全文获取类型
收费全文 | 2385篇 |
免费 | 215篇 |
国内免费 | 264篇 |
专业分类
电工技术 | 6篇 |
综合类 | 233篇 |
化学工业 | 1083篇 |
金属工艺 | 371篇 |
机械仪表 | 68篇 |
建筑科学 | 23篇 |
矿业工程 | 43篇 |
能源动力 | 9篇 |
轻工业 | 51篇 |
水利工程 | 4篇 |
石油天然气 | 10篇 |
武器工业 | 14篇 |
无线电 | 65篇 |
一般工业技术 | 801篇 |
冶金工业 | 69篇 |
原子能技术 | 5篇 |
自动化技术 | 9篇 |
出版年
2024年 | 6篇 |
2023年 | 34篇 |
2022年 | 77篇 |
2021年 | 85篇 |
2020年 | 63篇 |
2019年 | 73篇 |
2018年 | 64篇 |
2017年 | 83篇 |
2016年 | 68篇 |
2015年 | 73篇 |
2014年 | 101篇 |
2013年 | 117篇 |
2012年 | 162篇 |
2011年 | 158篇 |
2010年 | 138篇 |
2009年 | 152篇 |
2008年 | 109篇 |
2007年 | 197篇 |
2006年 | 186篇 |
2005年 | 176篇 |
2004年 | 119篇 |
2003年 | 99篇 |
2002年 | 76篇 |
2001年 | 67篇 |
2000年 | 48篇 |
1999年 | 45篇 |
1998年 | 54篇 |
1997年 | 38篇 |
1996年 | 42篇 |
1995年 | 36篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1981年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有2864条查询结果,搜索用时 250 毫秒
101.
钛及钛合金具有优良的生物相容性和机械性能,已应用于临床.尤其是用作骨替换与修复材料。但是.钛属于生物惰性材料.不能与骨组织形成化学键合或称骨键合。通过表面改性可使其在生理环境具有诱导羟基磷灰石在表面自发生长的能力.即生物活性化。这是当今生物医用材料研究的热点领域之一。本文评述了钛表面生物活化的研究现状.简要总结了本课题组在这方面的研究工作。 相似文献
102.
103.
正挤压对SiCw/6061Al晶须形貌的影响 总被引:1,自引:0,他引:1
为了研究正挤压加工对SiCw/6061Al复合材料晶须形貌的影响规律,通过改变挤压温度、挤压比等工艺条件正挤压成形了挤压铸造法制备的15vol.%SiCw/6061Al复合材料,利用SEM技术观察和分析了正挤压加工前后复合材料的微观组织形貌.研究表明:正挤压加工导致SiC晶须沿着复合材料的塑性流动方向呈现出一定程度的定向排列趋势,并伴随有比较明显的折断现象;挤压温度、挤压比等工艺参数都是影响SiC晶须形貌的主要因素. 相似文献
104.
M. Gelinsky U. Knig A. Sewing W. Pompe 《Materialwissenschaft und Werkstofftechnik》2004,35(4):229-233
Porous scaffolds made from mineralised collagen – a biomimetic bone graft material Using biomimetically mineralised collagen type I, a new porous bone graft material has been developed, the composition of which mimics extracellular matrix of bone tissue. The pore structure is generated by a freeze drying process, whereas the pore size can be controlled by temperature and velocity of the freezing over a wide range. The structure is stabilized by crosslinking of the collagen with the water soluble carbodiimide derivative EDC. For the seeding with bone cells, pores with diameters of about 200 μm have turned out to be optimal. These scaffolds are elastic in the wet state which allow for cell culture experiments under mechanical stimulation. 相似文献
105.
XianJia XiaomeiLing 《北京科技大学学报(英文版)》2004,11(1):39-43
SiC whiskers with ″rosary bead″ morphology were synthesized using suitable silicon source and carbon source through solid reaction at the temperature above 1537 K. The diameter and length of the SiC whiskers were about 0.1-1.0 μm and 20-100 μm,respectively. The largest diameter of their enlarged ends of the whiskers was about 0.2-1.0 μm, and it gradually and smoothly decreased to the size of the plain part of the whiskers. The results of X-ray diffraction analysis show that the crystalline structure of the obtained SiC whiskers is β-SiC. It is considered that the SiC whiskers grow via a vapor-solid mechanism. 相似文献
106.
