全文获取类型
收费全文 | 2285篇 |
免费 | 46篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 163篇 |
综合类 | 3篇 |
化学工业 | 385篇 |
金属工艺 | 55篇 |
机械仪表 | 46篇 |
建筑科学 | 42篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 193篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 256篇 |
一般工业技术 | 348篇 |
冶金工业 | 558篇 |
原子能技术 | 50篇 |
自动化技术 | 172篇 |
出版年
2022年 | 23篇 |
2021年 | 42篇 |
2020年 | 20篇 |
2019年 | 13篇 |
2018年 | 32篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 48篇 |
2013年 | 72篇 |
2012年 | 58篇 |
2011年 | 105篇 |
2010年 | 78篇 |
2009年 | 89篇 |
2008年 | 91篇 |
2007年 | 78篇 |
2006年 | 72篇 |
2005年 | 78篇 |
2004年 | 56篇 |
2003年 | 47篇 |
2002年 | 60篇 |
2001年 | 34篇 |
2000年 | 51篇 |
1999年 | 62篇 |
1998年 | 206篇 |
1997年 | 131篇 |
1996年 | 101篇 |
1995年 | 71篇 |
1994年 | 66篇 |
1993年 | 71篇 |
1992年 | 39篇 |
1991年 | 29篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 28篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 22篇 |
1976年 | 19篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1967年 | 6篇 |
排序方式: 共有2341条查询结果,搜索用时 46 毫秒
101.
Yoshihiko Hibi Katsuyuki Fujinawa Seiji Nishizaki Kazuo Okamura Masaharu Tasaki 《Soils and Foundations》2010,50(1):143-159
Diffusion, dispersion, and advection are important processes in multi-gas systems in soils. To date, both Fick's model and the Dusty Gas (DG) model have been used to model the movement of gases in these systems. Dispersion is included in the dispersion-advection equation with Fick's Model for the movement of gases in gas-phase of soil, yet the movement of gases in multi-component gas-soil systems is considered to be expressed more accurately by the DG model than by Fick's model. However to date, no study has investigated the necessity of considering dispersion in the Dusty Gas (DG) model. We carried out column experiments for nitrogen-methane, nitrogen-carbon dioxide, and carbon dioxide-methane binary gas systems in sandy soil, and also did simulations on the same systems using both Fick's model and the DG model. A comparison of the results of the column experiments with our simulations confirmed that there was no need to consider the dispersion in the advection-diffusion equations with the DG model when the velocity of gas was 0.05-0.4 cm/s in Toyoura sand. Furthermore, our experiments and simulations with the DG model showed that, rather than dispersion, tortuosity should be taken into account in application of the DG model to the above condition. 相似文献
102.
N. Fujita K. IshiiH. Ogawa 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(9):1023-1025
We have developed the two-dimensional mapping technique with in-air-PIXE (2D-PIXE) using a metal capillary as a guide to extract ion beam to air. The metal capillary is the conventional injection needle with a 200 μm inside diameter. For the target which is the character made of the copper wires on aluminum basement, 2D-PIXE measurements were performed by irradiating 3 MeV proton beam. As a result, the character was tend to be restored clearly by this method. We discuss about the result of the two-dimensional map from a viewpoint of the signal-to-noise ratio and the resolution. This technique is expected to be applicable to various fields such as biology, nano-technology, archeology and so on. 相似文献
103.
104.
P. Calvani M. Ortolani A. Lucarelli S. Lupi A. Perla P. Maselli N. Kikugawa T. Fujita 《Journal of Superconductivity》2002,15(6):539-542
The in-plane optical conductivity of three metallic La2–x
Sr
x
CuO4 single crystals with 0.10 x 0.15 has been studied between 30 and 295 K. Strong peaks in the far-infrared are observed, which cannot be explained by Drude-like models. Their similarity with peaks reported in Cu–O ladders with one-dimensional charge-ordering, their extremely low frequency, and their behavior with temperature allows us to conclude that those anomalous features are excitations of charge stripes in the Cu–O planes. 相似文献
105.
