全文获取类型
收费全文 | 3469篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 92篇 |
综合类 | 1篇 |
化学工业 | 453篇 |
金属工艺 | 1570篇 |
机械仪表 | 36篇 |
建筑科学 | 19篇 |
矿业工程 | 1篇 |
能源动力 | 74篇 |
轻工业 | 93篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 271篇 |
一般工业技术 | 313篇 |
冶金工业 | 428篇 |
原子能技术 | 44篇 |
自动化技术 | 113篇 |
出版年
2023年 | 11篇 |
2022年 | 25篇 |
2021年 | 22篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 17篇 |
2016年 | 39篇 |
2015年 | 17篇 |
2014年 | 48篇 |
2013年 | 119篇 |
2012年 | 105篇 |
2011年 | 106篇 |
2010年 | 70篇 |
2009年 | 119篇 |
2008年 | 130篇 |
2007年 | 112篇 |
2006年 | 101篇 |
2005年 | 92篇 |
2004年 | 78篇 |
2003年 | 115篇 |
2002年 | 127篇 |
2001年 | 129篇 |
2000年 | 104篇 |
1999年 | 124篇 |
1998年 | 247篇 |
1997年 | 208篇 |
1996年 | 163篇 |
1995年 | 103篇 |
1994年 | 101篇 |
1993年 | 160篇 |
1992年 | 152篇 |
1991年 | 136篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1976年 | 15篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有3511条查询结果,搜索用时 15 毫秒
1.
2.
3.
H. Okamoto 《Journal of Phase Equilibria and Diffusion》2002,23(4):384-385
4.
1-GHz-spaced 16-channel arrayed-waveguide grating for a wavelength reference standard in DWDM network systems 总被引:3,自引:0,他引:3
We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz. 相似文献
5.
Wakejima A. Matsunaga K. Okamoto Y. Ando Y. Nakayama T. Miyamoto H. 《Electronics letters》2005,41(25):1371-1372
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power. 相似文献
6.
X. S. Ning K. Suganuma T. Okamoto A. Koreeda Y. Miyamoto 《Journal of Materials Science》1989,24(8):2879-2883
Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and
the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics
formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina
non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints.
The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints. 相似文献
7.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
8.
Uyematsu T. Okamoto E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1997,43(3):992-996
This correspondence proposes an explicit construction of codes achieving capacity for arbitrary discrete memoryless channels. The proposed code is obtained by concatenating variable inner codes and an algebraic geometry code. Further, we clarify that the proposed code achieves the error exponent obtained by Forney for concatenated codes 相似文献
9.
The incidence of Campylobacter jejuni and Campylobacter coli in broiler farms was 33.9% (19/56). C. jejuni-positive flocks accounted for 20.0% (17/85) and C. coli-positive ones was 4.7% (4/85). There were 14 patterns (fla type) of restriction fragment length polymorphism (RFLP) of flagellin A gene among these 22 strains of C. jejuni and C. coli including the standard strain C. jejuni ATCC 33560. Different fla types of Campylobacter were isolated from broilers in different growing cycles on the same farms. Four strains of C. jejuni were isolated from four breeder farms and four fla types of C. jejuni were detected from their progenies reared on growing farms. Three fla types of C. jejuni detected from the progenies were different from those of each breeder. Also, the other three fla types of C. jejuni were detected from different progenies of each growing farm during the next growing cycle. These findings indicate that the RFLP analysis may contribute to epidemiological studies of C. jejuni and C. coli contamination of broilers and suggest the risk of contamination with different types of Campylobacter in every growing cycle of broilers on the farm even on the same farm. They also supported that there was little likeliness of the vertical transmission of C. jejuni and C. coli from breeders to broilers. 相似文献
10.