全文获取类型
收费全文 | 9717篇 |
免费 | 470篇 |
国内免费 | 577篇 |
专业分类
电工技术 | 80篇 |
综合类 | 487篇 |
化学工业 | 1730篇 |
金属工艺 | 1539篇 |
机械仪表 | 525篇 |
建筑科学 | 61篇 |
矿业工程 | 53篇 |
能源动力 | 276篇 |
轻工业 | 216篇 |
水利工程 | 41篇 |
石油天然气 | 103篇 |
武器工业 | 37篇 |
无线电 | 1426篇 |
一般工业技术 | 3613篇 |
冶金工业 | 259篇 |
原子能技术 | 184篇 |
自动化技术 | 134篇 |
出版年
2024年 | 9篇 |
2023年 | 94篇 |
2022年 | 133篇 |
2021年 | 157篇 |
2020年 | 206篇 |
2019年 | 169篇 |
2018年 | 178篇 |
2017年 | 261篇 |
2016年 | 191篇 |
2015年 | 208篇 |
2014年 | 366篇 |
2013年 | 613篇 |
2012年 | 513篇 |
2011年 | 940篇 |
2010年 | 639篇 |
2009年 | 783篇 |
2008年 | 704篇 |
2007年 | 612篇 |
2006年 | 445篇 |
2005年 | 457篇 |
2004年 | 454篇 |
2003年 | 449篇 |
2002年 | 391篇 |
2001年 | 200篇 |
2000年 | 191篇 |
1999年 | 192篇 |
1998年 | 177篇 |
1997年 | 143篇 |
1996年 | 129篇 |
1995年 | 95篇 |
1994年 | 118篇 |
1993年 | 98篇 |
1992年 | 88篇 |
1991年 | 79篇 |
1990年 | 75篇 |
1989年 | 51篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The synthesis and characterization of Ti–xMg (x=4, 9, 12, 15, 21, 24 at%) alloys using mechanical alloying was investigated. A nanometer-sized Ti–24Mg alloy was produced. During mechanical alloying, the height of the XRD peaks of the Mg in the Ti–9Mg alloy decreased, and then disappeared, whereas the Ti XRD peaks broadened, and the grain size decreased with increasing milling time. The Mg firstly dissolved in the grain boundaries of the Ti, and then diffused into the Ti grain interiors. The grain boundaries played an important role in enhancing the solid solubility of Mg in Ti. With increasing Mg content the volume fraction of grain boundaries increased, and a decrease in grain size occurred after mechanical alloying for 48 h. 相似文献
112.
113.
Omar Hatamleh Iris V. Rivero Jed Lyons 《Journal of Materials Engineering and Performance》2007,16(5):549-553
The effects of laser, and shot peening on the residual stresses in friction stir welds (FSW) has been investigated. The surface
residual stresses were measured at five different locations across the weld in order to produce an adequate residual stress
profile. The residual stresses before and after sectioning the coupon from the welded plate were also measured, and the effect
of coupon size on the residual stress relaxation was determined and characterized. Measurements indicate that residual stresses
were not uniform along the welded plate, and large variation in stress magnitude could be exhibited at various locations along
the FSW plate. Sectioning resulted in significant residual stress relaxation in the longitudinal direction attributed to the
large change in dimensions in this direction. Overall, laser and shot peening resulted in a significant reduction in tensile
residual stresses at the surface of the specimens. 相似文献
114.
In this paper the heteropoly complexes K_n[Ga(H_20)MW_(11)O_39)]·xH_20 [M=Cu(Ⅱ), Co(Ⅱ), Cr(Ⅲ),Fe(Ⅲ), Mn(Ⅳ)] have been prepared in this laboratory firstly. The products were characterized by chemicalanalysis, ionexchange, IR, UV and X-ray powder diffraction. 相似文献
115.
