全文获取类型
收费全文 | 26727篇 |
免费 | 2939篇 |
国内免费 | 1472篇 |
专业分类
电工技术 | 4070篇 |
综合类 | 2045篇 |
化学工业 | 3881篇 |
金属工艺 | 3560篇 |
机械仪表 | 1901篇 |
建筑科学 | 395篇 |
矿业工程 | 1934篇 |
能源动力 | 608篇 |
轻工业 | 1073篇 |
水利工程 | 107篇 |
石油天然气 | 849篇 |
武器工业 | 305篇 |
无线电 | 1903篇 |
一般工业技术 | 4749篇 |
冶金工业 | 2073篇 |
原子能技术 | 456篇 |
自动化技术 | 1229篇 |
出版年
2024年 | 115篇 |
2023年 | 570篇 |
2022年 | 807篇 |
2021年 | 1084篇 |
2020年 | 954篇 |
2019年 | 848篇 |
2018年 | 820篇 |
2017年 | 1018篇 |
2016年 | 1102篇 |
2015年 | 1118篇 |
2014年 | 1439篇 |
2013年 | 1584篇 |
2012年 | 1728篇 |
2011年 | 1929篇 |
2010年 | 1299篇 |
2009年 | 1451篇 |
2008年 | 1332篇 |
2007年 | 1699篇 |
2006年 | 1572篇 |
2005年 | 1348篇 |
2004年 | 1114篇 |
2003年 | 1034篇 |
2002年 | 797篇 |
2001年 | 651篇 |
2000年 | 613篇 |
1999年 | 528篇 |
1998年 | 431篇 |
1997年 | 402篇 |
1996年 | 321篇 |
1995年 | 259篇 |
1994年 | 246篇 |
1993年 | 196篇 |
1992年 | 149篇 |
1991年 | 102篇 |
1990年 | 86篇 |
1989年 | 90篇 |
1988年 | 49篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 32篇 |
1984年 | 41篇 |
1983年 | 33篇 |
1982年 | 42篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1959年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Shunsuke Ohashi 《Electrical Engineering in Japan》2005,150(1):71-77
Magnetic bearing using pinning force of a permanent magnet and a high‐temperature superconductor has been developed. Additional permanent magnet is introduced to increase the levitation force of the magnetic bearing. In this hybrid magnetic bearing system, levitation force is mainly given by the repulsive force of the permanent magnets, and stability for the lateral direction is given by pinning force of the superconductor. The experimental device is developed. A ring‐type superconductor and a bulk one are examined. Levitation characteristics of the hybrid magnetic bearing are measured. The bulk superconductor shows better characteristics of both levitation and lateral stability than the ring one. Levitation force of the hybrid system becomes about twice as large as that of the nonhybrid one. Although, the repulsive force of the permanent magnet decreases the lateral stability of the system, its influence becomes small by choosing an adequate position of the permanent magnets and the superconductor. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 71–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10350 相似文献
102.
103.
V. Salgueiriño‐Maceira M. A. Correa‐Duarte 《Advanced materials (Deerfield Beach, Fla.)》2007,19(23):4131-4144
This Review article ponders core/shell structured nanoparticles that can be prepared with features that combine properties of different materials, including ligands that enhance their biocompatibility. These nanocomposites are not classified in terms of synthesis, but rather by how these features are distributed in the final morphology, attending to connected or isolated materials that end up in interacting or not‐interacting functionalities. In particular, we have focused on magnetic core/shell‐structured particles with a directly connected, coupled, or isolated second functionality. The current progress on methods in colloidal solution that have allowed the great development of these multifunctional magnetic and active spheres on biological and biomedical fields is reported. 相似文献
104.
超微粉石墨层间化合物FeCl3-NiCl2-GICs的制备及电磁性能研究 总被引:2,自引:0,他引:2
以微粉石墨为主体材料合成出不同阶结构的FeCl3-NiCl2-GICs.应用XRD、SEM对产物的晶体结构与表面形貌进行分析表征.采用范德保法测量产物在常温常态下的电阻率,用MODEL9600振动磁强计测量GICs在0~7.958×105A/m磁场强度下的磁化强度、磁化率.测量数据表明异类原子FeCl3、NiCl2插入石黑层间后,GICs的电导率增加1.3~2.9倍,其磁性由石墨的抗磁性转变为顺磁性. 相似文献
105.
Yi Kai Zhou Sung Woo Choi Shigeya Kimura Shuichi Emura Shigehiko Hasegawa Hajime Asahi 《Journal of Superconductivity and Novel Magnetism》2007,20(6):429-432
GaGdN layers were grown at temperatures below 300°C by radio-frequency plasma-assisted molecular beam epitaxy on sapphire
substrates. GaGdN samples with high Gd concentration as high as 12.5% were obtained by lowering the growth temperature. X-ray
diffraction results showed no obvious secondary phase, which means that the phase separation can be suppressed by the growth
at low temperatures. All samples, including those grown at room temperature, showed ferromagnetic characteristics. Photoluminescence
emission was observed, though spectra exhibit broad and sharp luminescence bands related to many kinds of defects. It is suggested
that electrons coming from defects, especially, nitrogen vacancy, stabilize ferromagnetism, and that the carrier-induced ferromagnetism
occurs in the low-temperature-growth GaGdN. 相似文献
106.
Sintered Nd-Fe-B magnet was manufactured by advanced equipment via a SC (Strip casting) technology.It has integrative performance. 相似文献
107.
Crystalline Behavior and Magnetic Properties of Nd60Fe30-x Al10Cox(x = 0,5,10) Bulk Amorphous Alloys
Crystalline behavior and magnetic properties of Nd60Fe30-xAl10Cox( x = 0, 5, 10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X-ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as-cast Nd60Fe30-xAl10Cox ( x = 0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as-cast Nd60Fe30-xAl10Cox (x = 0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity (iHc) increases while the saturation magnetization(σs) and remanence (σr) decrease. The Curie temperature for the as-cast Nd60Fe30-xAl10Cox alloys increases from 451 K for x =0 to 468 K for x = 10. Some pre-cipitation of crystalline phases does not affect the hard magnetic properties of Nd60Fe30-xAl10Cox(x = 0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized. 相似文献
108.
在前新生代油气资源选区评价中,前志留面之下未变质沉积地层(简称前志留基础层)的分布具有重要的参考价值。从提高纵向分辨率的处理和反演技术的应用入手,结合约束条件,利用大地电磁测深数据反演,揭示前志留面等界面的埋深和分布;同时应用小波分析技术,从磁场中分解出区域磁异常,反演结晶基底的埋深。通过这2个界面埋深的差异来分析前志留基础层的分布 相似文献
109.
We have studied properties of quaternary alloy magnetic semiconductor (InGaMn)As grown on InP substrates by low-temperature molecular-beam epitaxy (LT-MBE). A large MCD peak whose intensity is larger than 500 mdeg for (InGaMn)As was observed. This peak intensity was about three times larger than that of typical (GaMn)As films. Relatively high Curie temperature of 83 K of [(In0.53Ga0.47)0.88Mn0.12]As was observed by Hall measurements. The carrier concentration of [(In0.53Ga0.47)0.88Mn0.12]As was estimated to be more than 1.0 × 1021 cm–3 by using the Curie–Weiss fitting of the Hall coefficient R
H, indicating that more than 40% of Mn atoms are activated. This means that (InGaMn)As has a higher activation ratio of Mn as acceptors than (GaMn)As. 相似文献
110.