电 | 1264篇 |
一般工业技术 | 9269篇 |
冶金工业 | 1316篇 |
原子能技术 | 93篇 |
自动化技术 | 859篇 |
出版年
2024年 | 233篇 |
2023年 | 578篇 |
2022年 | 1050篇 |
2021年 | 1285篇 |
2020年 | 1371篇 |
2019年 | 1166篇 |
2018年 | 1134篇 |
2017年 | 1515篇 |
2016年 | 1574篇 |
2015年 | 1510篇 |
2014年 | 2015篇 |
2013年 | 2040篇 |
2012年 | 2677篇 |
2011年 | 2780篇 |
2010年 | 2192篇 |
2009年 | 2347篇 |
2008年 | 1865篇 |
2007年 | 2631篇 |
2006年 | 2448篇 |
2005年 | 2042篇 |
2004年 | 1630篇 |
2003年 | 1481篇 |
2002年 | 1257篇 |
2001年 | 1139篇 |
2000年 | 983篇 |
1999年 | 798篇 |
1998年 | 643篇 |
1997年 | 553篇 |
1996年 | 453篇 |
1995年 | 368篇 |
1994年 | 299篇 |
1993年 | 265篇 |
1992年 | 166篇 |
1991年 | 130篇 |
1990年 | 73篇 |
1989年 | 46篇 |
1988年 | 40篇 |
1987年 | 26篇 |
1986年 | 4篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1967年 | 1篇 |
1957年 | 1篇 |
1956年 | 2篇 |
1955年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
WC对铜基和镍基喷焊覆层材料耐气蚀性能的影响 总被引:2,自引:0,他引:2
在CuNiSiB,NiCrSiB自熔合金粉末中添加WC陶瓷颗粒,利用氧乙炔焰粉末喷焊工艺制备覆层材料,用超声波振动气蚀仪对覆层材料进行耐气蚀性能研究,用扫描电子显微镜对覆层材料表面气蚀破坏形貌进行观察,结果表明:复合覆层材料的耐气蚀能力比基体强;提高CuNiSiB覆层材料耐气蚀能力的途径是强化晶界,还探讨了覆层材料的气蚀破坏机理。 相似文献
83.
84.
对云母粒子化学镀镍及以LDPE为基材,镀镍云母粒子为填料制备的导电复合材料进行研究。认为此种导电复合材料只有质量轻、强度大及良好的导电等性能。 相似文献
85.
Resilient metal spring silicone-matrix conducting composites for separable interconnections in electronics were fabricated
by the impregnation of silicone into a preform comprising randomly oriented C-shaped Cu-Be springs and a small proportion
of Sn-Pb solder, which served to connect the springs at some of their intersections. Composites containing 6.1-9.8 vol.% total
filler exhibited volume electrical resistivity 0.5-1.0 mΩ.cm and contact resistivity (with copper) 11-17 mΩ.cm2. A compressive stress of about 30 kPa was needed for the low contact resistivity to be reached. The volume 17-26% and the
contact resistivity increased by 5% after heating in air at 130-150°C for seven days. Composites containing <9 vol.% total
filler showed no stress relaxation for seven days at 6.0% strain. 相似文献
86.
87.
粉末布法制备SiC/Ti基复合材料 总被引:2,自引:0,他引:2
用粉末布法制备了低成本SiC/Ti基复合材料.结果表明,采用合适的轧制参数即可容易地获得厚度合适、均匀的粉末布;热失重分析和热解残余物分析指出用来制备粉末布的有机粘结剂的去除过程分成两个阶段,合理除气后,基本没有残余物.使用真空热压工艺制备的SiC/Ti基复合材料,纤维分布基本均匀,纤维与基体的界面结合良好. 相似文献
88.
Daniela D'Amato Maria Rosaria Corbo Matteo Alessandro Del Nobile & Milena Sinigaglia 《International Journal of Food Science & Technology》2006,41(10):1152-1157
In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae. 相似文献
89.
Fatigue behaviour and endurance limit of graphite and of aluminium‐infiltrated graphite Fatigue properties of polycrystalline, isotropic graphite FU2590 and of FU2590 infiltrated with AlSi7Mg (FU2590/AlSi7Mg) were investigated in reversed bending tests at 25 Hz at numbers of cycles below 107 and in tension‐compression tests at 20 kHz below 109 cycles. The open porosity of Graphite (10‐11 Vol.‐%) was infiltrated with the aluminium alloy using the squeeze casting infiltration method, which led to an increase of the bending strength by 50 %, increase of tensile strength by 30 % and increase of stiffness by 15 %. Fully reversed tension‐compression loading of FU2590 delivers a mean endurance limit at 109 cycles at the normalized maximum stresses (i.e. maximum tension stress of a cycle divided by the static strength) of 0,65±0,03. Mean numbers of cycles to failure of 104 were found in fully reversed bending tests at the normalized maximum stress of 0,78. The infiltrated material shows approximately 30 % higher cyclic strength in reversed bending tests, and the mean endurance limit under tension compression loading increases by 15 %. The increased endurance limit of the infiltrated material is caused by the increased stiffness. The increased toughness of graphite due to the infiltration with aluminium is of additional beneficial influence at the higher cyclic stresses investigated in reversed bending tests and in static tests. 相似文献
90.
M. Nishida T. Hanabusa Y. Ikeuchi N. Minakawa 《Materialwissenschaft und Werkstofftechnik》2003,34(1):49-55
Stress measurement methods using neutron and X‐ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten‐fiber reinforced copper‐matrix composite. Surface stresses were measured by X‐ray stress measurement with the sin2ψ method. Furthermore, the sin2ψ method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement. 相似文献