全文获取类型
收费全文 | 723篇 |
免费 | 14篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 46篇 |
综合类 | 2篇 |
化学工业 | 184篇 |
金属工艺 | 21篇 |
机械仪表 | 19篇 |
建筑科学 | 15篇 |
能源动力 | 36篇 |
轻工业 | 57篇 |
水利工程 | 3篇 |
无线电 | 69篇 |
一般工业技术 | 133篇 |
冶金工业 | 74篇 |
原子能技术 | 32篇 |
自动化技术 | 51篇 |
出版年
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 39篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 35篇 |
2009年 | 38篇 |
2008年 | 49篇 |
2007年 | 38篇 |
2006年 | 24篇 |
2005年 | 32篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 12篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 27篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有742条查询结果,搜索用时 15 毫秒
61.
Containerless processing was used to investigate the glass-forming behavior of Al2 O3 –Y2 O3 glass. The amorphous bulk samples were obtained at compositions with 25–37.5 mol% yttria when the melt was cooled at a cooling rate of ∼250 K/s. Although small spherical particles (∼10 μm) with the same composition of the matrix were detected in the amorphous samples with 32.5–37.5 mol% yttria, the microfocus X-ray diffraction result indicated that the small spherical particles were crystalline Y3 Al5 O12 garnet (YAG), rather than being amorphous. This observation suggested that small YAG particles could not grow larger after their nucleation, because of the high viscosity at high undercooling and the high cooling rate, which would graze the nose of the continuous cooling temperature diagram of YAG. 相似文献
62.
A numerical analysis technique that incorporates Voronkov's model were examined and used to estimate the distribution of defects during crystal growth. By comparisons of the distribution of the density of LSTD and the position of R-OSF in non-nitrogen-doped (non-N-doped) and nitrogen-doped (N-doped) silicon crystals, it is found that the results of the numerical analyses agree with practically evaluated data. The observations suggest that the R-OSF nucleus is a VO2 complex that is formed by bonds between oxygen atoms and residual vacancies consumed during the formation of void defects. This suggests that Voronkov's model can be used to accurately predict the generation and growth of defects in silicon crystals. This numerical analysis technique was also found to be an effective method of estimating the distribution of defects in silicon crystals during crystal growth. 相似文献
63.
Shingo Urata Hiroyuki Hijiya Kazuhiko Niwano Jun Matsui 《Journal of the American Ceramic Society》2022,105(6):4200-4207
To theoretically explore amorphous materials with a sufficiently low dielectric loss, which are essential for next-generation communication devices, the applicability of a nonequilibrium molecular dynamics simulation employing an external alternating electric field was examined using alkaline silicate glass models. In this method, the dielectric loss is directly evaluated as the phase shift of the dipole moment from the applied electric field. This method enabled us to evaluate the dielectric loss in a wide frequency range from 1 GHz to 10 THz. It was observed that the dielectric loss reaches its maximum at a few THz. The simulation method was found to qualitatively reproduce the effects of alkaline content and alkaline type on the dielectric loss. Furthermore, it reasonably reproduced the effect of mixed alkalines on the dielectric loss, which was observed in our experiments on sodium and/or potassium silicate glasses. Alkaline mixing was thus found to reduce the dielectric loss. 相似文献
64.
The discovery of Lgr5+ intestinal stem cells (ISCs) triggered a breakthrough in the field of ISC research. Lgr5+ ISCs maintain the homeostasis of the intestinal epithelium in the steady state, while these cells are susceptible to epithelial damage induced by chemicals, pathogens, or irradiation. During the regeneration process of the intestinal epithelium, more quiescent +4 stem cells and short-lived transit-amplifying (TA) progenitor cells residing above Lgr5+ ISCs undergo dedifferentiation and act as stem-like cells. In addition, several recent reports have shown that a subset of terminally differentiated cells, including Paneth cells, tuft cells, or enteroendocrine cells, may also have some degree of plasticity in specific situations. The function of ISCs is maintained by the neighboring stem cell niches, which strictly regulate the key signal pathways in ISCs. In addition, various inflammatory cytokines play critical roles in intestinal regeneration and stem cell functions following epithelial injury. Here, we summarize the current understanding of ISCs and their niches, review recent findings regarding cellular plasticity and its regulatory mechanism, and discuss how inflammatory cytokines contribute to epithelial regeneration. 相似文献
65.
