全文获取类型
收费全文 | 256787篇 |
免费 | 1287篇 |
国内免费 | 642篇 |
专业分类
电工技术 | 4857篇 |
综合类 | 224篇 |
化学工业 | 36480篇 |
金属工艺 | 9531篇 |
机械仪表 | 7589篇 |
建筑科学 | 6157篇 |
矿业工程 | 880篇 |
能源动力 | 7324篇 |
轻工业 | 21441篇 |
水利工程 | 2285篇 |
石油天然气 | 3285篇 |
武器工业 | 15篇 |
无线电 | 34553篇 |
一般工业技术 | 50309篇 |
冶金工业 | 48575篇 |
原子能技术 | 5228篇 |
自动化技术 | 19983篇 |
出版年
2021年 | 2301篇 |
2020年 | 1794篇 |
2019年 | 2140篇 |
2018年 | 3287篇 |
2017年 | 3321篇 |
2016年 | 3487篇 |
2015年 | 2269篇 |
2014年 | 3986篇 |
2013年 | 11545篇 |
2012年 | 6279篇 |
2011年 | 8649篇 |
2010年 | 6930篇 |
2009年 | 7906篇 |
2008年 | 8454篇 |
2007年 | 8324篇 |
2006年 | 7403篇 |
2005年 | 6528篇 |
2004年 | 6307篇 |
2003年 | 6584篇 |
2002年 | 6091篇 |
2001年 | 6527篇 |
2000年 | 5991篇 |
1999年 | 6408篇 |
1998年 | 16506篇 |
1997年 | 11428篇 |
1996年 | 8812篇 |
1995年 | 6623篇 |
1994年 | 5917篇 |
1993年 | 5854篇 |
1992年 | 4150篇 |
1991年 | 4028篇 |
1990年 | 3868篇 |
1989年 | 3652篇 |
1988年 | 3564篇 |
1987年 | 3027篇 |
1986年 | 2946篇 |
1985年 | 3210篇 |
1984年 | 2931篇 |
1983年 | 2831篇 |
1982年 | 2638篇 |
1981年 | 2546篇 |
1980年 | 2474篇 |
1979年 | 2308篇 |
1978年 | 2108篇 |
1977年 | 2609篇 |
1976年 | 3564篇 |
1975年 | 1767篇 |
1974年 | 1733篇 |
1973年 | 1667篇 |
1972年 | 1466篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Common pharmaceutical excipients and compounds were dried either by a simple convection method or by a combined convection and microwave method in a static bed or by a combined microwave and vacuum method in a mixed bed. A simple placebo granulation was dried by an exclusive vacuum method and by a combined microwave and vacuum method in a mixed bed. The results were compared. 相似文献
192.
Trapping of net positive charge at low gate stress voltage, and of net negative charge at high gate stress voltage, is observed through changes in the gate-to-drain capacitance of the stressed junction. These observations can be explained in terms of electron trapping, hole trapping, and generation of acceptor-like interface states located in the upper half of the bandgap. Channel shortening is also observed and found to exhibit a logarithmic time dependence 相似文献
193.
194.
Chang E.Y. Dean R. Proctor J. Elmer R. Pande K. 《Semiconductor Manufacturing, IEEE Transactions on》1991,4(1):66-68
A dicing process for GaAs MMIC (monolithic microwave integrated circuit) wafers using spin-on wax for wafer mounting and a hybrid process of wet chemical etching/mechanical sawing for chip dicing is described. This process minimizes ragged chip edges and reduces generation of microcracks in addition to the elimination of the plated gold burrs on the backside of the diced MMIC chips. This process gives a uniformity of -3 μm across a 2-in wafer following the completion of the whole backside process. This GaAs chip dicing technique is amenable to production because it exhibits both a very high chip yield (>90%) and nearly flawless edges 相似文献
195.
196.
197.
198.
199.
Horiguchi T. Shimizu K. Kurashima T. Tateda M. Koyamada Y. 《Lightwave Technology, Journal of》1995,13(7):1296-1302
This paper reviews the developments of a distributed strain and temperature sensing technique that uses Brillouin scattering in single-mode optical fibers. This technique is based on strain- and temperature-induced changes in the Brillouin frequency shift. Several approaches for measuring the weak Brillouin line are compared 相似文献
200.
Integrated-optic double-ring resonators with a wide free spectral range (FSR) of 100 GHz are fabricated using GeO2-doped silica waveguides with a high relative refractive index difference (Δ) of 1.5%. The resonators are composed of two ring resonators comprising small ring waveguides with radii of 1.75 and 2.0 mm. The double-ring resonator module exhibited a wide FSR of 98.0 GHz, a finesse of higher than 138, a low crosstalk of less than -11.7 dB, and a low insertion loss of 6.1 dB. The measured FSR of 98.0 GHz is wider than any previously reported ring resonator composed of optical waveguides 相似文献