Taniguchi Shigeji Zhu Yao-Can Fujita Kazuhisa Iwamoto Nobuya 《Oxidation of Metals》2002,58(3-4):375-390
Coupon specimens of TiAl were implanted with Nb ions at an acceleration voltage of 50 kV with a dose of 1021 ions m.–2 They were then slightly oxidized during heating to 900 or 1200 K, or at 1200 K for 3.6 ksec (1 hr) in a flow of purified oxygen under atmospheric pressure. The implanted specimens and oxidized specimens were characterized and observed by AES, X-ray diffractometry, SEM, TEM, EDS, and EPMA. Implantation improves the oxidation resistance significantly by forming virtually -Al2O3 scales. The implanted layer is about 75 nm thick; the outer part of 30-nm thickness is -Ti phase and the rest of 45-nm thickness is amorphous. Heating to 900 K in O2 results in partial crystallization of the amorphous layer to Ti5Al3O2 (Z-phase) and to 1200 K results in oxide scales of 270 to 400 nm thickness consisting mainly of Al2O3. The fraction of Al2O3 in the scale increases toward the substrate. Oxidation at 1200 K for 3.6 ksec results in Al2O3-rich scales of about 400-nm thickness. The oxide grain size is very fine, about 80 nm in size, and becomes smaller toward the outer scale surface. This implies that implantation enhanced the nucleation of Al2O3 grains relative to the growth of TiO2 grains. This finding and the formation of -Ti phase are thought to be responsible for the excellent oxidation resistance obtained. 相似文献
106.
Recent computational studies (Phys. Rev. Lett. 70 (1993) 1960; Phys. Rev. B 62 (2000) 17055) predicted that friction of ordered organic monolayer had characteristic dependence on temperature, where the maximum friction was observed around rotator transition point of the monolayer. This remained to be confirmed experimentally. Using a friction force microscope (FFM) combined with a temperature regulation module, we attempted to investigate such dependence on temperature (130 K-room temperature) on a self-assembled monolayer of dodecanethiol prepared on Au(1 1 1). The observed friction showed strong dependence on temperature and good agreement with the computational prediction. 相似文献
107.
108.
Burkhard H.D. Duhaut D. Fujita M. Lima P. Murphy R. Rojas R. 《Robotics & Automation Magazine, IEEE》2002,9(2):31-38
The ultimate goal of the RoboCup initiative is stated as follows: by mid-21st century, a team of fully autonomous humanoid robot soccer players shall win the soccer game, comply with the official rule of the FIFA, against the winner of the most recent World Cup. The authors consider this goal from the perspective of how close we are to it and what has to be done to reach it 相似文献
109.
N. Kikugawa J. Hori F. Nakamura T. Fujita 《Journal of Low Temperature Physics》1999,117(5-6):1139-1143
We have investigated the effect of the impurity scattering due to a small amount of oxygen defect, ( < 0.01) on the anisotropic resistivity of La
2–x
Sr
x
CuO
4–
in a wide x range up to x = 0.26. In the superconducting region with 0.06 x 0.22, we found that impurity scattering by the oxygen defect remarkably decreases the c-axis resistivity c over the whole temperature range. The finding is interpreted in terms of the nonmetallic conduction along the c axis which is enhanced by scattering the confined carriers in the CuO
2
plane. On the other hand, the enhancement of the c-axis conduction diminishes in the nonsuperconducting region. This is consistent with the two-dimensional nature of the electronic state which stabilizes the superconducting ground state in the cuprates. 相似文献
110.
S. Nakao K. Ueno T. Hanaguri K. Kitazawa T. Fujita Y. Nakayama T. Motohashi J. Shimoyama K. Kishio T. Hasegawa 《Journal of Low Temperature Physics》1999,117(3-4):341-345
We have performed scanning tunneling microscopy/spectroscopy (STM/STS) on single crystals of heavily Pb-doped Bi
2
Sr
2
CaCu
2
O
y
(Pb-Bi2212). The obtained STM images clearly demonstrated phase separation into the and phases with lamella-type and new zigzag-like microstructures. From the site-specified tunneling measurements, it was directly confirmed that the phase possesses higher T
c
. This suggests that the phase boundaries act as strong pinning sites especially at higher temperatures. 相似文献