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991.
Photocatalytic degradation of methyl orange using heteropolytungstic acid-encapsulated TiSBA-15 总被引:1,自引:0,他引:1
Heteropolyphosphotungstic acid (H3PW12O40) (HPA)-encapsulated titanium-supported SBA15 nanoporous materials (HPA-TiSBA-15) were synthesized as a new photocatalyst, and they were characterized by FT-IR and 31P NMR MAS spectroscopic methods. Their photocatalytic effects on degradation of methyl orange in water were investigated under natural conditions, and it was found that a 4-fold increase in the photodegradation rate is observed in the presence of HPA-TiSBA-15 as compared to the rate observed in the presence of titanium-supported SBA15 nanoporous materials (TiSBA-15) without HPA. 相似文献
992.
F.O Adurodija S.K Kim S.D Kim J.S Song K.H Yoon B.T Ahn 《Solar Energy Materials & Solar Cells》1998,55(3):1362
Sputtering technique for Cu–In precursor films fabrication using different Cu and In layer sequences have been widely investigated for CuInSe2 production. But the CuInSe2 films fabricated from these precursors using H2Se or Se vapour selenization mostly exhibited poor microstructural properties. The co-sputtering technique for producing Cu–In alloy films and selenization within a close-spaced graphite box resulting in quality CuInSe2 films was developed. All films were analysed using SEM, EDX, XRD and four-point probe measurements. Alloy films with a broad range of compositions were fabricated and XRD showed mainly In, CuIn2 and Cu11In9 phases which were found to vary in intensities as the composition changes. Different morphological properties were displayed as the alloy composition changes. The selenized CuInSe2 films exhibited different microstructural properties. Very In-rich films yielded the ODC compound with small crystal sizes whilst slightly In-rich or Cu-rich alloys yielded single phase CuInSe2 films with dense crystals and sizes of about 5 μm. Film resistivities varied from 10−2–108 Ω cm. The films had compositions with Cu/In of 0.40–2.3 and Se/(Cu+In) of 0.74–1.35. All CuInSe2 films with the exception of very Cu-rich ones contained high amount of Se (>50%). 相似文献
993.
The power spectral density of a signal can be estimated most accurately by using a window with a narrow bandwidth and large sidelobe attenuation. Conventional windows generally control these characteristics by only one parameter, so there is a trade-off problem: if the bandwidth is reduced, the sidelobe attenuation is also reduced. To overcome this problem, we propose using a Butterworth window with two control parameters for power spectral density estimation and analyze its characteristics. Simulation results demonstrate that the sidelobe attenuation and the 3 dB bandwidth can be controlled independently. Thus, the trade-off problem between resolution and spectral leakage in the estimated power spectral density can be overcome. 相似文献
994.
Bum Suk Kim Maksym Spiryagin Bong Soo Kim Hong Hee Yoo 《Journal of Mechanical Science and Technology》2009,23(4):960-963
In the design process of an automobile part, several analysis methods are usually used to evaluate the performance of the
part. However, most automobile design engineers do not directly use CAE (computer aided engineering) tools since specific
skills are required to obtain practical results. Moreover, CAE requires a huge amount of computation time and cost. To resolve
these problems, a new design approach, termed first order analysis (FOA), has been proposed. In this paper, the FOA technique
is employed to design a vehicle sub-frame. An equivalent model of the vehicle subframe which only consists of beam elements
is proposed and the modal properties obtained with the model are compared to those obtained with a full scale finite element
model. The effects of some parameter variations on the modal characteristics of the vehicle sub-frame are investigated by
employing the FOA equivalent model.
This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008.
Hong Hee Yoo graduated from the Department of Mechanical Design and Production Engineering at Seoul National University in 1980 and received
his Master’s degree from the same department in 1982. He received his Ph.D. degree in 1989 from the Department of Mechanical
Engineering and Applied Mechanics at the University of Michigan at Ann Arbor, U.S.A. He is currently working as a professor
in the School of Mechanical Engineering in Hanyang University, Seoul, Korea. 相似文献
995.
