全文获取类型
收费全文 | 5986篇 |
免费 | 476篇 |
国内免费 | 196篇 |
专业分类
电工技术 | 303篇 |
综合类 | 262篇 |
化学工业 | 1109篇 |
金属工艺 | 203篇 |
机械仪表 | 264篇 |
建筑科学 | 230篇 |
矿业工程 | 74篇 |
能源动力 | 181篇 |
轻工业 | 336篇 |
水利工程 | 67篇 |
石油天然气 | 122篇 |
武器工业 | 37篇 |
无线电 | 1145篇 |
一般工业技术 | 923篇 |
冶金工业 | 469篇 |
原子能技术 | 53篇 |
自动化技术 | 880篇 |
出版年
2024年 | 19篇 |
2023年 | 85篇 |
2022年 | 161篇 |
2021年 | 211篇 |
2020年 | 164篇 |
2019年 | 146篇 |
2018年 | 168篇 |
2017年 | 169篇 |
2016年 | 154篇 |
2015年 | 197篇 |
2014年 | 270篇 |
2013年 | 443篇 |
2012年 | 407篇 |
2011年 | 411篇 |
2010年 | 351篇 |
2009年 | 352篇 |
2008年 | 317篇 |
2007年 | 328篇 |
2006年 | 290篇 |
2005年 | 203篇 |
2004年 | 172篇 |
2003年 | 172篇 |
2002年 | 153篇 |
2001年 | 107篇 |
2000年 | 100篇 |
1999年 | 107篇 |
1998年 | 181篇 |
1997年 | 123篇 |
1996年 | 105篇 |
1995年 | 71篇 |
1994年 | 84篇 |
1993年 | 59篇 |
1992年 | 58篇 |
1991年 | 36篇 |
1990年 | 41篇 |
1989年 | 41篇 |
1988年 | 30篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有6658条查询结果,搜索用时 0 毫秒
81.
This research focuses on the fabrication of glass fiber/epoxy nanocomposites containing organoclay as well as understanding the organoclay effect on the transverse compressive strength of nanocomposites. To demonstrate the organoclay effect, three different loadings of organoclay were dispersed, respectively, in the epoxy resin using a mechanical mixer followed by sonication. The corresponding glass/epoxy nanocomposites were produced by impregnating dry glass fiber with organoclay epoxy compound through a vacuum hand lay-up procedure. Unidirectional block specimens were employed for transverse compression tests on a hydraulic MTS machine. Experimental observations indicate that glass/epoxy nanocomposites containing organoclay exhibit higher transverse compressive strength than conventional composites. Furthermore, the failure mechanisms for all tested specimens were found to be fiber and matrix debonding. Therefore, results indicate that the increasing characteristic in transverse failure stress may be ascribed to the enhanced fiber/matrix adhesion modified by the organoclay. 相似文献
82.
The detection of process problems and parameter drift at an early stage is crucial to successful semiconductor manufacture. The defect patterns on the wafer can act as an important source of information for quality engineers allowing them to isolate production problems. Traditionally, defect recognition is performed by quality engineers using a scanning electron microscope. This manual approach is not only expensive and time consuming but also it leads to high misidentification levels. In this paper, an automatic approach consisting of a spatial filter, a classification module and an estimation module is proposed to validate both real and simulated data. Experimental results show that three types of typical defect patterns: (i) a linear scratch; (ii) a circular ring; and (iii) an elliptical zone can be successfully extracted and classified. A Gaussian EM algorithm is used to estimate the elliptic and linear patterns, and a spherical-shell algorithm is used to estimate ring patterns. Furthermore, both convex and nonconvex defect patterns can be simultaneously recognized via a hybrid clustering method. The proposed method has the potential to be applied to other industries. 相似文献
83.
Hwi-Ming Wang Tai-Haur Kuo 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(7):580-584
An automatic coefficient design method for synthesis of bandpass sigma-delta modulators (BPSDMs) is presented in this brief. Single-stage BPSDM structures, cascade-of-resonator with distributed feedback, cascade-of-resonator with distributed feedforward, and a new structure with lower coefficient spread, are all used to fit the synthesized coefficients. The automatic coefficient design method is realized in an easy-to-use computer program. Even for inexperienced designers, reliable and high-tolerance BPSDM coefficients for various applications can be automatically and efficiently generated. The methodology covers many design concerns including BPSDM coefficient tolerance for circuit component mismatch, design tradeoffs among in-band noise suppression, oversampling ratio, modulator order and quantizer bit number. Finally, design examples with orders of 6 and 8, and quantizer bit number of 1-bit and 3-bit, respectively, are used for the verification of the proposed automatic coefficient design method. 相似文献
84.
Triple-frequency planar monopole antenna for side-feed communication device on GSM/DCS/PCS operation
A novel side-feed planar monopole antenna capable of triple-frequency operation at about 900, 1800 and 1900 MHz is presented. The planar monopole antenna occupies a small area of 6/spl times/31 mm, and is easily made using thin copper. The planar monopole antenna can be side-fed and mounted perpendicularly to the main circuit board of a communication device so that it offers a novel design with a free degree of feed point so as to save device space, resulting in a low profile to the system ground plane. In addition, the obtained impedance bandwidths of the proposed antenna at about 900, 1800 and 1900 MHz can cover the GSM (890-960 MHz), DCS (1710-1880 MHz) and PCS (1850-1990 MHz) bands. 相似文献
85.
86.
Research on Poly(Styrene-Crylicacid)-Suported Neodymium Complex Catalytic Copolymerization of Styrene and 4-Vinylpyridine 相似文献
87.
88.
89.
90.