Mg6Si4O10(OH)8修复剂应用于滑动轴承的模拟试验研究 总被引:1,自引:0,他引:1
采用模拟轴承试验机,考察在设计的试验条件下金属磨损自修复层在45#钢/巴氏合金摩擦副间的原位生成及其摩擦学性能。润滑剂使用含适量Mg6Si4O10(OH)8修复剂的SD/CC 40汽油机/柴油机通用油。27 h摩擦试验结束后,采用表面形貌仪、扫描电镜和显微硬度计分析摩擦表面。结果表明,在45#钢表面形成了约2μm厚的自修复层,2个摩擦副表面的表面形貌均有明显改善;显微硬度均有一定的提高,金属磨损自修复层表现出优良的抗磨粒磨损和抗粘着磨损的性能。 相似文献
66.
The thermal behavior of polyacrylonitrile (PAN) has been investigated using X-ray diffraction, differential scanning calorimetry (DSC), and ultrafast DSC. In conventional DSC, it is difficult to prevent the concurrent occurrence of the exothermic reactions of PAN with melting. However, in the ultrafast DSC curve, the exothermic peak due to these reactions disappears over the temperature range 0–400 °C at heating rates above 250 °C s−1. Alternatively, the glass transition and the melting of PAN are observed over the temperature range 109–129 °C and 335–362 °C, respectively. Moreover, upon cooling from the molten state at a rate of −7500 °C s−1, PAN crystallization is observed at 204 °C. These findings were observed repeatedly during heating and cooling measurements. From the extrapolation analysis, the zero-entropy-production melting temperature of PAN is found to lie in the temperature range 320–350 °C. Finally, the equilibrium melting temperature of PAN is estimated to be ca. 465 °C. 相似文献
67.
Dr. Chikara Dohno Prof. Kazuhiko Nakatani 《Chembiochem : a European journal of chemical biology》2019,20(23):2903-2910
We introduce the concept of molecular glues for RNA, in which specific RNA-binding small molecules induce designed structural changes in target functional RNAs, resulting in modulation of the functions. (Z)-NCTS is an RNA-mismatch-binding small molecule that recognizes 5′-r(XGG)-3′/5′-r(XGG)-3′ sequences (X=U or A) and acts as a molecular glue for RNA. The binding of (Z)-NCTS brings two distinct 5′-r(XGG)-3′ domains into contact with each other, and this can result in higher-order structural changes of target RNAs. We applied (Z)-NCTS to induce the formation of a proposed tertiary structure of a ribozyme together with activation of RNA-cleaving ability. The concept of a molecular glue could inspire new small-molecule-based strategies for regulating biological functions: a synthetic small molecule targeting functional RNAs could regulate the RNA structure and function. 相似文献
68.
Tetsuya Ōgushi Gopal N. Suresha Yutaka Honjo Yoshihisa Ōzono Iwazo Kawano Tadashi Numata Yoshinori Hakuraku 《Journal of Low Temperature Physics》1987,69(5-6):451-457
We prepared La-Sr-Nb-O system samples both in bulk form and as a film, with sharp resistive transitions at temperatures of 228–323 K, depending on the annealing conditions. The sharp resistive transitions might be attributable to superconductivity. Magnetic ordering was observed over a narrow temperature range around 40 K for some of the samples. 相似文献
69.
70.
Kazuhiko Honda Eiji ૿ sawa Zdenek Slanina Takatoshi Matsumoto 《Fullerenes, Nanotubes and Carbon Nanostructures》1996,4(5):819-834
As a continuation of the studies on thermal transformation of the [2+2] C60 dimer (1), the consequence of the pyracylene-rearrangement-like valence isomerization of the fulvalene partial structure at the bridge of the ring-opened product from 1, namely 2, was searched by dynamic reaction coordinate /AM1 semiempirical MO calculations. It is predicted that the fulvalene bridge of 2 rearranges into naphthalene partial structure by the concerted 'in-plane' mechanism to give a wide-bridged C120 intermediate having twenty five-membered rings and two ten-membered rings (3). The computed energy of activation (145 kcal/mol) is 40 kcal/mol lower than those computed for pyracylene rearrangements. In contrast, the recently reported analogous rearrangement of indigo (13) to dibenzonaphthyridindione (14) is computed to occur by the stepwise 'sp3' mechanism. 相似文献