全文获取类型
收费全文 | 5653篇 |
免费 | 578篇 |
国内免费 | 185篇 |
专业分类
电工技术 | 65篇 |
综合类 | 93篇 |
化学工业 | 1792篇 |
金属工艺 | 336篇 |
机械仪表 | 262篇 |
建筑科学 | 21篇 |
矿业工程 | 43篇 |
能源动力 | 426篇 |
轻工业 | 80篇 |
水利工程 | 1篇 |
石油天然气 | 12篇 |
武器工业 | 8篇 |
无线电 | 1015篇 |
一般工业技术 | 1834篇 |
冶金工业 | 186篇 |
原子能技术 | 102篇 |
自动化技术 | 140篇 |
出版年
2024年 | 13篇 |
2023年 | 104篇 |
2022年 | 103篇 |
2021年 | 232篇 |
2020年 | 202篇 |
2019年 | 205篇 |
2018年 | 194篇 |
2017年 | 232篇 |
2016年 | 212篇 |
2015年 | 201篇 |
2014年 | 312篇 |
2013年 | 314篇 |
2012年 | 280篇 |
2011年 | 498篇 |
2010年 | 295篇 |
2009年 | 344篇 |
2008年 | 338篇 |
2007年 | 319篇 |
2006年 | 277篇 |
2005年 | 195篇 |
2004年 | 171篇 |
2003年 | 177篇 |
2002年 | 164篇 |
2001年 | 134篇 |
2000年 | 121篇 |
1999年 | 121篇 |
1998年 | 120篇 |
1997年 | 103篇 |
1996年 | 89篇 |
1995年 | 84篇 |
1994年 | 69篇 |
1993年 | 39篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 25篇 |
1988年 | 27篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有6416条查询结果,搜索用时 15 毫秒
131.
介绍一种采用石英晶体振荡器作计数脉冲振荡源,用光电耦合器将触发电路和主电路进行隔离的数控可控硅触发电路。该电路具有可靠性和控制精度高,抗干扰能力强等特点。 相似文献
132.
Monuko du Plessis Herzl Aharoni Lukas W. Snyman 《Sensors and actuators. A, Physical》2000,80(3):242-248
A novel multi-terminal silicon light emitting device (TRANSLED) is described where both the light intensity and spatial light pattern of the device are controlled by an insulated MOS gate voltage. This presents a major advantage over two terminals Si-LEDs, which require direct modulation of the relatively high avalanche current. It is found that, depending on the bias conditions, the light intensity is either a linear or a quadratic function of the applied gate voltage. The nonlinear relationship facilitates new applications such as the mixing of electrical input signals and modulating the optical output signal, which cannot readily be achieved with two terminal Si-LEDs, since they exhibit a linear relationship between diode avalanche current and light intensity. Furthermore, the control gate voltage can also modulate the emission pattern of the light emitting regions, for example, changing the TRANSLED from an optical line source to two point sources. 相似文献
133.
Summary Microindentation experiments have recently shown that silicon can exhibit plastic flow when subjected to high pressure. Assuming that under these conditions the relevant reference structure is the -Sn high-pressure phase of silicon, we apply the magic-strain concept to explore the space of configurations that could describe the observed behavior. We use first-principles total-energy calculations (including full relaxation of the atomic basis for every structure) to evaluate the relevance of strained configurations. Using this approach, we were able to identify a low-energy path that corresponds to planar flow of the atoms. The atomic configurations along this path provide insight into possible microscopic motions under high pressure that may be relevant to plastic flow in silicon. 相似文献
134.
Nickel layer deposition on SiC nanoparticles by simple electroless plating and its dielectric behaviors 总被引:3,自引:0,他引:3
Surface modification of the silicon carbide nanoparticles (SiCP) by electroless nickel plating was performed. The XRD, TEM and XPS results showed that a nanoscale agglomerative nickel layer was coated on the SiCP. Dielectric permittivities of the original SiCP and nickel-coated SiCP were measured respectively in the GHz frequency range from 8 to 12 GHz. The real part and dielectric loss tangent of the nickel-coated SiCP were significantly enhanced. The origin of the enhancement was discussed in theory, and also explained by discussing practical influence factors. 相似文献
135.