Seok-Young Oh Hyeong-Woo Kim Jun-Mo Park Hung-Suck Park Chohee Yoon 《Journal of hazardous materials》2009
The oxidation of polyvinyl alcohol (PVA) by persulfate (S2O82−) activated with heat, Fe2+, and zero-valent iron (Fe(0)) was investigated via batch experiments. It was hypothesized that elevated temperature and the addition of Fe2+ or Fe(0) into a persulfate-water system could enhance the oxidation of PVA by activated persulfate. Increasing the temperature from 20 to 60 °C or 80 °C accelerated the oxidation rate of PVA, which achieved complete oxidation in 30 and 10 min, respectively. At 20 °C, the addition of Fe2+ or Fe(0) to the persulfate-water system significantly enhanced the oxidation of PVA. The optimal persulfate-to-Fe2+ or Fe(0) molar ratio was found to be 1:1. Complete oxidation of PVA was obtained by Fe(0)-activated persulfate in 2 h. Synergistic activation of persulfate by heat and Fe2+ or Fe(0) was also shown to enhance the oxidation of PVA in the persulfate-water system. By using GC–MS analysis, an oxidation product of PVA was identified as vinyl acetic acid (C4H6O2), which is readily biodegradable. Our results suggest that the oxidative treatment of PVA by activated persulfate is a viable option for the pretreatment of PVA-laden wastewater to enhance its biodegradability. 相似文献
996.
997.
It is necessary to measure the attributes of the parts in any manufacturing process. It is also important to monitor measurement
system in the manufacturing process because repeated measurements of the attributes include variability as well as target
value. This paper considers variabilities due to repeated measurements, operators, and gauge in a measurement system. The
measurement system is statistically modeled as a two-factor mixed model with one covariate and interaction. That is, this
model employs J operators randomly chosen to conduct measurements on I randomly selected parts from a manufacturing process. In this experiment each operator measures each part K times.
This paper aims to provide engineering practitioners with statistically optimal confidence intervals on the variation due
to operators and gauge resulted from a measurement system statistically modeled. The optimal confidence intervals are based
on a moderate large sample method (MLS) and a generalized p-value method (GEN). The confidence intervals proposed can be useful
tools to determine whether a manufacturing process is adequate for monitoring a measurement system. 相似文献
998.
V. N. Sekhar T. C. Chai S. Balakumar Lu Shen S. K. Sinha A. A. O. Tay Seung Wook Yoon 《Journal of Materials Science: Materials in Electronics》2009,20(1):74-86
In the present study, we have investigated the thickness dependence of mechanical properties of the Black Diamond? (SiOC:H, BD, Low-k) films, which are of great interest in current Cu/low-k Back End of the Line (BEOL) interconnect/packaging technologies. For this investigation the BD thin films of six different thicknesses 100, 300, 500, 700, 1,000 and 1,200 nm were deposited on the 8″ Si wafer by using plasma enhanced chemical vapor deposition (PECVD) technique. Nanoindentation and nanoscratch tests of the BD films were performed by using the Nano Indenter® XP (MTS Corp. USA). In nanoindentation testing of the BD films, significant differences in the elastic modulus of the BD films were observed. In nanoscratch testing, it is found that the critical load (Lc) and scratch width increases as the thickness of the film increases. Cross-sectional analysis of residual nanoindentation impressions was carried out using atomic force microscopy (AFM) to study the deformation behavior. The nanoindentation and nanoscratch responses of the BD thin films of six different thicknesses are different and they are expected mainly due to the molecular reorganization in thin/ultra thin films. 相似文献
999.
Mechanical and dynamic mechanical properties of various montmorillonite (MMT)/epoxy nanocomposites were investigated. 3-aminopropyltriethoxysilane
functionalized MMT was compared with commercial pristine MMT and ammonium salt substituted MMT. Qualitative evidence of silane
functionalization was confirmed by FT-IR. XRD and TEM were used to characterize the degree of intercalation of MMT in epoxy
nanocomposite. Tensile stress and elongation of MMT/epoxy nanocomposite were improved significantly by the silane functionalization
of MMT. Dynamic mechanical analysis showed that silane functionalization of MMT resulted in active interactions between MMT
and epoxy. 相似文献
1000.
Jung Sang Cho Dae Soo Jung Seung Kwon Hong Yun Chan Kang 《Journal of Electroceramics》2009,23(2-4):236-241
Nano-sized Pb-based glass powders with different mean size, ranging from 38 to 84 nm were prepared by flame spray pyrolysis. The mean sizes of the glass powders were controlled by changing the concentration of spray solution. The glass powders prepared by flame spray pyrolysis from the spray solutions with different concentration had broad peaks at around 28° in the XRD patterns. The dielectric layers formed from the glass powders with the mean size of 38 nm had dense inner structures at firing temperatures of 480 and 520°C. On the other hand, the dielectric layer formed from the glass powders with the mean size of 84 nm had some voids inside the layer. The transmittances of the dielectric layer formed from the glass powders with the mean sizes of 38 and 84 nm were each 91% and 74% at firing temperature of 480°C. 相似文献