全文获取类型
收费全文 | 3234篇 |
免费 | 89篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 1篇 |
化学工业 | 434篇 |
金属工艺 | 19篇 |
机械仪表 | 43篇 |
建筑科学 | 46篇 |
矿业工程 | 3篇 |
能源动力 | 37篇 |
轻工业 | 273篇 |
水利工程 | 10篇 |
石油天然气 | 5篇 |
无线电 | 66篇 |
一般工业技术 | 268篇 |
冶金工业 | 1927篇 |
原子能技术 | 12篇 |
自动化技术 | 162篇 |
出版年
2024年 | 5篇 |
2023年 | 15篇 |
2022年 | 50篇 |
2021年 | 71篇 |
2020年 | 56篇 |
2019年 | 70篇 |
2018年 | 53篇 |
2017年 | 69篇 |
2016年 | 66篇 |
2015年 | 34篇 |
2014年 | 63篇 |
2013年 | 98篇 |
2012年 | 85篇 |
2011年 | 108篇 |
2010年 | 79篇 |
2009年 | 83篇 |
2008年 | 67篇 |
2007年 | 61篇 |
2006年 | 39篇 |
2005年 | 34篇 |
2004年 | 33篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 61篇 |
1998年 | 638篇 |
1997年 | 359篇 |
1996年 | 244篇 |
1995年 | 122篇 |
1994年 | 100篇 |
1993年 | 113篇 |
1992年 | 17篇 |
1991年 | 25篇 |
1990年 | 29篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 17篇 |
1986年 | 25篇 |
1985年 | 32篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 18篇 |
1978年 | 3篇 |
1977年 | 34篇 |
1976年 | 69篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有3325条查询结果,搜索用时 15 毫秒
1.
Ricardo Cambraia Parreira Diana Paola Gmez‐Mendoza Itamar Couto Guedes de Jesus Rafael Pereira Lemos Anderson Kennedy Santos Cristiana Perdigo Rezende Henrique Csar Pereira Figueiredo Mauro Cunha Xavier Pinto Frank Kjeldsen Silvia Guatimosim Rodrigo Ribeiro Resende Thiago Verano‐Braga 《Proteomics. Clinical applications》2020,14(4)
2.
3.
The present study focuses on the sintering of silicon carbide-based ceramics (SiC) by liquid phase sintering (LPS) followed by characterization of the produced ceramics. AlN/Re2O3 mixtures were used as additives in the LPS process. In the first step, the LPS-SiC materials were produced in a graphite resistance furnace in the form of discs at different temperatures. The conditions with the best results regarding real density and relative density were taken as reference for sintering in the form of prismatic bars. In the second step, these samples were evaluated regarding fracture toughness (KIC), by the Single Edge V Notch Beam – SEVNB – method, and flexural strength. KIC behavior was evaluated according to the depth and curvature radius of the notches. Reliable KIC values were presented when the ceramic displayed a small curvature radius at the notch tip. When the radius was large, it did not maintain the square root singularity of the notch tip. Tests were carried out to determine KIC values in atmospheric air and water. KIC results were lower in water than air, with a decrease ranging between 2.56% and 11.26%. The observations indicated a direct grain size correlation between KIC values and fracture strength of the SiC ceramics. 相似文献
4.
5.
6.
The wetting of Ti–Cu alloys on Si3N4 was analyzed by the sessile drop method, using an imaging system with a CCD camera during the heating under argon flow. The contact angle was measured as a function of temperature and time. The samples were cut transversally and characterized by scanning electron microscopy and energy dispersive spectrometry (SEM/EDS). Wettability of the Ti–Cu alloy on Si3N4 is influenced by the reaction between the Ti and the ceramic. The TC1 and TC2 alloys presented low final contact angle values around 2° and 26°, respectively, indicating good wetting on Si3N4. 相似文献
7.
Pedro Ribeiro 《International journal for numerical methods in engineering》2004,61(15):2696-2715
A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
8.
Combined time and wavelength multiplexing technique of optical fiber grating sensor arrays using commercial OTDR equipment 总被引:1,自引:0,他引:1
Valente L.C.G. Braga A.M.B. Ribeiro A.S. Regazzi R.D. Ecke W. Chojetzki C. Willsch R. 《IEEE sensors journal》2003,3(1):31-35
The use of a commercial optical time domain reflectometry device for simultaneous wavelength and time domain multiplexing of fiber-optic Bragg grating sensors is proposed and demonstrated. The realization of such systems provides an inexpensive way of interrogating several hundreds of sensors in a single fiber. Strain resolution of 30 /spl mu/m/m over a strain measuring range of 0.5% was obtained. 相似文献
9.
A new method for seed oil body purification and examination of oil body integrity following germination 总被引:1,自引:0,他引:1
Plant seeds store triacylglycerols as energy sources for germination and postgerminative growth of seedlings. The triacylglycerols are preserved in small, discrete, intracellular organelles called oil bodies. A new method was developed to purify seed oil bodies. The method included extraction, flotation by centrifugation, detergent washing, ionic elution, treatment with a chaotropic agent, and integrity testing by use of hexane. These processes subsequently removed non-specifically associated or trapped proteins within the oil bodies. Oil bodies purified by this method maintained their integrity and displayed electrostatic repulsion and steric hindrance on their surface. Compared with the previous procedure, this method allowed higher purification of oil bodies, as demonstrated by SDS-PAGE using five species of oilseeds. Oil bodies purified from sesame were further analyzed by two-dimensional gel electrophoresis and revealed two potential oleosin isoforms. The integrity of oil bodies in germinating sesame seedlings was examined by hexane extraction. Our results indicated that consumption of triacylglycerols reduced gradually the total amount of oil bodies in seedlings, whereas no alteration was observed in the integrity of remaining oil bodies. This observation implies that oil bodies in germinating seeds are not degraded simultaneously. It is suggested that glyoxisomes, with the assistance of mitochondria, fuse and digest oil bodies one at a time, while the remaining oil bodies are preserved intact during the whole period of germination. 相似文献
10.
A 78-year-old Chinese woman presented with recurrent postprandial abdominal pain. Computerised tomography revealed a small bowel tumour causing volvulus of a segment of the small bowel. Laparotomy confirmed an extraluminal ileal tumour with partial volvulus of the involved small bowel segment. Small bowel resection was done. Histological and ultrastructural studies confirmed a gastrointestinal autonomic nerve tumour. We review the medical literature on this rare tumour. 相似文献