锡、硅负极材料由于具有高的比容量等优点,成为提高锂离子电池能量密度的首选负极材料。首先介绍了目前产业界开发锡、硅负极材料的进展,并从商业化的角度比较了这两类材料在开发工艺及实际使用电性能方面的区别。进一步从基础研发角度重点阐述了不同结构的硅基材料(单质硅、硅氧化物、硅碳复合物及硅合金)的电性能改性研究进展,指出了具有工业化前景的工艺方法。 相似文献
136.
M. Tanaka K. Higashida H. Nakashima H. Takagi M. Fujiwara 《International Journal of Fracture》2006,139(3-4):383-394
Fracture toughness of silicon crystals has been investigated using indentation methods, and their surface energies have been
calculated by molecular dynamics (MD). In order to determine the most preferential fracture plane at room temperature among
the crystallographic planes containing the 〈001〉, 〈110〉 and 〈111〉 directions, a conical indenter was forced into (001), (110)
and (111) silicon wafers at room temperature. Dominant {110}, {111} and {110} cracks were introduced from the indents on (001),
(011) and (111) wafers, respectively. Fracture occurs most easily along {110}, {111} and {110} planes among the crystallographic
planes containing the 〈001〉, 〈011〉 and 〈111〉 directions, respectively. A series of surface energies of those planes were calculated
by MD to confirm the orientation dependence of fracture toughness. The surface energy of the {110} plane is the minimum of
1.50 Jm−2 among planes containing the 〈001〉 and 〈111〉 directions, respectively, and that of the {111} plane is the minimum of 1.19
Jm−2 among the planes containing the 〈011〉 direction. Fracture toughness of those planes was also derived from the calculated
surface energies. It was shown that the K
IC value of the {110} crack plane was the minimum among those for the planes containing the 〈001〉 and 〈111〉 directions, respectively,
and that K
IC value of the {111} crack plane was the minimum among those for the planes containing the 〈011〉 direction. These results are
in good agreement with that obtained conical indentation. 相似文献
137.
Particle-free silicon and nickel thin films were successfully fabricated by laser-ablating a melted section of their target surface, which gives a high evaporation pressure at the melting point. The influence of direct evaporation from a melted target was reduced negligibly by melting the target only locally with a focused electron beam (e-beam) and increasing the laser frequency. The silicon films fabricated by the present method, pulse laser deposition of a partially molten target, were able to firmly adhere to the substrates and withstood steel needle scratching, unlike e-beam-evaporated films. 相似文献
138.
In this work we study the evolution of porous silicon photoluminescence under illumination. Samples were obtained by electrochemical etching of crystalline silicon wafers of different types. For the p-type samples the evolution of the spectra is explained in terms of photoinduced oxidation of nanostructures, which in turns leads to a discrete change in the photoluminescence spectra, as we reported in previous works. For the n-type material, a progressive decrease of the luminescence intensity is observed, which is attributed to the photoinduced generation of dangling bond related defect states at the surface layer surrounding the nanostructures. This model explains qualitatively well the kinetics of the evolution of the measured photoluminescence. Preliminary results of electronic paramagnetic resonance spectroscopy agree with this model. 相似文献
139.
SiO2 thin film deposition on the inner surface of a poly(tetra-fluoroethylene) narrow tube by atmospheric-pressure glow microplasma 总被引:1,自引:0,他引:1
SiO2 thin films were deposited on the inner surfaces of a commercial poly(tetrafluoroethylene) narrow tube with an inner diameter of 0.5 mm using tetraethoxysilane/O2 feedstock gases and He carrier gas by atmospheric-pressure microplasma-enhanced chemical vapor deposition. A glow microplasma was generated inside the tube by radio frequency (RF) capacitively coupled discharge. X-ray photoelectron spectroscopy spectra showed that the tube inner surface was covered by a SiO2 thin film. Transparent SiO2 thin films were obtained with a deposition rate of 230 nm/min at an RF power of 6 W and substrate temperature of 100 °C. The wettability of the SiO2-coated tube was about 3 times as large as that of an untreated sample tube. 相似文献
140.
Till Böcking Michael James Christopher L. Brown Kevin D. Barrow 《Thin solid films》2006,515(4):1857-1863
Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 Å for the alkyl region of the undecanoic acid monolayer and 12 Å for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer. 相似文献