Lianfeng Guo Wenguang Zhang and Chengtao WangSchool of Mechanical Power Engineering Shanghai Jiaotong University Shanghai China 《北京科技大学学报(英文版)》2004,(5)
Nanoparticle hydroxyapatite was prepared by a wet chemical precipitation method. The effects of different synthesis conditions, i.e. contents of reagents (0.2, 0.5 and 0.8 mol/L), reaction temperatures (20, 37, 55 and 75℃) and reaction time (0-24 h), were studied based on crystallization process analysis and the effects of washing methods (with water or alcohol) were also studied. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED) and inductively coupled plasma spectroscopy (ICP) were used to characterize the powders. Chemical analysis shows that the purity of the precipitated hydroxyapatite largely depends on reaction time. X-ray diffraction and TEM micrographs results show that reaction temperature is a key factor affecting crystallinity, morphology and particle size. Degree of supersaturation and stirring also affects the crystallization. Particles are in a shape of short rod and have a size of 20-40 nm in lengt 相似文献
107.
108.
109.
I-Ming Hung Wei-Jen Shih Min-Hsiung Hon Moo-Chin Wang 《International journal of molecular sciences》2012,13(10):13569-13586
In order to obtain the properties of the sintered as-dried calcium phosphate with [Ca]/[P] = 1.50, the characteristics of sintered pellets have been investigated using X-ray diffraction (XRD), inductively coupled plasma-mass spectrometry (ICP-MS), Fourier-transform infrared (FT-IR) spectra, Vickers hardness indentation and scanning electron microscopy (SEM). When the pellet samples were sintered between 700 °C and 1200 °C for 4 h, the hydroxyapatite (Ca10(PO4)6(OH)2, HA) still maintained the major phase, accompanied with the rhenanite (NaCaPO4) as the secondary phase and β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP) as the minor phases. In addition, the HA partially transformed to α-tricalcium phosphate (α-Ca3(PO4)2, α-TCP) and tetracalcium phosphate (Ca4(PO4)2O, TTCP), when the pellet samples were sintered at 1300 °C and 1400 °C, respectively, for 4 h. The maximum density and Vickers Hardness (HV) of sintered pellet samples were 2.85 g/cm3 (90.18% theoretical density (T.D.)) and 407, which appeared at 1200 °C and 900 °C, respectively. 相似文献
110.
Subha Balakrishnan Varun Prasath Padmanabhan Ravichandran Kulandaivelu T.S. Sankara Narayanan Nellaiappan Suresh Sagadevan Suriati Paiman Faruq Mohammad Hamad A. Al-Lohedan Prasanna Kumar Obulapuram Won Chun Oh 《Ceramics International》2021,47(4):5061-5070
Hydroxyapatite (HAP) is the naturally occurring mineral form of calcium apatite and the most studied material as a bone substituent. Considering HAP's inherent properties, this study explored changes in HAP's characteristics from doping with other metals such as Fe. To form pure HAP and Fe-HAP with different amounts of Fe, we used the hydrothermal approach, and the composites that formed were thoroughly analyzed for their crystallinity, surface bonding, morphology, magnetic behavior, mechanical strength, biocompatibility, hemocompatibility, and in vitro cytotoxicity. The powder XRD studies confirmed the samples' crystallinity, and the lowest crystalline size was 19.7 nm in 10Fe-HAP. The FTIR analysis confirmed the formation of HAP by the hydroxyl, phosphate, and carbonate groups. The FESEM demonstrated that the morphology of the pure HAP was rod-shaped, which transformed into spheres after Fe doping. The EDS analysis confirmed the successful formation of HAP and Fe-HAP composites. The magnetic studies indicated the diamagnetic behavior of the pure HAP, while the Fe-doped HAPs had a superparamagnetic nature with saturation magnetizations (Ms) of 2Fe-HAP, 4Fe-HAP, and 10Fe-HAP at 0.0062, 0.0092, and 0.029 emu/g respectively. Assessment of the mechanical properties, biocompatibility, hemocompatibility, and cytotoxicity indicated that the Fe-doped HAPs were superior to the pure HAP, and among the Fe-HAPs, the 10Fe-HAP) had the highest amount of Fe and the best characteristics. The studies also indicated that Ca2+ interactions influenced the cells via HAP doping with that of Fe, equally increasing the physicochemical and biological properties. 相似文献