全文获取类型
收费全文 | 1109篇 |
免费 | 19篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 115篇 |
综合类 | 6篇 |
化学工业 | 222篇 |
金属工艺 | 50篇 |
机械仪表 | 29篇 |
建筑科学 | 28篇 |
矿业工程 | 1篇 |
能源动力 | 43篇 |
轻工业 | 77篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 83篇 |
一般工业技术 | 202篇 |
冶金工业 | 178篇 |
原子能技术 | 39篇 |
自动化技术 | 54篇 |
出版年
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 52篇 |
2012年 | 47篇 |
2011年 | 57篇 |
2010年 | 37篇 |
2009年 | 39篇 |
2008年 | 50篇 |
2007年 | 46篇 |
2006年 | 27篇 |
2005年 | 35篇 |
2004年 | 34篇 |
2003年 | 33篇 |
2002年 | 31篇 |
2001年 | 27篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 53篇 |
1997年 | 51篇 |
1996年 | 33篇 |
1995年 | 22篇 |
1994年 | 24篇 |
1993年 | 25篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 26篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有1134条查询结果,搜索用时 15 毫秒
1.
2.
Ken Kanazawa Shoji Yoshida Hidemi Shigekawa Shinji Kuroda 《Science and Technology of Advanced Materials》2015,16(1)
The reconstructed surface structure of the II–VI semiconductor ZnTe (110), which is a promising material in the research field of semiconductor spintronics, was studied by scanning tunneling microscopy/spectroscopy (STM/STS). First, the surface states formed by reconstruction by the charge transfer of dangling bond electrons from cationic Zn to anionic Te atoms, which are similar to those of IV and III–V semiconductors, were confirmed in real space. Secondly, oscillation in tunneling current between binary states, which is considered to reflect a conformational change in the topmost Zn–Te structure between the reconstructed and bulk-like ideal structures, was directly observed by STM. Third, using the technique of charge injection, a surface atomic structure was successfully fabricated, suggesting the possibility of atomic-scale manipulation of this widely applicable surface of ZnTe. 相似文献
3.
Shohei Minagawa Shoji Fujiwara Takeshi Hashimoto Takashi Hayashita 《International journal of molecular sciences》2021,22(9)
Cyclodextrins (CyDs) are water-soluble host molecules possessing a nanosized hydrophobic cavity. In the realm of molecular recognition, this cavity is used not only as a recognition site but also as a reaction medium, where a hydrophobic sensor recognizes a guest molecule. Based on the latter concept, we have designed a novel supramolecular sensing system composed of Zn(II)-dipicolylamine metal complex-based azobenzene (1-Zn) and 3A-amino-3A-deoxy-(2AS,3AS)-γ-cyclodextrin (3-NH2-γ-CyD) for sensing adenosine-5′-triphosphate (ATP). 1-Zn showed redshifts in the UV-Vis spectra and induced circular dichroism (ICD) only when both ATP and 3-NH2-γ-CyD were present. Calculations of equilibrium constants indicated that the amino group of 3-NH2-γ-CyD was involved in the formation of supramolecular 1-Zn/3-NH2-γ-CyD/ATP. The Job plot of the ICD spectral response revealed that the stoichiometry of 1-Zn/3-NH2-γ-CyD/ATP was 2:1:1. The pH effect was examined and 1-Zn/3-NH2-γ-CyD/ATP was most stable in the neutral condition. The NOESY spectrum suggested the localization of 1-Zn in the 3-NH2-γ-CyD cavity. Based on the obtained results, the metal coordination interaction of 1-Zn and the electrostatic interaction of 3-NH2-γ-CyD were found to take place for ATP recognition. The “reaction medium approach” enabled us to develop a supramolecular sensing system that undergoes multi-point interactions in water. This study is the first step in the design of a selective sensing system based on a good understanding of supramolecular structures. 相似文献
4.
In the CA1 region of rat hippocampal slices, H2O2 (0.294-2.94 mM) caused initial augmentation, and subsequent long-lasting depression, of population spikes and excitatory postsynaptic potentials. The effect of H2O2 may not be mediated by its degradation product, hydroxyl radicals, because an iron chelator deferoxamine did not block the effect. A catalase inhibitor 3-amino-1,2,4-triazole only modestly attenuated the initial augmentation, suggesting that the effect of H2O2 is not attributable to catalase-dependent O2 generation, either. An N-methyl-D-aspartate receptor antagonist DL-2-amino-5-phosphonovaleric acid had no influence on the effect of H2O2, whereas a gamma-aminobutyric acid type A receptor channel blocker picrotoxin attenuated long-lasting depression, indicating that gamma-aminobutyric acid-mediated inhibition is altered during the depression phase. The initial augmentation but not subsequent depression was attenuated by a phospholipase A2/C inhibitor 4-bromophenacyl bromide, suggesting the involvement of lipid signaling molecule(s) in the enhancement of excitatory synaptic transmission. These results suggest that H2O2 regulates hippocampal synaptic transmission via multiple mechanisms. 相似文献
5.
Takashi Itoh Hitoe Habuchi Shoji Nitta Shuichi Nonomura 《Fullerenes, Nanotubes and Carbon Nanostructures》1994,2(2):181-187
Gas effusion spectra of fullerenes are studied. Three peaks of toluene are found in gas effusion spectra dp/dT-T. Two peaks of oxygen are found in gas effusion spectra dN/dt-T of samples kept in the air after annealing to avoid the toluene. These phenomena confirmed to be reversible are discussed by treating fullerenes as intercalated materials. 相似文献
6.
7.
Shoji Eguchi 《Fullerenes, Nanotubes and Carbon Nanostructures》1997,5(5):977-987
Recent progress of synthesis of C60 derivatives functionalized with hetero-cycles is reviewed, focusing attention on [4+2]- and [3+2] cycloaddition methodologies and oxidative heterocyclization. 相似文献
8.
9.
10.
Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress 总被引:2,自引:0,他引:2
K. Matsuki N. Kaga T. Yokoyama N. Tsuda 《International Journal of Rock Mechanics and Mining Sciences》2004,41(7):1167-1190
To determine all of the components of in situ stress from core discing, both the directions and magnitudes of the principal in situ stresses must be determined for a disc of a given thickness. In this study, we analyzed the direction and magnitude of tensile stress below an HQ core stub for 11 core lengths using stress conditions under which core discing is likely to occur. First, based on an analysis of the direction of tensile stress below the core stub, we propose a method for determining directions of in situ stress from the height distribution at the periphery of the end surface of a disc. This method can be used with a disc of any thickness. Next, based on an analysis of the magnitude of tensile stress in the central part of a core, we propose a linear criterion for core discing, which can be applied to a core of any length. This criterion was in good agreement with an empirical formula obtained previously in laboratory experiments. By combining information on the direction of in situ stress and the linear criterion for core discing, we propose a method for determining all of the components of in situ stress from core discing under the assumption that vertical stress is given by the overburden stress. Finally, these methods were applied to discs obtained from a field where hydraulic fracturing was performed to measure horizontal stresses. The results showed that the azimuths of the principal stresses estimated from core discing were consistent with those of the principal horizontal stresses determined by hydraulic fracturing and that while the magnitudes of the principal horizontal stresses estimated from core discing showed a large scatter, they were similar to those determined by hydraulic fracturing. 相似文献