全文获取类型
收费全文 | 475939篇 |
免费 | 4412篇 |
国内免费 | 1532篇 |
专业分类
电工技术 | 8095篇 |
综合类 | 599篇 |
化学工业 | 72113篇 |
金属工艺 | 23343篇 |
机械仪表 | 16354篇 |
建筑科学 | 9968篇 |
矿业工程 | 4614篇 |
能源动力 | 10082篇 |
轻工业 | 30199篇 |
水利工程 | 6476篇 |
石油天然气 | 16022篇 |
武器工业 | 68篇 |
无线电 | 49149篇 |
一般工业技术 | 105917篇 |
冶金工业 | 76072篇 |
原子能技术 | 15614篇 |
自动化技术 | 37198篇 |
出版年
2021年 | 4387篇 |
2019年 | 4230篇 |
2018年 | 7831篇 |
2017年 | 8162篇 |
2016年 | 8635篇 |
2015年 | 4949篇 |
2014年 | 8512篇 |
2013年 | 20087篇 |
2012年 | 12828篇 |
2011年 | 16880篇 |
2010年 | 13428篇 |
2009年 | 15255篇 |
2008年 | 15614篇 |
2007年 | 15328篇 |
2006年 | 12871篇 |
2005年 | 11682篇 |
2004年 | 11551篇 |
2003年 | 11252篇 |
2002年 | 10879篇 |
2001年 | 10821篇 |
2000年 | 10415篇 |
1999年 | 10161篇 |
1998年 | 22046篇 |
1997年 | 16259篇 |
1996年 | 12452篇 |
1995年 | 9800篇 |
1994年 | 8798篇 |
1993年 | 8956篇 |
1992年 | 6963篇 |
1991年 | 6895篇 |
1990年 | 6807篇 |
1989年 | 6707篇 |
1988年 | 6340篇 |
1987年 | 5917篇 |
1986年 | 5839篇 |
1985年 | 6344篇 |
1984年 | 5962篇 |
1983年 | 5670篇 |
1982年 | 5271篇 |
1981年 | 5423篇 |
1980年 | 5402篇 |
1979年 | 5353篇 |
1978年 | 5554篇 |
1977年 | 5879篇 |
1976年 | 7167篇 |
1975年 | 4912篇 |
1974年 | 4968篇 |
1973年 | 5014篇 |
1972年 | 4350篇 |
1971年 | 3946篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
M.E.W. Eggenkamp V. A. Shvarts R. Blaauwgeers A. Storm R. Jochemsen G. Frossati 《Journal of Low Temperature Physics》1998,110(1-2):299-304
This paper focuses on the hydrodynamics of third sound on a superfluid
3
He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range. 相似文献
112.
P Rutgeerts 《Canadian Metallurgical Quarterly》1996,19(1):44-46
Absorbable and nonabsorbable buried sutures were studied in primary cleft lip repair. Group 1 (N = 56) consisted of patients repaired with buried nonabsorbable material (monofilament nylon). Group 2 (N = 47) consisted of patients repaired with absorbable materials (polyglyconate, polydioxanone). All patients were monitored for 12 months. There were stitch abscesses in Group 1 (14%). There were no abscesses in Group 2. This difference was significant (p = 0.007). Abscesses were located in the suture line with no identifiable distribution. There was no significant difference in the cosmetic appearance of the scars in Groups 1 and 2. These results support the view that absorbable sutures are preferable to nonabsorbable sutures for primary cleft lip repair. 相似文献
113.
Auld B.A. Chimenti D.E. Shull P.J. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(2):319-325
The transverse resonance approach to guided wave analysis is applied to shear horizontal (SH) wave propagation in periodically layered composites. It is found for SH waves that at high values of the guided wavevector β, the wave energy is trapped in the slower of the two media and propagates accordingly at the slower wavespeed. At low values of β, however, the modes demonstrate a clustering behavior, indicative of the underlying Floquet wave structure. The number of modes in a cluster is observed to correlate with the number of unit cells in the layered plate. New physical insights into the behavior of these systems are obtained by analyzing the partial waves of the guided SH modes in terms of Floquet waves. We show that the fast and slow shear waves in the periodically layered composite play an analogous role to the longitudinal and shear partial waves comprising Lamb waves in a homogeneous plate 相似文献
114.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献
115.
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
116.
Thanapalan Murugesan G. S. Venkat Rathnam S. Panduranga Rao P. Gangadhar Rao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):290-294
In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature. 相似文献
117.
118.
119.
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
120.
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