全文获取类型
收费全文 | 17502篇 |
免费 | 1460篇 |
国内免费 | 784篇 |
专业分类
电工技术 | 946篇 |
技术理论 | 3篇 |
综合类 | 1172篇 |
化学工业 | 3069篇 |
金属工艺 | 859篇 |
机械仪表 | 943篇 |
建筑科学 | 1414篇 |
矿业工程 | 470篇 |
能源动力 | 501篇 |
轻工业 | 970篇 |
水利工程 | 292篇 |
石油天然气 | 1371篇 |
武器工业 | 109篇 |
无线电 | 2046篇 |
一般工业技术 | 2448篇 |
冶金工业 | 773篇 |
原子能技术 | 189篇 |
自动化技术 | 2171篇 |
出版年
2024年 | 62篇 |
2023年 | 289篇 |
2022年 | 457篇 |
2021年 | 682篇 |
2020年 | 461篇 |
2019年 | 459篇 |
2018年 | 502篇 |
2017年 | 505篇 |
2016年 | 454篇 |
2015年 | 615篇 |
2014年 | 792篇 |
2013年 | 902篇 |
2012年 | 1053篇 |
2011年 | 1152篇 |
2010年 | 1014篇 |
2009年 | 1012篇 |
2008年 | 955篇 |
2007年 | 925篇 |
2006年 | 985篇 |
2005年 | 863篇 |
2004年 | 595篇 |
2003年 | 555篇 |
2002年 | 489篇 |
2001年 | 417篇 |
2000年 | 453篇 |
1999年 | 483篇 |
1998年 | 424篇 |
1997年 | 407篇 |
1996年 | 365篇 |
1995年 | 333篇 |
1994年 | 241篇 |
1993年 | 190篇 |
1992年 | 153篇 |
1991年 | 89篇 |
1990年 | 103篇 |
1989年 | 104篇 |
1988年 | 67篇 |
1987年 | 32篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
探讨了用电解铝液直接生产高品质6061铝合金圆铸锭工艺技术,主要在熔体处理、炉内精炼、晶粒细化、炉外在线净化、均匀化处理和生产设备等方面采取了相应的技术措施.结果表明,优化后的生产工艺制度能够满足高品质6061铝合金圆铸锭的质量要求,在均匀化过程中适宜的均匀化工艺为560℃×8h. 相似文献
963.
964.
965.
Bubble emergence in a gas‐liquid flow in a T‐junction microchannel of 100 μm diameter, operated under a squeezing regime, was simulated with the computational fluid dynamics method. In general, bubble formation in channels includes three stages: expansion, collapse and pinching off. After analyzing and comparing quantitatively the three forces of pressure, surface tension and shear stress acting on the gas thread in the whole process, their effects in the different stages were identified. The collapse stage was the most important for bubble formation and was investigated in detail. It was found that the collapse process was mostly influenced by the liquid superficial velocity, and the rate and time of collapse can be correlated with empirical equations including the liquid superficial velocity, the capillary number and the Reynolds number. 相似文献
966.
On December 2, the broad masses of R & D personnels of Shuguang Rubber Industry Research and Design Institute united, cooperated, hard researched and successful developed the second-generation security tires which are passed the testment of various machines, which marked the another breakthrough in the safety tire field from Shuguang institute. 相似文献
967.
Chen Hao‐Sen Yu Xia Guo Ya‐Zhou Fang Dai‐Ning 《Journal of the American Ceramic Society》2013,96(7):2036-2038
Both dynamic and static three‐point bending fracture testings of 32 piezoelectric ceramic samples were performed in four different poling directions. A modified split Hopkinson pressure bar method with a polyvinylidene fluoride (PVDF)‐based gauge was utilized for the dynamic experiments. The loading rate greatly influenced the fracture toughness in two ways: the dynamic fracture toughness values were much higher than those of the static fracture toughness, and unlike the static fracture toughness, the influence of poling direction on the dynamic fracture toughness was not obvious. 相似文献
968.
部分传输序列(PTS)是一种降低OFDM信号的峰值平均功率比(PAPR)的有效方法。PTS采用是在子序列中添加旋转相位因子[0,21π)。通过对OFDM信号相位分布情况进行研究,本文提出一种改进的PTS方法。改进点在其相位旋转因子的选择上,采用每个子块乘以非均匀分布的旋转因子。 相似文献
969.
We report the ductile fracture behavior of a tough Zr-based bulk metallic glass (BMG) in the dynamic regime, where a rapid moving crack initiates by a Mode II shearing and then advances through plastic voids growth and linking. A clear fractographic evolution from river-like vein pattern to chevron-like zone where microscopic dimples and voids coexist, followed by crack microbranching pattern, was observed on the dynamic fracture surfaces. A terminal crack velocity of about 0.5 of the Rayleigh wave velocity was determined for the onset of such microbranching instability. Furthermore, the dynamic branched daughter cracks are favored to continue in their original mother crack plane, having “directional stability”. Our findings may increase the understanding of the dynamic fracture of BMGs with both glassy nature and metallic bonding character. 相似文献
970.
Qin-Yu Zhu Yu Liu Zhe-Jun Lu Jin-Po Wang Li-Bin Huo Yu-Rong Qin Jie Dai 《Synthetic Metals》2010,160(7-8):713-717
A new paddlewheel dinuclear complex with a pyridyl-tetrathiafulvalene (TTF-py) ligand has been obtained and characterized crystallographically as [(DMT-TTF-py)2Cu2(OAc)4]·2C6H6 (1). Meanwhile a mononuclear compound [(DMT-TTF-py)2Cu(PhCOO)2(CH3OH)2]·2CH2Cl2 (2) was also isolated. UV–vis spectra and cyclic voltammogram of the paddlewheel complex were studied, showing that compound 1 can undergo an oxidization to form a stable cation of [(DMT-TTF-py)2Cu2(OAc)4]2+. By this strategy, compound 3, [(DMT-TTF-py)2Cu2(OAc)4](I3)2 as a radical salt, has been prepared and its conductivity of powder sample was 1.02 × 10?3 ohm?1 cm?1. Antiferromagnetic coupling of Cu(II)–Cu(II) was found from the results of ESR spectra, but the coupling between the radical–Cu(II) was very weak. 相似文献