全文获取类型
收费全文 | 60947篇 |
免费 | 4926篇 |
国内免费 | 2647篇 |
专业分类
电工技术 | 3212篇 |
技术理论 | 6篇 |
综合类 | 4116篇 |
化学工业 | 10141篇 |
金属工艺 | 3827篇 |
机械仪表 | 3832篇 |
建筑科学 | 4666篇 |
矿业工程 | 2171篇 |
能源动力 | 1950篇 |
轻工业 | 3492篇 |
水利工程 | 1056篇 |
石油天然气 | 4481篇 |
武器工业 | 482篇 |
无线电 | 6402篇 |
一般工业技术 | 7127篇 |
冶金工业 | 3293篇 |
原子能技术 | 720篇 |
自动化技术 | 7546篇 |
出版年
2024年 | 99篇 |
2023年 | 934篇 |
2022年 | 1372篇 |
2021年 | 2275篇 |
2020年 | 1786篇 |
2019年 | 1605篇 |
2018年 | 1808篇 |
2017年 | 2015篇 |
2016年 | 1795篇 |
2015年 | 2338篇 |
2014年 | 2997篇 |
2013年 | 3458篇 |
2012年 | 3679篇 |
2011年 | 4024篇 |
2010年 | 3691篇 |
2009年 | 3311篇 |
2008年 | 3274篇 |
2007年 | 3224篇 |
2006年 | 3208篇 |
2005年 | 2776篇 |
2004年 | 2052篇 |
2003年 | 2148篇 |
2002年 | 2491篇 |
2001年 | 2078篇 |
2000年 | 1588篇 |
1999年 | 1687篇 |
1998年 | 1239篇 |
1997年 | 1064篇 |
1996年 | 1103篇 |
1995年 | 842篇 |
1994年 | 628篇 |
1993年 | 467篇 |
1992年 | 361篇 |
1991年 | 272篇 |
1990年 | 204篇 |
1989年 | 164篇 |
1988年 | 151篇 |
1987年 | 86篇 |
1986年 | 69篇 |
1985年 | 37篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1965年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Duan Haiyang Wang Xudong Bai Yu Yao Man Guo Qingtao 《Metallurgical and Materials Transactions B》2019,50(5):2343-2353
Metallurgical and Materials Transactions B - Mold breakout is a catastrophic accident that has serious impacts on smooth production, slab quality, and caster equipment. Accurate identification and... 相似文献
72.
在裂缝性致密储层中,裂缝既是油流通道又是水驱窜流通道,在注水开发中由于裂缝的存在导致水驱波及效率低,从而形成无效注水开发。此外,裂缝性储层的封堵又存在大裂缝封堵效果差、有效期短等问题。鉴于此研制了水溶性酚醛树脂冻胶和单体地层聚合高强度堵剂体系,测定了堵剂在70℃下的成胶性能、稳定性以及封堵强度等。通过细管模拟裂缝研究了不同因素对堵剂突破压力的影响;通过可视化细管研究了堵剂在管中的突破方式以及影响因素。研究结果表明,水溶性酚醛树脂冻胶的突破压力随着冻胶强度的增加而增加,随着管径的增加而减小,随着注水速度的增加先减小、后增加,最后稳定;单体地层聚合堵剂的突破压力随着堵剂强度的增加而增加,随着管径的增加先增大、后减小。在可视化细管实验中,堵剂突破时并不完全沿细管中心突破,其堵剂的强度与黏附性等因素有关。 相似文献
73.
通过扭转试验和扫描电镜评价了焊丝钢ER70S-6的氧化皮剥离性能。氧化皮和基体之间存在的铁硅氧化物Fe2SiO4(2FeO·SiO2)和FeO为主要成分的富硅层,在机械折弯及砂带打磨过程中难以除净,使焊丝表面镀铜效果及焊接性能恶化。提出了通过提高加热炉加热段温度至985℃、提高均热段温度至1110℃,进而阻碍氧向富硅层的扩散;建立PF线保温墙和保温通廊,进而促进FeO的歧化反应;缩短精轧机换辊时间3h,进而减少氧化铁皮对铁基体的压入;降低吐丝速度至90m/s、提高吐丝温度至930℃进而增加氧化铁皮厚度等方式来改善ER70S-6表面氧化皮剥离性能。工艺优化后,ER70S-6表面氧化铁皮由粉末状脱落变为片层状脱落,粗细拔半成品表面间断性发黑现象消失,镀铜层平均厚度由1.45μm增加至3.6μm,表面光亮度显著提高。 相似文献
74.
