全文获取类型
收费全文 | 692篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 49篇 |
化学工业 | 132篇 |
金属工艺 | 17篇 |
机械仪表 | 19篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 20篇 |
轻工业 | 26篇 |
无线电 | 97篇 |
一般工业技术 | 116篇 |
冶金工业 | 153篇 |
原子能技术 | 12篇 |
自动化技术 | 54篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 28篇 |
2011年 | 22篇 |
2010年 | 17篇 |
2009年 | 19篇 |
2008年 | 41篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 17篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 69篇 |
1997年 | 38篇 |
1996年 | 26篇 |
1995年 | 14篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1974年 | 5篇 |
1973年 | 2篇 |
排序方式: 共有706条查询结果,搜索用时 15 毫秒
701.
A graded-index plastic optical fiber (GI POF) has been proposed as the transmission medium to realize high-speed information transmission. We have succeeded in fabricating a GI POF by the dopant diffusion coextrusion process, a method that allows continuous fabrication of GI POF. Although it has been indicated that the refractive index distribution of GI POF fabricated by this process is formed by Fick diffusion with the diffusion coefficient dependent on dopant concentration, the method to control it remains unknown. The purposes of this study are to establish the technology of stable fabricating of GI POF by the coextrusion process and to analyze the bandwidth. 相似文献
702.
Yasutaka Kuwahara Tetsutaro Ohmichi Kohsuke Mori Iwao Katayama Hiromi Yamashita 《Journal of Materials Science》2008,43(7):2407-2410
Steel slag, commercial waste material containing silica and alumina which are the chemical components elements of zeolite,
was used as a source for synthesis of FAU zeolite (Y-zeolite, X-zeolite). Through acid-treatment to remove CaO species from
steel slag and hydrothermal treatment, well-crystallized Na type FAU zeolite was obtained. Furthermore the synthesized FAU
zeolite was applied as a support of photocatalyst. It was found that hydrophobic surface property of zeolite enhances photocatalytic
activity for decomposition of organic pollutants and the zeolite synthesized from steel slag would be applicable as promising
support of TiO2 photocatalyst. 相似文献
703.
Iwao Y 《Reproduction (Cambridge, England)》2012,144(1):11-22
Fertilization is indispensable not only for restoring diploid genomes but also for the initiation of early embryonic cell cycles in sexual reproduction. While most animals exhibit monospermy, which is ensured by polyspermy blocks to prevent the entry of extra sperm into the egg at fertilization, several animals exhibit physiological polyspermy, in which the entry of several sperm is permitted but only one sperm nucleus participates in the formation of a zygote nucleus. Polyspermy requires that the sperm transmit the egg activation signal more slowly, thus allowing the egg to accept several sperm. An increase in intracellular Ca(2+) concentration induced by the fertilizing sperm is both necessary and sufficient for egg activation in polyspermy. Multiple small Ca(2+) waves induced by several fertilizing sperm result in a long-lasting Ca(2+) rise, which is a characteristic of polyspermic amphibian eggs. We introduced a novel soluble sperm factor for egg activation, sperm-specific citrate synthase, into polyspermic newt eggs to cause Ca(2+) waves. Citrate synthase may perform dual functions: as an enzyme in mitochondria and as a Ca(2+)-inducing factor in egg cytoplasm. We also discuss the close relationship between the mode of fertilization and the Ca(2+) rise at egg activation and consider changes in this process through evolution in vertebrates. 相似文献
704.
705.
Kaveh Delfanazari Hidehiro Asai Manabu Tsujimoto Takanari Kashiwagi Takeo Kitamura Kazuya Ishida Chiharu Watanabe Shunsuke Sekimoto Takashi Yamamoto Hidetoshi Minami Masashi Tachiki Richard A. Klemm Toshiaki Hattori Kazuo Kadowaki 《Journal of Infrared, Millimeter and Terahertz Waves》2014,35(1):131-146
Recent developments of coherent terahertz (THz) oscillators based on the intrinsic Josephson junctions (IJJs) in mesas of the high temperature superconductor Bi2Sr2CaCu2O8+δ are reviewed. Experimental and theoretical studies of the emission from equilateral, right-angled isosceles, and acute isosceles triangular mesas are compared with those obtained from rectangular, square, and disk mesas, in order to determine the role of the mesa geometry. The superconducting properties and emission frequency f spectra are presented for a variety of triangular mesa geometries. Analytic and finite difference time domain numerical calculations of the emissions from the internal electromagnetic (EM) cavity modes of triangular mesas are compared with experiment. The experimental f always satisfies the ac Josephson relation, and its narrow linewidth arises from the synchronized emissions from many IJJs. For some mesa geometries, f also strongly locks onto an EM cavity mode frequency, enhancing the emission’s stability and output power. For other geometries, such cavity mode locking is weak, and f is highly tunable. 相似文献
706.