H. Mughrabi H. Biermann T. Ungar 《Journal of Materials Engineering and Performance》1993,2(4):557-564
The γ-γ lattice mismatch of specimens of the monocrystalline nickel-base superalloy SRR 99 has been measured by a high-resolution
X-ray diffraction technique for the undeformed state and after high-tem-perature creep deformation. During creep deformation
beyond the minimum creep rate (total strain =0.5%), the lattice mismatches, measured in and perpendicular to the [001] stress
axis, respectively, un-dergo changes in opposite directions. This reflects the buildup of a complex deformation-induced triaxial
state of internal stress in the phases y and γ. The overall resolved shear stresses that act in γ and y due to the combined
action of the external and internal stresses are estimated, and the conditions under which cutting of the γ phase by dislocations
should occur are discussed. 相似文献
116.
117.
A comprehensive quantification of the various phases of clinkers by X-ray diffraction with a Rietveld-like analysis is an important industrial challenge. Various available structural models are used for the most frequent M1 and M3 polymorphs of alite usually found in industrial clinkers, referred to as M1- or M3-based clinkers. In this paper, the effect of C3S structural model is investigated. Four models are tested and compared using either synthetic M1 and M3 alites or M1- and M3-based clinkers. The comparison validates the available models for M1 and M3 alites and an average model, given here, derived from our recently proposed M1 structure as a catch-all model when the nature of the clinker is unknown. The latter model is meant to be used for industrial on-line quantification. 相似文献
118.
Two conflicting structural models (platelet and fibril) have been proposed in the literature for pristine cis-poly(acetylene). The respective models have separate, distinct implications for the chemical, physical and electrical properties of the material, in particular, the cis-trans isomerization, doping and conduction mechanisms. Luttinger-type cis-poly(acetylene) was prepared and studied in the transmission electron microscope (TEM) by low-dose conventional imaging, in dark-field mode and by electron diffraction. Thin ‘films’ of the material were shown to consist of fibrillar nets, having fibrils of diameter 5–25 nm. Combined electron diffraction and dark-field observations in the TEM indicated the structural arrangement within the fibrils as that having polymer molecular chains aligned parallel to fibril axes. 相似文献
119.
The mineralogy of clay-rich mineral matter isolated from a range of Australian bituminous coals has been evaluated in quantitative terms from X-ray powder diffraction (XRD) patterns using a Rietveld-based data processing technique. The chemical composition of coal ash derived from this mineral matter has been calculated and compared to the directly determined composition of the ash prepared from the same coal samples. Although there are some minor differences due in part to uncertainty regarding the actual composition of several minerals, the compositions indicated by the two methods show a relatively high correlation, suggesting that the Rietveld technique provides mineralogical analyses that are consistent with independently determined chemical data. Comparison of the normalised clay mineral percentages from the Rietveld analysis to quantitative interpretations based on a peak intensities in glycolated and heat-treated oriented aggregates of the respective clay fractions also shows a high correlation, confirming mutual consistency of the two different mineralogical analysis methods. Such quantitative mineralogical data are significant to a range of coal exploration, mining and utilization activities, including seam correlation, material handling and ash and slag formation in combustion processes. 相似文献
120.
T.I.T. Okpalugo P. Papakonstantinou H. Murphy J. Mclaughlin N.M.D Brown 《Carbon》2005,43(14):2951-2959
The surface compositional and any structural changes that occur on carbon nanotubes using air-atmospheric pressure dielectric barrier discharge (APDBD) for functionalization are investigated employing Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and neutron diffraction techniques. Atmospheric pressure plasmas (APP) are suggested to be particularly suitable for functionalization of aligned nanotubes, where wet chemical manipulation could damage or even destroy the highly desirable vertical alignment. In this work a detailed experimental study elucidating the effects of APDBD plasma treatment parameters (e.g. power density, discharge composition, inter-electrode gap and treatment time) on the electronic structure, physical, and chemical behaviour of carbon nanotubes has been conducted. In an atmospheric air we find an optimal oxidative functionalization of CNTs in our DBD system within few seconds (<5 s) at a discharge power of ∼0.5 kW. This investigation may find useful application as functionalization technique for CNT engineered devices and sensors. 相似文献