全文获取类型
收费全文 | 42351篇 |
免费 | 1704篇 |
国内免费 | 5902篇 |
专业分类
电工技术 | 3167篇 |
综合类 | 6171篇 |
化学工业 | 3745篇 |
金属工艺 | 6180篇 |
机械仪表 | 2628篇 |
建筑科学 | 2229篇 |
矿业工程 | 1161篇 |
能源动力 | 865篇 |
轻工业 | 2771篇 |
水利工程 | 1057篇 |
石油天然气 | 4723篇 |
武器工业 | 423篇 |
无线电 | 4182篇 |
一般工业技术 | 2890篇 |
冶金工业 | 1367篇 |
原子能技术 | 1665篇 |
自动化技术 | 4733篇 |
出版年
2023年 | 136篇 |
2022年 | 252篇 |
2021年 | 275篇 |
2020年 | 257篇 |
2019年 | 202篇 |
2018年 | 174篇 |
2017年 | 264篇 |
2016年 | 228篇 |
2015年 | 327篇 |
2014年 | 669篇 |
2013年 | 656篇 |
2012年 | 1014篇 |
2011年 | 4599篇 |
2010年 | 2426篇 |
2009年 | 1536篇 |
2008年 | 1648篇 |
2007年 | 1225篇 |
2006年 | 1424篇 |
2005年 | 1593篇 |
2004年 | 4915篇 |
2003年 | 3191篇 |
2002年 | 3198篇 |
2001年 | 2180篇 |
2000年 | 1384篇 |
1999年 | 2127篇 |
1998年 | 1447篇 |
1997年 | 1452篇 |
1996年 | 777篇 |
1995年 | 695篇 |
1994年 | 591篇 |
1993年 | 2170篇 |
1992年 | 1712篇 |
1991年 | 1192篇 |
1990年 | 1171篇 |
1989年 | 882篇 |
1988年 | 580篇 |
1987年 | 333篇 |
1986年 | 242篇 |
1985年 | 124篇 |
1984年 | 85篇 |
1983年 | 52篇 |
1982年 | 47篇 |
1981年 | 37篇 |
1980年 | 79篇 |
1979年 | 63篇 |
1965年 | 62篇 |
1963年 | 25篇 |
1959年 | 32篇 |
1958年 | 27篇 |
1957年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Thermosetting materials are widely used as encapsulation in the electrical packaging to protect the core electronic components from external force, moisture, dust, and other factors. However, the spreading and curing behaviors of such kind of fluid on a heated surface have been rarely explored. In this study, we experimentally and numerically investigated the spreading and curing behaviors of the silicone(OE6550 A/B, which is widely used in the light-emitting diode packaging) droplet with diameter of ~2.2 mm on a heated surface with temperature ranging from 25 ℃ to 250 ℃. For the experiments, we established a setup with high-speed camera and heating unit to capture the fast spreading process of the silicone droplet on the heated surface. For the numerical simulation, we built a viscosity model of the silicone by using the Kiuna's model and combined the viscosity model with the Volume of Fluid(VOF) model by the User Defined Function(UDF) method. The results show that the surface temperature significantly affected the spreading behaviors of the silicone droplet since it determines the temperature and viscosity distribution inside the droplet. For surface temperature varied from 25 ℃ to 250 ℃, the final contact radius changed from ~2.95 mm to ~1.78 mm and the total spreading time changed from ~511 s to ~0.15 s. By further analyzing the viscosity evolution of the droplet, we found that the decreasing of the total spreading time was caused by the decrease of the viscosity under high surface temperature at initial spreading stage, while the reduction of the final contact radius was caused by the curing of the precursor film. This study supplies a strategy to tuning the spreading and curing behavior of silicone by imposing high surface temperature, which is of great importance to the electronic packaging. 相似文献
4.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
5.
6.
7.
鱼肉中的肌原纤维结合型丝氨酸蛋白酶(myofibril-bound serine proteinase,MBSP)在加工过程中可降解肌原纤维,引起鱼糜制品的凝胶劣化。一种新型特异性高的鲨源抗体——单域抗体(single-domain antib odies,sdAbs),能直接与抗原结合并抑制酶的活性。研究主要完成了针对MBSP单域抗体制备的前期工作:文本库建立及淘选过程,以克隆表达的MBSP为抗原免疫铰口鲨鱼(nurse shark,Ginglymostoma cirratum),构建鲨鱼单域抗体文本库,并从中淘选针对MBSP的特异性单域抗体噬菌粒,最终得到31个能与MBSP特异性结合的噬菌粒,为获得抗MBSP单域抗体鉴定了基础,以期抑制或消除MBSP的活性,解决现有鱼糜制品凝胶劣化的问题。 相似文献
8.
采用固相反应法在制备温度923 K,保温时间约30 min的条件下,快速合成了铜掺杂方钴矿Cux Co4 Sb12(x=0、0.1、0.3、0.5、0.7、0.9),对样品进行了物相结构(XRD)、微观结构和不同温度条件下的热电性质测试分析.结果表明,所制备的样品Cux Co4 Sb12在0≤x≤0.7的范围内均为单相的方钴矿结构,样品含有许多微气孔,晶粒细小,平均直径在微纳米级.当测试温度为696 K时,样品Cu0.1 Co4 Sb12获得最低电阻率为48.71μΩ·m.在测试温度为462 K时,样品Cu0.3 Co4 Sb12获得最大Seebeck系数为233.14μV/K.样品Cu0.1 Co4 Sb12在测试温度为578 K时,获得最大的ZT值为0.24. 相似文献
9.
10.
A 25 Gbit/s clock and data recovery(CDR) circuit with 1:2 demultiplexer for 100 Gbit/s Ethernet(100 Gb E) optical interconnects has been designed and fabricated in Taiwan Semiconductor Manufacture Company(TSMC) 65 nm complementary metal-oxide-semiconductor(CMOS) technology. A novel quadrature voltage-controlled-oscillator(QVCO) structure adopts two pairs of transconductance cell and inverters to acquire rail-to-rail output swing. A half-rate bang-bang phase detector adopts four flip-flops array to sample the 25 Gbit/s input data and align the data phase, so the 25 Gbit/s data are retimed and demultiplexed into two paths 12.5 Gbit/s output data. Experimental results show that the recovered clock exhibits a peak-to-peak jitter of 7.39 ps and the recovered data presents a peak-to-peak jitter of 7.56 ps, in response to 312-1 pseudorandom bit sequence(PRBS) input. For 1.2 V voltage supply, the CDR circuit consumes 92 m W(excluding output buffers). 相似文献