全文获取类型
收费全文 | 1111篇 |
免费 | 30篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 63篇 |
综合类 | 5篇 |
化学工业 | 332篇 |
金属工艺 | 30篇 |
机械仪表 | 41篇 |
建筑科学 | 18篇 |
能源动力 | 55篇 |
轻工业 | 116篇 |
水利工程 | 2篇 |
无线电 | 57篇 |
一般工业技术 | 230篇 |
冶金工业 | 115篇 |
原子能技术 | 39篇 |
自动化技术 | 50篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 5篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 27篇 |
2013年 | 60篇 |
2012年 | 35篇 |
2011年 | 70篇 |
2010年 | 58篇 |
2009年 | 65篇 |
2008年 | 55篇 |
2007年 | 49篇 |
2006年 | 49篇 |
2005年 | 39篇 |
2004年 | 52篇 |
2003年 | 41篇 |
2002年 | 44篇 |
2001年 | 30篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 52篇 |
1997年 | 34篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1153条查询结果,搜索用时 109 毫秒
121.
Yoshiyuki Abe Fabrizio Tappero Yuki Tanaka Yoshiki Takagi Giovanni Maizza 《Microgravity science and technology》2006,18(3-4):178-183
The effect of gravity on materials processing is rather complicated, and a large number of considerably unexpected results due to high gravity or sometimes centrifugation have been reported. The authors have been conducting high gravity diamond thin film growth by the DC-plasma CVD method up to 100 G. The effects of high gravity appeared in the nucleation site density, growth rate, grain size, uniformity, film coverage and morphology. With the increase in gravity, the nucleation site density, growth rate, grain size were all found to be increased, the uniformity and film coverage were improved, and {100} facet became dominant rather than {111} facet. To understand the deposition mechanism in these effects observed in high gravity, a diagnostic apparatus for spectroscopic study of the optical emission from the DC-plasma was developed, and the OES (optical emission spectroscopy) apparatus has been employed in high gravity CVD experiments. The influence of gravity on the most active species in the plasma, such as H, CH, C2 was discussed together with the results from the Raman spectroscopy and X-ray diffraction study. 相似文献
122.
123.
Tetsuo Fukuchi Yukihiro Yamaguchi Takuya Nayuki Koshichi Nemoto Kiichiro Uchino 《Electrical Engineering in Japan》2004,146(4):10-17
A laser wavefront sensor of the Shack‐Hartmann type capable of simultaneous measurement at two wavelengths was constructed. The sensor uses a single optical path, and is suited for applications such as high‐voltage discharges in air, in which large insulation distances are necessary. The sensor was used to detect optical path differences due to an impulse discharge in air across a needle–plane electrode gap of gap length 17 mm. Optical path differences were measured at laser wavelengths of 532 and 1064 nm at 1.6 µs after insulation breakdown across the gap. From the difference in optical path differences at the two wavelengths, a line‐integrated electron density distribution in the direction perpendicular to the gap was obtained near the high‐voltage electrode. The distribution had a peak value of 1.4 × 1020m?2 and a full width at half maximum of 4.4 mm. Because of the coverage of a large observation area including the entire gap, the spatial resolution was 1.4 mm, which was inadequate to obtain the precise form of the electron density distribution. However, the results show the possibility of applying laser wavefront sensing to electron density measurement. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 10–17, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10247 相似文献
124.
125.
E.s.r. spectra of peroxy radicals trapped in isotactic and atactic polypropylenes have been observed at various temperatures. The spectrum observed at 77 K was shown to be composed of one component by comparing it with that at 4 K. The spectra observed at higher temperatures comprised of two spectra arising from the rigid peroxy radicals and the mobile peroxy radicals. All of the observed spectra have been reconstructed by means of computer simulation and the changes in anisotropic g-values with temperature were estimated. The motion of the mobile fraction was shown to be rotation or rotatory vibration of the radicals around the chain axis both in the isotactic polypropylene and in the atactic polypropylene as well as in polyethylene and poly(tetrafluoroethylene) although the structures of the polymers are different, that is helical (polypropylene) or planar zigzag (polyethylene, poly(tetrafluoroethylene)). 相似文献
126.
127.
Yoshinori Iwahashi Zenji Horita Minoru Nemoto Terence G. Langdon 《Metallurgical and Materials Transactions A》1998,29(10):2503-2510
Experiments were undertaken to compare the equal-channel angular (ECA) pressing of Al-1 pct Mg and Al-3 pct Mg solid-solution
alloys with pure Al. The results reveal both similarities and differences between these three materials. Bands of subgrains
are formed in all three materials in a single passage through the die, and these subgrains subsequently evolve, on further
pressings through the die, into an array of grains with high-angle boundaries. However, the addition of magnesium to an aluminum
matrix decreases the rate of recovery and this leads, with an increasing Mg content, both to an increase in the number of
pressings required to establish a homogeneous microstructure and to a decrease in the ultimate equiaxed equilibrium grain
size. It is concluded that alloys exhibiting low rates of recovery should be especially attractive candidate materials for
establishing ultrafine structures through grain refinement using the ECA pressing technique. 相似文献
128.
129.
Buckmaster R Hanada T Kawazoe Y Cho MW Yao T Urushihara N Yamamoto A 《Nano letters》2005,5(4):771-776
By using a Ga FIB system to spatially control the implantation of Ga into SiO(2) followed by vacuum annealing, we have fabricated self-assembled surface Ga nanodots with a high degree of control of nucleation location. The morphology of the Ga nanodots is closely related to Ga dose, showing a critical dose needed for nucleation that results in Ga nanodot formation just below the surface, while at higher doses Ga nanodots form on the surface as metallic Ga droplets. Possible applications include defining nucleation sites for subsequent growth, use as Ga source for GaN or GaAs quantum dots, or as catalyst for nanowire growth. 相似文献
130.
The role of the C-terminal region of the 74-kDa form of L-histidine decarboxylase (HDC) in the targeting to the endoplasmic reticulum (ER) was investigated in COS-7 cells. The deletion of a 10-kDa segment (residues 578-662) of the C-terminal end of HDC, especially a 20 amino acid sequence (residues 588-607), abrogated the targeting to the ER. The C-terminal 10-kDa portion is sufficient to target the green fluorescent protein (GFP) to the ER. The 74-kDa form of HDC synthesized in an in vitro translation system post-translationally associated with the heterogeneous canine microsomal membranes. These results suggest that the C-terminal 10-kDa portion of HDC contains a signal necessary for HDC to be targeted to the ER membrane. 相似文献