全文获取类型
收费全文 | 39631篇 |
免费 | 4389篇 |
国内免费 | 2635篇 |
专业分类
电工技术 | 1583篇 |
综合类 | 2322篇 |
化学工业 | 8249篇 |
金属工艺 | 3277篇 |
机械仪表 | 1505篇 |
建筑科学 | 2308篇 |
矿业工程 | 839篇 |
能源动力 | 1420篇 |
轻工业 | 1519篇 |
水利工程 | 305篇 |
石油天然气 | 314篇 |
武器工业 | 503篇 |
无线电 | 4933篇 |
一般工业技术 | 13786篇 |
冶金工业 | 2055篇 |
原子能技术 | 390篇 |
自动化技术 | 1347篇 |
出版年
2024年 | 174篇 |
2023年 | 916篇 |
2022年 | 975篇 |
2021年 | 1395篇 |
2020年 | 1674篇 |
2019年 | 1445篇 |
2018年 | 1304篇 |
2017年 | 1429篇 |
2016年 | 1404篇 |
2015年 | 1431篇 |
2014年 | 2092篇 |
2013年 | 2275篇 |
2012年 | 2524篇 |
2011年 | 3323篇 |
2010年 | 2342篇 |
2009年 | 2568篇 |
2008年 | 2356篇 |
2007年 | 2711篇 |
2006年 | 2394篇 |
2005年 | 2202篇 |
2004年 | 1767篇 |
2003年 | 1574篇 |
2002年 | 1290篇 |
2001年 | 961篇 |
2000年 | 862篇 |
1999年 | 603篇 |
1998年 | 543篇 |
1997年 | 378篇 |
1996年 | 313篇 |
1995年 | 252篇 |
1994年 | 247篇 |
1993年 | 168篇 |
1992年 | 149篇 |
1991年 | 139篇 |
1990年 | 121篇 |
1989年 | 98篇 |
1988年 | 47篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 22篇 |
1984年 | 36篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1963年 | 2篇 |
1955年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The present paper includes experimental and analytical data on the fracture properties of a nickel-iron superalloy, a ferromagnetic austenite, at 4 K in magnetic fields of 0 and 6 T. The tensile, notch tensile and small punch tests are employed. A finite element analysis is also performed to convert the experimentally measured load-displacement data into useful engineering information. To interpret the results we review the available theory of the influence of magnetic field on the stress intensity factor for a crack in ferromagnetic materials. 相似文献
63.
64.
滑坡相似材料试验结果优化分析研究 总被引:2,自引:0,他引:2
在运用模糊综合评判确定的滑坡相似材料试验配合比隶属度基础上,利用方差分析确定各因素的数学优化区间,结合变量有上下界的改进单纯形法,获得技术,经济上的最佳配合比,克服了统计优化理论不能在连续区间寻优的缺点,这对从事滑坡相似材料试验研究具有一定的实际意义。 相似文献
65.
机械合金化Fe-Ni粉末的相结构 总被引:1,自引:0,他引:1
使用XRD和Moessbauer等方法,研究了在Ar气氛下机械合金化Fe—Ni粉末相结构的变化.结果表明,在机械合金化Fe64-Ni36粉末过程中,fcc相的数量随着球磨时间的增加先增加然后减少,与加乙醇球磨Fe64-Ni36的情形相同.当Ni的含量(原子分数)大于50%时,有fcc相、顺磁相和FeNi3形成,当Ni的含量低于50%时,bcc相的数量随着Ni含量减少而增加.Moessbauer谱的结果表明,因球磨时间或Fe、Ni比例的不同,Fe—Ni球磨粉末固溶体具有不同结构的原子配比。 相似文献
66.
67.
Based on the concept of complete stress–strain diagrams, we propose a new model describing the law of stress distribution in the prefracture zone in plastic materials in view of the type of the stressed state. 相似文献
68.
69.
Toshiyuki MasuiTakanobu Chiga Nobuhito Imanaka Gin-ya Adachi 《Materials Research Bulletin》2003,38(1):17-24
Fine particles of a blue emission phosphor Sr2CeO4 have been synthesized using a chemical co-precipitation technique, and the textual and luminescent properties were compared with the one synthesized by the conventional solid-state reaction method. Particle size and distribution of the Sr2CeO4 fine powder prepared by the co-precipitation process were smaller and narrower than those obtained by the samples prepared from the conventional one. The emission intensity of the fine particles was equal to that of the larger particles prepared from the solid-state reaction, on the contrary to the general tendency that emission intensity decrease with particle size reduction. Although no Ce3+ peaks were observed in EPR measurements, X-ray photoelectron spectra of the samples clearly elucidated the existence of Ce3+ only on the surface of Sr2CeO4. 相似文献
70.
J. B. Quinn G. E. Schumacher L. W. Schultheis 《Journal of Failure Analysis and Prevention》2004,4(1):41-46
Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage,
recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist
during placement of a breathing tube at the start of surgery.
In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture
characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be
described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken
by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken
canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied
during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing
tube during recovery was the likely cause of fracture.
This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic
analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing. 相似文献