全文获取类型
收费全文 | 574037篇 |
免费 | 8601篇 |
国内免费 | 1868篇 |
专业分类
电工技术 | 10530篇 |
综合类 | 661篇 |
化学工业 | 85004篇 |
金属工艺 | 22643篇 |
机械仪表 | 18251篇 |
建筑科学 | 12880篇 |
矿业工程 | 3300篇 |
能源动力 | 15636篇 |
轻工业 | 44901篇 |
水利工程 | 6119篇 |
石油天然气 | 10795篇 |
武器工业 | 32篇 |
无线电 | 67045篇 |
一般工业技术 | 115573篇 |
冶金工业 | 109749篇 |
原子能技术 | 12584篇 |
自动化技术 | 48803篇 |
出版年
2021年 | 5508篇 |
2020年 | 4183篇 |
2019年 | 5208篇 |
2018年 | 8958篇 |
2017年 | 8865篇 |
2016年 | 9484篇 |
2015年 | 6267篇 |
2014年 | 10047篇 |
2013年 | 27909篇 |
2012年 | 15965篇 |
2011年 | 21235篇 |
2010年 | 17005篇 |
2009年 | 19094篇 |
2008年 | 19650篇 |
2007年 | 19378篇 |
2006年 | 17063篇 |
2005年 | 15360篇 |
2004年 | 14454篇 |
2003年 | 14387篇 |
2002年 | 13444篇 |
2001年 | 13346篇 |
2000年 | 12715篇 |
1999年 | 13321篇 |
1998年 | 34559篇 |
1997年 | 23868篇 |
1996年 | 18371篇 |
1995年 | 13545篇 |
1994年 | 12057篇 |
1993年 | 11861篇 |
1992年 | 8630篇 |
1991年 | 8131篇 |
1990年 | 7950篇 |
1989年 | 7691篇 |
1988年 | 7338篇 |
1987年 | 6478篇 |
1986年 | 6235篇 |
1985年 | 7146篇 |
1984年 | 6530篇 |
1983年 | 5989篇 |
1982年 | 5406篇 |
1981年 | 5657篇 |
1980年 | 5175篇 |
1979年 | 5129篇 |
1978年 | 5099篇 |
1977年 | 5844篇 |
1976年 | 7908篇 |
1975年 | 4378篇 |
1974年 | 4147篇 |
1973年 | 4236篇 |
1972年 | 3472篇 |
排序方式: 共有10000条查询结果,搜索用时 537 毫秒
991.
992.
A narrow linewidth has been obtained in a new 1.5 ?m distributed feedback laser integrated monolithically with a tunable external cavity. The linewidth of 18 MHz has been achieved by tuning the current in the external cavity, and the FM response was flat from 100 kHz to 500 MHz. 相似文献
993.
High-resolution positive and negative photoresists were used to fabricate ?/4-phase-shifted corrugations by holographic exposure. To avoid mixing these photoresists, cyclised polyisoprene was used as a midlayer. The shape and depth of the corrugations on the positive and negative photoresist regions were almost the same. Single-mode operation at the Bragg wavelength was confirmed in lasers with the corrugation. 相似文献
994.
/sup T/he University of Minnesota's Scout is a small cylindrical robot capable of rolling and jumping. Models describing the robot's motion are developed. These models can be employed for motion prediction and simulation. The results suggest that the determining factor of the Scout's behavior is the length of the winch cable. 相似文献
995.
This paper considers the principles of algorithmic and software implementation of the software system NADRA 3D designed to
analyze processes in three-dimensional multicomponent soil media. The principles of operation of NADRA 3D are described.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 157–174, November–December 2006. 相似文献
996.
997.
L. GbahoueF. Barbeu S. Martemianov 《International Journal of Heat and Mass Transfer》2002,45(18):3865-3873
Electrochemical method is applied to study coherent structures in a complex three-dimensional flow generated by a rotating magnetic rod. In order to detect these structures, the power spectral density (PSD) analysis of the limiting diffusion current fluctuations is provided. This analysis reveals the existence of resonance frequencies when the probe is located in the very vicinity of the stirrer. The main resonance is related to the mechanical excitation frequency. The detailed analysis of the PSD curves points out some mechanisms of development of turbulence as sub-harmonics and non-linear interactions. For different locations of the probe and different angular rates of the stirrer Ω, a similarity of the energy repartition is obtained when the PSD is plotted versus the adimensional frequency f/Ω. Flow visualization by laser tomography is also provided and the local secondary flow past the electrode probe is sketched. The laser Doppler velocimetry (LDV) at a given location in a horizontal z-plane indicates a tornado wise mean flow structure. 相似文献
998.
Incorporation of silicon species from an alloy substrate into anodic titania is shown to stabilise the structure of the film, facilitating investigation of the ionic transport processes in amorphous titania grown at high efficiency. Thus, an amorphous anodic film developed on a sputtering-deposited Ti-6 at.%Si alloy formed to 100 V in phosphoric acid electrolyte in contrast to a partially crystalline film developed on relatively pure titanium at <20 V. Silicon species, which are immobile and act as marker species in the growing film, are present in the inner 58% of the film thickness. Evidently, the film material forms simultaneously at the film/electrolyte and alloy/film interfaces by co-operative transport of cations and anions, as is usual in amorphous anodic oxides. The phosphate anions incorporated from the electrolyte migrate inward at 0.34 times the rate of O2− ions and hence are present in the outer 62% of the film thickness. 相似文献
999.
1000.