全文获取类型
收费全文 | 245591篇 |
免费 | 27510篇 |
国内免费 | 8355篇 |
专业分类
电工技术 | 12205篇 |
技术理论 | 13篇 |
综合类 | 11811篇 |
化学工业 | 49447篇 |
金属工艺 | 12929篇 |
机械仪表 | 13543篇 |
建筑科学 | 15174篇 |
矿业工程 | 5269篇 |
能源动力 | 5653篇 |
轻工业 | 18674篇 |
水利工程 | 4401篇 |
石油天然气 | 11793篇 |
武器工业 | 1417篇 |
无线电 | 28758篇 |
一般工业技术 | 41815篇 |
冶金工业 | 13357篇 |
原子能技术 | 5442篇 |
自动化技术 | 29755篇 |
出版年
2024年 | 926篇 |
2023年 | 2987篇 |
2022年 | 5853篇 |
2021年 | 8239篇 |
2020年 | 7308篇 |
2019年 | 7927篇 |
2018年 | 9063篇 |
2017年 | 9967篇 |
2016年 | 9880篇 |
2015年 | 10839篇 |
2014年 | 12888篇 |
2013年 | 15893篇 |
2012年 | 14686篇 |
2011年 | 15366篇 |
2010年 | 13891篇 |
2009年 | 13405篇 |
2008年 | 12716篇 |
2007年 | 12135篇 |
2006年 | 11300篇 |
2005年 | 9599篇 |
2004年 | 7573篇 |
2003年 | 7413篇 |
2002年 | 7564篇 |
2001年 | 6653篇 |
2000年 | 5897篇 |
1999年 | 4849篇 |
1998年 | 3495篇 |
1997年 | 2906篇 |
1996年 | 2631篇 |
1995年 | 2241篇 |
1994年 | 1906篇 |
1993年 | 1592篇 |
1992年 | 1496篇 |
1991年 | 1278篇 |
1990年 | 1242篇 |
1989年 | 1137篇 |
1988年 | 1008篇 |
1987年 | 895篇 |
1986年 | 819篇 |
1985年 | 738篇 |
1984年 | 727篇 |
1982年 | 681篇 |
1979年 | 744篇 |
1978年 | 786篇 |
1977年 | 743篇 |
1976年 | 758篇 |
1975年 | 714篇 |
1974年 | 721篇 |
1973年 | 725篇 |
1972年 | 706篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
Hao Li Pengcheng Zhang Shengquan Yu Hongyu Yang Bin Tang Fuhai Li Shuren Zhang 《Ceramics International》2019,45(9):11639-11647
Mg2(Ti1-xSnx)O4 (x?=?0–1) ceramics were prepared through conventional solid-state method. This paper focused on the dependence of microwave dielectric properties on crystal structural characteristics via crystal structure refinement, Raman spectra study and complex chemical bond theory. XRD spectrums delineated the phase information of a spinel structure, and structural characteristic of these compositions were achieved with the help of Rietveld refinements. Raman spectrums were used to depict the correlations between vibrational phonon modes and dielectric properties. The variation of permittivity is ascribed to the Mg2(Ti1-xSnx)O4 average bond covalency. The relationship among the B-site octahedral bond energy, tetrahedral bond energy and temperature coefficient are discussed by defining on the change rate of bond energy and the contribution rate of octahedral bond energy. The quality factor is affected by systematic total lattice energy, and the research of XPS patterns illustrated that oxygen vacancies can be effectively restrained in rich oxygen sintering process. Obviously, the microwave dielectric properties of Mg2(Ti1-xSnx)O4 compounds were obtained (= 12.18, ?=?170,130?GHz, ?=??53.1?ppm/°C, x?=?0.2). 相似文献
8.
P. B. Lovyrev A. I. Lavrov V. A. Babkin A. N. Aminov S. M. Melekhin Yu. P. Kazantsev P. M. Korol’kov 《Metallurgist》2006,50(3-4):152-157
Specifications require that all the welds in 12-m-diam. decomposers with a capacity of 3600 m3 be subjected to high-temperature tempering before going into service in order to alleviate the stresses from the welding
operation. Specialists at the organizations VNIIPTkhimnefteapparatury and VNIImontazhspetsstroi have proposed out-of-furnace
volumetric (complete) of the assembled decomposer with the use of special heaters. The use of this heating method has shortened
assembly operations while providing the welds with a highquality heat treatment and reducing the stresses overall (including
welding stresses, stresses from assembly of the decomposer, etc.) The technology ensures uniform heating of the housing of
the decomposer and provides for close control over the process. The experience gained in heat-treating decomposers can also
be used in the construction of other containers that come into contact with corrosive media.
__________
Translated from Metallurg, No. 3, pp. 61–64, March, 2006. 相似文献
9.
10.
N. I. Nikolaikin E. Yu. Barzilovich N. E. Nikolaikina 《Chemical and Petroleum Engineering》2006,42(5-6):332-338
The paper discusses optimal control of ecosystem state for observation of a generalized monotonically varying random parameter.
A model is proposed for the controlled vector random process, whose components are assigned acceptable ranges and the observations
are performed discretely.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 40–44, June, 2006. 相似文献