全文获取类型
收费全文 | 51436篇 |
免费 | 4122篇 |
国内免费 | 2676篇 |
专业分类
电工技术 | 1456篇 |
综合类 | 2028篇 |
化学工业 | 14461篇 |
金属工艺 | 4592篇 |
机械仪表 | 1299篇 |
建筑科学 | 826篇 |
矿业工程 | 1465篇 |
能源动力 | 4574篇 |
轻工业 | 1566篇 |
水利工程 | 133篇 |
石油天然气 | 1263篇 |
武器工业 | 120篇 |
无线电 | 6664篇 |
一般工业技术 | 13487篇 |
冶金工业 | 2881篇 |
原子能技术 | 503篇 |
自动化技术 | 916篇 |
出版年
2024年 | 155篇 |
2023年 | 906篇 |
2022年 | 1194篇 |
2021年 | 1671篇 |
2020年 | 1615篇 |
2019年 | 1553篇 |
2018年 | 1558篇 |
2017年 | 1784篇 |
2016年 | 1680篇 |
2015年 | 1683篇 |
2014年 | 2512篇 |
2013年 | 3079篇 |
2012年 | 3207篇 |
2011年 | 4337篇 |
2010年 | 3226篇 |
2009年 | 3199篇 |
2008年 | 2908篇 |
2007年 | 3276篇 |
2006年 | 2820篇 |
2005年 | 2299篇 |
2004年 | 2063篇 |
2003年 | 1816篇 |
2002年 | 1634篇 |
2001年 | 1348篇 |
2000年 | 1244篇 |
1999年 | 912篇 |
1998年 | 838篇 |
1997年 | 648篇 |
1996年 | 537篇 |
1995年 | 448篇 |
1994年 | 375篇 |
1993年 | 312篇 |
1992年 | 302篇 |
1991年 | 252篇 |
1990年 | 198篇 |
1989年 | 144篇 |
1988年 | 103篇 |
1987年 | 67篇 |
1986年 | 43篇 |
1985年 | 55篇 |
1984年 | 44篇 |
1983年 | 26篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The metalorganic chemical vapor deposition of aluminum oxide has been studied over a wide process parameter range. Electrical properties of as-grown and annealed layers have been investigated using planar aluminum/aluminum oxide/silicon capacitors. The best processing conditions resulted in a leakage current of 10 nA/cm2 at an equivalent oxide thickness of 3.6 nm. In addition, the film conformality was evaluated on silicon trench structures with aspect ratios of up to 60. Excellent step coverage of over 90% (thickness at trench bottom to thickness at trench middle) was achieved at temperatures below 400 °C and a pressure of 100 Pa. After annealing the electrical properties of these layers, analyzed on planar test structures, were comparable to the results obtained at higher deposition temperature. 相似文献
992.
Sang-Hoon Shin Sung-Dae Kim Jong-Ha Moon Jin-Hyeok Kim 《Journal of Electroceramics》2006,17(2-4):1097-1101
Er3+/Pr3+ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical
properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning
electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence
and binding characteristics have been investigated using a prism coupler and X-ray photoelectron spectroscopy. Er3+/Pr3+ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp. ∼550∘C), RF power (90 W–130 W), and Ar/O2 gas flow ratio at processing pressure of 4 mTorr. Glass thin films could be obtained at the optimized processing condition
at 350∘C, RF power of 130 W, and gas flow of Ar:O2 = 40:0 with maximum deposition rate of 1.6 μm/h. Refractive index and birefringence increased from 1.5614 to 1.5838 and from
0.000154 to 0.000552, respectively, as the content of Pr3+ increased. Binding energy of Pr3d also increased as the content of Pr3+ increased. 相似文献
993.
D. Y. Wang Y. Wang J. Y. Dai H. L. W. Chan C. L. Choy 《Journal of Electroceramics》2006,16(4):587-591
Heteroepitaxial Ba0.7Sr0.3TiO3 thin films were grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) (LSAT) and SrTiO3 (001) (STO) single crystal substrates using pulsed laser deposition (PLD). X-ray diffraction characterization revealed a
good crystallinity and a pure perovskite structure for films grown on both LSAT and STO substrates. The in-plane ferroelectric
and dielectric properties of the films were studied using interdigital electrodes (IDE). The film grown on LSAT substrate
exhibited an enhanced in-plane ferroelectricity, including a well-defined P-E hysteresis loop with the remnant polarization
P
r
= 10.5 μC/cm2 and a butterfly-shaped C-V curve. Nevertheless, only a slim hysteresis loop was observed in the film grown on STO substrate. Curie temperature T
c
of the film grown on LSAT substrate was found to be ∼105∘C, which is nearly 70∘C higher than that of the bulk Ba0.7Sr0.3TiO3 ceramics. T
c
of the film grown on STO substrate has almost no change compared to the bulk Ba0.7Sr0.3TiO3 ceramics. The dielectric tunabilities were found to be 64% and 52% at 1 MHz for the films grown on LSAT and STO substrates,
respectively. 相似文献
994.
