全文获取类型
收费全文 | 92826篇 |
免费 | 12211篇 |
国内免费 | 5838篇 |
专业分类
电工技术 | 7254篇 |
技术理论 | 3篇 |
综合类 | 7249篇 |
化学工业 | 20099篇 |
金属工艺 | 6641篇 |
机械仪表 | 5125篇 |
建筑科学 | 4969篇 |
矿业工程 | 3103篇 |
能源动力 | 4171篇 |
轻工业 | 11724篇 |
水利工程 | 2278篇 |
石油天然气 | 5838篇 |
武器工业 | 980篇 |
无线电 | 10146篇 |
一般工业技术 | 10543篇 |
冶金工业 | 4852篇 |
原子能技术 | 1329篇 |
自动化技术 | 4571篇 |
出版年
2024年 | 625篇 |
2023年 | 2013篇 |
2022年 | 3162篇 |
2021年 | 3918篇 |
2020年 | 4204篇 |
2019年 | 3777篇 |
2018年 | 3356篇 |
2017年 | 3882篇 |
2016年 | 4015篇 |
2015年 | 3968篇 |
2014年 | 5553篇 |
2013年 | 5903篇 |
2012年 | 6594篇 |
2011年 | 6585篇 |
2010年 | 4761篇 |
2009年 | 4974篇 |
2008年 | 4339篇 |
2007年 | 5338篇 |
2006年 | 4888篇 |
2005年 | 4152篇 |
2004年 | 3429篇 |
2003年 | 3205篇 |
2002年 | 2744篇 |
2001年 | 2426篇 |
2000年 | 2220篇 |
1999年 | 1837篇 |
1998年 | 1520篇 |
1997年 | 1316篇 |
1996年 | 1056篇 |
1995年 | 994篇 |
1994年 | 809篇 |
1993年 | 644篇 |
1992年 | 563篇 |
1991年 | 410篇 |
1990年 | 359篇 |
1989年 | 318篇 |
1988年 | 185篇 |
1987年 | 128篇 |
1986年 | 103篇 |
1985年 | 101篇 |
1984年 | 101篇 |
1983年 | 65篇 |
1982年 | 66篇 |
1981年 | 44篇 |
1980年 | 54篇 |
1978年 | 12篇 |
1976年 | 9篇 |
1964年 | 14篇 |
1959年 | 16篇 |
1951年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
文章以介电测井理论为基础,借鉴感应仪的模拟刻度方法,对大庆油田的60MHz相位介电井仪的模拟刻度进行了研究。参照国内外有关资料,提出了模拟刻度器的设计模型,通过理论分析与计算,建立了一套模拟刻度方法。现场初步试验,该方法取得了一定物效果,为进一步提高仪器的测量精度提供了依据。 相似文献
62.
The static and dynamic properties of solutions of a side chain polysiloxane liquid crystal polymer have been studied in a cyanobiphenyl nematic host as a function of concentration and temperature. Refractive index measurements were carried out on aligned samples and the data used to determine the macroscopic order parameter, S, using Haller's method. Photon correlation spectroscopy has been used to measure () for the pure nematic solvent and the solutions. From these measurements it appears that the static properties vary slowly and linearly with increasing polymer concentration whilst the dynamic or viscoelastic properties change markedly. This change has been attributed to γ1, the twist viscosity, and the results have been discussed in terms of the function of the siloxane polymer backbone. 相似文献
63.
A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380 相似文献
64.
Research has continued in the field sidechain liquid crystal polymers over recent years, but it is becoming clearer that this research is being directed away from the traditional technology areas of electro-optic devices and researchers are developing new and exciting applications for this novel state of matter. 相似文献
65.
66.
本文以TEM和XRD为主要手段,研究WC-TiC-Co硬质合金(YT14)在直接淬火后WC相的微观结构和微观应力,比较了常规烧结态与淬火态试样WC相之间的差异,探讨了直接淬火对合金力学性能的影响。结果表明,在保持合金其他性能不降低的同时,直接淬火的抗弯强度比常规烧结提高28%左右。并首次发现,经直接淬火热处理的YTI4合会中与Co相相邻的WC晶粒边界出现滑移台阶,这是淬火过程中热应力使WC晶粒内位错在{0001}密排面聚集,并可能沿{0001}<1120>易滑移系统强滑移的结果。直接淬火试样的微观应力比重新加热淬火的低。 相似文献
67.
Solid-liquid phase equilibria of the benzene + 2-methyl-2-propanol system have been investigated at temperatures from 278 to 323 K and pressures up to 300 MPa using a high-pressure optical vessel. The uncertainties of the measurements of temperature, pressure and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. The freezing pressure at a constant composition increases monotonously with pressure. The eutectic point shifts to a higher temperature and benzene-rich composition with increasing pressure. In order to describe the pressure-temperature-composition relation of high-pressure solid-liquid phase equilibria, a new simple equation has been proposed as follows:
相似文献
68.
1 INTRODUCTIONTheorthorhombicalloysareofgreattech nolog icalinterestinhightemperatureapplicationssincetheyhaveagoodbalanceamongst 相似文献
69.
F. Otsubo K. Kishitake T. Akiyama T. Terasaki 《Journal of Thermal Spray Technology》2003,12(4):555-559
It is known that the corrosion resistance of stainless steel is deteriorated by blasting, but the reason for this deterioration
is not clear. A blasted austenitic stainless steel plate (JIS-SUS304) has been characterized with comparison to the scraped
and non-blasted specimens. The surface roughness of the blasted specimen is larger than that of materials finished with #180
paper. A martensite phase is formed in the surface layer of both blasted and scraped specimens. Compressive residual stress
is generated in the blasted specimen and the maximum residual stress is formed at 50–100 μm from the surface. The corrosion
potentials of the blasted specimen and subsequently solution treated specimen are lower than that of the non-blasted specimen.
The passivation current densities of the blasted specimens are higher those of the non-blasted specimen. The blasted specimen
and the subsequently solution treated specimen exhibit rust in 5% sodium chloride (NaCl) solution, while the non-blasted specimen
and ground specimen do not rust in the solution. It is concluded that the deterioration of corrosion resistance of austenitic
stainless steel through blasting is caused by the roughed morphology of the surface. 相似文献
70.
E. Q. Xie W. W. Wang N. Jiang D. Y. He Department of Physics Lanzhou University Lanzhou China 《金属学报(英文版)》2002,15(2):221-226
1. IntroductionThe transition metal silicides have attraeted much attention because of their potentialapplicatiOIl in very large scale integration (VLSI) de.ice[1]. Near-noble metal silicides canbe used as Schottky al1d ohn1ic col1tacts in silicon-based d… 相似文献
|