全文获取类型
收费全文 | 112156篇 |
免费 | 12382篇 |
国内免费 | 8264篇 |
专业分类
电工技术 | 9894篇 |
技术理论 | 4篇 |
综合类 | 10882篇 |
化学工业 | 14869篇 |
金属工艺 | 7674篇 |
机械仪表 | 7888篇 |
建筑科学 | 8922篇 |
矿业工程 | 3820篇 |
能源动力 | 3187篇 |
轻工业 | 12014篇 |
水利工程 | 3407篇 |
石油天然气 | 4481篇 |
武器工业 | 1605篇 |
无线电 | 11818篇 |
一般工业技术 | 10245篇 |
冶金工业 | 4263篇 |
原子能技术 | 1719篇 |
自动化技术 | 16110篇 |
出版年
2024年 | 501篇 |
2023年 | 1770篇 |
2022年 | 4069篇 |
2021年 | 5299篇 |
2020年 | 3898篇 |
2019年 | 2816篇 |
2018年 | 3070篇 |
2017年 | 3489篇 |
2016年 | 3196篇 |
2015年 | 5058篇 |
2014年 | 6162篇 |
2013年 | 7481篇 |
2012年 | 9246篇 |
2011年 | 9721篇 |
2010年 | 9068篇 |
2009年 | 8660篇 |
2008年 | 8883篇 |
2007年 | 8480篇 |
2006年 | 7262篇 |
2005年 | 5828篇 |
2004年 | 4271篇 |
2003年 | 3180篇 |
2002年 | 2960篇 |
2001年 | 2681篇 |
2000年 | 1993篇 |
1999年 | 1104篇 |
1998年 | 555篇 |
1997年 | 459篇 |
1996年 | 343篇 |
1995年 | 298篇 |
1994年 | 214篇 |
1993年 | 164篇 |
1992年 | 115篇 |
1991年 | 116篇 |
1990年 | 93篇 |
1989年 | 58篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 32篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 16篇 |
1980年 | 40篇 |
1979年 | 15篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1959年 | 18篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Hui Chen D.T.K. Tong 《Photonics Technology Letters, IEEE》2005,17(4):801-803
Symmetric interference in two-dimensional multimode silicon waveguides is experimentally investigated. For a 100/spl times/100 /spl mu/m/sup 2/ cross section, 2700-/spl mu/m-long waveguide fabricated on silicon-on-insulator substrate, an 8/spl times/8 matrix of replicated images with high contrast ratio is demonstrated for 1530-1570 nm wavelength range. Symmetric interference results in reduced device length, and the actual device length is consistent with the theoretical expectation. The device also exhibits stable imaging in terms of good loss uniformity, and low wavelength and polarization dependencies among the replicated images. 相似文献
142.
We report the growth of highly C-axis orientation of Sr
x
Ba1−x
Nb2O6 (SBN) thin films on p-type (100) Si substrates by using a potassium-substituted SBN template layer with the sol–gel method. The crystallization of SBN thin films was found closely related to the potassium ion doping concentration and the postannealing temperature of the K-SBN template layer. Secondary ion mass spectrometry analysis showed that potassium elements were accumulated at the interface of the template layer and silicon substrate. SBN films postannealed at 750 °C with K-SBN template layer has a smaller full width at half maximum of X-ray rocking curve of 2.45° than that of 5.40° for the pure SBN films. By introducing a template layer, the surface morphologies of SBN films fabricated on silicon substrate were greatly improved. 相似文献
143.
144.
PENG Zhensheng GUO Huanyin YAN Guoqing MAO Qiang 《稀有金属(英文版)》2007,26(4):317-322
The perovskite manganite sample La0.3Ca0.7Mn1-xWxO3 (x = 0.08, 0.12) was prepared by the solid-state reaction method. The effect of W doping on the Mn site to La0.3Ca0.7MnO3 charge ordering phase and the changing process of magnetic properties were studied through the measurement of the M-T curve, M-H curves, and ESR curves of the sample. The results showed that when x = 0.08, the charge ordering (CO) phase exists in the system, the transition temperature Tco= 275 K, and the system exhibits PM when T 〉 275 K. The system transforms from spin-disordering paramagnetism to spin-ordering antiferromagnetism in the charge ordering state with the temperature decreasing from 275 K to 230 K. The long-range antiferromagnetism forms and AFM/CO states coexist between 230 K and 5 K. There is a little ferromagnetic component in the AFM/CO background in a low temperature range. When x = 0.12, the CO phase in the system has almost melted completely. There is a little remnant of the CO phase below 150 K. The system exhibits paramagnetism when T 〉 150 K and transforms from paramagnetism to ferromagnetism when T〈 150 K. 相似文献
145.
A high-density gas jet supersonic nozzle is reported in this paper. The jitter and actuation time of the nozzle is determined by the pin discharge and laser spark radiation respectively. The jitter time of the nozzle is within 10μs with the backing pressure as high as 25 bar. With a nanosecond laser pulse focused on the gas jet about 1 mm below the nozzle, the actuation time is calculated to be about 15 ms by detecting the laser produced spark radiation, which reveals the existence of the gas jet and the relative gas density evolving with time. Consequently the gas density is estimated to be well above 10^19 cm^-3, compared with theoretical simulations from the nozzle parameters. 相似文献
146.
147.
148.
149.
150.
喷墨打印相纸及打印图像质量的分析 总被引:2,自引:1,他引:1
喷墨打印相纸随着数码相机的发展近几年在国内发展迅速。针对目前产品质量没有测量标准的现状,提出喷墨相纸的质量指标主要为4个,即白度、光泽度、油墨吸收性和防水性。给出了相应的测量方法。并指出相纸上油墨点的面积是衡量质量的第一重要指标,其次是点的圆度。另外对图像输出的质量介绍了一种科学的评价方法,即图像的逼真性分析。说明图像的打印墨点直径不应小于方形像素的对角线长,图像才能真实再现。 相似文献