K. Daoudi T. Tsuchiya I. Yamaguchi T. Manabe S. Mizuta T. Kumagai 《Journal of Electroceramics》2006,16(4):527-532
Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films were successfully prepared by the metal-organic deposition process on various (001) single-crystal substrates:
MgO, LaAlO3 (LAO), SrTiO3 (STO), and (LaAlO3)0.3-(SrAlTaO6)0.7 (LSAT). The crystallinity and the epitaxial growth of the LCMO films were characterized by X-ray diffraction (θ − 2θ scans
and pole-figure analysis). The temperature dependence of the resistance of the LCMO/LSAT, LCMO/STO and LCMO/LAO films exhibit
typical characteristics with a transition from the paramagnetic-insulator state to the ferromagnetic-metallic state at a temperature
peak (T
p
) ranging from 258 to 270 K. However, the LCMO/MgO films exhibited a semiconducting behavior without any transition. Based
on the R(T) measurement, we calculated the temperature coefficient of resistance (TCR) for a bolometric application and we obtained
22%/K, 10.2%/K and 27.5%/K for the film grown on the LSAT, STO and LAO substrates, respectively. This difference in the TCR
properties is related to the strain induced by the lattice mismatch between LCMO and the different substrates. 相似文献
995.
Chul-Ho Park Mi-Sook Won Chul-Su Lee Won-Hyo Cha Young-Gook Son 《Journal of Electroceramics》2006,17(2-4):619-623
PZT thin films and interlayers were fabricated by the radio frequency (r.f.) Magnetron-sputtering from the Pb1.1Zr0.53Ti0.47O3, PbO and TiO2 target. As a result of the XPS depth profile analysis, we can confirm that the substrate temperature affects the oxidation
condition of each element of interlayers and the PZT film. Compared to the PZT/Pt structure, the dielectric and pyroelectric
properties of PZT thin films inserted by interlayers were measured to a relatively high value. In particular, the PZT/PbO
structure had the highest pyroelectric properties (P = 189.4 μC/cm2K; F
D = 12.7×10−6 Pa−1/2; F
V = 0.018 m2/C). 相似文献
996.
Tin oxide thin films have been deposited by a custom-designed inductively coupled plasma chemical vapor deposition (ICP-CVD)
system in order to explore its application as an alternative approach for thin film gas sensor preparation. The as-deposited
SnO2 films were of polycrystalline structure with nano-size grains of 12 nm. The SnO2 films exhibited a maximum sensitivity of 43 to 1000 ppm H2 at an optimum operating temperature of 350∘C. The response time of the SnO2 films was 12 s and full recovery was achievable. 相似文献
997.
The initiation and growth of porous oxide on Ta was investigated in mixed H2SO4/HF electrolytes. Under selected potentiodynamic anodic oxidation conditions the formation of nearly uniform porous Ta2O5 layer was observed. The porous Ta2O5 layers consist of self-organized pore arrays with single pore diameters ranging from 2 to 10 nm. The morphology and the thickness
of the layer depend strongly on the applied potential, the scan rate and on HF presence. The composition of the porous oxide
layer is Ta2O5. 相似文献
998.
针对(Co0.35Fe0.65)99O1薄膜,研究了两种不同热处理工艺对其磁性能的影响。结果表明:快速循环热处理可以改善高磁矩(Co0.35Fe0.65)99O1薄膜磁性能,在450℃几个快速循环热处理后,沉积薄膜的矫顽力从105下降到3 Oe,电阻率下降到70%,a-Fe (Co)相晶粒尺寸可以减小到15~35 nm,该处理方法较以往的热处理更能改善软磁薄膜的性能。 相似文献
999.
Wei Shao Ruixin Ma Bin Liu 《北京科技大学学报(英文版)》2006,13(4):346-349
Aluminum-doped zinc oxide (ZnO:Al), abbreviated as ZAO, is a novel and widely used transparent conductive material. The ZAO powder was synthesized by chemical coprecipitation. The ZAO ceramic sputtering target materials were fabricated by sintering in air, and ZAO transparent conductive films were prepared by RF magnetron sputtering on glass substrates. XRD proved that such films had an orientation of (002) crystal panel paralleled to the surface of the glass substrate. The average transmittance of the films in the visible region exceeded 80%. 相似文献
1000.
Qifeng Shu Jianhua Liu Jiayun Zhang Mei Zhang 《北京科技大学学报(英文版)》2006,13(5):456-460
The thermal decomposition process of air-aged La203 in argon atmosphere was studied using nonisothermal TG-DSC. X-ray diffraction and TG-DSC analysis showed that the aged powder was composed of La(OH)3 with small amounts of oxycarbonate. The decomposition process of air-aged La2O3 involves the two-step decomposition of La(OH)3 and the decomposition of oxycarbonate. The kinetic analysis of the two-step decomposition of La(OH)3 was carried out using Coats-Redfern and isoconversion (Ozawa) methods. The kinetics of the two-step decomposition can be described in terms of the nucleation and growth model A (m=1.5, m is the model parameter) and A (m=2.5), respectively. The apparent activation energy for the first step is 136-144 (Coats-Redfern) and 137-164 kJ/mol (isoconversion). The apparent activation energy for the second step is 191-194 (Coats-Redfern) and 186-213 kJ/mol (isoconversion). 相似文献