Liu Chunwei Huang Shuigen Blanpain Bart Guo Muxing 《Metallurgical and Materials Transactions B》2019,50(1):271-281
Metallurgical and Materials Transactions B - Basic oxygen furnace (BOF) steel slag is a main byproduct that is produced during the converter steelmaking process. The volume instability and fast... 相似文献
75.
An active band‐notched frequency selective absorber (BNFSA) with switchable notch band is proposed in this article. The BNFSA is a two‐layer structure composed of a lossy layer at the top and a ground plane at the bottom, separated by an air spacer. The element of the lossy layer is a lumped‐resistor‐loaded metallic dipole with a parallel LC resonance structure, which is realized by complementary n‐shaped resonator (CnR) inserted in the center, and PIN diode is welded at two arms of CnR. The bias circuit printed on the back of the substrate of the lossy layer connects to anode and cathode of the diode by via hole and isolates by the inductor. Simulation results show that the notch bands are located at 4.50 and 6.81 GHz when the diode sets to ON and OFF, respectively. To validate the performance of switchable BNFSA, the prototypes are fabricated and measured, reasonable agreement between simulated and measured results is obtained. 相似文献
76.
77.
Lihong Zhang Xiangyu Guo Shiping Huang 《International Journal of Hydrogen Energy》2021,46(53):26950-26960
By virtue of their wide band gaps, the photocatalytic ability of MnPS3 and ZnPS3 for water splitting is subject to narrow visible light adsorption. In this work, the first-principle calculations are adopted to study the impact of biaxial strain and electric field on photocatalytic performance of MnPS3 and ZnPS3. Our theoretical calculations demonstrate that MnPS3 under ?10% biaxial strain, ?5% biaxial strain and a 0.05 V/Å electric field possess appropriate band gaps and band edge positions required for photocatalytic water splitting as well as pronounced absorbance in the visible and ultraviolet spectrum. Whereas, the band structures for ZnPS3 can not be altered significantly either by applying biaxial strain or electric field. Through the free energy change analysis, it is found that water splitting reactions on MnPS3 under ?10% biaxial strain as well as ?5% biaxial strain can be thermodynamically spontaneous at pH 7–10 using natural sunlight. 相似文献
78.
Sun Xiaohao Miao Linchang Wang Hengxing Chen Runfa Guo Xin 《Bulletin of Engineering Geology and the Environment》2021,80(6):4957-4966
Bulletin of Engineering Geology and the Environment - Bio-cementation is currently applied to solidify sandy soils, but only few studies use it to cement loess soil particles. In this study, the... 相似文献
79.
Three Brønsted acidic imidazole dicationic ionic liquids (ILs) with different length of alkyl chains, [Cn(Mim)2][HSO4]2 (n = 3, 6, 12), were prepared and used as catalyst for the esterification reaction of free fatty acids and methanol. Taking oleic acid as model acid, the catalytic performances of the synthesized ILs for the esterification were evaluated. The main physicochemical properties of the ILs, thermal stability, acidity, solubility in common solvents, and causticity on Austenitic stainless steel 316, were examined. [C3(Mim)2][HSO4]2 demonstrated the highest catalytic activity and enabled to assess the preliminary optimum esterification condition of oleic acid and methanol. Under optimized reaction conditions, the yield of oleic acid methyl ester was up to 95 %. The ILs have great potential as catalysts for producing fatty acid methyl esters from long‐chain free fatty acids. 相似文献
80.
Natural Computing - The fiber stretching process plays the key role in the process of fiber production and its effects is measured by the stretching ratio. The stretching ratio is determined by the... 相似文献