全文获取类型
收费全文 | 350637篇 |
免费 | 2687篇 |
国内免费 | 420篇 |
专业分类
电工技术 | 5616篇 |
综合类 | 193篇 |
化学工业 | 55798篇 |
金属工艺 | 19796篇 |
机械仪表 | 12921篇 |
建筑科学 | 6378篇 |
矿业工程 | 4489篇 |
能源动力 | 6169篇 |
轻工业 | 17210篇 |
水利工程 | 5687篇 |
石油天然气 | 16554篇 |
武器工业 | 31篇 |
无线电 | 30199篇 |
一般工业技术 | 83511篇 |
冶金工业 | 51403篇 |
原子能技术 | 13622篇 |
自动化技术 | 24167篇 |
出版年
2021年 | 3525篇 |
2019年 | 3466篇 |
2018年 | 6756篇 |
2017年 | 6983篇 |
2016年 | 7451篇 |
2015年 | 3885篇 |
2014年 | 6831篇 |
2013年 | 14276篇 |
2012年 | 9743篇 |
2011年 | 12187篇 |
2010年 | 9948篇 |
2009年 | 11033篇 |
2008年 | 11167篇 |
2007年 | 10841篇 |
2006年 | 9048篇 |
2005年 | 8049篇 |
2004年 | 7824篇 |
2003年 | 7603篇 |
2002年 | 7401篇 |
2001年 | 7275篇 |
2000年 | 7092篇 |
1999年 | 6555篇 |
1998年 | 13030篇 |
1997年 | 9986篇 |
1996年 | 7470篇 |
1995年 | 5910篇 |
1994年 | 5398篇 |
1993年 | 5595篇 |
1992年 | 4641篇 |
1991年 | 4737篇 |
1990年 | 4863篇 |
1989年 | 4675篇 |
1988年 | 4563篇 |
1987年 | 4434篇 |
1986年 | 4362篇 |
1985年 | 4565篇 |
1984年 | 4406篇 |
1983年 | 4292篇 |
1982年 | 4020篇 |
1981年 | 4212篇 |
1980年 | 4141篇 |
1979年 | 4424篇 |
1978年 | 4735篇 |
1977年 | 4802篇 |
1976年 | 5759篇 |
1975年 | 4339篇 |
1974年 | 4388篇 |
1973年 | 4465篇 |
1972年 | 4055篇 |
1971年 | 3689篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
V. M. Yakovenko M. V. Burtyka I. V. Yakovenko 《Journal of Infrared, Millimeter and Terahertz Waves》1996,17(3):559-568
The theory of interaction of charged particle beams with 2D electron gas, located in the field of the delta-like potential wallU(y) =U oδ(y) has been developed. The kinetic equation for plasmons in 2D electron gas was obtained; the conditions of arising of their instability are given and the corresponding expressions for the increment of plasmons are found. 相似文献
113.
114.
115.
A method is described for experimentally determining the dose rate created in building bricks by incorporated natural radionuclides.
It was established using the thermoluminescence dosimetry method that the measured dose rate depends on the detector thickness,
the mass of the ceramic product investigated, and the irradiation geometry. The contributions to the measured dose of weakly
penetrating α and β radiation and hard ψ radiation are separated, the ratio between them depending on the experimental conditions.
Translated from Izmeritel'naya Tekhnika, No. 7, pp. 62–66, July, 1996. 相似文献
116.
A.G. Berkovski G. Chiodi J.-P. Fabre A. Frenkel S.V. Golovkin Yu.I. Gubanov G.N. Kislizkai E.N. Kozarenko I.E. Kreslo A.E. Kushnirenko G. Martellotti D. Mazza A.M. Medvedkov G. Penso 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):537-543
We present the performance of a high-speed gateable vacuum image pipeline, which permits individual images to be delayed and selected from continuous non-repetitive image stream. This device is composed of a vacuum tube equipped with a photocathode at one end, a phosphor screen at the other end, and a system of metal grids in between. Photoelectrons produced by the images focused on the photocathode, are guided by a uniform magnetic field, parallel to the tube axis. By changing the grid potentials, the drift time of the photoelectrons inside the tube can be varied from 0.35 to 1.5 μs. An image can then be selected by an external trigger with a time resolution in the range of 4–30 ns, depending on the delay time. The selected photoelectrons are finally accelerated onto the phosphor screen, set at 10 kV, where they reproduce the desired image. With a magnetic field of 0.1 T, a spatial resolution of 33 lp/mm was obtained. The high spatial and time resolution make this device an interesting tool for high-energy physics and astrophysics experiments, and for high-speed photography. 相似文献
117.
118.
N Sobel V Prabhakaran JE Desmond GH Glover EV Sullivan JD Gabrieli 《Canadian Metallurgical Quarterly》1997,78(1-2):115-123
A method for generating olfactory stimuli for humans within a functional magnetic resonance imaging (fMRI) experimental design is described. The system incorporates a nasal-mask in which the change from odorant to no-odorant conditions occurs in less than 500 ms and is not accompanied by visual, auditory, tactile, or thermal cues. The mask provides an ordorant-free environment following prolonged ordorant presence. Specific imaging parameters that are conducive to the study of the human olfactory system are described. In a pilot study performed using these methods, the specific patterns of activation observed converged with published experimental and clinical findings. 相似文献
119.
120.
Fahmy H.I. Develekos G. Douligeris C. 《Selected Areas in Communications, IEEE Journal on》1997,15(2):226-237
Communication network design is becoming increasingly complex, involving making networks more usable, affordable, and reliable. To help with this, we have proposed an expert network designer (END) for configuring, modeling, simulating, and evaluating large structured computer networks, employing artificial intelligence, knowledge representation, and network simulation tools. We present a neural network/knowledge acquisition machine-learning approach to improve the END's efficiency in solving the network design problem and to extend its scope to acquire new networking technologies, learn new network design techniques, and update the specifications of existing technologies 相似文献