全文获取类型
收费全文 | 1730篇 |
免费 | 196篇 |
国内免费 | 82篇 |
专业分类
电工技术 | 57篇 |
综合类 | 49篇 |
化学工业 | 244篇 |
金属工艺 | 61篇 |
机械仪表 | 176篇 |
矿业工程 | 12篇 |
能源动力 | 51篇 |
轻工业 | 10篇 |
水利工程 | 1篇 |
石油天然气 | 5篇 |
武器工业 | 56篇 |
无线电 | 614篇 |
一般工业技术 | 252篇 |
冶金工业 | 11篇 |
原子能技术 | 11篇 |
自动化技术 | 398篇 |
出版年
2024年 | 3篇 |
2023年 | 77篇 |
2022年 | 56篇 |
2021年 | 77篇 |
2020年 | 64篇 |
2019年 | 58篇 |
2018年 | 55篇 |
2017年 | 195篇 |
2016年 | 90篇 |
2015年 | 139篇 |
2014年 | 156篇 |
2013年 | 162篇 |
2012年 | 209篇 |
2011年 | 193篇 |
2010年 | 88篇 |
2009年 | 110篇 |
2008年 | 36篇 |
2007年 | 35篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 8篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
排序方式: 共有2008条查询结果,搜索用时 15 毫秒
91.
92.
93.
《Remote sensing of environment》1987,21(2):201-213
The information content of Landsat TM and MSS data was examined to assess the ability to digitally differentiate urban and near-urban land covers around Miami, FL. This examination included comparisons of unsupervised signature extractions for various cover types, training site statistics for intraclass and interclass separability, and band and band combination selection from an 11-band multisensor data set. The principal analytical tool used in this study was transformed divergence calculations. The TM digital data are typically more useful than the MSS data in the homogeneous near-urban land-covers and less useful in the heterogeneous urban areas. 相似文献
94.
《Thin solid films》1987,146(3):283-289
The effect of hydrogen as a dilution gas on the deposition of diamond-like carbon by the decomposition of methane in a microwave discharge was studied from surface analysis of the substrate and from plasma diagnostics. When carbon deposited from a CH4-Ar plasma and consisting of large amounts of graphite and small amounts of diamond, was placed in the hydrogen plasma chemical sputtering of carbon to form hydrocarbons and adsorption of hydrogen on the carbon substrate were observed. The reaction occured only on graphite and not on diamond. The effects of hydrogen as a dilution gas on the deposition of diamond-like carbon from CH4-H2 plasma are to cause the formation of CH3 radicals in the plasma, the removal of graphite from the deposit and the adsorption of atomic hydrogen on the deposit as an active participant in the diamond crystallization process. 相似文献
95.
《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1987,253(2):235-244
We have built a transition radiation detector consisting of four sets of multilayered polyethylene radiators each followed by a xenon-filled proportional chamber. This detector has been used in a hadron-proton scattering experiment at CERN SPS to discriminate electrons from hadrons in the final state. Using the technique of recording chamber signals of amplitude exceeding a fixed threshold we normally achieved 0.5% pion contamination at 80% electron efficiency. 相似文献
96.
针对飞行试验中对设备温度测量的需求,设计了一种适用于飞行测试的高精度多通道温度采编装置。设计以FPGA构建信号采集处理系统,采用AD8227和AD590来实现信号的调理和温度冷端补偿,通过标准RS422协议实现16路温度信号传输,并采取线性拟合的方式对输出进行非线性校正,提高了系统准确率和稳定性。测试结果表明,测温电路全量程内最大测量误差为±0.083%F.S.。经过测试验证,该方案传输过程无丢帧零误码,系统运行高效、可靠。 相似文献
97.
《International Communications in Heat and Mass Transfer》1988,15(5):669-679
It is shown in this paper that the wrong choice of boundary conditions in the evaluation of diffusion coefficients in solids can lead to quite unreliable estimates. In particular the two frequent assumptions of immediate reequilibration at the interface or of a radiation--like boundary condition are shown to be completely inadequate if the process kinetics is different. To overcome these difficulties we describe a new method that estimates the unknown boundary conditions along with the diffusion coefficient. A numerical example is examined for comparison. 相似文献
98.
提出一种利用2张正交照片和细分曲面进行真实感三维人脸建模的方法,并实现了不同模型间的三维变形.为了构造个性化的人脸几何模型,将网格简化、自由曲面变形和细分结合起来,得到多个层次细节下的人脸模型;再经过纹理融合和映射,完成个性化的真实感三维人脸建模;同时利用线性插值实现了同拓扑真实感模型间的光滑变形.实验结果表明:该方法不仅可以进行有效的真实感三维人脸建模,而且变形简单流畅,具有广阔的应用前景. 相似文献
99.
《Ceramics International》2020,46(14):22282-22289
Self-assembly is an emerging strategy for preparing composite cathodes with good oxygen electrochemical reduction activity and congenital chemical compatibility for intermediate-temperature solid oxide fuel cell (IT-SOFC). Here we report that a self-assembled BaCo0.6Zr0.4O3-δ (BZC-BC) nanocomposite is prepared through one-pot glycine-nitrate process and exhibits high cathode performance. The BZC-BC nanocomposite is composed of 62 mol% cubic perovskite BaZr0.82Co0.18O3-δ (BZC) as an ionic conductor and 38 mol% hexagonal perovskite BaCo0.96Zr0.04O2.6+δ (12H-BC) as a mixed ionic and electronic conductor. The BZC-BC nanocomposite has the pomegranate-like particles aggregated with a larger number of nanoparticles (50-100 nm) which greatly enlarge the three-phase boundary sites. The BZC-BC nanocomposite exhibits a thermal expansion coefficient of 12.89 × 10−6 K−1 well-matched with that of Ce0.8Gd0.2O3-δ (12.84 × 10−6 K−1) electrolyte. The high electro-catalytic activity of BZC-BC nanocomposite cathode for oxygen reduction is reflected by the low polarization resistances of oxygen ions incorporation at cathode/electrolyte interface (0.02823 Ω cm2), oxygen species diffusion (0.03702 Ω cm2) and oxygen adsorptive dissociation (0.07609 Ω cm2) at 700 °C. The single cell with BZC-BC nanocomposite cathode achieves the maximum power density of 1094 mW cm−2 at 650 °C and shows good stability under 25 h run. 相似文献
100.
《Ceramics International》2020,46(13):21378-21387
A systematic density functional theory investigation of Cs2PbX6 (X = Cl, Br, I) double perovskites is presented. The lattice constants are computed after structure optimization and using Birch-Murnaghan equations, which agree to the experimental literature. The mechanical stability conditions satisfy Born criteria, and the ductile nature is evidenced by the calculated Poisson's (v) and Pugh's ratios (B0/G) because all three double perovskites exhibit values higher than the respective critical values v = 0.26 and B0/G = 1.75. A detailed study of the optoelectronic properties reveals these double perovskites as promising candidates for future optical devices due to their direct band gaps (within 0.45–2.54 eV) and large absorption coefficients 5.95 × 105 cm−1, which are suitable for solar cell applications. ZT calculations demonstrate minute variations within 200–800 K and computed parameter values are quite favorable for thermoelectric applications of these materials in the future. A p-type semiconducting nature is predicted by the computed thermoelectric properties. Additionally, computed refractive indices show Cs2PbBr6 and Cs2PbI6 exhibiting super-luminescent properties in the UV range. Therefore, the studied double perovskites provide further interest for future energy conversion and photonic based technologies. 相似文献